intermittent miss fire or shuttering

2000bonny · 08-06-2010, 11:13 AM

I have a 2000 bonneville with 134k on her. I have had it for 4 years and always had the same problem with intermittent miss firing and shuttering. This happens when approaching slight grades in the road, and sometimes under acceleration. I had the entire fuel system cleaned and flushed. I replaced the plugs, and it briefly stopped, then came back. I find that when this occurs, if I get off the throttle then slightly ease back in, it temporarily stops. Does anyone have any idea what my problem is?

happydog500 · 08-16-2010, 07:53 PM

Yes, this is a known problem.

Please read and research before you do what I did and argue with someone.

The problem, the exact problem you describe is in the transmission. It's a known problem.

It seems, or more likely seems FOR SURE it is a misfire, but is not. Research valve body in the 4T65E (or the 4T80E if you got it) transmission. What it is, is a worn valve body where fluid is getting by a valve in the valve body.

When I was told it wasn't the motor, I went almost a year not believing it. The guy at a transmission shop even told me it was a misfire. To prove it, he put it in gear with brake and revved and revved the motor. He couldn't understand why he couldn't get it to misfire ("That's how you get it to misfire" he said. After doing research, I found a site that talked about the "common valve body problem" with these transmissions.

It seems for sure the motor is misfiring, but it's not. The description is EXACTLY what you describe.

It's good when it happens you back off and ease into it. If you kept it right at the place where it does it and had it buck and sputter for as long as you can, notice you don't get a "misfire" Check Engine Light. You won't because the engine is working great.

Mine over the years has slowly gotten worse. Now, it bucks and violently jerks. I see your mileage is right about where I was when I noticed it.

I read on the forums where a guy bought a used transmission. One of the things I noticed he did besides gaskets was a "new valve Body."

Hope this gets you in the right direction. One transmission shop who has been in business for "over 20 years" didn't know of the problem so be prepared to have people not understand.

Chris.

2000bonny · 08-17-2010, 11:55 AM

That really sucks. I just had the tranny out in April to replace a stripped 4th input hub shaft. That was a major job, and took 3 days to complete. I am really dreading having to perform that task again. I think I will sell the car before I perform that repair myself. The whole subframe assy had to be removed to remove the tranny.UGGGGH!
Thank you for the input.

maxwedge · 08-17-2010, 12:24 PM

That shudder can be caused by the TCC valve in the valve body wearing, causing a loss of pressure to the lock up convertor, power braking will not cause a loaded misfire because the convertor does not load the engine sufficiently like pulling a hill in o/d would. This buck could still be ign related. I would do a full scan and look at misfire counts before I went into the trans. Usually the worn tcc valve would set a p1870 code.

Jrs3800 · 08-17-2010, 08:24 PM

The TCC bore is more of a common issue with the 4T60E...

For the OP..

When they were in there to replace the 4th Hub shaft what else did they do? As well did they suggest to you that it would be a good time to replace the EPC( Electronic Pressure Control ) commonly referred to as the PCS ( Pressure Control Solenoid ) ? With the 97-02 4T65E transmissions the PCS is a big problem and will fail in time... The PCS controls the line pressure in the trans and can cause a lot of issues with TCC Apply if the pressures are not correct... As well when a 4th hub shaft fails, it can throw some trans into the torque converter, and when it does this it can do damage to the converter..

When you replaced the Plugs what kind of plugs did you use and have you ever replaced the wires? These cars run a Waste Spark system... If one cylinder has a bad wire or plug it will cause issues with the opposing cylinder on that coil...

happydog500 · 08-25-2010, 01:28 PM

Quote:

Originally Posted by Jrs3800

did they suggest to you that it would be a good time to replace the EPC( Electronic Pressure Control ) commonly referred to as the PCS ( Pressure Control Solenoid ) ? With the 97-02 4T65E transmissions the PCS is a big problem and will fail in time...

jrs3800, how come you didn't' tell me this when you posted in my, "what to do to a used transmission?"

http://www.automotiveforums.com/vbul....php?t=1011034

This is the kind of stuff I was asking about. You are the transmission guy on these forums, so thank you again for all the help and answers you give on the forums. You have helped me understand a lot of things about cars and transmissions.

Chris.

Jrs3800 · 08-25-2010, 01:59 PM

Quote:

Originally Posted by happydog500

jrs3800, how come you didn't' tell me this when you posted in my, "what to do to a used transmission?"

http://www.automotiveforums.com/vbul....php?t=1011034

This is the kind of stuff I was asking about. You are the transmission guy on these forums, so thank you again for all the help and answers you give on the forums. You have helped me understand a lot of things about cars and transmissions.

Chris.

Chris Buddy...

Read this closely... I never said this in your thread as you have a 1997 4T60E.... The OP has a 4T65E that used the same parts from 97-02...

The items I was talking about in this thread have nothing to do with the 4T60E, its more specific to the 4T65E...

Now let me go off the deep end a little here...

The 4T60E was in production through 1999, but was used in the H bodies( like the Buick LeSabre ) through 97, if you had a supercharged 97 you had the 4T65E... 98+ is 4T65E for all 3800's...

So there is a huge difference between the trans you have in your car and the trans the OP has in the 2000 Bonneville..

Your 4T60E has no Electronic Pressure Control solenoid...

happydog500 · 08-25-2010, 02:12 PM

OK, thanks!
I thought his was a 99. I was looking at several different threads so I got mixed up. This also explanes why the 98 Lesabre in the wrecking yard by me "won't work in my 97."

Remember, if you ever come out west, bring your tools!

Chris.

2000bonny · 08-31-2010, 04:15 PM

I did all of the repairs myself. The guy I spoke with when ordering the parts did not recommenced replacing any of the solenoids. I replaced the stripped shaft, installed a shift kit and all gaskets.

When I replaced the plugs, the problem went away briefly, but I do not recall the brand. I did not replace the wires since they were replaced 6 months prior.

I just took this car from Dallas to NY and back over the past week. Absolutely every time I approached an incline, it would act up. I would back off the throttle, then immediately get right back into it and it stops. This is very agrivating.

Jrs3800 · 08-31-2010, 05:13 PM

The stripped 4th input shaft may have done some damage to the torque converter...... Hard to say...

IIRC you car from the factor has a maximum TCC duty cycle of 96% as the TCC is designed to slip to a certain degree.... On certain GM cars I have been able to set this to 100%, not sure if that would help you at all..

Its very highly recommended that the PCS( Pressure Control Solenoid ) is replaced when you are in the Trans as the 97-02 version has a very high failure rate, if this was not recommended to you then this person does not have decent knowledge of the 4T65E

I would like to know what kind of plugs you used, say a plug like Bosch Platinum would be a no no in a 3800..

Keep in mind you could still have a trans or ignition issue...

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