Pulsation when taking off from a stop. Revived see post #13

[Whitecrystal1]

I've noticed this before and the car (99SSEi) did it again today. When it did it before I turned off the traction control and I thought it stopped after doing so, but today I tried that again and it continued to pulsate or shutter the car when taking off with anything more than a very light throttle at take off. I was thinking a bad wheel speed sensor at first but now I dunno.. There is no lights light on the dash except a security light sometimes and that has been that way since I purchased the car more than a year ago.

Thanks

[Jfridge92]

By the type of shudder you're describing, to me it almost sounds like your transmission is slipping. What color is the trans fluid, and when was the last time you had the fluid and filter changed? That's if the shuddering seems like a trans related issue to you though. From the initial read, that's what come to mind for me.

[Need For Steve]

Cut your A/C off and see if it smooths out. Sometimes the compressor can decide to not stay locked, and the constant engaging/disengaging of the a/c clutch can cause surging

[Whitecrystal1]

It has not done it since I posted this thread, and it's only done this a few times since I purchased the car which was almost two yeas ago. Transmission fluid is clean. I am still unsure as to what is causing this but still feel that it may be ABS or traction control realated. I will try to turn the AC off next time, but when it's doing this, the whole car shudders like crazy on take offs from a stop. I am not talking a little shaking..

[Need For Steve]

o0o, i gotcha. the A/C clutch pulsing is more rhythmic and steady. from the way you word it just now, it sounds to me like torque converter shudder or possibly even an EGR selonoid on the way out. if the EGR is just starting to fail, it'll make the car feel like it's trying to fall on it's face under light throttle. next time you notice the shutter, stop somewhere convenient and unplug the EGR.

[Whitecrystal1]

ok I'll try that, thanks

[LeSabre in Buffalo]

Does it go away if you let off of the gas and then gently re-apply the gas? In my case it was a flaky PCS inside the transmission case. Replacing the PCS solved the problem for me.

[Whitecrystal1]

Yes, if I am very gentle on the throttle it will not do it. Hmmm if that is it, that sucks LOL!! I would have never guessed that to be the cause because when I had the PCS go bad on my 02 Bonnie it caused a hard shift every gear no matter how soft the gas was applied. This does not have a shifting issue at all.

Did your car have a SES light or code stored to confirm that was your issue? I don't have any SES light lite or codes stored. I am not able to scan the ABS at this time though.

Thanks

[LeSabre in Buffalo]

No codes stored, no SES light. Sometimes it would rev up, then slam into gear with a screech of the tires when giving it too much gas from a stop.

It eventually got bad enough where anything more than 2k RPM's accelerating from a stop would make it "bang-screech".

[Whitecrystal1]

Mine doesn't rev up, slam into gear or screech at all it just shudders (pulsates) on acceleration from a stop. I hope to catch it with my camera when it does it again so everyone can see it and maybe have a better view as to what's going on. I am surprised this has never been talked about here. Out of the 4 Bonnies I've owned this is the only one that's done this but there are a lot here in the club.

Thanks

[LeSabre in Buffalo]

I'm thinking it's a 1998-1999 4T65 issue. I don't hear of earlier or later cars doing it, just 1998-1999 H-bodies. Go figure...

[Whitecrystal1]

Hope it's ok to revive this thread.

Car is still shuddering on take off at times but does seem to do it more than not now when the fluid is warm. I do not notice it when cold. It is doing this under moderate to heavy throttle when the gear shifter is in D or 4. I have found that if I put it in first gear it does not do it at all no matter how much throttle I give it from a stop. And again this only happens from a stop, when the car is moving there is no issue with how it shifts or anything.

I dropped the tranny pan a couple months ago and the pan and magnet was very clean. I was suprised how clean it was. I am about 1,000 miles away from turning 100,000 miles on it

[MattStrike]

Do you have a shift kit installed? Sometimes, not always, that helps with shuddering.

I thought that commanding 1st gear causes the computer to bump up the line pressure (I'd have to check though). Do you have someone who can scan the transmission codes? They won't cause a SES light.

[Whitecrystal1]

No shift kit. I do have a scan tool to check it with (Actron 9190). I have scanned it in the past but have not seen any tranny codes for this issue. I know it scans transmission codes because I've scanned two different codes form two different Bonnies. One on a 96 Bonnie that had a slip issue I was looking to purchase a while back and on the 02 Bonnie I had when it had the code for a bad PCS. I will scan and report the codes if any.

Does this sound like it's hunting between 1st and 2nd gear at takoff?

[MattStrike]

Might check the line pressures and verify against the PCS if your scanner can report that. My bet is on the PCS, it's known for causing hard shift and/or shudder from a stop. In our '99 montana, it felt like the chain was skipping when you punched it from a stop (on a 3400 torque-less engine no less) - which is what I believed until I tore it apart to find it wasn't even worn out yet, and no other mechanical parts were worn...

(these aren't mine, I found them on google)



Edit:

Notice the line pressure in D1 range is boosted? Probably why it works fine with the selector in 1.

[Goodfellow]

I had a similar problem, check your MAF senser on the throtle body. Mine had some hard chystle looking stuff on it. They should look like 2 thin metal wires.

[Whitecrystal1]

Might check the line pressures and verify against the PCS if your scanner can report that. My bet is on the PCS, it's known for causing hard shift and/or shudder from a stop. In our '99 montana, it felt like the chain was skipping when you punched it from a stop (on a 3400 torque-less engine no less) - which is what I believed until I tore it apart to find it wasn't even worn out yet, and no other mechanical parts were worn...

(these aren't mine, I found them on google)



Edit:

Notice the line pressure in D1 range is boosted? Probably why it works fine with the selector in 1.

I will check this soon. I am not sure that my scan tool reads line pressure though. I will report back what I find. Thanks Matt

[Whitecrystal1]

I had a similar problem, check your MAF senser on the throtle body. Mine had some hard chystle looking stuff on it. They should look like 2 thin metal wires.

I'll check it thanks