97 Q45T runs rough after warm up

[cigardave007]

Greetins All,Have poured over the many post on rough running Q45's and have done a lot of work to no avail

She runs fine when cold. Afeter the temp gage reaches just below half way (normal running temp) She will "stumple" while accelarating or driving steady. Kinda feels like cutting the key off and on. If I stomp the gas she revs up fine. Idle after warm up is "choppy" and will eventually go dead.CEL cold is EGR.

Things I did are

1) Removed EGR and ACC and cleaned with solvent2) Removed about all of the electrical connections and spray with electrical cleaner.3) Check the plugs. Looked fine. Number 6 looked like new!?? I replaced all the plugs about 8k ago. NGK4) Change fuel filter5) Did a BG44 treatment thru the brake vacuum hose. and in the tank. It did run better but didn't solve the problem

My next step is the MAF. When I unplug it the car does go dead. Is that suppose to happen??

I don't seem to get a lot of vacuum(air) at the EGR. When I unplug it I don't get a noticable hiss. Also if I push the valve thing up with my finger the car will go dead.

Looking for any ideas. I'm learning way too much about Q45's

I'm going thru a rough time and just don't have the bucks for a trip to the dealer.

Thanks

[email protected]

[maxnix]

Well, read the stumble thread. There seems to be some problems with coilpacks on the VH41De, but they are not particularly cheap.
Modified by maxnix at 7:34 AM 4/5/2008

[96Qowner]

Here's the stumble thread:

My 1999 Q45t with 94,000 miles has a stumble at idle

And another about the same misfire problem:

y33 idle jerk / hesitation discussion (lets fix this!!)

It's not an uncommon problem, but it can be a real biatch to nail down.

[jonseyq45]

In a prior post I mentioned that the fuel injection goes through a couple of states, open loop and closed loop. The state relies on the engine temp. Search the forum ( There's that phrase again). The first order of diagnosis is to determine is it fuel or fire (electrical). In this case both are controlled by the ECU which in turn is fed information from all the different sensors and pickups.

I wish there was an easy answer.

First: Fuel or fire

Second: Match symptoms and possible source to create a forum search

Third: After finding possible answer, check all connections and systems related to that process.

Fourth: If no answer yet, search forum again with wider description

Fifth: Gather as much info as possible, Temp, Time , what gear, cruise or under a load, Full moon or high tide. Any secondary issues, no matter how small.

Now create a secound post and see what our collective brain power can do......

Finally prayer can't hurt

Jonsey....

"U Can Do IT"

[levsal]

possibly a bad 02 sensor. unplug the 02 sensor. if that fixes the problem, replace it.

[NightRiderQ45]

O2 sensor wouldn't cause it to idle rough.

[1994InfinitiQ45]

Wow...my cars seems to run faster when the temperature gauge is on Cold. IDK y?!

[cigardave007]

Seems like a used MAF solved my problem

Keeping the fingers crossed!!

cigar

[96Qowner]

Awright!

It's great to see someone take full advantage of the NICO archives!