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Discussion Starter · #1 ·
Hi! I have a 2006 PT Cruiser Limited, and I'm almost at the end of my rope. It's pretty much been a project car since I got it, which was never the plan. (I nicknamed it "the Lump" when I got it because I thought PTs looked funny, but it's turned out to be a much more accurate name than I wanted.) I won't go into detail now, but the most recent development was that it was idling very rough, so I cleaned the idle air control valve, and since then, it's been doing the same thing. It revs really high, about 3000-4000 RPM, before just about dying, at which point it repeatedly revs up to 1500 RPM and then almost stalls. Here is a video:


Right now my biggest suspect is a vacuum leak, but I don't want to make any assumptions. What's the best course of action? I've done everything myself so far because there aren't many mechanics where I live that I can afford, but like I said, I'm almost at the end of my rope.

-Michael
 

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These are usually vacuum leaks. Things to check include: all vacuum hoses and rigid tubing, including brake booster hose; intake manifold and its gasket; throttle body (bolted tight to intake) and its gaskets.
 

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Any fault codes? Was the throttle body removed to service the IAC valve? Was the upper intake removed to replace spark plugs? Are the plug tips black or white?
Was it revving high before the IAC service or just the rough idle?
 

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Agree with Bob Lincoln that it is likely a vacuum leak and a significant one. I had these symptoms when I reinstalled the intake plenum and 2 of the gaskets had fallen off.
 

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Agree, vacuum leak or IAC is sticking somehow after cleaning. Do the key dance, see if there are any error codes, and just to make sure it isn't weird, disconnect the battery for 15 minutes or more to reset the computer so if something was wrong and the computer was overcoming a problem and is now fighting a cleaned component, factory settings are the new starting point not the bad/dirty part to correct function (if that makes sense). There are a couple hoses (EGR attaches to the intake manifold located between the intake manifold and firewall, it has an O-ring in there), and there should be another rubber hose connection, too, that may not be properly seated.
 

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Can't hear it in the video, but listen for a loud hiss. Then try to find the source. Wetting joints with a spray bottle of water may change the sound and the engine speed.
The key-dance may not work on a 2006. The cluster self-test with the odometer button may work or an OBDII scan tool will.
 

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Discussion Starter · #8 ·
Alright, so I finally did some hunting around and it turns out it was not a vacuum leak causing that (although I've still not ruled that out completely). Instead, it just a very dumb mistake that I made. When I cleaned and reinstalled the throttle position sensor, I put it back in with the prongs on the wrong side of the tab, meaning that it was holding the throttle open no matter what. I fixed that and it stopped revving high--but now it's back to rough idling, badly enough that it stalled and now it won't even start. I have a code reader and it gave me P2074, which is "Manifold Absolute Pressure/Mass Airflow - Throttle Position Correlation at Higher Load" and P0118, which is "Engine Coolant Temperature Sensor Circuit High Input", as well as an issue with my generator (P063A) that I knew about but haven't gotten to yet.
 

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P2074 can be a vacuum leak. It can also be high resistance grounds at the TPS or MAP or defective TPS/MAP sensors.
How did you 'clean' the TPS sensor? Usually if there is a TPS problem, it is best to replace it with OEM.
Possibly the high resistance ground is causing the ECT sensor voltage high fault as well?
The generator P063a code is known on 2006 PTs and is addressed in TSB 18-007-07:
https://www.dixie-electric.com/tsb/TSB_852.pdf
 

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Two items to check regarding the MAP/Throttle code. The EGR could be stuck partially open (not a failed EGR as it still opened enough to pass the EGR test) allowing in enough air to trigger the code or the air hose running from the intake plenum and the air filter box may be cracked and letting air in. I was chasing a MAP code and found the air hose was soft and cracked. Under high vacuum (like at idle) the hose would partially collapse and the cracks would open.
 

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Two items to check regarding the MAP/Throttle code. The EGR could be stuck partially open (not a failed EGR as it still opened enough to pass the EGR test) allowing in enough air to trigger the code or the air hose running from the intake plenum and the air filter box may be cracked and letting air in. I was chasing a MAP code and found the air hose was soft and cracked. Under high vacuum (like at idle) the hose would partially collapse and the cracks would open.
Some good suggestions. However, the 2006 PT does not have an EGR valve.
 

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Some TPS units have an O-ring to seal up the vacuum, so if you had one and it's damaged or loss, you can get a vacuum leak at the TPS.
 

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Discussion Starter · #13 ·
Alright, so I replaced the TPS with OEM, just in case I'd damaged it while cleaning. Now it starts and runs, but after revving up to higher RPMs, it dies. As long as I keep on the gas, it will run, but as soon as I let off the pedal, it falls to zero.
 

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Any fault codes return yet? Can you carefully drive it using both feet?
 

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Someone recently installed a TPS with the tabs referenced wrong on the throttle shaft. Are you sure you didn't do that? With engine off and key on, check voltages with throttle closed and with it wide open, at the TPS. Should be about 0.7 and 3.8 volts.
 

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On a 2006 PT Turbo that did that, the key dance worked and the fault code indicated mismatch between TPS position and MAP sensor. An ohmmeter check of the TPS looked okay so a new MAP sensor...had to use aftermarket from Autozone as the Chrysler dealers didn't have one...was installed and solved the issue.
 
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