Chrysler Repair: 1997 Plymouth Breeze idle and trans shift problems continue..., throttle position sensor, plymouth breeze

Question
Roland,

I am continuing to have problems with my 1997 Plymouth Breeze, but the problems have changed to some degree. After your answer to my original question (below), I have been all over the vacuum system and have not found a leak. I replaced the downstream O2 sensor with no change. The transmission symptom has been getting worse and worse. I replaced the trans filter and fluid, but that did not change anything. Then the car gets into one of these "modes", the up-shift and down-shift patterns are all off. It will not shift until the RPM is way up. When the shifting pattern is off, I notice that I am at High idle when stopped. Ussually, after driving a bit, the car will run fine again, like a switch was thrown and all is well. I still have not been able to determine a pattern to these events.

Could a vacuum leak affect the transmission this way? Could the car be slipping in and out of "limp mode"?

When the car is not in this "mode", it runs great. Seems to me there is something happening that is telling the car to run this way. Seems to be more pronounced when I have driven the car someplace, stopped for a while, but not long enough for the car to completely cool down, and then drive again.

Any other thoughts. what's left of my hair is getting thinner and thinner.

Thanks

John


Previous Question and answer:

Expert: Roland Finston
Date: 5/9/2007
Subject: 1997 Plymouth Breeze erratic idle

Question
I have a 1997 Plymouth breeze with the 2.0L 4-Cylinder engine with automatic trans. The car has 216000 miles on it. Recently I have been noticing that the idle has been erratic. The car normally idles at around 850 RPM. I am noticing that the idle will jump up to around 1400 RPM, run there for a while, then come back down to normal, then jump up again, then back to normal. There does not seem to be a pattern to this. I have changed the Throttle position sensor,  and cleaned the throttle body. I took the idle control valve off and made sure it was clean. I changed the MAP sensor thinking it may be related to the temperature being sensed or the manifold pressure. I also recently changed the EGR valve, but that also did not help this problem. The computer has no codes in it. I am stumped. It will do this when I am in park or Neutral, or in drive. I can feel it pull when I am sitting at a stop sign and the idle kicks up. Sometimes, it does not come back down to normal idle when I come to a stop.

So what would cause the idle to jump up like that. When it jumps up, sometimes it will stay up for minutes, sometimes, just a second and then back down.

I thought it may be a vacuum leak, and I am searching the vacuum lines, but have not found a leak yet Vacuum at the intake manifold is around 18.

I will also mention that when driving along at highway speed and the transmission is in overdrive, it will occassionally come out of overdrive and then go back into overdrive. It is not slipping, it is shifting down, then back up. I am hoping these are related somehow.

I am pulling out what little hair I have left. Any ideas?

Thanks for any help you can provide.

John



Answer
Hi John,
It appears that you have covered almost all the possibilities for the problem. I agree that the intake manifold leak is the most likely reason at this point. Have you tried using a spray can of starter fluid to do the search? It is very flammable so you have to be careful to just use short spritzs at each connection and along major manifold gasket interfaces while listening for a surge in the rpm with each burst. You might also want to check the speed control cable if you have cruise for malfunction/binding.
I would use the vacuum line diagram on the underhood sticker as a roadmap to check all the vacuum line connections and the hoses proper for cracks.
Please let me know when you find the cause as this is shared by others I am certain.
Roland  

Answer
Hi John,
Some thoughts: Have you had a readout for fault codes done lately because it seems that one or more of those behaviors would cause a code?
I don't believe any vacuum issue would impact the transmission directly. You are now over 200,000 miles where many electronic transaxles would have required some sort of repair if not rebuild, so you have done well. But it would seem that a code should have been set for the shifting problems you describe.
Have you tried to shake the various harnesses while idling to see if you can induce a sudden change of state? You may have a bad connection that this might reveal. How about the resistance of the coolant temp sensor, has that been measured (7-13K when cold, 700-1,000 ohms when at 200F) and its wires checked (any signs of instability in the temp. gauge reading which is also dependent on this sensor)?
I know it is costly, but you might want to consider a full flushout of the trans fluid and replacement with 9 qts of the Mobil synthetic trans fluid. I have seen anecdotal reports of major improvement as the result.
I believe you are doing a great job of looking for the reasons. Something is going to show up...but now I'm sounding like one of the 'psychic' experts here on Allexperts! I better quit before it gets worse.
Roland