Silverado Rough Idle No Codes

NEED HELP! 2005 Silverado Idle Problems. It eventually set off the check engine light with cylinder 1 misfire and random cylinder misfire. Idle was somewhat better - it starts and runs at 1000 RPM until I stop to let son out at school. Try unplugging and plugging them in, see if anything changes. 3L with 27000 miles. No codes makes it tough,it could be something simple like a weak coil or it could have the leaking valve issue causing a misfire at idle. rough idle and hesitation once engines is hot, no codes on DIC. You can use a can of carb & choke clean to find vacuum leaks. I had the fuel pump replaced and have been using Lucas Injector Cleaner with every tank of gas. Ok guys, I have a problem and am looking for help/advice. Silverado Rough Idle and Hesitation This is a discussion on Silverado Rough Idle and Hesitation within the Automotive Support forums, part of the Tech Support Forum category. Long story short he replaced the fuel regulater. Save up to $14,350 on one of 31,125 used 2010 Chevrolet Silverado 1500s near you. Truck never stalls and has good smooth power about 1k rpm. It would idle a little rough and when it was cold (just backed out to the garage) and I pull away from the house it would even surge just a bit. 7liter 350 engine, i replaced the motor,the other motor had 225,000plus miles. Cleaned with some Seafoam and it has been OK. You also may check fuel system pressure, should be almost 60p. Deaerlship said no codes were set so nothing is wrong. Will cause a rough idle/clatter, and no throttle response, because the engine is in limp mode and running on four cylinders. How to fix a rough idle/clean, replace IAC valve and the P0300 code chuck kososky. It turned out the solution, for me, was to replace a spark plug coil that had gone bad. " I have changed the plugs and wires, what's going on? Also, there is a squeak that sounds like a belt when I first start the truck and sometimes continues, and sometimes doesn't (may or may not be related). seemed to have fixed it or at least made it better. 7liter 350 engine, i replaced the motor,the other motor had 225,000plus miles. Not throwing any codes right now. The always pesky and always mysterious check engine light has turned on. 3 with 77k on it. 2004 Chevrolet Silverado 1500HD Engine Technical Service Bulletins (TSBs). I've been having a pretty rough idle for about a month now. I got rid of a 1999 S10 with 200,000 miles that puured like a kitten. We've tried resetting the ECM by disconnecting the negative battery cable for awhile. I'm driving a 1996 Chevy Silverado with 260,000 miles on it. change fuel filter and air filter. A few weeks ago I also had a rough idle and no code or anything. Changed all the plugs while it was apart too since there were about 85000 miles on the truck. owned it since new. The truck was running fine until a fill up a few weeks ago. Important: During the drive cycle the check engine light may come on with idle speed DTCs. I then changed the belt and idler tension pulley, still had a rough idle but slightly better. Q: Rough idle, thermostat code asked by inspect your vehicle firsthand to find the right fix for your rough idle. After replacing both, the problem persisted. the more i teach myself about this car the more it seems that its got a lot of different parts than other coupes since it was only made for a year or two. Page 1 of 3: How to Troubleshoot a Misfire (GM 4. 3 Liter FIXED rough idling by stoping UNMETERED Air inflow AIR WAS CAUSING MY ENGINE TO ROUGH IDLE. Just the other day I drove it down to my folks place and when I pulled in the driveway the engine started running rough. Did a compression test and everything was actually great for it having 237,000 miles. Plugs have about 40k on them. A faulty camshaft position sensor is one of them. One last thing for those who are new to this and are experiencing same problemplease read my first post under "Urgent!!!! P0300 Misfire, Rough Idle, Fuel Trim Error" thread which contains my description of my current situation in details and the parts that I've replaced thus far up to this point without success. at idle the voltage goes from 12 to 14 just bouncing around , i tryed the the MAF sensor cleaning and it helped somewhat i have already. Register Log In Home Forums Mechanical/Maintenance Forum P1345 codes and rough idle at cold startup issues: Flywheel broke 2012 V8 Silverado, with pics by. The engine will still run, albeit quite powerless, and rough. it has about 112000 miles. it runs fine when i first start it, but soon idles low/rough, but only in gear. RE: 07 tahoe 5. This article applies to the Chevrolet Silverado GMT800. This avoids "parts darts" where more and more parts are replaced until the fault goes away. Just recently say in the last 1 thousand miles its been idling rough once put in gear, occasionally when not in gear. suggestions all assuming no codes as you have stated. No Misfire Diagnostic Trouble Codes. Also replaced fuel filter. the below codes came up. The odometer should give you a code instead of mileage. I unplugged the connector and put some nolox on the terminals and also done the same to all the other sensor connectors. 7 Vortec Warning lights = check engine soon. Average failure mileage is 1,500 miles. Duramax Second Generation: 2004. unplugging the MAF helps the idle. New fuel/air filters. Try unplugging and plugging them in, see if anything changes. Yesterday i noticed when i would put my truck in drive it would idle rough for about 4sec then smooth out, then when i put it in park same thing. Rough Idle, Surge, Hesitation, Stall. If the code comes back you may have to replace the Electric Throttle Control Actuator (Motor) to repair the problem. models 2009-2013 express, silverado, suburban, savana, sierra. 3 There are no codes and the engine runs rough, we have three of these trucks and only this one does this. Umm, I'm thinking maybe you do have a problem. Re: HELP!! 2008 Silverado idles/runs rough, No codes Aug 31 2012, 3:53pm My 2008 does the same thing though not as often, I can't recall what the dealer said other than is was normal and that they had checked everything, I'll be sitting at a light and you can watch the tach dip just a bit. 3L rough idle, anybody else has the same ? There is no buildup on the injectors in 1200 miles. Rough idle and increased cranking to start are two of the main problems, but there are other parts of the fuel system that need to operating correctly for a smooth running, easy starting, engine. P0300 Diagnostic Trouble Code Discussion for September 2007 Multiple Misfire Detected * Note: This is a professional automotive technician's resource. The first sign of the problem was the service engine light would blink intermittently when driving on the highway or revving the gas. The thing is the truck idles fine when cold but gets rough once warmed up. After that my truck worked great. I have same problem on my 07 silverado, code for stabilitrak problems and fuel injector 8; this the third time time happen, I has replaced the brake light switch (29. Chances are that if you fix the misfire; you’ll also repair the rough idle at cold start. 3, has a rough idle, (kinda sounds like it has a aftermarket cam) runs good when you get it on the road but when you stop at a red light it sounds like its going to die, the truck has tru duals, straight pipes for most of its life with no cats, now the previous owner paid $400 for new cats which are on the truck now but still has no muffler, just. This article covers a wide variety of noises common to the hard working Chevrolet Silverado. Discussion in 'Chevy Trucks' started by MikeRi24, Oct 10, There is no CEL on and I scanned the computer for codes and nothing in the. This avoids "parts darts" where more and more parts are replaced until the fault goes away. But you can definitely feel a change in the smoothness of the idle. Its a V6 4. Re: HELP!! 2008 Silverado idles/runs rough, No codes Aug 31 2012, 3:53pm My 2008 does the same thing though not as often, I can't recall what the dealer said other than is was normal and that they had checked everything, I'll be sitting at a light and you can watch the tach dip just a bit. In fact it just throws P035* codes that way. just thought I would make this video to try to help yall out. My Cat is not in a motorhome, but an "05" M2 Freightliner that avgs 2600 miles/week. I also have an 05 silverado z71 crew cab with a 5. How to fix a rough idle/clean, replace IAC valve and the P0300 code chuck kososky. We've tried resetting the ECM by disconnecting the negative battery cable for awhile. Also replaced fuel filter. -Rough idle (misfires) after the engine has warmed up. It’s a 1998 w/ 164,000 miles and excellent maintenance-- needs new front brakes soon. Also remembered I got so what sounded like popping out the exhaust if I tried to rev it when it was struggling. Rough idling, how do I fix my particular issue? 13 Answers. Did a compression test and everything was actually great for it having 237,000 miles. Just recently say in the last 1 thousand miles its been idling rough once put in gear, occasionally when not in gear. 7 in my '04 GTO or the 5. I'm no expert but that's the pcv valve that you plugged the hose onto at 3:50. It did nothing. So far the idle problem has stopped and no other codes have appeared. There is no throttle cable. Average failure mileage is 1,500 miles. I have taken to a mechanic friend and he pulled no codes from the truck. It stumbles and hesitates during driving. The CEL has been on duri. The truck runs fine no obvious problem. In recent weeks it began to idle rough when sitting at stoplights with my foot on the brake. Brent 2005 Chevrolet Silverado Crew Cab 2500HD LLY 4x4, EFI Live V2 DSP5 tuned by Idaho Rob (ATP) Edge Insight CTS w/ ebay backup camera,EGR Blocker Plate, LBZ MP, PCV Reroute, Pump Rub Upgrade Transgo SK, swap over to TranSynd, Earl's Temp-A-Cure, Transmission Cooler, MBRP 4" Turbo Back Aluminized Exhaust (no CAT), BD Full Bore Exhaust Manifold, Insynerator DSL 3" Down Pipe, Banks 3" Monster. Having a a major dilema with a rough idle / Multiple Cylinder Misfire on my 2001 Chevy S10. 2015 Silverado code P050D I keep getting a P050D code cold start/rough idle. Purchased the truck in December and have been having rough idle conditions and what feels to be misfiring(on morning start up, sitting at lights I can feel it, and during the daytime if it has sat for a couple hours). I bought my Altima about a year ago and always had a rough idle, it's not so bad now but I feel it and it just bothers me. models 2009-2013 express, silverado, suburban, savana, sierra. P0106 AND STABILITRAK ROUGH IDLE. I figured well it could be a vacuum leak. Mine is a Non-turbo just in case it matters. I have not had good luck cleaning MAF sensors, or buying aftermarket ones. Some older cars use a carburetor to process fuel, rather than a fuel injection system. (Not positive of this but it feels like that) truck will still start, but when applying gas it gets rougher. Re: Cold weather rough idle Unread post by carriedi » Wed Nov 19, 2014 5:26 pm the first thing to do is leave your truck at a shop that can park it outside overnight and start it up in the morning with a scanner hooked up and see what the engine is doing (or what the computer sees the engine to be doing). It would idle a little rough and when it was cold (just backed out to the garage) and I pull away from the house it would even surge just a bit. rough idle and hesitation once engines is hot, no codes on DIC. Two codes of P0440 in the past 3 weeks since the fuel pump was replaced. Re: Rough idling 2005 Chevy Silverado start by cleaning the throttle plate and throttle bore, this engine is drive by wire and doesnt use idle air control valve, this is done with the throttle body. Bought new Silverado because of complications with the old one ran good for about a week then it started to idle rough like it was missing. 2019 Chevrolet Reviews; 2019 Chevrolet Equinox Review By Larry Nutson; 2019 Chevrolet Tahoe 4WD Premire By John Heilig; 2018 Chevrolet Reviews; 2018 Chevrolet Colorado Real World. when i put it in park or nuetral it idle up but it still lopes. One time, it did completely misfire and limped back to my shop. My work truck, 08 K1500 with the 5. After that my truck worked great. Once i tightened things down, the blue smoke was pretty much entirely gone. It's very annoying. If I apply a bit of gas in neutral and bring the RPM to 1000, the roughness is still present but is less pronounced. Rough idle in drive, and loss of power - My 2014 gmc Sierra tx edition, idles rough while in drive, smooth while parked. Here's maybe a challenge for y'all. Hi, I have 2009 Chevy Silveraor with about 88,000 kms. After the above repairs were complete the car was started and there is a loud squeak, knock, then a rough Idle. This code comes on for every hick-up it sees. I need to know what this code is and what needs to be fixed. The 2003 Chevrolet Silverado has 7 problems reported for rough idle, runs roughly. However, it is easy to recognize the problem, as during rough idling either the engine would run at an irregular rate or it may have varying RPMs without your foot on the gas pedal. The engine is the 5. it runs fine when i first start it, but soon idles low/rough, but only in gear. Ive had my 2011 silverado 5. 6 ltr Chevrolet Silverado pick-up 1/2 ton. I've read most threads on the subject (much appreciation!), and will try some more solutions today. All FIXED 5. These connectors can be plugged into with an affordable car code reader/eraser to check what codes have tripped. when i put it in park or nuetral it idle up but it still lopes. Shop refused to do the leakdown because no code was logged. 3, has a rough idle, (kinda sounds like it has a aftermarket cam) runs good when you get it on the road but when you stop at. Vibration during idle was intermittent as well. the below codes came up. I have a bank 2 lean code also. Engine didn't throw any codes. just thought I would make this video to try to help yall out. Chevrolet Silverado 1999-2006: How to Replace Exhaust Gas Recirculation (EGR) Valve. The CEL has been on duri. No, the cold knock is nowhere near as bad as the 5. You are looking at a 2004 Chevy Silverado 1500 Z 71 four-wheel-drive extended cab. as far as reliability that is good but idles poorly. Rough idle after plug and valve cover gasket change If this is your first visit, be sure to check out the FAQ by clicking the link above. As soon as I crank my truck the electric fan cuts on and idles rough. i drive between 100 and 200 miles a day. It reads exactly the same codes and i was told to try changing the plugs and cleaning the air flow sensor that is located right beside the air box wich houses the filter. Check out other FullyDriven. This results in a rough idle and unburned gas making it into the exhaust, creating a gasoline smell in the exhaust. I have a 2017 6. I have a 2005 H2 SUT with 200,000 miles and over the past couple of months, I have noticed that there is slight hesitation on acceleration and the idle is very rough once the engine is hot or has been running for. -CEL codes: Bank 1 Fuel trim, Bank 2 Fuel trim, misfires on all six cylinders, O2 sensor switching Things I've Done:-Cleaned MAF. Ok guys, I have a problem and am looking for help/advice. I had the fuel pump replaced and have been using Lucas Injector Cleaner with every tank of gas. Re: Rough idling 2005 Chevy Silverado start by cleaning the throttle plate and throttle bore, this engine is drive by wire and doesnt use idle air control valve, this is done with the throttle body. I discuss how to check a coolant temp sensor and clean the throttle body and idle air control valve A lot of people overlook the simple things when most of the time something simple is the fix. After I have it all fixed and can drive it some, I will report back as to the success of the. 3 Liter FIXED rough idling by stoping UNMETERED Air inflow AIR WAS CAUSING MY ENGINE TO ROUGH IDLE. I have a 2011 Silverado that just went in for a throttle positioning sensor service bulletin. This "high idle’ condition is causing the Automatic Transmission to “slam” when put in gear. Sputter, rough idle, and fuel odor A few weeks ago (on 8/15 to be exact), I made a post about sputtering and rough idle. hey my 03 silverado 5. Rough idle and misfiring, but no codes. They claimed to run a VAGCOM on it and found no faults, they resetted the computer, re positioned the throttle body and "messed" with the idle control. 8T has been idling really rough after it is started cold. 97 Chevy C1500 idles great, runs rough when put in gear 12 Answers. P050D CHEVROLET Meaning During a cold start, the Engine Control Module commands dual-pulse mode during Open Loop operation to improve cold start emissions. 3L V8 with 200k miles on it. 2001 Chevrolet Silverado 2500HD Engine Technical Service Bulletins (TSBs). Since I bought the car I have done the following: 1. 3 Vortec V6. Idle is smooth and no more surge. Anyway, so I tried taking a look at it today to see if I could figure it out and no luck so far. I have not had good luck cleaning MAF sensors, or buying aftermarket ones. It would idle a little rough and when it was cold (just backed out to the garage) and I pull away from the house it would even surge just a bit. When the car is fully warmed up after driving the idle (roughly 600-800 RPM) would be a little Rough Warm Idle - Honda Prelude Forum. When the engine idle rises you have found your leak. Average failure mileage is 1,500 miles. IAC, EGR, EGR controller, MAP, temp sensor, vacuum leaks, O2 etc. it has about 112000 miles. I took off. Although my opinion (supported by others too) is that the idle speed needs to be re-learned, the system should still be capable of maintaining an idle speed. Without knowing what code was set, I would say its a bad terminal in one injector connector. Pretty low milage for a 2005, Don't drive it that much because with it being an EXT it only get's 10 miles to the gallon. Car / Truck Won't Run or Idle / Fix - F150 is the patient TOP 5 REASONS WHY YOUR CAR WON'T IDLE. Shop refused to do the leakdown because no code was logged. If the new one does it, you bet your butt it will be in code or no code. Also replaced fuel filter. It doesn't do it all the time but most of the time it does and when your driving down the road it runs perfect. 7 in my '04 GTO or the 5. Learn what does P0300 Chevrolet Cylinder Misfire Detected Random Cylinders means, location and how to repair? When a misfire occurs, engine speed will fluctuate. The car's acceleration under heavy throttle began to suffer and it no longer responded smoothly. Re: 87 Silverado 350 tbi idling rough « Reply #24 on: April 18, 2011, 07:52:18 PM » have you checked for codes and make sure the egr valve is working accordingly with acceleration it could have carbon or be sticking open at idle, also check the vent on the egr vacuum control solenoid, it has to be open to allow the egr valve to function quick. No Misfire Diagnostic Trouble Codes. Pull the EGR off, spray it down with some carb cleaner, put it back on and use a scanner to clear the code. change fuel filter and air filter. Re: HELP!! 2008 Silverado idles/runs rough, No codes Aug 31 2012, 3:53pm My 2008 does the same thing though not as often, I can't recall what the dealer said other than is was normal and that they had checked everything, I'll be sitting at a light and you can watch the tach dip just a bit. 1994 s10 (ss) rough idle no C. i have a 1995 gmc 2500 with 454 tbi, misses at idle and gives code 36 (OBD 1). Rough idle comes back and will even go dead a few times. Did better once warm but. so i got a e46 328ci 2000. Please Help 1999 Silverado!!!! Silverado Car Forums. suggestions all assuming no codes as you have stated. the below codes came up. I've read most threads on the subject (much appreciation!), and will try some more solutions today. No codes, intermittent rough idle and rare misfire was created by DanB - 2001 Taurus w/ DOHC V6 24v Duratec, 158,000 miles - I just bought it and know a little about the maint. The 2017 Chevrolet Silverado 1500 has 20 NHTSA complaints for the engine at 20,423 miles average. 2000 Chevy Silverado 1500 5. 6 ltr Chevrolet Silverado pick-up 1/2 ton. unplugging the MAF helps the idle. 3 is having idle issues. No codes in computer, replaced MAF sensor, plug wires, IAC control valve, spark plugs, cleaned TB, replaced gasket, fuel pump w/fuel level sending unit. Both trucks also have a good amount of features. I have a 2011 Silverado that just went in for a throttle positioning sensor service bulletin. Cause: Coolant getting into the cylinders. My truck is a 02 Chevy Silverado v6 4. Has a rough idle and "Service engine soon" light. The RPMs fluctuate between about 520 to 580 in jerky fashion it almost feels twitchy at an idle. It's controlled by the computer. I will check for some vacuum leaks and the egr valve. 3 L GM tech = MW question = I have a 1999 Chevy Silverado that i bought about 2 months ago. Register Log In Home Forums Mechanical/Maintenance Forum P1345 codes and rough idle at cold startup issues: 2002 Silverado Cabin Air filters 2 years by Rat407. OBD-II Code Decreased engine performance is defined as a Cold Start Rough Idle The engine control module (PCM) monitors misfires on initial startup. Bought new Silverado because of complications with the old one ran good for about a week then it started to idle rough like it was missing. To find intermittent wiring and connector faults. Above 1000 RPM you cannot feel it anymore. Rough idle no power lean codes. After replacing both, the problem persisted. Changed all the plugs while it was apart too since there were about 85000 miles on the truck. Two codes of P0440 in the past 3 weeks since the fuel pump was replaced. I have a bank 2 lean code also. It reads exactly the same codes and i was told to try changing the plugs and cleaning the air flow sensor that is located right beside the air box wich houses the filter. I have a 1995 4WD 5. Rough idle no power. models 2009-2013 express, silverado, suburban, savana, sierra. After a couple weeks I noticed that at idle the engine would stumble and my rpms would drop slightly. I have a 2005 LS Silverado 5. Average failure mileage is 27,500 miles. I only got the P0300 code, no code for specific cylinder. I unplugged the connector and put some nolox on the terminals and also done the same to all the other sensor connectors. This happens while driving and sitting still (for the lights and rough idle) not the hard shifting. It also idles rough aftter getting off of the hiway and having to sit a a red light. Silverado Rough Idle and Hesitation This is a discussion on Silverado Rough Idle and Hesitation within the Automotive Support forums, part of the Tech Support Forum category. 2003 silverado 4. Confirming a stuck EGR valve can be as simple at giving it a light tap on the side of the valve,. Idle problems may originate in a worn out component, a. Random Cylinder Misfire in Cylinders 2, 5, 6, and 8; P0300; Chevy Silverado 1500 4WD Put everything back together still rough idle and P0300 and P0102 codes. There is no throttle cable. Upstream o2 sensors are disconnected shop did the tune and I had no CEL or issues untill now. Answer: Well, with no codes to go by, and the things you have already replaced, it sounds like a problem with the Idle Air Control motor (IAC). 95) each time before, this always seem to work, it restored curse control, brakes light,lack of power,rough shifting,and stabilizing service message, reset code and no more engine. com Car Forums! Read real discussions on thousands of topics and get your questions answered. It doesn't do it all the time but most of the time it does and when your driving down the road it runs perfect. If anyone has any suggestions, any info would be appreciated. cleaned the MAF today as i suspected it as my culprit for my idle hunting. i've been lurking 4 yrs. Rough idling, how do I fix my particular issue? 13 Answers. I will reset ECM and the engine will run perfect for about 2 days and then start giving me this problem. 3 with 230k miles. bmw e46 rough idle p0441 code cant figure out Hey everyone. 3L with 27000 miles. Replaced: coolant temp sensor, tps, map sensor, fuel filter, and o2 sensor. the more i teach myself about this car the more it seems that its got a lot of different parts than other coupes since it was only made for a year or two. i have a 2008 Silverado Crew Cab w/ 5. All vacuum hoses look in good order, sprayed carb cleaner around intake to check for leaks at intake/throttle body, no leaks. Try unplugging and plugging them in, see if anything changes. I have > > turned up the idle screw in the base plate of the TBI, which does not > > seem to help, it just goes back to low idle and stalling again, is the > > a way to get that back to the original factory setting? I am presuming > > that screws up the main computer. The causes might vary, but most idle problems are caused by a mixture issue. My wife has a 2000 1. 3 and it idles rough sporadically. Whenever I cold start the truck it runs really rough for a few seconds, about 200-300 rpm, then to compensate it starts running at about. This results in a rough idle and unburned gas making it into the exhaust, creating a gasoline smell in the exhaust. Did a compression test and everything was actually great for it having 237,000 miles. i have a 04 chevy silverado with the 5. Not throwing any codes right now. Re: Duramax LB7 Smokes at idle Ray, I had a 2002 GMC 2500HD with the Duramax and I had problems with the injectors that caused excessive smoking at idle. 3-liter was a surge at idle when warmed up. A faulty camshaft position sensor is one of them. I was on my way home from Clearwater and the idle became rough. But in the day and age where the Chevy Silverado has a sensor for everything, it could literally mean that your gas cap is off, or it could mean catastrophic engine failure is about to happen. Top 10 Causes of a Rough Idle | JL Motorworks. rough idle, check engine w/ P0171 & P0174 codes - I have a 98 Expedition with a 5. There was no real rhyme or reason to when it would act up. New filters all around, new battery all GM/Delco parts. Start up was rough but the truck did idle but never smoothed out. 3 Rough Start/Idle - Duration: 6:12. It seems to run fine but at a slightly higher idle then norm. What does computer code P0340 98 Chevrolet Silverado mean? Hard starting or no start Rough running. The RPMs fluctuate between about 520 to 580 in jerky fashion it almost feels twitchy at an idle. I have a 2005 LS Silverado 5. Hopefully someone else has experienced this problem. it has about 112000 miles. Visit the post for more. When I got my Blackbear tune, Justin noticed it too. I took off. With 2004 Chevy Silverado Code P0300 With P0171 And Rough Idle, all of these problems are never an issue. If I apply a bit of gas in neutral and bring the RPM to 1000, the roughness is still present but is less pronounced. Although my opinion (supported by others too) is that the idle speed needs to be re-learned, the system should still be capable of maintaining an idle speed. However, after searching for a while and reading a bunch of threads, I have noticed that mostly idle problems are something that happens pretty much constantly. 3L with 100K miles on it. I have a bank 2 lean code also. As explained earlier, in many cases the computer may set codes which can lead you to the EGR valve as the prsoblem. Re: Rough idling 2005 Chevy Silverado start by cleaning the throttle plate and throttle bore, this engine is drive by wire and doesnt use idle air control valve, this is done with the throttle body. Rough idle and worse in cold temps. 2001 Chevrolet Silverado 2500HD Engine Technical Service Bulletins (TSBs). I took it to the dealership and they said it was a fuel injector going bad. My truck had a rough idle that varied it seemed depending on the weather so I figured I had a gasket leak. Re: HELP!! 2008 Silverado idles/runs rough, No codes Aug 31 2012, 3:53pm My 2008 does the same thing though not as often, I can't recall what the dealer said other than is was normal and that they had checked everything, I'll be sitting at a light and you can watch the tach dip just a bit. The A/C will shut off at times to keep the engine running. the black wire has continuity. Its a V6 4. My understanding is the P0172 and P0175 are rich codes and the P0446 is regarding the Evap system. I haven't checked the codes recently (5K). Without knowing what code was set, I would say its a bad terminal in one injector connector. It does also get a p0446 code not as frequently and has given a P0172 Code. Replaced: coolant temp sensor, tps, map sensor, fuel filter, and o2 sensor. In fact it just throws P035* codes that way. They poured some 3M gas additive in the tank and the idle cleared up and light went off. I have a 2017 6. Check out other FullyDriven. It's very annoying. This article applies to the Chevrolet Silverado GMT800.