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mattchrz

miss at low rpm (idle) sound familiar?

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Posted (edited)

ok, my truck sometimes misses at low rpm parked or stopped in drive(at a light), its a 05 silverado 2500hd 6.0 base 2 door rwd, 86,000 miles. i've changed  (using all ac delco or delphi electric products except) msd coils , msd wires, ac delco  platinum spark plugs, crank sensor, cam sensor, map sensor, cleaned the throttle body and mass air flow sensor (with correct fluids), exhaust manifold gaskets and broken bolts, gas cap vapor canister purge valve, vapor canister vent valve, ac delco knock sensors with gaskets (few years ago), cleaned the grounds (i could find), fuel pressure is good, no dtc codes. still at idle the engine will kick down to about 560 rpms and will have a miss or sometimes not (but the miss will come it will come than stop than start), rain or dry, hot or cold outside. RUNS STRONG other than that and using high test gas 93 octane. i have a hyper tech mpg  programmer but same miss happens programmed or back to stock. thanks for your time!

Edited by mattchrz
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Try some techron,might have a bad spray pattern on a injector

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Check the intake gaskets.

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On 5/23/2020 at 6:09 AM, mattchrz said:

ok, my truck sometimes misses at low rpm parked or stopped in drive(at a light), its a 05 silverado 2500hd 6.0 base 2 door rwd, 86,000 miles. i've changed  (using all ac delco or delphi electric products except) msd coils , msd wires, ac delco  platinum spark plugs, crank sensor, cam sensor, map sensor, cleaned the throttle body and mass air flow sensor (with correct fluids), exhaust manifold gaskets and broken bolts, gas cap vapor canister purge valve, vapor canister vent valve, ac delco knock sensors with gaskets (few years ago), cleaned the grounds (i could find), fuel pressure is good, no dtc codes. still at idle the engine will kick down to about 560 rpms and will have a miss or sometimes not (but the miss will come it will come than stop than start), rain or dry, hot or cold outside. RUNS STRONG other than that and using high test gas 93 octane. i have a hyper tech mpg  programmer but same miss happens programmed or back to stock. thanks for your time!

MAF  or IAT sensor is bad  more then likely   common failure on the NBS and NNBS  I had to replace mine(IAT was bad  I had the combo version)   as it would backfire on start up,full throttle and/or oscillate idle  rough idle(misfire on idle)   randomly    

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Thanks for your time! My wife noticed the bucking, (miss) happened when jumped on it trying to make a red light. Took off great than at the next light had to stop and setting there the engine started to buck(miss) than drove a couple miles and cleared up! Crazy!

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Tried the fuel injector cleaner, idled smoother, miss way more infrequent. Probably bad or dirty injector. Thanks for the info!  Good Numbers for mas and intake vac  

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There was a thread a few months ago,guy decided to pull rails and injectors and cleaned them himself,he had a misefire on #7,worth a try?or techron it again?

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