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scott96tahoe
New User
Nov 20, 2011, 9:07 PM
Post #1 of 13
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1996 Chevy Tahoe Misfire
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1996
Chevy
Tahoe
5.7L V8
185k miles
Would like some advice if any of you would like to offer.
What typically happens is a shuddering at about 50-55mph while in 4th gear (though to a lesser degree, it will shudder at speeds above that too) and lightly accelerating or keeping speed on a small incline (~5-10% grade). During this time, there is no change on the tach. My check engine light is not on. Spark plugs and wires are new. The problem occurs while using 93 octane fuel. The shuddering is never noticeable in gears 1, 2 or 3, and is not noticeable at full throttle while in gear, or in neutral at an idle. I replaced the fuel pump about 6 years ago.
I brought it to the transmission shop, but was told that isn't where the problem lies. Second, I took it to a mechanic. He told me that he couldn't pin-point the cylinder, as there were no codes to unveil the problem.
My question is what are the causes I should look for, and how can I address them short of an engine overhaul? I recently read for the first time about Seafoam, and I'm intrigued. I've taken good care of this truck and can't afford a new one. Thanks for any help.
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Hammer Time
Ultimate Carjunky
/ Moderator
Nov 21, 2011, 4:21 AM
Post #2 of 13
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Re: 1996 Chevy Tahoe Misfire
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The "check engine" light is an indicator for a system that monitors many electronic functions in the system, also called the "malfunction indicator lamp" (MIL). It can come on for any of hundreds of different causes from any of the systems that the computer monitors. Some are very important and can lead to further component or engine damage and some are emissions related not as serious but still a problem and need to be repaired.
Your first step is to have the computer scanned to retrieve the trouble codes that were set when the check engine light came on. Those codes will give you specific information about what the computer saw and will get you pointed in the right direction to find your problem. With a 1996 or newer and some 95 cars and you have an AutoZone or Advanced auto parts in your area, they will read them for free. Once you have these code numbers, we can be a lot more specific about what your problem may be.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
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Nov 21, 2011, 5:51 AM
Post #3 of 13
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Re: 1996 Chevy Tahoe Misfire
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He/she just typed that the check engine light isn't on and their mechanic wasn't able to pinpoint the cylinder because there are no codes stored.
Have your mechanic connect up his/her enhanced scan tool and watch the current misfire PIDs while inducing the misfire. There might not be enough missing going on to turn on the check engine light.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Nov 21, 2011, 5:53 AM)
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Tom Greenleaf
Ultimate Carjunky
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Nov 21, 2011, 6:13 AM
Post #4 of 13
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Re: 1996 Chevy Tahoe Misfire
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Guesses. If this is fine in 1,2,3 but not when torque converter locks (4th feeling) it may be 'shudder' you feel and not the engine. Just a maybe,
T
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scott96tahoe
New User
Nov 21, 2011, 9:00 PM
Post #6 of 13
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Re: 1996 Chevy Tahoe Misfire
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Thank you all for your comments. Tom, I think you're on to something. I'm going to have this looked into further. I posted the same question on another message board and someone suggested it may be the EGR valve as well. That also sounds like a possibility.
Again, thanks to all who posted. This has really helped me.
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Discretesignals
Ultimate Carjunky
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Nov 22, 2011, 5:35 AM
Post #7 of 13
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Re: 1996 Chevy Tahoe Misfire
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One thing that you can try if you suspect the torque converter clutch is causing the shudder is to tap the brake pedal while keeping your foot on the gas maintaining the speed as the shudder is occurring. Tapping the brake causes the torque converter clutch to disengage.
Usually an EGR problem won't cause a shudder or misfire while cruising. A malfunctioning EGR usually causes a surge while cruising, pinging under load, or stalling at idle. If you suspect the EGR is causing your shudder or misfire, unplug the electrical connector from the EGR valve and drive the vehicle to see if the symptoms disappear. Note: the check engine light may come on if you disconnect the EGR connector.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Nov 22, 2011, 5:42 AM)
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Tom Greenleaf
Ultimate Carjunky
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Nov 22, 2011, 6:14 AM
Post #8 of 13
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Re: 1996 Chevy Tahoe Misfire
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Good test DS. OP - not a great believer in tricks or magic in a bottle but if and only if you can really suspect this is torque converter shudder there is a product that dang I forget and never used mentioned by the site famous " way2old " used in almost exclusively Ford products.
Trans-X is one I will use but less than 1/4 of any suggestions on container. It does dissolve shellacking and in very small amounts once may take a little while. Always some risk in more damage from magic in a bottle stuff. Trans-X absolutely will swell rubber so go easy.
A story on that one I do and have used. GM Plow truck w insanely low miles had a sticky spot in PS (Trans-X for trans and PS) - no leaks and figured some front end part was going but checked and all was fine. Two or less ounces of that crap and it was gone in a day now two or more years ago! Also to confuse it as to what fixed what was to partially change PS fluid to synthetic.
There are additive in new fluid by the makers and generally nothing else needed. Again, most IMO cause more harm than good and use much less than they say. Face it, they don't care and motivated to sell product. Dare say 99% are junk to be avoided,
T
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scott96tahoe
New User
Dec 17, 2011, 8:29 PM
Post #9 of 13
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Re: 1996 Chevy Tahoe Misfire
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As a follow up, after I did a lot of reading on several message boards, I ended up using a can of Seafoam as directed and the problem disappeared. I was shocked that the shuddering went away, but it's been about a month since using it and my Tahoe is still without any shuddering and still no check engine light.
I really appreciate everyone's advice on this message board. Without these exchanges, I would never been able to solve the problem myself. Thanks again to all of you.
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Discretesignals
Ultimate Carjunky
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Dec 17, 2011, 8:43 PM
Post #10 of 13
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Re: 1996 Chevy Tahoe Misfire
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Where did you put the seafoam?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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dmac0923
Enthusiast
Dec 17, 2011, 8:50 PM
Post #11 of 13
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Re: 1996 Chevy Tahoe Misfire
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ive used seafoam for a couple years now.
you put a 1/3 of the can through a vacuum source on the intake manifold
a 1/3 in the crankcase 100 miles or so away from an oil change
and 1/3 in the fuel tank.
__________________________________________________
2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1
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Discretesignals
Ultimate Carjunky
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Dec 17, 2011, 8:51 PM
Post #12 of 13
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Re: 1996 Chevy Tahoe Misfire
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I'm just curious where the OP put his seafoam.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 17, 2011, 8:52 PM)
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Tom Greenleaf
Ultimate Carjunky
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Dec 17, 2011, 10:19 PM
Post #13 of 13
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Re: 1996 Chevy Tahoe Misfire
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Carefull DS you might get an answer!
Tom
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