Unstable Idle on warm/HOT days????

[clex2]

Anyone have this problem (M42):

On cool days car runs like a champ. When the weather is warmer or frankly hot, the engine obviously needs more cooling. What I have noticed, and it was pretty bad today, is that when the electric cooling fan kicks on, the electric drain from the fan causes the engine to stumble, but not stall and the ICV compensates for the dip in RPM and brings the engine speed back up to normal. I'm guessing the alternator is called into action to drive the electric fan motor, increasing parasitic drag on the motor. I just wouldn't expect it to be so pronounced and annoying. There have been a handful of times when the car has stalled, but the A/C was on and I was turning and using the power steering.

Anyone think it's a bad alternator? bad eletric fan motor? ICV?

[wolferj-RIP]

My best guess is ICV. Bad alternator wouldn't produce that kind of drag (unless the bearings have gone bad) and a bad fan motor just couldn't produce that kind of drain... Another thought is maybe the bearings on the belt tensioners?

On further pondering, it most likely is a combination of two or more things... nothing you've mentioned would cause this by itself.

One quick question... Do you have multiple ti's? Your signature car sure doesn't have a an M42...

(I also would love to see the Z8 remote starter button and how you installed it... I'm in the east bay, maybe I could come and drool?)

[clex2]

My best guess is ICV. Bad alternator wouldn't produce that kind of drag (unless the bearings have gone bad) and a bad fan motor just couldn't produce that kind of drain... Another thought is maybe the bearings on the belt tensioners?

On further pondering, it most likely is a combination of two or more things... nothing you've mentioned would cause this by itself.

One quick question... Do you have multiple ti's? Your signature car sure doesn't have a an M42...

(I also would love to see the Z8 remote starter button and how you installed it... I'm in the east bay, maybe I could come and drool?)

Yes, I have two ti's. 330ti sig car and 318tia DD. Look in my gallery. You can come by anytime to talk about cars. PM me and we can meet up.

[clex2]

As luck would have it, my starter went totally out recently. Had the car towed to Edge Motorworks in Dublin, where they replaced my starter and while they were at it, I gave them a new ICV and hoses to put in.

The new starter sounds great. No more loose bearing sound on start up. After several hot days, I can confirm that the new ICV has solved the idle surge problem. The rpm do dip a bit at idle when the radiator fan turns on, but it dips and stays steady. No more bouncing, almost stalling idle. The old ICV had been cleaned out, but with little improvement. Maybe it wasn't reacting fast enough to the change in load.

However, another prolem still exists, and I guess must not be related to the ICV. With the AC on, after gently accelerating and letting off the gas, if and when the off throotle rpm drops to about 1500 rpm, the idle bounces several hundered rpm up and down while the car is coasting. You can feel the slight surging from this rpm fluctuation. As the car slows, the rpm stabilizes and goes to a normal idle as you come to stop. If you get off throttle at a higher rpm and speed and the rpm drops to anything above 1500-2000 rpm, there is no rpm fluctation.

Possible culprits might be:
1) Ac compressor and/or associated electrical gear
2) Ac clutch?
3) Auto Tranny?

Anyone have any other ideas as to what this could be? I 'm glad I solved at least one of the idile issues.