Hi, I have an '87 L4 engine and I was told that these two sensors/senders are mounted on the engine next to the thermostat housing, one is vertical and one is horizontal. So I was wondering if anyone knows which is which and do all engines have these two parts? I always thought one did both jobs.

And I was wondering if a bad coolant temp sensor could be responsible for low idle at normal engine operating temperature? The idle gets down to 650 or so in drive at a stop and then slowly drops down to 500 and right when it sounds like it's going to stall something kicks in and the tach jumps back up to 650, and keeps doing this. I've replaced almost every sensor and valve.

Thanks,
Mike

My memory tells me that the coolant sensor on my (1988 4-cylinder Fiero) is mounted horizontally, and sticks out of the thermostat housing so that it points toward the rear of the vehicle. It has a 2-terminal connector on it - one yellow wire, one black wire. The coolant sensor talks to the computer (ECM).

I really am no expert on the 4-cylinder engine. Keeping that in mind, for the idle problem, I might suggest removing the IAC valve, and cleaning it and the associated passages in the throttle body.

That's about all I know. Hope it helps .

I don't know about the 2.5, but my S/C 3800 has 2 also. Each has a two pin connector. Each on has a black wire for ground. The one sensor has a green wire that goes to the gauge. The other has a yellow wire that goes to the ECM. This may be the same as yours. GM usually is pretty consistant on their colors.

Good Luck,

MOBILE

------------------
Member MN Fieros Forever 1986 GT. Self Installed SC3800/getrag almost everything performance wise is modified/upgraded, inside and out. Over 10 years in Car Audio and Car Electronics Experiance P.S. GOT 19"s??(all the way around)

Thanks guys, I think I've got it figured out now.