V8rough running

[Andy777]

my v8 runs rough and missfires after about 20mins of driving also it only boosts to about half the normal amount. the car will then run the same the next day but it missfires straightaway, if you leave it for about a week it again takes 20 mins or so to play up. I've replaced a faulty coil pack the ignition leads spark plugs and a split vaccum pipe and its still the same. Anyone got any ideas??

[ErnestM]

You may want to have your timing belt checked. My understanding is that the ECU monitors timing an retards or advances based on what it sees. Your symptoms sound an awful lot like it's time for a check...

ErnestM

[egomes]

Andy-

My 2000V8 also did the same. I replaced my spark plugs then went back in and cleaned up the wires with some WD40 and vacumed and cleaned out the plug cylinders. I reset my ECU and it wasn't till about my 4th full tank of gas that ALL symptoms went away. It now idles better and NO misfiring... Not sure if this is what's happening to you? Mine would misfire so bad that ANY acceleration would bring the LOUD pops from the exhaust.

Ed-

[Andy777]

thanks yes the timing could well be a cause of the problem, would the engine not run badly all the time if the timing was out? because some of the time mine runs ok!

[Andy777]

egomes,

so how do you reset the ecu? is it a simple process, also where is it?
cheers

[Skerd]

If it is the same as on the 4 cylinder cars, just pull out the two ECM fuses in the black plastic fuse box by the battery. Leave them out for 30 minutes, put back in, done.

[egomes]

Andy-

It is the box in front of the battery. Remove the 5amp fuse (B2) for about 30min. That's it.. Afterwords, allow the car to idle until at 100 then allow for the fans to kick on. Drive the car through all gears and turn on the AC several times. It will learn about 2full tanks later and run better.

Ed-