legendr35

hi guys

when my car is in any gear with the clutch depressed. my RPMs will jump up and down or fluctuates(it will go up 100 RPMs, then go down 100 RPMs, and it keeps doing that until I let go of the clutch, or put it back into neutral.


plus, my car runs extremely rich during idle. On cold starts I can see fuel spit out of my muffler....

anybody have a clue on why it does this?


thanks

Tim McCreary

I answered a post several weeks ago about the same symptoms. I had two 1985 GSL-SE cars that did the same thing. Mine was noticeable to the point that if the clutch was in, it would rev up and down, but if you put the car in neutral and let the clutch out, it would hang up on a higher rpm. I was always told it whas the throttle position sensor (always the obvious answer), but mine checked out fine.

I later found a post on another website that somebody had the same problem and replaced the TPS, checked grounds, etc, but to no avail. Ended up he pulled the throttle body off and thoroughly cleaned it with throttle body cleaner and reinstalled. His problem disappeared and never returned.

My suggestion is to check all ground wires, then check the TPS and replace if you can afford it. If this does not work, then remove the throttle body and clean it and make sure all gaskets are sealed when reassembled.

Also, the "fuel" that you see spitting out the muffler at start up is acutally water. It is a byproduct of combustion that condenses in the cold metal pipe and is blown out the back or leaks out a small hole in the muffler end. It appears to be fuel-like because unburned hydrocarbons also cool and "attach" to the water causing it to smell like gas.

With the engine running rich, check the O2 sensor and replace it. Most O2 sensors slowly wear out. Also check your air pump to see if it is working properly. This will supply your catalytic converter the oxygen to burn the unburned hydrocarbons with a chemical reaction.

Tim

legendr35

Thanks Tim...I think i'll try cleaning the TB next time, but as for my o2, i replaced it just under 1000 miles ago...so I don't think it could be that. But how would I go about checking the Air Pump? Thanks again

supercell

legend,

I dont know if it helps, but you may want to check out your PCV valve as well - I have run across this in the factory manual before with regard to fluctuating idle. You also should check out your clutch switches to make sure they are working right.

Tim -

I think these cars' systems are surprisingly akin to the GSL-SE emissions system.....There are many similarities with different names, and it seems like the manifolds are also prone to excessive 'crudding'. I may need to pull mine off just to clean the ISC and AWS valves because of idle problems as well!


Jon
'93 MB Touring
'85 Silver GSL-SE