2000 silverado 1500 5.3 "miss" at idle

WDDOBLER · 01-30-2006, 06:38 PM

Shure could us the input. First, hot or cold in drive there is a "miss" or "buck" in idle. 1st dealer (found no error codes) changed fuel filter and cleaned throttle body with spray claener (made no differance) then i changed spark plugs,wires. (made no diffeance) 2nd dealer (different dealer) still no codes checked fuel injector wireing and all checked "ok" and recommend cleaning fuel enjectors (moto-vac or similar) (made no differance) Back to dealer (2nd one) cleaned fuel enjector system again (this time with special "gm" recommended service bulliten cleaner.did this procedure 2 times and said if this doesn't do it , injectors will need to pulled and cleaned/checked. (made no differance) Know i pulled the injectors and had them checked and cleaned. (injector service said no bad or out of spec injectors ,but while out might as well clean them. Said he remembered a similar problem, may be low fuel pressure (but would be exspensive to install and adjust a pressure regulator) reinstalled (made no differance) I like my truck ,but being a mechanic myself I feel someting is wrong and would like to fix it right. Thanks Dave

gmtech · 01-31-2006, 05:32 PM

This misfire just happens at start up and last a short while?? We have had alot of intake gaskets leaking vacuum moreso since the cold wether hit but can be checked with some carb cleaner sprayed around base of plastic intake at start up to see if there is an idle change. Fuel pressure regulator is also common just pull off the vacuum hose and see if any fuel drips out either with it running or after sitting for a short time either of these can cause a mis and no codes til they get worse. These are 2 easy checks and common concerns.

WDDOBLER · 01-31-2006, 06:09 PM

gmtech...I'm glad to get a reply from you, I read alot of your replies and beleive you know what yor talking about. the truck "misses/bucks" all the time (hot or cold) and never goes away at idle (in drive)( notisable at a stop light/ runs great and strong thru acceleration range) this has been an issure since last feburary so cold weather not a culprate. as soon as i locate the fuel pressure regulator i'll try your vacuum hose test. Thanks Dave. P.S. since reinstalling the cleaned injectors it sems to to "fire up" (not crank over) did I need to "bleed/purge" the fuel rails when reinstalling ? Thanks again hope i'm not being to much of a pain!

gmtech · 01-31-2006, 07:14 PM

No problem, the fuel injectors self bleed so thats not an issue. As far as the misfire just when did it start and what happened or under what situations made it come on? Its hard to believe it has been misfiiring for about a year and you say no check engine light and no codes stored right? The fuel pressure regulator is more of a concern at start up . Its on the drivers side of the engine about half way back right at the edge of the plastic engine cover but like i said probably not it. Is this a steady mis/buck or just an occasional or random thing? All the more info I can get I can try to narrow it down for you.

WDDOBLER · 02-01-2006, 07:06 PM

gmtech...The rough idle started about 1 year ago. I bought it 2004 with 120000 miles on it and i swear it didn't rough idle then. (maybe the rough idle is in my head) but when it bucks (like a coil didnt fire) it concerns me. I tried your tests (no difference with carb cleaner around the intake/pulled the vacuum hose-no drips) This is a very steady miss, the buck is ocasional or random thing. I may be totally wrong in my thinking ,but it seems like one of the coils not firing right.(once again gm service people found no error codes and electrical #'s were in spec) Anyway you've been a very appreciated voice and if you or your freinds ever need any golf car advice, let me know, I've been doing for over 20 years. Thanks again. Dave

lebrowr · 02-01-2006, 07:30 PM

I'm having the same problem with my 93. I changed over from a 305 to a 350 and it misses at idle but is ok through the driving range. My problem is the fuel mixture, it's running rich. I need new PROM but perhaps you have a bad sensor or a ground/open in one of the circuits??

gmtech · 02-02-2006, 02:54 PM

Dobler I'm starting to think it is in your head. if the engine has any misfires the computer watches for this all the time and would turn on the check engine light and the light would even flash while the misfire is happening. The occasional hickup or bump at idle has been a normal situation on all v6 and v8 truck engines since I've been turning wreches (1985) til now. My own 2001 5.3 does it along with my old 94 5.7. this bump/hickup/lean mis is more noticable in neutral than drive but its common. If you have a misfire the shops who looked at it would be able to watch the misfire counts on the scan tool and it would turn on the check engine light. I find it vertualy impossible that you had a misfire for a year and if you did it would have taken out the catalytic convertor do to raw fuel going into it. I don't know what more to tell you sounds like the other shops have gone through it have you had it to an actual GM dealer?

WDDOBLER · 02-02-2006, 06:44 PM

gmtech...both shops that worked on my truck were Gm dealers. They were courtius and sincere in trying to help. If your riggs do it and your comfortable with it, I guess I can stop throwing money at it. By the way it did pass state emmissions test. guess that means the cat is ok too. Thanks again for your time.

01-30-2006, 06:38 PM	#1
WDDOBLER Junior Member Join Date: Jan 2006 Posts: 4	2000 silverado 1500 5.3 "miss" at idle Shure could us the input. First, hot or cold in drive there is a "miss" or "buck" in idle. 1st dealer (found no error codes) changed fuel filter and cleaned throttle body with spray claener (made no differance) then i changed spark plugs,wires. (made no diffeance) 2nd dealer (different dealer) still no codes checked fuel injector wireing and all checked "ok" and recommend cleaning fuel enjectors (moto-vac or similar) (made no differance) Back to dealer (2nd one) cleaned fuel enjector system again (this time with special "gm" recommended service bulliten cleaner.did this procedure 2 times and said if this doesn't do it , injectors will need to pulled and cleaned/checked. (made no differance) Know i pulled the injectors and had them checked and cleaned. (injector service said no bad or out of spec injectors ,but while out might as well clean them. Said he remembered a similar problem, may be low fuel pressure (but would be exspensive to install and adjust a pressure regulator) reinstalled (made no differance) I like my truck ,but being a mechanic myself I feel someting is wrong and would like to fix it right. Thanks Dave

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01-31-2006, 05:32 PM	#2
gmtech Senior Member Join Date: Dec 2005 Location: farmville Va Posts: 343	This misfire just happens at start up and last a short while?? We have had alot of intake gaskets leaking vacuum moreso since the cold wether hit but can be checked with some carb cleaner sprayed around base of plastic intake at start up to see if there is an idle change. Fuel pressure regulator is also common just pull off the vacuum hose and see if any fuel drips out either with it running or after sitting for a short time either of these can cause a mis and no codes til they get worse. These are 2 easy checks and common concerns.

01-31-2006, 06:09 PM	#3
WDDOBLER Junior Member Join Date: Jan 2006 Posts: 4	gmtech...I'm glad to get a reply from you, I read alot of your replies and beleive you know what yor talking about. the truck "misses/bucks" all the time (hot or cold) and never goes away at idle (in drive)( notisable at a stop light/ runs great and strong thru acceleration range) this has been an issure since last feburary so cold weather not a culprate. as soon as i locate the fuel pressure regulator i'll try your vacuum hose test. Thanks Dave. P.S. since reinstalling the cleaned injectors it sems to to "fire up" (not crank over) did I need to "bleed/purge" the fuel rails when reinstalling ? Thanks again hope i'm not being to much of a pain!

01-31-2006, 07:14 PM	#4
gmtech Senior Member Join Date: Dec 2005 Location: farmville Va Posts: 343	No problem, the fuel injectors self bleed so thats not an issue. As far as the misfire just when did it start and what happened or under what situations made it come on? Its hard to believe it has been misfiiring for about a year and you say no check engine light and no codes stored right? The fuel pressure regulator is more of a concern at start up . Its on the drivers side of the engine about half way back right at the edge of the plastic engine cover but like i said probably not it. Is this a steady mis/buck or just an occasional or random thing? All the more info I can get I can try to narrow it down for you.

02-01-2006, 07:06 PM	#5
WDDOBLER Junior Member Join Date: Jan 2006 Posts: 4	gmtech...The rough idle started about 1 year ago. I bought it 2004 with 120000 miles on it and i swear it didn't rough idle then. (maybe the rough idle is in my head) but when it bucks (like a coil didnt fire) it concerns me. I tried your tests (no difference with carb cleaner around the intake/pulled the vacuum hose-no drips) This is a very steady miss, the buck is ocasional or random thing. I may be totally wrong in my thinking ,but it seems like one of the coils not firing right.(once again gm service people found no error codes and electrical #'s were in spec) Anyway you've been a very appreciated voice and if you or your freinds ever need any golf car advice, let me know, I've been doing for over 20 years. Thanks again. Dave

02-01-2006, 07:30 PM	#6
lebrowr Junior Member Join Date: Jan 2006 Location: Princeton ON Posts: 6	I'm having the same problem with my 93. I changed over from a 305 to a 350 and it misses at idle but is ok through the driving range. My problem is the fuel mixture, it's running rich. I need new PROM but perhaps you have a bad sensor or a ground/open in one of the circuits??

02-02-2006, 02:54 PM	#7
gmtech Senior Member Join Date: Dec 2005 Location: farmville Va Posts: 343	Dobler I'm starting to think it is in your head. if the engine has any misfires the computer watches for this all the time and would turn on the check engine light and the light would even flash while the misfire is happening. The occasional hickup or bump at idle has been a normal situation on all v6 and v8 truck engines since I've been turning wreches (1985) til now. My own 2001 5.3 does it along with my old 94 5.7. this bump/hickup/lean mis is more noticable in neutral than drive but its common. If you have a misfire the shops who looked at it would be able to watch the misfire counts on the scan tool and it would turn on the check engine light. I find it vertualy impossible that you had a misfire for a year and if you did it would have taken out the catalytic convertor do to raw fuel going into it. I don't know what more to tell you sounds like the other shops have gone through it have you had it to an actual GM dealer?

02-02-2006, 06:44 PM	#8
WDDOBLER Junior Member Join Date: Jan 2006 Posts: 4	gmtech...both shops that worked on my truck were Gm dealers. They were courtius and sincere in trying to help. If your riggs do it and your comfortable with it, I guess I can stop throwing money at it. By the way it did pass state emmissions test. guess that means the cat is ok too. Thanks again for your time.