Hi Scotty! I have a 1989 Grand Marquis and that has a specific, difficult-to-test problem. When I…

Bayou50

Hi Scotty! I have a 1989 Grand Marquis and that has a specific, difficult-to-test problem. When I start the engine, It revs up and then immediately dies about 2 seconds after starting. On starting it again, after this, it stays started, but the engine will idle really low and act like it wants to die for about 15 seconds. This issue only happens under these conditions: The engine must have reached operating temperature and then shut off, then be restarted after 20-40 minutes. Any other time (cold start, Warm start) it will not do this. The car is Fuel injected and the fuel-air mixture and idle speed is computer-controlled. I have used an EEC-IV code reader to scan the computer and have always gotten code-11 (pass) on both the KOEO and CM tests. However I did get a code 12 (idle RPM out of range-high) on the KOER test once, after cleaning the throttle body and IAC valve that code has not come back up. I have done the following things as a part of its 30,000 mile tune up in the past week: Changed the oil in the Rear Differential and Automatic transmission, Changed the fuel filter (this was very constricted compared to the new one I put on), Changed the spark plugs, Replaced the Distributor cap, rotor, and ignition wires. I also changed the air filter (the one that was in there had a date of 1993 written on it) and flushed the coolant system. I didn't do all this stuff to try to fix the problem, I was going to do it anyway as a part of standard maintenance.My Haynes manual says that there may be a vacuum leak around the intake manifold, and that is what I was thinking about trying to troubleshoot next. Or Maybe its a bad IAC valve? I can confirm that the IAC valve does actuate, because it will frantically open to try to keep the engine from dying the second time that I try to start it. Sorry for the long post, and thank you!

Comments (2)
No. 1-2
Bayou50
Bayou50

I forgot to add that the car only has 47000 miles on it, Could the injectors be worn out with only that many miles? Or do you think that age has just gotten to them? The IAC does have a good deal of carbon on it that I can't get off. Also even when cold starting the engine idle speed will fluctuate for the first minute or so then smooth out and run well.

ScottyKilmer
ScottyKilmer

Editor

try a new iac valve and have the fuel injectors pressure cleaned by a pro, could be vaccuum leak OR just old worn out injectors