Intermediate bad miss at part throttle

[yellowducman]

I have a 89 325IS with 190000 miles on it. The other day with the cruise on it got a little miss that only lasted a few seconds. Was fine until this morning. On the way to drop my son off at school it started to miss really bad to the point I could only get to about 35mph.

Heres the symtoms:
Idles fine.
Runs fine when cold
runs fine under very light throttle.
Misses really bad once hot while motors is under load.
Quits missing when throttle is pushed to wide open.

Things done to the car since I have had it (within a year)
new fuel pump and gas tank
new fuel filter
new timing belt
new plugs
new wires
new cap and rotor

I don't think it is pump related because I can pull the access cover off the pump and feel the fuel hose get hard when the car starts and I never changes when car starts acting up.

I've been having a problem with the temp gauge reading high when the car is running but it has been all over the place and will change from half way on the gauge to hot by changing the electrical load on the car like turn signals make it jump or holding the window button down when window is already down. If I cut the car off and turn the switch back on the gauge reads normal.

Anybody ever run into this?

[Curt Hayes]

I've been having a problem with the temp gauge reading high when the car is running but it has been all over the place and will change from half way on the gauge to hot by changing the electrical load on the car like turn signals make it jump or holding the window button down when window is already down. If I cut the car off and turn the switch back on the gauge reads normal.

This sounds like a bad ground. Check the ground at the battery in the trunk where it connects to the inside of the quarter panel. Check the ground from the body to the engine: on the left side down where the oil pan sticks out under the ps pump. These should be nice and clean, with low resistance.

[yellowducman]

Thanks for the reply, I replaced the engine ground strap when I did the rack a couple of months ago but I haven't checked the one at the battery. Does the DME have it's own ground somewhere or is it grounded through the main computer harness?

[jlevie]

The DME is grounded by the group of wires that come from the engine harness and attach to the ground point on the right strut tower.

[yellowducman]

The DME is grounded by the group of wires that come from the engine harness and attach to the ground point on the right strut tower.

Probably another good place to check for a bad ground. Thanks.

[yellowducman]

Does anyone think that the AFM could be at fault. The only reason I'm kind of thinking that is because the car runs well at idle and full throttle. I'm not sure if the car uses the AFM at wide open throttle.

[jlevie]

The AFM could have a worn spot in the resistance trace, or the vane could be sticking.