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96 saturn misfiring runs rough when hot


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stockfish
New User

Jul 11, 2008, 8:17 PM

Post #1 of 3 (7036 views)
96 saturn misfiring runs rough when hot Sign In

My 96 saturn sl2 with 165000 miles continues to run rough and misfire on cyl 3 when at operating temp. It runs fine until warmed up, then starts missing, with the cyl 3 misfire code coming on. I suspected a leaking injector flooding the cylinder and replaced the injector on cyl 3. I have also replaced the plugs, wires, both coils and checked wiring. The cylinders tested 185-200 psi on all 4. I just ran a can of cleaner into the intake and haven't rechecked compression. I dont know what else to check or replace to get the engine to stop running rough. I had the car to a garage and they ran their scan tools and couldn't find anything to replace, other than suggesting trying to replace the #3 injector which I did. They also tried another new plug in case i had a dud. Does anyone have any suggestions on what to try next?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 12, 2008, 3:29 AM

Post #2 of 3 (7033 views)
Re: 96 saturn misfiring runs rough when hot Sign In

http://www.autozone.com/...eId=0900c1528017e959

This caught my attention so I did some looking. Link above was under repair itself but had some thoughts.

A few things come to mind to test out and be looking for noting that it DOES run well cold??

* Fuel pump pressure when warmed up and actively misfiring

* Try swapping new injector with another known good, replace o rings.

* Integrity of wiring to the injector is in question along with connectors

* Check and is oil pressure up to spec when warmed up. Perhaps a hydraulic lifter can't maintain it's clearance with thinner oil and lower pressure when warm.

MECHANICAL POSSIBILITIES

* Valve springs?? Weak - hairline cracks can allow good compression test results and not be adequate.
-- Vacuum testing may show something up for this.

* Head and intake gasketing can be temp sensitive and not show classic problems

* Spark plugs may show telltale evidence - now new - what did old ones look like?
________________

Guess it will be tricky as things may test fine by the time you can check anything may be cool enough to test ok--------

T



stockfish
New User

Jul 12, 2008, 5:02 PM

Post #3 of 3 (7024 views)
Re: 96 saturn misfiring runs rough when hot Sign In

Thanks for the info. I switched a couple injectors with no results. After testing continuity from the ecm to the injector plug (OK) I did another compression test and found that the #2 cylinder that is missing is now only getting 20 psi compression. I wonder if the can of carbon remover I used opened up a bad valve. At this point I guess I will be pulling the head. I watched at the starter turned it over from the top with the valve cover removed and didnt see any problems from on top. Your info was helpful in finding the problem as I didnt think of another compression test as all 4 were ok 2 weeks ago.






 
 
 






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