I've been having trouble with my 2005 Neon (2.0) for the last several months, and I'm now out of ideas as is my mechanic...

The engine runs beautifully while cold or driving - no significant issues. However, once the engine gets up to running temperature it starts to have idle problems when in drive (e.g. at stoplights). It will begin to shake and run rough, and the oil light eventually comes on. However, if I drop the transmission into neutral it immediately idles properly.

I added a oil pressure gauge to help troubleshoot, and see that the car slowly drops to 600 RPM and 8 PSI while idling in drive. I didn't let it go further, as I didn't want to damage the engine.

I tried everything I could think of myself, and then took it into my local mechanic. He ran a compression test and a leak down test, and both showed leakage in the compression rings on cylinder 2.

As a result, we decided that the engine needed to be replaced. He did so (with a used engine - 69k miles), and I just got the car back today.

Now guess what - it's doing the same thing again (rough idle at driving temperature). It seemed to stabilize at 12 PSI at 600 RPM, but that seems way too low.

Note that there is no check engine light, and no obvious computer codes. Also, I define running temperature as about half way up the temperature gauge (almost totally horizontal, at the middle mark if you happen to know this gauge layout).

I'm going to take it back in the morning for another compression test, but I think the odds are low that two engines in a row would both have blown rings...

Any suggestions where else to look? Anyone heard of similar problems caused by other systems (ECM, Transmission, Faulty Accessories)???

Thank you!

 

Dodge says something like idle oil PSI is 3PSI; just FYI. Is the motor mount the original or an OEM? Is it good?

 

That seems awfully low for idle oil PSI - particularly since the oil sensor (also replaced) kicks on somewhere around 8-10 PSI. It did the same both before and after the replacement. Any confirmation on the idle oil PSI?

I just replaced motor mounts with new after-market mounts about 3 months ago (at least the three on the engine side - someone told me later there might be one on the transmission side also which I did not do). The old (original) motor mounts were trashed (the one that mounts into the wheel well was practically metal-on-metal), but the new ones looked to match the old extremely closely...

 

I learned the hard way with motor mounts on my neon, replace them all at once or the new ones will just tear within a few months.... That one in the uni-body sure looks like a fun one is there any tricks to r&r this that I need to know of?

 

Aftermarket engine mounts (the rear mount as Dodge calls it) are not fluid filled like the factory ones, so they allow more vibration. You also have to make sure they are all aligned.

 

12 psi? Mine chills out around 25 psi at warm idle and around 50 psi when driving. The issues kinda make me think TPS and IAC even though there's no codes being thrown.

 

We had the transmission mount replaced, and it reduced the vibrations, but it still vibrates more than I think it should.

Can anyone tell me what the warm idle RPM is / should be? 550 - 600 RPM seems lower than I'm used to in other vehicles (and lower than what I remember in this car before)...