DanielD

When the car is cold it cranks fine and idles around 650 as it should.

Once the car warms up the idle will drop to around 600 rpm and its rough.
As you slow down for a stoplight, you can feel the engine surging as you come to a stop. At the light, there is a surge to the idle and sometimes the car dies. If you put the car in neutral and hold the rpm at 1000, you can still feel the surging going on. It is not enought to vary the tach but you can still feel it. You can sometimes see the voltage needle swinging a bit and the oil pressure swinging with the surging.

The car accelerates normally and runs smooth at speed. Any suggestions on this one?

blitz928

Check the vacuum check valve, at the brake booster. Little blue and black thingy on the rear of the drivers side cam cover.

Mongo

Does it crank fine when its warm?

I have this same issue and I'm starting to consider my O2 sensor isn't functioning correctly, or the O2 loop is not being read by the LH.

DanielD

Matt, I'll check the check valve when the rain stops!

Andy, It always cranks fine, hot or cold.

Rob Edwards

Any post with the words 'dies' and 'warm' should also have the words 'flexplate last released on XX/XX/XXXX' . Good, of course, that it cranks fine when warm, but you should add the pertinent negatives too...

Shark Attack

If its and AT I would still have the flex plate checked if you never have.

DanielD

The flexplate was checked last September, end play was checked and everything was fine then.
The starter doesn't bog or anything when its warm; normal operation. Besides, TBF is not an option!

borland

Ask Mongo. He's been there, done that.

If you look at his threads with the same problem. Easy test, run engine with O2 sensor disconnected at Fuse/Relay panel. Another is run engine with MAF connector disconnected at MAF.

DanielD

borland, yes I just saw his thread. OUCH! I hope mine's not that much trouble. I just remembered one thing to add here: Last spring the rpms were surging somewhat like they are now. I fixed it by accident. I disconnected the battery cable to work on the electrical. When I hooked it back up the car idled fine.
???? I'll try that again this weekend but why would that fix an idle? Sensor issues maybe??

blitz928

Now that sounds like the start of a failing LH computer. I did that a few times and it worked before my LH finally went Kaput.

DanielD

Just great Matt. Make my day!

blitz928

Sorry...

But back to the brake booster vacuum issue, if the idle drops or fluctuates when the brake pedal is depressed, this may be the problem. If it does that when the engine is warm without the brake pedal depressed then it is probably not.

Mongo

I doubt it's the brake booster. How old is your O2 sensor Daniel?

On a side note to cheer you up, I just changed the oil on my car doing the same symptoms and there was not one metal shaving in it. No TBF for our cars.

blitz928

Probably not, but always start with the easy stuff first and work your way up.

Mongo

I agree but 3,000 dollars later all the easy stuff is fine and new again