In Dec. I bought a 99 Vanden Plas with 43000 miles.
Restricted Performance and check Eng lights were on.
Diagnosed as 4 seperate misfires with the #4 as the only specific misfire.
I changed 4 ingnition coils as well as plugs. Rechecked and the #4 still misfires, other
3 are fine now. The Res Perf Light is on when I start car it rides rough for 10-15 miles then the light
goes out and stays out and the car runs fine till the engine is turned off for any given time and the same thing happens again.
Any Ideas?

 

well, there are many possibilities for the misfire. first off its to expensive to just guess, you need a consiensous Diagnostic tech who will have the right tools to figure this out. I would first use my Ignition scope to see if it is a ignition problem such as coil, ecu driver, internal engine problem, timing issue, dead injector ect. So the best way for me to diagnose is to have a diagnostic plan of attack, and have the right tools.

Good luck,

Master tech
vizcarra44

 

thanks for input.
going to test the fuel injector as well as swapping coil on #4.
by the way just changed front brake pads. had a hard time finding a 7mm allen wrench.
2 auto stores and a hardware store later found 1. this size is not included in standard set.

cbgb

 

How do you plan on testing the injector? with an OTC injector tester and fuel gauge to see if it drops the correct amount of pressure, or with a lab scope to see if it has an internal problem or to see if the Ecu driver is at fault, or may be test the #4 ignition circuit with Dvom or ignition scope. See this is what I mean, if you guess right then great, but if not, then it can get expensive and time consuming. I stress having the right tools to diagnose and diagnsostic plan. These cars are not your simple carbureated fords. Iused to work in the dealer and my expertise was diagnsotics, fixing the
problem right the first time around was my pleasure. I always recommend to have the shop foreman look at the car since he is usually the brightest
of the lot.