engine surging

[jsoroka]

My 1997 Bonneville surges when under load above about 35 mph when I try to maintain speed. I can see the tach begin to jump and feel it. Sometimes the tach will jump more than 1000 rpm and then come down again. If I accelerate, no problem, but, the surging returns when I try to maintain speed. Seems to happen once engine has warmed up. I spoke to a friend who has the same car and he's had this for two years now! He says he noticed that GM posted a Tech Service Bulletin describing engine surging but never followed up on it.

MY mechanic has checked the engine and says its AOK and told me to have the tranny checked. The local Lee Myles could find nothing wrong, either. No engine codes or anything.

Anybody have any ideas?

[markwb]

Several years ago I had a similar prob with my 97 SE. The tech took it up on I-95 with a hand held diagnostic device connected to a recept. under the steering wheel (OBD II) I think, and was able to monitor transmission parameters and actually observe the surges in eng. rpm.
The resolution to the prob was to replace a valve body on, or in the transmission. I'm sorry I can't be more specific with the exact faulty component, but hope this helps a little. I think the lock up was cutting in and out at light up hill/straight away loads on transmission. The tach appeared to be pulsating when this anomaly occured.

[toma]

I just got my 97 Bonneville back from the trans shop. I went to two others who told me that I needed a trans rebuild. This was a smaller shop that took the time to track it down.

Turns out that Pontiac started to use pulse width modulation for the TCC apply circuit, and this causes the TCC valve to wear out prematurely. Basically, to soften the apply of the torque converter they rapidly pulse the apply valve (kinda like ABS). The result is that the valve is almost constantly in motion. After a while the valve starts to wear out and fluid leaks by. This reduces the line pressure to the converter, and it can't maintain lock.

The trans shop replaced the valve with a teflon coated one that ran about $75, but the total repair was about $800.

BTW - My symptoms were a little different, when going down the highway with the cruise on and start going up a hill it starts to surge. 50-500 rpm. Only happens when hot out and trans is good and warm.

[Flatrater]

Yes GM does have a bullentin for bad PWM soleniods I have replaced many of them!!

[dradz]

Originally Posted by Flatrater

Yes GM does have a bullentin for bad PWM soleniods I have replaced many of them!!

I'm getting similar symptoms in a 94 Bonnie, but also at a stop the car hesitates -- they replaced the EGR valve, but has not helped either condition. Could the PWM problem cause a hesitation when accelerating from a stop?

[Cardiak]

=P 94 bonne guy u sound like u got what i had..
My car hesitated from a stop and would stall out of hte blue after it started doing that awhile.. u couldnt really go at high speeds or it would surge. It turned out to be the throttle position sensor.. I replaced the EGR Valve on mine first thinking that was the prob.. but it wasnt it was the Trottle position sensor. so i wasted 170 on a egr =P

[turbo2002]

My family had a 2000 lumina and it did the same thing,we got the tranny replaced and replaced some kind of valve and it ran great after that.If you have any Cottman Transmisions near you they are the place to go to.

[dradz]

[quote=Cardiak]=P 94 bonne guy u sound like u got what i had..
My car hesitated from a stop and would stall out of hte blue after it started doing that awhile.. u couldnt really go at high speeds .../QUOTE]

Now the dealership is saying the "mass air flow sensor" -- anyone have any experience with that...

And regarding the Tranny on the Lumina -- how much did that cost?

The car runs OK when at highway speeds, just when it's hot out and there is a load on the car, it will surge. The biggest complaint is the hesitation from a stop, BUT there is little if any hesitation if you are even rolling a little....

[keystone]

Originally Posted by Flatrater

Yes GM does have a bullentin for bad PWM soleniods I have replaced many of them!!

Flatrater
Can you give me some additional info about the TCC valve. Can it be replaced by droping the pan or does the transmission need to be removed to replace.
Thanks
Gary

[Flatrater]

The TCC is under the side cover of the trans. The way I do it is I drop the engine cradle lower the engine and trans to get the side cover off. Its not an easy job doing it with a florr jack and stuff. It takes me 3 hours to do it on the lift. And after you change the solenoid you have to clear the taps on the transmission. TAPS are a learned thing which changes over the life of a trans it compensates for trans wear.


94 Bonnies had a different setup they didn't use PWM solenoids.

[keystone]

Originally Posted by keystone

Flatrater
Can you give me some additional info about the TCC valve. Can it be replaced by droping the pan or does the transmission need to be removed to replace.
Thanks
Gary

Thanks for the help. Sounds like a bigger job than I want to tangle with. Any recommendations about a good trans shop in cincinnati-dayton OH area?
Gary

[jetter]

I have the same surging problem as decribed above; When the car warms up, after about 45 minutes of driving, at speeds above about 40mph the car seems to go in and out of torque converter lock-up. This occurs when going uphills or a light load is applied. It also can be seen by a change of approx. 200 RPM on the tach.

My question is; Are the TCC valve and PWM solonoid refered to above the same thing?

Thank you,
jetter

[DOpey85]

Check your coils, plugs and wires.