Has anyone else had a problem with a '92 SL2 running rough and stalling when the engine is cold? My car runs fine after the engine has warmed up. I have changed the coolant temp sensor and did a tune-up but it still runs bad when cold. [img]smileys/smiley5.gif[/img]


I don't want to paymucho $$ for a diagnostic, plus a premium price for a part through a repair shop, plus the labor to install whatever part is bad. [img]smileys/smiley6.gif[/img]


There must be a simple solution for this symptom.

 

What's the mileage?

For starters (simple stuff)

1) Did you change the connector for the Engine coolant temp sensor (ECTS) when you swapped out the sensor for the brass-tipped replacement? Corrosion is a killer here. MUST replace the connector (saturn only part) especially if the present connector and the sensor you just replaced are the originals (14 yrs old)....

2) Did your tuneup include new plug wires and a throttle body cleaning?

3) Have you ever cleaned the corrosion off of the coil tower posts?

4) Have you ever pulled the egr and cleaned it? I'm sure you burn a lot of oil-- the egr can get gunked up with carbon deposits and may not move freely enough until warm.

Let us know...

Derf






Edited by: derf

 

I don't know about theconnectors. Why did theyuse different metals? That's kind of dumb. [img]smileys/smiley5.gif[/img]


I did a minor tune-up, not a major tune-up. So no, I didn't do the additional steps you mentioned.


This problem of stalling when cold has been there for many years, it's not something that started happening last season. [img]smileys/smiley6.gif[/img]


The EGR valve was replaced three years ago, I have no way to test it to see if it is moving correctly or not.


My car has over 198,000 miles on it but does not smoke. I do have to add 1/2 to 1 quart of oil between oil changes though. [img]smileys/smiley16.gif[/img]

 

The ECTS connector -- a must. It is not the difference in metals that
is the problem - -it was that the original design of the ECTS had a
resin-tipped sensor, whch cracked and allowed coolant to seep through
the senor to the connector. If the new connector was in there, you'd
see evidence of it being spliced into the original wiring.

Definitely clean the throttle body with intake/throttle body cleaner. Replace all plug wires. Use a very FINE polishing cloth to remove corrosion from the coil towers -- if you've never done this (14 years), you'll be quite surprised at what you may find. If the corrosion is bad enough, you may wish to replace both coil packs. If you do so, get the entire assembly from Saturn (both coil packs plus control circuit, mounted on a base plate. Be sure the mating surface on the block is clean and corrosion free-- this is the grounding surface.
-------


When you start it cold, it feels as though it is missing (not firing) , yes? I used to think it had something to do with oil fouling on the plugs preventing proper spark and combustion -- but I proved myself wrong on many tune-ups as new plugs made no difference whatsoever w/r/t this phenomenon.

Given mileage, oil consumption, and general behavior of S-car engines, it sounds as though your oil control rings on the pistons have seized in their channels and are not sweeping the cylinder walls properly, allowing oil to seep past into the combustion chamber. Also, the valve guides and valve guide seals are most likely worn.

Compression rings are also probably worn, resulting in decreased compression-- which may be sufficiently excessive in one (or more) of the cylinders such that there is barely sufficient compression to ignite the air/fuel mix in that cylinder when the engine is cold.

Try a compression check (pull fuse for injectors BEFORE doing this). You may find one low cyl and/or all are pretty low..


Derf




Edited by: derf

 

I'll check the ignition coils this weekend. I don't have the tools to do a compression test. The entire cylinder head was replaced three years ago so the valve guides shouldbein decent shape. The bottom end has not been rebuilt and the rings probably are a little worn after close to 200K miles. At least it doesn't smoke and only uses a little oil between oil changes.


It really acts like the choke is not working, but there is no choke. No misfiring, more like lack of power and chugginga little until it warms up. The plug wires have been replaced three years ago also, maybe they need to be changed again. Weak spark may be the problem, I thought it was the computer getting the wrong temp from a sensor somewhere and not adjusting for conditions.

 

BAsed on your followup: The symptoms you describe are textbook ECTS+ Connector for an S car....


Change the ECTS connector.
</span>Actually, since you'll be at Saturn, buy an OEM ECTS (brass tipped) and replace that too (unless you just swapped in an OEM Saturn replacement, of course)-- this way you'll know you have the correct sensor and good contact at the connector.

Derf