Consistent Misfire At Idle - Any way to track down?
TECH Resident
Joined: Jun 2013
Posts: 853
Likes: 32
From: Kernersville, NC
An area that includes California, three dealerships in TX and Virginia. Stories galore of GM “tech” mouthbreathing wizardry. One of which, the SS was in for warranty work at a Plano dealership and a ******* tried to steal my Hurst shifter, put in a stock one and tried to tell me it was the original, and somehow the Hurst magically reappeared and couldn’t be explained why it was off the car. Another where I had to sue a dealership in Irving, TX over a rotor screw opti issue when they tried to tell me it was a blown head gasket and wanted a CC number so they could do “exploratory surgery” and tried to void my entire warranty.
Point being you’re in a minority if you can trust a GM mechanic. Stores like this are everywhere. Mechanics are in the business of making money and they’ll do and say whatever they can to get the most out of a customer as possible. Especially when it comes to old cars.
Hell, just the other day my friend had his ‘02 Avalanche at a Chevy dealership because of a clunking noise and they tried to tell him not only did he have a bad axle, which is where the noise was originating, but his catalytic converters were also bad which added another thousand dollars to the bill.
Point being you’re in a minority if you can trust a GM mechanic. Stores like this are everywhere. Mechanics are in the business of making money and they’ll do and say whatever they can to get the most out of a customer as possible. Especially when it comes to old cars.
Hell, just the other day my friend had his ‘02 Avalanche at a Chevy dealership because of a clunking noise and they tried to tell him not only did he have a bad axle, which is where the noise was originating, but his catalytic converters were also bad which added another thousand dollars to the bill.
I just thank God above that he gave me the brains and physical ability to work on my cars. It can be wallet breaking/frustrating to have others do it.
An area that includes California, three dealerships in TX and Virginia. Stories galore of GM “tech” mouthbreathing wizardry. One of which, the SS was in for warranty work at a Plano dealership and a ******* tried to steal my Hurst shifter, put in a stock one and tried to tell me it was the original, and somehow the Hurst magically reappeared and couldn’t be explained why it was off the car. Another where I had to sue a dealership in Irving, TX over a rotor screw opti issue when they tried to tell me it was a blown head gasket and wanted a CC number so they could do “exploratory surgery” and tried to void my entire warranty.
Point being you’re in a minority if you can trust a GM mechanic. Stores like this are everywhere. Mechanics are in the business of making money and they’ll do and say whatever they can to get the most out of a customer as possible. Especially when it comes to old cars.
Hell, just the other day my friend had his ‘02 Avalanche at a Chevy dealership because of a clunking noise and they tried to tell him not only did he have a bad axle, which is where the noise was originating, but his catalytic converters were also bad which added another thousand dollars to the bill.
Point being you’re in a minority if you can trust a GM mechanic. Stores like this are everywhere. Mechanics are in the business of making money and they’ll do and say whatever they can to get the most out of a customer as possible. Especially when it comes to old cars.
Hell, just the other day my friend had his ‘02 Avalanche at a Chevy dealership because of a clunking noise and they tried to tell him not only did he have a bad axle, which is where the noise was originating, but his catalytic converters were also bad which added another thousand dollars to the bill.
Staging Lane
Joined: Sep 2018
Posts: 72
Likes: 11
I'm with SS RRR, too many people I know have been F-ed over by the dealerships and repair shops here. One friend of mine quit his job (tech) at the dealership because of their shady practices. The service writers get paid on commission so there is incentive to inflate the repair estimates.
I can think of three cars in the last two years that were brought to me because the stealership estimate was north of $2500. The most expensive one to fix - I charged them $150 (including the part). The worst one (they told her it was gonna be over $4k) I fixed in 5 mins, no parts needed. Stealer claimed it needed a whole new wiring harness.
It's so bad here I won't even let the dealer do warranty or recall repairs.
I can think of three cars in the last two years that were brought to me because the stealership estimate was north of $2500. The most expensive one to fix - I charged them $150 (including the part). The worst one (they told her it was gonna be over $4k) I fixed in 5 mins, no parts needed. Stealer claimed it needed a whole new wiring harness.
It's so bad here I won't even let the dealer do warranty or recall repairs.
I've seen the same in our shop from certain dealers in the area. Typically in our area we find it's the import dealers that are the worst. Like I said, I know this kinda crap happens and it's unfortunate that it does because it keeps good folks from trusting the dealer. I get that and with my time at the dealer I also witnessed service writers and Managers pull off some shady stuff, I hate that nonsense but again, not every tech is like that and sometimes it's great to know the better ones personally and be able to request that they be the one that works with you and your car. I also know that it's not always possible to be fortunate enough to know a good tech personally but again, not every tech is a dealership dirtbag and some of those seasoned veteran techs really can be a wealth of knowledge on these older platforms.
Would, I want a Young, fresh out of school kid to be the guy on my car, no, no I wouldn't but I have had some warranty work done on my car and I've tried to take it to a dealership I've been familiar with and know the techs there. I just hope the OP is able to find someone he can trust because dealerships aren't the only shops filled with crooks and subparr So called technicians. There are many independent shops treating their customers just as badly, just with a lower shop rate.
Would, I want a Young, fresh out of school kid to be the guy on my car, no, no I wouldn't but I have had some warranty work done on my car and I've tried to take it to a dealership I've been familiar with and know the techs there. I just hope the OP is able to find someone he can trust because dealerships aren't the only shops filled with crooks and subparr So called technicians. There are many independent shops treating their customers just as badly, just with a lower shop rate.
TECH Regular
Joined: May 2014
Posts: 426
Likes: 20
From: Houston Texas
After dealing with Toyota dealership "master techs" arguing with me about bearing noise in a RAV4, i dont think i could ever trust another dealership again. Even techs at my buddy's shop, good guys, wealth of knowledge,just not well rounded.
Ivebeen fudged packed by too many "mechanics". Haven't been screwed by the internet yet, however, i do see alot of bad info that can confuse even the wisest. Like another said, gottabe willing to figure out alot on your own, or pay mechanics to find this site.
Anyways, you say you ran starving the engine. Wonder if you fucked some lifters? Valves maybe? I know going too lean can burn some **** on other engines. LT1 has its issues. Fudged lifters/valves will certainly contribute to misfires. Would make more sense being low rpm only.
Running lean too long without being tuned for it, and even then to an extent, will burn things up quicker.
So, AFTER this misfire and fuel pump issue, what have you replaced? Im coming back to writing this a couple hours later. I remember a lengthy post catching everyone up, going over what youve done.
I would still double check plugs if you haven't. I dont know how to rule out valves really on LT1. Im sure theres a way, i i just dont see how to do old school method of removing valve covers and watching ****. Not alot of room.
ETA: so youve changed plugs after the issue started, how "delicate" are the LE1 head internals? I know big power can be had, but that doesn't always translate into durability. Thats where i would be looking if everything else ruled out.
Assuming since its low mileage, its the factory Opti unit?
Ivebeen fudged packed by too many "mechanics". Haven't been screwed by the internet yet, however, i do see alot of bad info that can confuse even the wisest. Like another said, gottabe willing to figure out alot on your own, or pay mechanics to find this site.
Anyways, you say you ran starving the engine. Wonder if you fucked some lifters? Valves maybe? I know going too lean can burn some **** on other engines. LT1 has its issues. Fudged lifters/valves will certainly contribute to misfires. Would make more sense being low rpm only.
Running lean too long without being tuned for it, and even then to an extent, will burn things up quicker.
So, AFTER this misfire and fuel pump issue, what have you replaced? Im coming back to writing this a couple hours later. I remember a lengthy post catching everyone up, going over what youve done.
I would still double check plugs if you haven't. I dont know how to rule out valves really on LT1. Im sure theres a way, i i just dont see how to do old school method of removing valve covers and watching ****. Not alot of room.
ETA: so youve changed plugs after the issue started, how "delicate" are the LE1 head internals? I know big power can be had, but that doesn't always translate into durability. Thats where i would be looking if everything else ruled out.
Assuming since its low mileage, its the factory Opti unit?
Last edited by demonsmokr; Feb 22, 2020 at 11:15 PM.
So just a stupid thought. The fuel injectors are rated at a certain psi. If the pump is not building the proper psi wouldnt the fuel flow be off? Possible causing a miss? Is it possible when they changed the pump one of the pins in the plug was damaged and not making good contact?
Also wont a vacuum leak cause a random misfire and not throw a code?
Also wont a vacuum leak cause a random misfire and not throw a code?
@Adam1203 yup, low fuel pressure and vacuum leaks both can cause a random misfire. Sometimes if it's a intake gasket issue people get lucky and find that as the engine warms up everything expands and the vacuum leak will temporarily seal until the engine cools again. Usually this results in random misfires on start up and clearing gradually as the engine warms. The fuel pressure I would think would have to be really abnormally low though. It doesn't take much fuel to simply idle but cold starts do demand more fuel. You could see where If you have a combination of the two problems you could potentially have a very poor running/idling engine.
Unfortunately this is a situation where diagnosing an engine that you're not right in front of is difficult. It's always easier when you're in front of the car, ideas start to ping off the brain and you can try things to see the engine reacts.
Unfortunately this is a situation where diagnosing an engine that you're not right in front of is difficult. It's always easier when you're in front of the car, ideas start to ping off the brain and you can try things to see the engine reacts.
@Adam1203 yup, low fuel pressure and vacuum leaks both can cause a random misfire. Sometimes if it's a intake gasket issue people get lucky and find that as the engine warms up everything expands and the vacuum leak will temporarily seal until the engine cools again. Usually this results in random misfires on start up and clearing gradually as the engine warms. The fuel pressure I would think would have to be really abnormally low though. It doesn't take much fuel to simply idle but cold starts do demand more fuel. You could see where If you have a combination of the two problems you could potentially have a very poor running/idling engine.
Unfortunately this is a situation where diagnosing an engine that you're not right in front of is difficult. It's always easier when you're in front of the car, ideas start to ping off the brain and you can try things to see the engine reacts.
Unfortunately this is a situation where diagnosing an engine that you're not right in front of is difficult. It's always easier when you're in front of the car, ideas start to ping off the brain and you can try things to see the engine reacts.
TECH Enthusiast
Joined: Jul 2010
Posts: 593
Likes: 29
From: Florida
If one is not familiar with mechanics at a dealership, how does one go about getting to know whether one can be trustworthy? Every dealership I’ve been in I’ve had to go through the service area/managers. No real way to wander into the garage at start conversations...
Not all shops are as strict, it depends on the people and the area. Word of mouth, a good tech in a shop will often have a reputation in his area, sometimes you just simply have to ask around the town. What do you know about the guys up at X dealership? I'm looking for a guy to fix my car and I'd like to know if you know anyone, etc etc. Just don't be bashful, people in town, especially smaller towns talk, why do you think gossip and rumors spread so fast?
**** dealerships. I'd rather spend time investigating local shops. I've had better luck at the drag strip finding good places.
Last edited by SS RRR; Feb 25, 2020 at 11:32 AM.