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Discussion Starter · #1 ·
Hi there,

I have a 2008 Pt Cruiser limited with 85750 miles on it. It has this issue where it stalls when it is warmed up at idle. At idle you can feel it slowly start to shake more and more until it stalls completely, but it starts right up with no problem. There is no check engine light and I just replaced the fuel pump yesterday thinking that was my issue.

Thanks for the support,

Leo
 

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Hi there,

I have a 2008 Pt Cruiser limited with 85750 miles on it. It has this issue where it stalls when it is warmed up at idle. At idle you can feel it slowly start to shake more and more until it stalls completely, but it starts right up with no problem. There is no check engine light and I just replaced the fuel pump yesterday thinking that was my issue.

Thanks for the support,

Leo

You may have a dirty inside bore of the throttle body. If so, the dirty bore and edge of the butterfly valve will not permit enough airflow at idle, causing a rough idle and stalling.

I would inspect and clean the inside of the throttle body first, and ensure all intake hoses are sealed tightly and have no splits or cracks.
 

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Discussion Starter · #3 ·
You may have a dirty inside bore of the throttle body. If so, the dirty bore and edge of the butterfly valve will not permit enough airflow at idle, causing a rough idle and stalling.

I would inspect and clean the inside of the throttle body first, and ensure all intake hoses are sealed tightly and have no splits or cracks.
Thanks for the response,
I just removed the throttle body and there wasn't much carbon build up but I cleaned it anyways and the problem is still there. What I did notice was that the connector for the Iac valve had the clip broken so it just slides in and out, other than that everything was fine as far as I can tell.
 

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A broken clip tells me the IAC was replaced once before. I am a firm believer in using mopar/oem for electrical sensors/actuators for accuracy and reliability.
 

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A broken clip tells me the IAC was replaced once before. I am a firm believer in using mopar/oem for electrical sensors/actuators for accuracy and reliability.
Me too, PT's do not like after market electrical items, mine spits them out like a bad taste in its mouth.
 

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Does the car act up if the hvac system is off? I've seen the low speed cooling fan fail which can cause excessively high pressures to occur when the a/c clutch is engaged. Causes rough idle and stalls at times. The a/c clutch is requested on when the hvac is set to a/c or if you have it set to a defrost setting.
 

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I'd suggest a bottle of Techron Fuel System Cleaner in the gas tank. It might help if the problem is dirty fuel injectors and it sure won't hurt anything. About $5 for a bottle at your auto parts store. Maybe cheaper at Walmart.
 

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Discussion Starter · #8 ·
A broken clip tells me the IAC was replaced once before. I am a firm believer in using mopar/oem for electrical sensors/actuators for accuracy and reliability.
Does the car act up if the hvac system is off? I've seen the low speed cooling fan fail which can cause excessively high pressures to occur when the a/c clutch is engaged. Causes rough idle and stalls at times. The a/c clutch is requested on when the hvac is set to a/c or if you have it set to a defrost setting.
I'd suggest a bottle of Techron Fuel System Cleaner in the gas tank. It might help if the problem is dirty fuel injectors and it sure won't hurt anything. About $8 for a bottle at your auto parts store. Maybe cheaper at Walmart.
Sorry for the long wait, but i finally got time to answer all of your suggestions

1. The car has had a few things replaced but as far as I can tell it is Oem.

2. The car does fail when the hvac is off I haven't used the A/C or heater in a while, but would the cooling fan cause it to stall randomly at a stop because it only stalls sometimes at a stop never when it is
driving. It does however have a rough idle at every stop and I do have it at the defroster setting at all times so I will have to look into this more for sure.

3. I just bought some and poured it in I'll have to wait and see what happens.

In addition to this, I decided to use an obd scanner to see if I can get something to pop up while parked in my driveway. I did this yesterday and it did stall on me, but for some reason when I did it today I couldn't get it to stall. What I got from the obd scanner is that fuel trim is high. When I have it at park the long term fuel trim is always around 19-27% (changes every time it starts up) and when I put it in reverse or drive it goes to 17.2%. I held the engine to 2000rpm while in park and the long term dropped to 15.4% but in all of these instances the short term is around -4.7-0% sometimes spiking to 7.7-9% (+ or -). I will have to check these while actually driving to get a better reading to see if it helps me figure out what is going on.

I really appreciate all of these suggestions hopefullt it's just a simple fix and not anything serious like a pcm or tipm.


Here are the pictures from the graphs of the obd scanner.

The first pic is with the car on Park and holding the engine at 2000rpms for a bit.

Second pic is with the car in drive.

Third pic is with the car on park after I shut it off and turned it back on.

IMG-0899.jpg IMG-0900.jpg IMG-0901.jpg
 

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. . .
Here are the pictures from the graphs of the obd scanner.
The first pic is with the car on Park and holding the engine at 2000rpms for a bit.
Second pic is with the car in drive.
Third pic is with the car on park after I shut it off and turned it back on. . . .
The excessively high (> 10%) long term fuel trim is indicative of a vacuum leak in the intake system between the throttle body and intake ports on the engine. The vacuum leak is adding excessive air over what the PCM (powertrain control module) has calculated entering the engine. This lean mixture burns and the oxygen sensor reports this back to the PCM. The PCM corrects and attempts to increase the fuel injector pulse time to eventually get the short term fuel trim in a very small range of positive and negative trim values. That is appearing to happen.

Check all the vacuum lines that attach to the upper intake plenum for cracked hoses. It is not very accessible but check the end of the vacuum hose that attaches to the power brake booster. See attached image.
Vacuum Lines at Intake Plenum.gif
 

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Discussion Starter · #10 ·
The excessively high (> 10%) long term fuel trim is indicative of a vacuum leak in the intake system between the throttle body and intake ports on the engine. The vacuum leak is adding excessive air over what the PCM (powertrain control module) has calculated entering the engine. This lean mixture burns and the oxygen sensor reports this back to the PCM. The PCM corrects and attempts to increase the fuel injector pulse time to eventually get the short term fuel trim in a very small range of positive and negative trim values. That is appearing to happen.

Check all the vacuum lines that attach to the upper intake plenum for cracked hoses. It is not very accessible but check the end of the vacuum hose that attaches to the power brake booster. See attached image.
View attachment 80422
I will check them when I get home in a few hours and update if I find anything.
 

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Discussion Starter · #11 ·
The excessively high (> 10%) long term fuel trim is indicative of a vacuum leak in the intake system between the throttle body and intake ports on the engine. The vacuum leak is adding excessive air over what the PCM (powertrain control module) has calculated entering the engine. This lean mixture burns and the oxygen sensor reports this back to the PCM. The PCM corrects and attempts to increase the fuel injector pulse time to eventually get the short term fuel trim in a very small range of positive and negative trim values. That is appearing to happen.

Check all the vacuum lines that attach to the upper intake plenum for cracked hoses. It is not very accessible but check the end of the vacuum hose that attaches to the power brake booster. See attached image.
View attachment 80422
So I just checked all the vacuum lines and everything seems to be in perfectly fine. I sprayed some water in all of the lines and there was no bubbles or anything of that matter. I don't know what else I

could check other than sensors maybe?
 

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. . . .So I just checked all the vacuum lines and everything seems to be in perfectly fine. I sprayed some water in all of the lines and there was no bubbles or anything of that matter. . . .
If you spray water on a vacuum hose at a suspected leak site, if there is a leak there will be no bubbles because the pressure inside the hose would be less than outside. If you spray sufficient quantity of water and there is a vacuum leak, the ingested water momentarily seals the air leak and the engine rpm should increase and cause it to run smoother.
Are the vacuum hose ends still pliable and not cracked?

Try this test to check the integrity of the vacuum hose from the intake manifold to the power brake booster. Warm up the engine such that the stalling at idle is occurring. Remove the power brake booster hose at the intake manifold. Plug and temporarily seal this vacuum port. Does the idle improve? If YES then the problem is a vacuum leak in the brake booster hose, check valve at the booster or an internal vacuum leak in the booster assembly. If NO then continue to look for the vacuum leak.

. . . . I don't know what else I could check other than sensors maybe? . . .
Does your scan tool have the capability to display the signal from the upstream oxygen sensor? If it is working properly it will show a value oscillating less than 0.45 V and greater than 0.45 V.

You indicated no telltale CHECK ENGINE symbol. But have you checked for diagnostic codes? If is possible to have a code but the symbol does not illuminate.
 

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Discussion Starter · #13 ·
If you spray water on a vacuum hose at a suspected leak site, if there is a leak there will be no bubbles because the pressure inside the hose would be less than outside. If you spray sufficient quantity of water and there is a vacuum leak, the ingested water momentarily seals the air leak and the engine rpm should increase and cause it to run smoother.
Are the vacuum hose ends still pliable and not cracked?

Try this test to check the integrity of the vacuum hose from the intake manifold to the power brake booster. Warm up the engine such that the stalling at idle is occurring. Remove the power brake booster hose at the intake manifold. Plug and temporarily seal this vacuum port. Does the idle improve? If YES then the problem is a vacuum leak in the brake booster hose, check valve at the booster or an internal vacuum leak in the booster assembly. If NO then continue to look for the vacuum leak.



Does your scan tool have the capability to display the signal from the upstream oxygen sensor? If it is working properly it will show a value oscillating less than 0.45 V and greater than 0.45 V.

You indicated no telltale CHECK ENGINE symbol. But have you checked for diagnostic codes? If is possible to have a code but the symbol does not illuminate.
Ok I will take that into consideration when I look at it tomorrow since I didn't have time today.
 

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Hi there,

I have a 2008 Pt Cruiser limited with 85750 miles on it. It has this issue where it stalls when it is warmed up at idle. At idle you can feel it slowly start to shake more and more until it stalls completely, but it starts right up with no problem. There is no check engine light and I just replaced the fuel pump yesterday thinking that was my issue.

Thanks for the support,

Leo if you haven't changed the sparkplugs and wires for a while, i would do that..after around 50,000 miles my wires start making the pt run bad, if that doesn't work try looking at the mass airflow censor ..Also run a head gasket check ..Just going off of what happened to mine...good luck
 

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Its a speed density system so it isnt that sensitive to airleaks on the intake side, you basically just get an high idle and a fault code for idlespeed if its really bad.
- high fuel trims suggest a couple of things.
Air leaks on the exhaust side. Note that even after the cat con and o2 sensor airleaks can play havoc.
Bad o2 sensors. Dont spray anything on the connectors/ new sensor and use just the slightest amount of antisieze on the threads. Clean connector on the car carefully with a good electriccleaner/ alchohol and let it dry before connecting.
A bad MAP sensor is also one that gives strange problems, you can compare it with a vacuum gage.
One or meoe injectors with a lousy spray pattern, this should set a cylinder misfire code so i belive its one or both of the previous suggestions.
 

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Discussion Starter · #16 ·
Try this test to check the integrity of the vacuum hose from the intake manifold to the power brake booster. Warm up the engine such that the stalling at idle is occurring. Remove the power brake booster hose at the intake manifold. Plug and temporarily seal this vacuum port. Does the idle improve? If YES then the problem is a vacuum leak in the brake booster hose, check valve at the booster or an internal vacuum leak in the booster assembly. If NO then continue to look for the vacuum leak.
One or meoe injectors with a lousy spray pattern, this should set a cylinder misfire code so i belive its one or both of the previous suggestions.
Ok so I had enough time to actually take off the intake manifold and look at the vacuum lines and you were right, the hose did have a rip. Hopefully that's all that it has. Thanks for all the help.
 

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Ok so I had enough time to actually take off the intake manifold and look at the vacuum lines and you were right, the hose did have a rip. Hopefully that's all that it has. Thanks for all the help.
Is it running better?
 

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The bigger question is did you replace the hose or just cut it off and reattach it? If the latter, I'd suggest the former.
 

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The bigger question is did you replace the hose or just cut it off and reattach it? If the latter, I'd suggest the former.
Yep, all that engine bay heat wreaks havoc on all the rubber and plastic parts.

A while back I had to replace some of the plastic wiring loom. It all looked fine to the eye, but when I touched it, it just crumbled in my hand. I had to go back to a spot where it was still good and flexible.
 
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