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PT cruiser runs rough at idle sometimes

 
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Old 07 Feb 2011, 07:33 pm
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Default PT cruiser runs rough at idle sometimes

I have a 2003 PT cruiser.
Limited Edition.
2.4L non-turbo, Automatic, ABS brakes.
Stock.
62K miles.
Fullerton, California.

Sometime the car runs rough at idle.
This has been going on for ~ one year now.
Some days it runs just fine.

I have at this car is the shop at three different independent service dealer.
The computer shows no problems when read.

I shop change my part plugs and wires to try to fix the problem, but it did not help.

One shop charge me $ 300.00 to try to dianose the problem with the computer, but could not fine the problem.

One shop thinks their is a short in the wiring hardness around the idle sensor.

Any comment would be welcome.

Last edited by Berthold; 08 Feb 2011 at 12:19 pm.
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Old 07 Feb 2011, 07:36 pm
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Location: Mooresville, NC
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Default Re: PT cruiser runs rough at idle sometimes

Where are you at, what type PT, what type engine??? Pictures help too!
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Old 08 Feb 2011, 08:44 am
quicksilverdon's Avatar
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Default Re: PT cruiser runs rough at idle sometimes

Well, the most common cause - plugs and wires - you've had done.
Next - when idle is rough, spray along the intake manifold seams with starting fluid - if idle smooths out, you have a bad intake gasket.
Next, could be an injector or two - get some Lucas fuel tratment and try that.
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'05 Limited Turbo Lite, (Silver, of course)4-wheel ABS, Sunroof, Spoiler. Mods: E&G Classic grill, K&N FIPK, BTG duals, rear lowered 1.5", LED washer lights, $20 catch can, Aoogah horn, Weatherflectors, Sunroof Deflector, Fuzzy Dice, rear logo flames, rear pinstripe graphic, Gen3 Taillights, rear sway bar, hood struts, Strut bar.
Traded in '02 Silver Touring Edition w/87,000 miles
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Old 08 Feb 2011, 12:17 pm
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Default Re: PT cruiser runs rough at idle sometimes

Sorry,

2003 PT Cruiser, limited edition.

Stock

2.4L non-turbo
62K miles
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Old 08 Feb 2011, 10:14 pm
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Location: Glendale, AZ
Posts: 496
Default Re: PT cruiser runs rough at idle sometimes

What gap did the garage set the plugs at? I've found that if they set them too wide, the car will run rough. Mine is much happier at about .038 inches to .040 inches. Also, did they fully seat the spark plugs? While not doing so is less common than over-torquing them, it can cause a problem (OK, it is really rare.)

I agree with the idea of using the fuel system cleaner. If you have been using the cut rate brands (if there is such a thing any more), try using only top tier brands and dumping in two bottles of Techron with each fill up. Another additive that really works super well is Amsoil PI, but it is very hard to find. It's actually the best detergent additive I have ever used.

Lastly, how long have you had the car? The PT Cruise 2.4 engine is not a smooth idling engine to begin with. It won't ever idle as glass-smooth as a Camry 4 cylinder. It's shouldn't idle rough enough to shake out your teeth, though.

(My recollection of cut rate gasoline was when Terrible Herbst sole regular leaded for 26 cents per gallon, and Shell sold it for 35 cents a gallon, full serve.)
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Old 09 Feb 2011, 01:06 pm
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Default Re: PT cruiser runs rough at idle sometimes

Hello Everyone.

I purchase this PT cruiser brand new in 2003.
It has 64K miles on it.
It started running rough ~ 1 year ago.
It only does about half time when the car is warm, and almost never when the car is cold.

The car drive chain is stock. The only changes I made to the car was to add flames to the finders back in 2003

I have only use Mobil or 76 gas in this car.
Most of the miles has been on short trips (I only worked 2 miles from my home).

I have try several different brands of fuel injection cleaner in this over the pass couple of years.
I also had the fuel injection system clean at the dealer ~ 2-1/2 years ago.

Bert
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Old 09 Feb 2011, 09:26 pm
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Default Re: PT cruiser runs rough at idle sometimes

I think the most important clue is that the car only does it when it warms up. Something is going on when the system changes over from open loop to closed loop operation.

Oxygen sensor?
Vacuum leak?
Bad connection at the wire harness around the idle sensor? That shop might have the closest idea, but I'm not sure that's it.

It is really difficult to think this one through without having the car here. When the car is cold, in other words not fully warmed up, the fuel system is permitted by the computer to run richer in gasoline than it would when it warms up. That can mask a vacuum leak, which could be as simple as the hose to the power brake unit being loose. Once the car warms up, the computer will then want to cut the fuel mixture to a leaner mix, and the computer will go berserk trying to deal with a vacuum leak--if that is what it is. By "berserk," I mean it can cause a rough idle.

The quick and cheap thing I would suggest from 450 miles away is to check the hoses that go to the thing that looks like a greenish gold lunch plate behind the brake master cylinder. The hose is about 3/4 inch in diameter, and it has some molded-in curves. Make sure that it isn't cracked and that the connections are tight. There will be some other, smaller hoses that come off of it. Do the same with them. Also check the electrical plugs in the vicinity.

After that, I have run out of ideas.

Anybody else?
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Old 09 Feb 2011, 10:43 pm
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Location: oak creek, wi
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Default Re: PT cruiser runs rough at idle sometimes

i vote for a vacuum leak. now that i think about it, on my mazda 626, i t did the same thing, fine when cold, rough idle when warm. changed the intake manifold gasket and was fine. it's a lot easier to change on a pt.
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Old 13 Mar 2015, 01:18 pm
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Default Re: PT cruiser runs rough at idle sometimes

If u have an electric throttle body disconnect batter and electric throttle body plug then take off throttle body. Get throttle body spray and clean all the carbon out of it , it should be black and that will fix the idle problem. If u don't want to do that just pull the air hose off throttle body and put key position on without running engine have somebody hold gas pedal down and clean the throttle body with throttle body spray..do not put straw on throttle body spray cause it will shoot out into throttle body.
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Old 13 Mar 2015, 06:57 pm
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Default Re: PT cruiser runs rough at idle sometimes

Quote:
Originally Posted by Emj2203 View Post
If u have an electric throttle body disconnect batter and electric throttle body plug then take off throttle body. Get throttle body spray and clean all the carbon out of it , it should be black and that will fix the idle problem. If u don't want to do that just pull the air hose off throttle body and put key position on without running engine have somebody hold gas pedal down and clean the throttle body with throttle body spray..do not put straw on throttle body spray cause it will shoot out into throttle body.
This is over THREE YEARS OLD.
__________________
"Anti-intellectualism has been a constant thread winding its way through our political and cultural life,
nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge."
Isaac Asimov"

'05 Limited Turbo Lite, (Silver, of course)4-wheel ABS, Sunroof, Spoiler. Mods: E&G Classic grill, K&N FIPK, BTG duals, rear lowered 1.5", LED washer lights, $20 catch can, Aoogah horn, Weatherflectors, Sunroof Deflector, Fuzzy Dice, rear logo flames, rear pinstripe graphic, Gen3 Taillights, rear sway bar, hood struts, Strut bar.
Traded in '02 Silver Touring Edition w/87,000 miles
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