Son's 88 running on only 5 cylinders (original post)

My son just rebuilt his '88 engine this winter. Now he has it running.....kinda. It is missing on three cylinders. The plugwires and plugs have been changed, the injectors are new and will work when placed in other cylinders. He can change the injector plugs (It is a batch fire setup) and that makes no difference. The valve lash has been adjusted/readjusted and the movement of all the rocker arms have been measured and they are all opening the same amount.

|UPDATED|7/4/2012 8:41:19 PM (AZT)|/UPDATED|

by any chance has he checked for any codes  that the ecu might have put out. i would check the wires  first. even though they are knew never can tell you might have gotten a bad set. would also take an inductive timing light and check each wire from the cap to make sure each is firing. few basics would be to check that the wires are in the right order and on the right place on the cap. just a few suggestions.

dave

No codes. Used old wires first and then new wires second. Checked, rechecked AND rechecked that wires in right place and firing order. Haven't used the timing light yet. He updated to ram-air and larger injectors during the rebuild and he has checked and rechecked all of them. It also has a mild cam added.

BTW: Thanks dave/eddie for getting me back in here to add a title.

did he run a compression test on the cly... that are not fireing .

Is it a steady miss at any rpm ? Or does the engine seem to smooth out once you come off of idle ? I would check for a vacuum/intake leak...EGR valve partially open etc..... if in fact it does clear up at higher rpms. I wouldn't think ign. timing would cause it to drop 3 cylinders unless it was wayyyy off      JMO

It is a steady miss all the time. He just took the intake off and resealed it yesterday and no go. He's taken it to a shop to see what they can find.  I hope it is just something super simple that we haven't thought of.

I remember reading on another thread that compression had been checked and ok. Since the plugs and wires have been changed...firing order checked and rechecked...injectors are new and also checked and rechecked...i'm guessing the dist. cap has also been checked and/or replaced.

I got a cap that was defective once...check the cap for continuity