View Full Version : SC Stalls When Let up on Throttle - Idle Or Drive

02-23-2011, 05:06 AM
90 SC - 245,000 miles - Daily Driver

I recently had an alternator and all belts replaced when I drove the car for 40 miles with the battery light on. It bucked and stalled at the end and would not re-start. Prior to this at least once a trip for 40 miles for 2 months the car would buck randomly and want to stall out if it was not feed additional gas at idle or in gear. I was just living with that.

Now it is at a point it will stall at idle or in motion all the time unless extra gas is feed. Actually I had to restart the car several times while in motion (at night!) just to get it home when I could not feed it gas (going down a mountain, curves, etc.) Too dangerous to drive now.

Could this be related to the alternator replacement? Fuel pump? Vacuum/sensors or worse?

There was some diagnosis on this when the alternator was replaced but it could not be solved. From their doco the engine misses/runs rich. They tested the ignition and emissions systems with a lab scope. Also tested MAP sensor and checked for vacuum leaks. They believe it is a possible internal engine problem/timing issue. This was not a Ford service shop and note the word POSSIBLE. I'm thinking a Ford dealer is my next option if I want to keep this car.

Update - Sat 2/26. The Ford dealer did a vacuum test and found a leak at the upper intercooler tube. I'm not sure if when the alternator was replaced if this tube was removed. They are waiting on a tube gasket E95Z 6F088 A. I noticed it is an obsolete part and was wondering if it is really needed for a tight connection. How do others tighten these tubes if the simple gasket is obsolete??

Final Update - Tue 3/2. The problem fixed by the dealer ended up being a leak at the inlet intercooler tube. They used Copper RTV High Temp sealant as obtaining the gaskets is a challenge. The question to me is how did it get loose. Was it loosened to replace the alternator and not retightened properly or did it just loosen from usage and high mileage. In summary if your car will not run at idle or in drive and it wants to stall as soon as gas is not feed even in motion check for leaks at the tubes.

02-23-2011, 10:12 AM
I can't think of anything internal that would cause a intermittent miss. Usually when something breaks internally it's permanent. Vacuum leaks are not usually intermittent. I would rule out fuel and ignition system by checking fuel pressure, wires and plugs. You can use a timing light to check injectors and plug wires. I would suspect a bad cam sensor, MAF, crank sensor, or bad harmonic balancer.


02-23-2011, 10:50 AM
I re-read your post and you didn't mention CEL. This would be a indication of sensor problem. Do a compression test to check HG, rings, piston, and timing components.


02-23-2011, 01:34 PM
Make sure to check your tubes leading to the intercooler and make sure they are tight! My SC was having the same issue (running like crap, no check engine light, etc.). I checked the tubes and the one coming off the bottom of the intercooler was only finger tight. I put a teflon gasket on it, tightened it up and the promlem was solved!

02-23-2011, 03:37 PM
Definitely check compression and fuel pressure.

If those test "good," then I would look at your ignition system. Could be a failing crank sensor or ignition module. Both of those can fail intermittently.

And, by the way, check that the harmonic balancer hasn't broken and shifted, which would feed bad data to the crank sensor, if it doesn't destroy it outright.