oscillating RPM

[Alpinweiße30]

check your exhuast mainifold . mine did the same thing . it had a big ass crack

i will be taking hem off this weekend. I can't say that I noticed this problem before doing the timing belt. Also I realized that its not fixed after the battery went dean, it was just that the car was not warmed up right when I jumped it. Later as the car got to operating temp it started to do it again.

[Alpinweiße30]

A friend and I took a look today and noticed the vac line running fro the FPR to the manifold was cracked on both sides. Figure this may have been the problem so we cut it off at both ends and reinstalled. Same problem. Surging from idle up until I shift and right back to it while moving and the slight fluctuation in RPM while revving at a stand still. I checked all the vac lines and tightened all hose clamps and still no change. any other suggestions?

[Alpinweiße30]

I was messing around with two of what seems to be 3 temp sensors in the thermostat housing, unplugging them while the car was running and noticed a difference in the problem, where the fluctation of power under load was not as noticeable. I have also noticed over time, now that I am driving the car on the regular basis that when the car has sat for a while and is started the RPM jumps to like 2-2.5k and then back to normal idle after a second. If the car is "warm" then it just revs up normally and levels out at the 1.5k idle. I have heard that the coolant temp sensor and the o2 sensor both have a part in the initial start up and idle. I have also noticed that the temp gauge on the dash will randomly go above 1/2 way where it normally sits and then fall back down to normal, as well as jump erratically and then return to normal.

Does any of this make sense? Does anyone know off the top of their head what all three of the sensors in the thermostat housing do? should I start with them, or o2, both?

Thanks in advance.

[Curt Hayes]

[QUOTE=Alpinweiße30;2093848] I have also noticed that the temp gauge on the dash will randomly go above 1/2 way where it normally sits and then fall back down to normal, as well as jump erratically and then return to normal.

Sounds like maybe you need to bleed your coolant system, like you have an air pocket right there.
OR maybe you have a bad ground? That'd mess up everything. I'm not positive, but I think that the coolant temp sender for the gauge grounds thru the housing, ie. a single wire connector. I know that the sensor for the Motronics does not (it's got two pins). Given the weirdness at warmup at the very least I'd suspect the temp sensor, but combined with the antics of the temperature gauge, seems like they're related.

[Alpinweiße30]

This is what I am talking about with the erratic temp gauge.



Its hard to see here maybe because of the camera angel but this is the slight fluctuation of the RMP at idle.


I have noticed a distinct difference between start up when the engine is cold, like left over night, and when it has sit for a few hrs, few min.

[SEdgell]

Did you ever figure anything out? My temp gauge does the same as yours, and I just adjusted my valves over the weekend and now I have an idle problem. It seems to fluctuate a little, and if you rev it a little, and quickly let off the throttle it dies out. I've since been searching for vacuum leaks, and I'm planing on cleaning the ICV, as soon as I find a how to.