intermittent power loss

[oldguy829]

This is my daughters 06 PT Cruiser, 42000 miles.
Sometimes, at a stop sign or light, it simply won't pull. This has been going on for months, been to the dealer several times. Nothing is wrong, no error codes. Last time they replaced the wires, plugs, etc .(about $300.00) and it did it again two weeks later.
It oftens happens when she stops and makes a right turn to accellerate onto the freeway (but this is a route she takes twice a day, so it could be coincidence). It has happened on left turn and straight away starts. The car doesn't die, just won't accelerate. If she shifts to neutral it still won't rev over 2000 rpm's. Ran injector cleaner thru it and it was fine for a month or so. Usually, if she pulls over, shuts it off and restarts, it will be fine. Often she can hit the brakes and touch the throttle and it will be fine. Only did it once for me, I started to pull over and shifted to neutral while still rolling, hit the gas and it reved up and away I went. I've put "heet" in the gas tank, thinking water in the gas. But so far, everything works for about 3 or 4 weeks (cause that's about how often it acts up, once a month.)
Always starts fine, only happens after idle has dropped (never when driving),
engine never dies, check engine light doesn't come on. Time of day, temperature, hot or cold engine, brand of gas, nothing matters. It just does it sometimes. Scary when you are pulling out into traffic.
Any suggestions?

[BLUEH20]

Question--does the no power condition exhibit itself when you are cruising at a constant speed, say for arguement sake-45 mph, and then you attempt to accelerate? Other than the weird combination of the non related items--I would look at the Throttle Position Sensor (TPS). Could have a dead or non-linear voltage spot in it?

Really need more information concerning what is going on with the throttle, transmission and and engine.

Let us know and we'll see if we can come up a more solid diagnosis.

[oldguy829]

No, once your get your speed up, even 20 miles an hour, it never falters.
You have to be at a complete stop, idled down to the minimum.
(On a related note, she says sometimes when she is stopped it will idle down so low it starts to shake. AC on or off doesn't matter, and only when stopped for a real long light, and again, only somethimes. She hadn't mentioned that, cause she just gives it a little gas and it's OK).
BTW, it's an automatic.
Thanks for hte help guys.

[oldguy829]

Other symptoms I wasn't aware of. In neutral, if she revs it up, somewhere between 3 & 4 k, it starts to pulsate. Revs bounce up and down. Won't hold steady. She also says, at idle when you turn the AC on, it will increase the revs, then back down, then increase, like it can't figure out where to settle in. Could all of these be related? like the throttle sensor?
She is 400 miles away at school, so I can't test anything myself. Thanks for helping diagnose this, before I send her to a shop that just starts throwing parts at it.

[BLUEH20]

Okay-

Dirty throttle body. Rough idle, hesitation and lurching out of the hole on light to moderate acceleration. Poor low end performance. If you get on it out of the hole it will run fine.....Is this correct.....visual inspection--not your daughters thing. Get a can of throttle body cleaner--not injector cleaner--follow the directs on the can and you will see a marked improvement. The other option is to have it done at a service facility (either dealership or independent) at a cost of around a hundred dollars>

The other concern of the RPM vasacillating around 2-4Krpm is most likely the rev limitermer kicking in to protect the engine--this is not a problem is so--it is a built in protection device.

Let us know if the throttle body cleaner works--should only cost about five bucks max.

[oldguy829]

Thanks Blue. With the IAC connected to the throttle body, that is probably the other half of the problem, rough low idle.
My daughter is not a mechanic, but she's pretty sharp around cars.
Could you provide a detailed explanation of how to use the throttle body cleaner, and how to clean the IAC. With pictures? If she gets any improvement it would confirm the diagnosis, and I'd pay a shop to do it properly. [Not doubting your knowledge, but we are diagnosing over the internet, based on a females description of the problem (sorry babe), and second hand at that]

I'm going to shoot her this thread when we're done.
thanks again. don

[BLUEH20]

Go to the "stickies" above the normal chatter.

Free Pt Cruiser Manual--look up throttle body--information you need is there. To use the cleaner--follow direction on the can.

[Mean Green]

Originally Posted by oldguy829

Other symptoms I wasn't aware of. In neutral, if she revs it up, somewhere between 3 & 4 k, it starts to pulsate. Revs bounce up and down. Won't hold steady. She also says, at idle when you turn the AC on, it will increase the revs, then back down, then increase, like it can't figure out where to settle in. Could all of these be related? like the throttle sensor?
She is 400 miles away at school, so I can't test anything myself. Thanks for helping diagnose this, before I send her to a shop that just starts throwing parts at it.

Around 4k there is a rev limiter when you are reving in neutral so you won't blow your engine.

[stanvett]

MY son's PT is having the exact symtom you spoke of, " while cruising along the throttle petal becomes non-respondsive ".. They pull to the side of the road; shut off the engine and upon restart every thing is fine for a few days. Is that a bad throttle postion sensor ?

[oldguy829]

Stanvet, sounds like the same problem, but ours doesn't do it while cruising, only upon acceleration from idle. Consensus seems to be the throttle sensor. She will be home for christmas in 2 weeks and I will tackle it then. It has only done it once since I posted. Makes it very hard to diagnose. It does not trigger the check engine light.