Running on 3 Cylinders

[aidanair]

I made a thread about a year ago about this issue. My 90 TT-z, while driving one day, kicked two cylinders and started running on 4. Swapped plugs, coil packs, tested spark. Put all new pigtails on (all my originals were stock and corroding) and that didnt help. Did a compression test and threw 150 on all cylinders. Leakdown was good. Swapped PTU and good. My next guess is injectors. I have 740cc deatschwerks that Ash Powers installed for me 2 years ago. Any other ideas on where to look/whats the best way to check injectors? Ohming and screwdriver to the ear test? Swapping around?

[BigTDogg (MA)]

Ohming and screwdriver to the ear test?

Start there, and pull codes on your ECU.

Did you do a power balance test to determine which cylinders are dead?

[aidanair]

Power balance test? I literally could just pull the coil pack connector off the cylinders and see which ones caused no change in the idle. And my ECU is throwing a code for knock sensor, probably because of the fact that it is running on three cylinders.

[aidanair]

So, screwdriver to the ear revealed the dead cylinders aren't firing the injectors. No sound came from them while the rhythmic clicking came from the good ones. Ohmed them, they all read 12 ohms about. Voltage to the injector read about 14 volts. I put 12 volts directly from the battery to all the injectors, and they all opened and clicked the same way. I'm puzzled at this point. I swapped ECU's with a buddies, same misfire so it isnt the ECU. I'm going to run a direct line from the ECU to the injector on Saturday to see if that fires it (to see if there is a problem in the EFI harness).. thats about all i can think of, maybe theres a short in the wire causing it not to pulse correctly. God I wish Ash Powers lived near me

EDIT: PS, idk i this has any impact, but the cylinders are #3,4, and 5.

[inlowm523_90tt]

Maybe its timing? Or a the ground came loose for wiring harness. There are three grounds at the back of the intake.

[datdude407]

Im going through the same problem on 1 of my cars, but its just cylinder #3. I have just determined that it has to be the harness. Im going to split the loom and trace the way back to the fire wall & replace it to see if in fact it is the wiring harness. everyone that I know including Ash, Adam & Nick (all from under the Ashpec umbrella) say they have not incountered this before

[Zero to 300]

If you haven't found the problem yet check out your PTU, i had a problem where 4,5,6 cylinders would cut in and out and finally just went out without ever coming back, running all the wires back to source i found that my connector on one side of the PTU was off because the metal clip was bent out of shape.

Depending on what PTU version you have it's best to test the output from it, the bigger ones are prone to the problem but check your connections and all that good stuff. Hope you find the issue.

[datdude407]

My problem was a old fuel injector connector. I replaced it & now I'm on all 6! The Z is a dream to drive. 1st time that I have driven the car on all 6 & she doesn't get awful gas mileage anymore

[minlow88]

Glad you got her fixed.

I'm having a similar issue. The car will just randomly start to mis-fire while driving. It will come back within like 10 seconds.But it is starting to do it more consistantly and for longer periods of time. It I shut her off, and then start it, she is as good as new.

I have ran codes, ohmed coils and injectors. Gonna test ptu next.

Car also may be slightly out of time. But idles real smooth.

Its driving me crazy.

[aidanair]

Last thing I am trying is I will run a wire from the ECU to the injector directly to see if that is why the cylinder isn't firing. It is getting correct power, and when given 12 volts, it clicks open correctly. however, during normal operation, the 3 cylinders' injectors do not make the proper clicking sound. I have heard bypassing the harness is a good way to see if the main EFI harness is the problem, so i will try this and report back.