couple of questions

[E30 B27]

#1
my car seems to be missfiring ill hit a certain rpm and itll fire funny or there will be a delay or something, and it violently jerks. what could this be?

#2
Im looking into bigger fuel injectors. i heard the mustang ones fit. i called all the auto shops and gave them the part number and they say they cant find it like that. so what year and model mustang injectors fit?

Thanks

[jlevie]

Does the tach needle drive towards zero when an event occurs? That would be a sign of a problem with timing data from the engine or a problem with DME power or ground. If the tach doesn't move but the econometer drives towards zero there is a fuel system problem. If working properly there is no reason to install larger injectors.

[timninja]

This is the same problem im having and I found my injector o-rings where bad,I haven't replaced them yet but when I do ill tell you my results,I also did a valve adjustment stone cold,.08mm intake valves and .010mm then changed all my spark plugs.if you figure out the issue let me know lol

[E30 B27]

well it only jerks while its in gear, if i throw it in nuetral it revs up fine, nice and quick like always. and it doesnt really start jerking until it warms up. if its cold it drives fine. i know there is some play in my flywheel, maybe this would be a cause too? im gonna check my injectors though, im pretty sure they are old as hell. as for spark plugs those are fairly new, got about 8 months on them. ill take them out and re-gap them and make sure they are firing.

as for the injectors. i want some 19# ones. im upgrading the head to an i head with a 288 cam so i figure i might as well go all out with injectors and the m30 MAF as well

[BMWManiac]

So your problems occur when your engine is under more load....sounds like a ground or battery having issue providing enough juice to your distributor....or your distributor/spark plug wires/cap and rotor....somewhere your electrical system is not meeting the demand to fire off your spark plugs

[E30 B27]

^^^ This actually sounds plausible... cause it only does it in gear. but its not like im pushing the motor. i could be babying it and itll still hiccup and jerk. it makes me feel like an idiot when i driving.

[E30 B27]

i mean i got a tune up about 8 months ago and they replaced everything but the coil and injectors.

[BMWManiac]

Make sure you have the correct spark plugs too....check the white, silicone around each plug. If they are cracked, they could cause arcing on the walls and cause misfires too.

[E30 B27]

thanks thats a lot of help. ill check that tonight after i get off work

[E30 B27]

update: drove it after work and the tach need drives towards 0 whenever it does that misfire. it shoots back about a 1/2in then pops back up.