98SE fluctuating rpms

[Ajno]

Hi, newbie here been lurking in the shadows. I have a 98SE with 137,000 miles on it. Just had the intake manifold gasket replaced along with a lifter also. Anyway my question is at highway speeds my rpms will jump high and drop and then straighten out for a while. Its been doing this for a while and its not all the time. Any ideas? Thanks

[maxwedge]

Originally Posted by Ajno

Hi, newbie here been lurking in the shadows. I have a 98SE with 137,000 miles on it. Just had the intake manifold gasket replaced along with a lifter also. Anyway my question is at highway speeds my rpms will jump high and drop and then straighten out for a while. Its been doing this for a while and its not all the time. Any ideas? Thanks

Welcome to your 1st post on AF. Your question is a little vague, do you see a change in speed when this happens, is it accompanied by the trans kicking out of lock up or overdrive, is there any misfire felt?

[Ajno]

This usually is very noticeable at 70mph. The speed does not change and doesn't seem to relate to any shifting by the transmission.It also does it at 55 mph. I bet it does it at lower speeds but I don't use cruise at 35mph.

[richtazz]

Did you put in new plugs and wires while it was apart, and if so, what brand did you install?

[Ajno]

My mechanic replaced the plugs and wires. The wires are autolite. Not sure about the plugs.

[richtazz]

From what you describe, it sounds like an engine miss at high load or a sticking TCC solenoid in the trans (same thing Max was getting at). More info is needed to narrow it down.

[Ajno]

So no chance of it being the egr valve? Sorry I wish I had more info to give. When I take long trips the jerking is more frequent.

[maxwedge]

Originally Posted by Ajno

So no chance of it being the egr valve? Sorry I wish I had more info to give. When I take long trips the jerking is more frequent.

Egr operation at that speed and throttle opening should have no effect on performance, Rich and I are both wondering how the rpm changes on the tach do not translate to a speed or trans change. See if it does it up a slight grade just before downshift would normally occur, might also scan it for pending codes.

[richtazz]

[Ajno]

Its hard to explain. It feels like its losing power but doesn't seem to. I have an appointment on the 12th to have it looked at. Hopefully its something not too bad. Today it was doing it as I was accelerating to 70mph. After a little while it stops.

[richtazz]

It still sounds like a TCC solenoid or Tune-up issue. If you have Bosch plugs in it, get rid of them. Have the car scanned for possible trans related codes and let us know what you find.

[Ajno]

Thanks for the info, I'll let you know next week...

[tick822]

Hello,

I’m also a newbie that has been “lurking in the shadows.” Not that it helps solve anything, but I believe I have also experienced this problem with a 2000 GT.

It was almost as if I was repeatedly taking my foot off of the pedal. It seemed to always happen near 70 and 55 Mph. Usually when accelerating up to freeway speed. At the time I had about 98k miles on it, I probably drove it for 3k while it was acting up. Accelerating faster seemed to lessen the chances of it occurring. It was certainly more noticeable when slowly accelerating up to freeway speeds. According to the scan tool, it was NOT occurring at shift points. It also occasionally happened with the car in third gear instead of “drive.”

I’m not sure from your description, but with my car the RPMs were almost oscillating. It was about +/- 500 rpm repeatedly until I either pressed on the accelerator more, or backed off and tried again.

I had a buddy look at it (an engineer who also used to run a tranny shop)...the scan tool reported that one of the computer’s “adaptions” was maxed out to one side. He replaced one of the valves (TCC) and also the torque converter. (Although that was more of a "might as well since we have it apart" kind of deal.)

Long story short, the day after the valve and torque converter were replaced, the problem came back...but before we had a chance to look into it further, the problem went away.... everything seems fine now. Dirty sensor? Electrical Problem? Warmer weather? No idea…

I'd be interested in hearing what you find out...

[Ajno]

Wow that sounds about right. But the problem has now progressed to occasional rough idle at stop lights and of course will go away. My mechanic is frustrated because when he road tests the car it doesn't do it. So thats why I am taking it to another mechanic. So got another week of waiting and wondering if I am going to be stranded in 101 heat....

[LyndsiK]

I had what sounds like the same problem in a grand am 3.1 that i had a while ago. when going about 55 and 70 the rpms would drop and it would start to jerk/shudder/whatever you wanna call it until you either pushed the gas harder or let off all together. went through several mechanics and of course the problem never occurred while they had it! it had pretty high miles and a bad head gasket so i ended up replacing the motor and still had the problem....never figured it out, just got rid of it!