Surging Problem 2001 PT 13k miles

[thebearII]

My 2001 PT Cruiser has developed a problem and I can't seem to figure out what is wrong.

My wife drives the car and she complained about it surging when sitting at a stop light. She always drives with the AC on.

I tested the car and it did exatly what she said, I also discovered when you rev it up in park, it acts almost like you're hitting a rev limiter. It revs about half way and then surges like a rev limiter has kicked in. Sorry I didn't look at the tach. The surge at idle in gear (automatic) seems to go away a little when you turn off the AC.

On my test drive the surge would happen while stopped at a light. While driving I floored the gas pedal and expected the surge to happen but it didn't the car felt fine all the way past 65MPH. That surprised me.

I thought the AC compressor might be freezing up but no evidence of any problem when watching the belt with the AC on in park at idle.

I did notice with the hood up and in park if I stomped on the gas pedal I would hear a sound similar to a pop off valve just before the engine began to rev up, almost as if a hose had come loose. I checked for loose hoses, didn't find any.

So I told my wife to drive the car the next day on her errands. She said it was fine except for the surging at the stop light. However, on her way home the temperature guage pegged, hot idiot light came on and when she parked the car she could hear the coolant boiling into the overflow tank.

I looked again to see if the belt had broken, thinking the AC compressor had foze up and the belt broke....it was fine and all looked OK. I could not see the water pump so I don't know if it froze up and is causing the problem. No squeal like the belt is rubbing against a dead pulley so I don't think the water pump is the problem.

No water shows on the oil dip stick.

Sorry for the long story but I wanted too make sure you had as much info as possible.

Any ideas ?????

The Bear II

[Mean Green]

Originally Posted by thebearII

My 2001 PT Cruiser has developed a problem and I can't seem to figure out what is wrong.

My wife drives the car and she complained about it surging when sitting at a stop light. She always drives with the AC on.

I tested the car and it did exatly what she said, I also discovered when you rev it up in park, it acts almost like you're hitting a rev limiter. It revs about half way and then surges like a rev limiter has kicked in. Sorry I didn't look at the tach. The surge at idle in gear (automatic) seems to go away a little when you turn off the AC.

On my test drive the surge would happen while stopped at a light. While driving I floored the gas pedal and expected the surge to happen but it didn't the car felt fine all the way past 65MPH. That surprised me.

I thought the AC compressor might be freezing up but no evidence of any problem when watching the belt with the AC on in park at idle.

I did notice with the hood up and in park if I stomped on the gas pedal I would hear a sound similar to a pop off valve just before the engine began to rev up, almost as if a hose had come loose. I checked for loose hoses, didn't find any.

So I told my wife to drive the car the next day on her errands. She said it was fine except for the surging at the stop light. However, on her way home the temperature guage pegged, hot idiot light came on and when she parked the car she could hear the coolant boiling into the overflow tank.

I looked again to see if the belt had broken, thinking the AC compressor had foze up and the belt broke....it was fine and all looked OK. I could not see the water pump so I don't know if it froze up and is causing the problem. No squeal like the belt is rubbing against a dead pulley so I don't think the water pump is the problem.

No water shows on the oil dip stick.

Sorry for the long story but I wanted too make sure you had as much info as possible.

Any ideas ?????

The Bear II

With surging it is usually the TPS, throttle position sensor. You come to a stop and the rpm's shoot up to like 2k.

[thebearII]

Come on folks I need help with this problem.

I want to work on the car this weekend and need suggestions on what to look at.

I will appreciate all suggestions. Thanks MeanGreen I'll check the TPS.

What else should I consider ?????

the Bear II

[Mean Green]

Originally Posted by thebearII

Come on folks I need help with this problem.

I want to work on the car this weekend and need suggestions on what to look at.

I will appreciate all suggestions. Thanks MeanGreen I'll check the TPS.

What else should I consider ?????

the Bear II

Wiggle the TPS wire while the car is running and see if it affects the surge. There have been problems with broken wires.

[CREWZIN]

Something else you might look at is the IAC (Idle Air Controller) that controls the idle speed. Located behind and attached to the throttle body. You can clean it or replace it.

[thebearII]

Okay, here's what I found in case anyone else experiences this problem.

Found the hose to the PCV was cracked and leaking. Replaced it, still had surge.

The surging was caused when the A/C was having to struggle due to the heat build up in the condenser.

The cause of the heat build up was due to the low and high speed cooling fan relays weren't working. The reason...... the 40A circuit breaker had corroded up and failed due to moisture getting in to the fuse box. The alarm installer had left the cover loose 7 years ago (never had the need to look at it).

Anyway I replaced the low speed relay and the circuit breaker, the cooling fan worked. The high speed relay is not working and had to order it, so I'm not 100% sure the problem is fixed.

The surging has gone away, but the car still heats up if I sit in traffic for a few minutes.

Will give the final wrap up once I replace the high speed relay.

[CREWZIN]

Right, it's the high speed fan that keeps the engine water temperature down when the A/C on and there's no air flowing through the radiator. Once you reach 35 mph the fans shut off as there's enough air flow to keep everything cool.

[brightlight07]

heyy crewzin whered u get all that engine chrome?

[CREWZIN]

Originally Posted by brightlight07

hey CREWZIN where did u get all that engine chrome?

Brightlight07,

The intake manifold was ordered thru Home

The replaced yellow pieces all over (dip stick, overflow cap etc) was ordered from www.Raceand Street.com

The radiator hose from eBay: chrome radiator hose, eBay Motors, Cooling System items on eBay.com

The air intake can be found on eBay also. pt cruiser air intake, eBay Motors items on eBay.com

The shroud (chrome over the area in front of the windshield) was also from Race and Street.

The 2 piece underhood polished stainless steel was from American Car Craft

[thebearII]

Final Outcome-

Here's what finally solved my problem. The plastic housing that the fan blades are molded into and mounts to the fan motor was cracked and broken in several places.

It was causing the fan to stop or drag at hi speed and would blow the 40amp fuse and blew the original relay.

Didn't see the cracks until I removed the fan. Found a new in box $100 replacement on ebay motors.

No more heating, no more surging.....all is OK.

Thanks for all the suggestions, they helped tremendously.