Engine Surge at highway speeds

[UncLarryWasRight]

I've owned my 2001 PT for almost 8yrs now and have put on almost 80k as of this writing. My problem is that at highway speeds 50+mph, the engine sometimes surges 300-450 rpm higher and it seems as if the trans is slipping or something. It only happens a couple time in a 200mile road trip. The car runs fine so i dont believe its negatively affecting the vehicle, but when it periodically happens it feels disconcerting.
Thanks,
Nick

[CREWZIN]

Nick,

Need a lot more info from you. What kind of mileage do your have? What regular maintenance have you done or had done and how long ago? Where the stock ignition components replaced with aftermarket or more Chrysler parts? Auto or manual trans? Was the trans fluid replaced and when?

Almost 8 years (same as me) and you've never visited the forum before? have you done any kind search on this or any other forum?

[UncLarryWasRight]

My 2001 PT has almost 80k miles on it, i have preplaces the coil and wires with Live Wire components, it is an auto, I've had regular maintenance done by a local shop and the dealer when it was still under warranty (though i'm starting to phase that out and learning to spin the wrench on the PT). Oil changes at 3k miles since new, the trans fluid was replaced at 32k miles because the diff pin broke.
I'll try and re-explain the symptoms: When driving down the highway at speeds above 50mph the engine rpms raise 300-500 rpm (say i'm going 65 and the rpms are around 2500, it might raise to 3000rpm. It feels like the car slows down because i'm lightly moved forward, as if the brakes were tapped lightly. It seems like the trans slips and the engine revs higher to compensate for the slippage to keep the same speed. This mainly happens when i use cruise control, i rarely do not use it when travelling on the highway.

Thanks again,
Nick

[CREWZIN]

I tried an extensive search on Chrysler cruise control problems and found nothing like what your experiencing, but it sure sounds like that may be your problem. On the other hand, the auto trans on these cruisers aren't the most reliable as you've already found out.

You've hit on the two most likely places for your trouble so hopefully one of our local mechanics will see your post and give you a good answer.

Welcome to the forum.

[frostygt]

I found a few tsb's for the 01 cruisers dealing with this
tsb 18-027-01
NOTE: THIS BULLETIN APPLIES TO VEHICLES WITH A 2.4L ENGINE.
SYMPTOM/CONDITION:
Moderate to severe highway speed 72-97 kph (45-60 mph) vehicle surge.
More prevalent on smooth flat roads or roads with a slight grade in warmer
ambient temperatures above 24 C. ( 75 F.).
NOTE: THIS PCM SOFTWARE UPDATE WILL PROVIDE A SURGE
IMPROVEMENT FOR THOSE VEHICLES EXHIBITING A MODERATE TO
SEVERE SURGE. THE IMPROVEMENT MAY BE NEGLIGIBLE FOR THOSE
VEHICLES EXHIBITING A LIGHT SURGE.

my recomendation would be to take it to a dealer you trust and have them check to see if your pcm is up to date and if its not get them to update it for you.
it might be a small price to pay if it fixes your problem and better then putting on unneeded parts or doing other un needed things to your car.

[cleverklutz]

That's interesting. My car does the same thing. I have the cruise set and all of a sudden the rpm's jump up. I think it's the trans jumping out of lockup for some reason. It used to never do it but now it's more frequent. It does it even with the cruise off. It will be brought on by a slight decline, or for no reason at all. Sometimes it will take a few miles to get back into lockup, and I'll pull it back into third, then push it into drive and it usually drops back in. I'm not sure what's causing it to do that. I haven't changed the tranny oil yet, but I have fairly low (55,000 miles) on it. I know the lockup is controlled electronically so it could be something electronic. My mechanic suggested a faulty TPS sensor. Apparently that's a common problem on the Dodge trucks. I can simulate this by giving a sharp application on the gas, it jumps out of lockup, then drops back in. But I can't simulate staying out of lockup and needlessly revving for several miles. I'm thinking my tranny is screwed up so I'm thinking about just replacing it with a good rebuilt unit.

Hopefully that gives some more insight into your problem. I'm glad to hear I'm not the only one that this happens to.

Ben

[UncLarryWasRight]

I'll have to go to a dealer and get that computer upgrade. Shouldnt the price be free for the software upgrade, or am i being optimistic?

[frostygt]

well depending on the dealer but most i know the software is free its the fact they have to pay someone to do the work that you will have to pay for.
before you agree to any work get a quote, it should be between half hour to 1 hour tops labour. for them to flash the pcm. but see if you can get them just to check if it is update able first so that there not charging you doing something thats already been done.
and also get them to scan for and write down any dtc's (trouble codes) some may be there without turning the engine light on.
good luck and hopefuly your trip to the dealer doesn;t turn out like a few of the others i have read about latly... to bad they all wheren't as good as my dealership.

[03TurboGT]

I have the AutoStick in mine, and when I have cruise control on the highway, the car will be in auto overdrive (the torque converter is locked), but if the car's cruise control lets off the gas and gets back on it, it will rev up a bit (300rpm) and then the torque convertor will lock again. If you have an auto tranny, I'd say its normal!

[charlieborg]

I have a 2001 my self and it is doing the same thing. I did some research and think it is a lock up solenoid causing the problem. keep me informed if you find out what it is. http://www.ptcruiserlinks.com/forum/...ies/tongue.gif