2001 PT Running rough

[ajhockey3]

Its my grandpas car we've been doing some work on it. 170,000km ish,

Everything on the car is good now except for the way its running, even got the AC working!
Its been sitting around for awhile, and developed a rough idle, sounds like a missfire, however no codes or pending codes. Car runs awfully, shuts off every 2-3 minutes while driving, let it sit for 5-10 minutes and starts back up.

New 91 octane fuel has been put in, New plugs, fuel rail cleaned, injectors have good resistance.

Problem developed over just sitting for a year or two.

Looking for ideas? My grandfather is considering scraping the poor PT

[Grasshopper77]

This might sound stupid, but when was the last time the transmission fluid/filter was changed? My PT had a rough idle (slight stumble/surge/vibrating and no codes), worst when in gear, even worst when A/C was on, but ran smooth while driving. It's always had a slight rough idle since we purchased new. Would even stumble and stall on a few rare occasions, when going from park to reverse (prompting dealer visits). Took it to the dealer a few times when it stalled, starting around 12K with no success (either plugs, wires or plenum seals changed at each visit), it just got progressively worst to the point it felt/sounded like i was driving an old diesel VW. Well, i replaced the tranny fluid and filter this weekend and it purrs like a kitten. I did not touch anything else under the hood (could have bumped a hose or wire), but after I swapped out the filter, the car has never idled so good! My wife drove it to work for the first time to day and sent me a text saying it felt like a new car. Maybe it was just a fluke or the fluid was just nasty enough to over burden the torque converter? No clue, but i thought I'd share my experience, while you waited on one of the more helpful/knowledgeable folks chime in.

[ajhockey3]

Originally Posted by Grasshopper77

This might sound stupid, but when was the last time the transmission fluid/filter was changed? My PT had a rough idle (slight stumble/surge/vibrating and no codes), worst when in gear, even worst when A/C was on, but ran smooth while driving. It's always had a slight rough idle since we purchased new. Would even stumble and stall on a few rare occasions, when going from park to reverse (prompting dealer visits). Took it to the dealer a few times when it stalled, starting around 12K with no success (either plugs, wires or plenum seals changed at each visit), it just got progressively worst to the point it felt/sounded like i was driving an old diesel VW. Well, i replaced the tranny fluid and filter this weekend and it purrs like a kitten. I did not touch anything else under the hood (could have bumped a hose or wire), but after I swapped out the filter, the car has never idled so good! My wife drove it to work for the first time to day and sent me a text saying it felt like a new car. Maybe it was just a fluke or the fluid was just nasty enough to over burden the torque converter? No clue, but i thought I'd share my experience, while you waited on one of the more helpful/knowledgeable folks chime in.

Original fluid and filter, however it still runs like trash while running and randomly quits, so I don't think this is it. even in neutral its bad

[Handy_Cruiser]

Originally Posted by ajhockey3

Its my grandpas car we've been doing some work on it. 170,000km ish,

Everything on the car is good now except for the way its running, even got the AC working!
Its been sitting around for awhile, and developed a rough idle, sounds like a missfire, however no codes or pending codes. Car runs awfully, shuts off every 2-3 minutes while driving, let it sit for 5-10 minutes and starts back up.

New 91 octane fuel has been put in, New plugs, fuel rail cleaned, injectors have good resistance.

Problem developed over just sitting for a year or two.

Looking for ideas? My grandfather is considering scraping the poor PT

You could try half a yellow bottle of HEAT and half a red bottle of STP fuel cleaner just to make sure the tank has not got a lot of trash and/or water.

However, this could be a bad fuel pump. Almost everything else that would cause this will throw a code or two.

[ptcruisersteve]

I would suggest pulling the camshaft sensor plug off and see if the PCM triggers the code for it.

[ajhockey3]

Originally Posted by Handy_Cruiser

You could try half a yellow bottle of HEAT and half a red bottle of STP fuel cleaner just to make sure the tank has not got a lot of trash and/or water.

However, this could be a bad fuel pump. Almost everything else that would cause this will throw a code or two.

Would the bad fuel pump show odd fuel pressure on the diagnostic port? Might be something to check

[soyomb]

Also, as it is a 2001, check to see if the wire harness has dropped underneath the passenger side of the engine and is rubbing on the half shaft.

[_PTGT03]

when is the last time oxygen sensors were changed

[Handy_Cruiser]

Originally Posted by ajhockey3

Would the bad fuel pump show odd fuel pressure on the diagnostic port? Might be something to check

If the fuel pump is causing the engine to run rough and if you can catch it while the engine is running rough, then yes, you would likely see low pressure at the Schrader valve.

Soyomb gave some good advice above too. Even though it would likely throw a code, check that the harness is not rubbing the CV shaft.

[ajhockey3]

Originally Posted by _PTGT03

when is the last time oxygen sensors were changed

never but that would have a code