My problem started about a month ago when I noticed as soon as the engine warmed up (I guess when it goes into closed-loop) it would shutter and buck like it had a dead-missfire. It feels like a bad TPS when you start to accelerate from closed throttle, it strumbles and goes away instantly. I checked the TPS and my readings matched the ones in the Chilton manual-not the issue either. It does not surge on a cold start up, only after I drive.5 mile. If I race around the gears, it is not so noticable. It lightly feels like a "quick slip or bog" when I shift at higher RPMs. Regardless, it feels like doesn't want to perform.
So my mechanic friend and I checked the ignition coils by GROUNDING OUT the each terminal with a screwdriver to determine a bad fire. None found. The ground test ruled out bad coils and resistance checking the wires was excellent too. (SALTWATER testing the ignition system ruled out any arcing of spark to wires, coils or ignition module) I checked the ignition module connector for corrosion at the terminals (beautiful like new). My mechanic friend suggested replacing spark plugs -due to thermal breakdown- so I did anyway (my new ones only had 10k miles).
I took the cheap test by replacing the crankshaft sensor (and still did not fix it).
We checked fuel pressure also. 55-60 psi normal-not the fuel pump. Checked fuel pressure regulator, no fuel leaking and RPMs increased with vacuum hose pulled- nope not that either.
Then I started unpluging items and took short test drives to rule out the operation of the MAP sensor, EGR valve, and ECT sensor, IAT sensor, and oxygen sensor. Each unpluged devices did not affect the shuttering or surge problem.
Today 5/17 --- I decided to unscrew the primary O2 sensor to check the restriction of the catalytic converter and take a quick drive - still shuttered like before! WHAT DO I DO NEXT?
I am probably going to kick myself if you suggest something basic to resolve this problem. I have read countless forums about Saturn owners and their problems. None of which have given this much detail of the problem they are trying to diagnose. I hope this is enough information for you to grind out a solution.
THANK YOU AND MUCH RESPECT TO YOU EXPERTS THAT CAN DIAGNOSE MY ISSUE. Jason
have the same problem?
Saturday, May 17th, 2014 AT 11:17 PM