Intermitten RPM surging

[oso]

As it always is the case with intermitten problems, I am having a hard time trying to figure out what may cause my car the sound and act as if someone has suddenly stomped on the gas pedal while I am simply sitting at idle or just shifting into the gear? That sudden surge comes and goes without any rhyme or reason ( at least to me...). Has anyone experienced a similar predicament? Any help solving the problem appreciated.

[winmutt]

Sound like a fault in the ELR.

[babymog]

Unplug the ELR (two-pin connector on the back of the IP) and see if it still occurs.

Does the tach act up at the same time?

[oso]

Originally Posted by winmutt

Sound like a fault in the ELR.

Forgot to mention that the cruise control stalk is kind of broke... Would that have anything to do wth it?

[oso]

Originally Posted by babymog

Unplug the ELR (two-pin connector on the back of the IP) and see if it still occurs.

Does the tach act up at the same time?

Will give it a try. Thanks as always.

[moon161]

Backpressure due to blockage in the exhaust can cause a surging idle.

[winmutt]

Originally Posted by oso

Forgot to mention that the cruise control stalk is kind of broke... Would that have anything to do wth it?

Unhook the CC actuator and see.

[rosenfe]

this was happening to me on my 87sdl.the problem went away when i removed catalytic converter because it was plugged .

[oso]

Originally Posted by babymog

Unplug the ELR (two-pin connector on the back of the IP) and see if it still occurs.

Does the tach act up at the same time?

I did unplug the ELR a couple of times to test it's effect and it looks like we got a winner- how do I go about fixing whatever needs fixing?

[winmutt]

Originally Posted by oso

I did unplug the ELR a couple of times to test it's effect and it looks like we got a winner- how do I go about fixing whatever needs fixing?

http://startekinfo.com/StarTek/outside/11832/Resources/201Create/PDF/70006.pdf

Section 7.1.190 is a complete breakdown of testing the EDS/P2 with generally easy to find tools (other than an scope which can be purchased cheaply enough).

[Alex300DT]

I just fixed the same problem on my car, the wires in the harness were rubbing against the intake manifold. Look where the harness snakes around the manifold, you might have to dissect it, separate the wires, and reinsulate the whole thing.

[oso]

Originally Posted by winmutt

http://startekinfo.com/StarTek/outside/11832/Resources/201Create/PDF/70006.pdf

Section 7.1.190 is a complete breakdown of testing the EDS/P2 with generally easy to find tools (other than an scope which can be purchased cheaply enough).

Wow! Now I just have to enroll in some kind of engineering program at the junior college and everything will be peachy... The link is great!! Thanks winmutt, appreciate your help.

[winmutt]

Anyone with an 87 and newer w124 should read that.

[oso]

Originally Posted by winmutt

Anyone with an 87 and newer w124 should read that.

Agreed! Just one more question: since my troubles are of an intermitten nature, will the testing procedure pick up on the fault even at the time when the engine is idling OK? You see, the thing sometimes chatters just fine and out of the blue it comes:wroooom! If I am not there right at that time will I be able to diagose the problem correctly anyway? It seems to me like some kind of "sticky" issue.... Some kind of solenoid within the ELR body...? And how involved would be the R/R process? OK, it was more then just one more question.... Sorry but it bugs me a lot!

[winmutt]

I am not actually sure how the ELR works. I believe it is just a big magnet with no moving parts. Could be totally wrong about that. I doubt the testing will indeed pick up anything however there is a trouble shooting flow chart, step one is unplugging the ELR. Certainly worth trying.