Zygrene

Hi all,

I recently bought a 2002 AP1 with 98k original miles.

About 1 week ago, I noticed that revving the engine slightly from idle will cause the rpms to "dip" below 1k very briefly and cause the engine the shudder before bouncing back up to around 1k. I checked a few threads here and decided to clean the IACV and throttle body, both of which had quite a bit of carbon buildup. After cleaning both, I disconnected and reconnected the battery's negative terminal to reset the ECU, then turned the engine on for 5 minutes to let it relearn the idle. I also poured in 1/3 can of Seafoam into the gas tank just for good measure.

It's now 5 days later, and the idle dipping issue is still here (not worse or better) and the CEL turned on (solid, not flashing) while driving to work this morning. The car still seems to run fine. I checked the oil dipstick while it was hot and it was reading a bit below the Low line.

Later today I'm going to:
1) add some oil
2) read the CEL code using an OBD2 Wifi reader and Torque Pro app

Before I do that, has anyone experienced the same thing or have any idea what to expect?

Thanks!

Jim Bravo

On both my previous '01 and current '02, the warm idle rpm have been below 1000 with A/C off (maybe in the 750-900 range). Some rpm dip after a quick throttle blip is not completely abnormal. I can't recall on my '01, but the '02 does have a slight dip after throttle blip. It doesn't drop low enough to concern me about stalling, so I just leave it alone.

I would check the CEL later and leave the dip alone unless it's dropping too low. Also, check your vacuum hoses. There are a couple connecting to hard lines on the manifold that seem to pop off pretty easily if bumped into.

Sabre

My 02 did the same idle dip after giving it a little rev.

First guess without knowing the CEL code is that the gas cap may not have been tightened enough.
Especially since it happened a few days after you did the Seafoam.

My AP1 had a notorious gas cap that could be tightened and would "click", but if you pinched the outer perimeter of the cap and kept twisting, it would tighten in another full 2 turns. Triggered a CEL every time if I wasn't careful.

Zygrene

You're right - the rpm doesn't drop low enough to stall the car, but the shuddering is very noticeable each time I blip the throttle from idle. Pretty annoying if this is normal behavior.

I'll check my vacuum hoses later since I did disconnect some of them to clean the throttle body.

I'll check the gas cap and top off the oil later before I drive home. Never had this gas cap issue with my 2004 AP2, so this is new to me. I always just turn it until I hear 3 clicks. As for the oil, I checked the dipstick when I test drove the car and it was reading fine (a bit high since the engine was warmed up) so I'm not sure how it's now reading below the Low marking a week later.

Also, once I'm home I'll read the fault code and post it here.

Soviet

There is really nothing to do with regards to the CEL until it is read. Be thankful that you actually have a CEL, this means that a problem is severe enough that the ECU can detect it. Much better than having strange behavior issues and no diagnosis help from the ECU.

Zygrene

P1456 evap emissions/fuel system leak detected

It was the gas cap. It wasn't tightened even though I clicked it 3 times. Cleared the code and good to go.

Sabre