Running on two cylinders

[EM.TT]

Heres the situation:

-Starts, runs normal. But on 2 cylinders.
-Let in run, pulled coil pack connectors and found its the #3 and #6 that are fine.
-Swapped coils around: Same two cylinders were going.
-Pulled a spark plug and it wasn't wet.
-Tested injectors: They all read 12.5 ohms (good I think?)
-Compression is in the 150's for all cylinders.


Im not sure where to go from here. PTU? The wiring harness is new as well so all the connectors are good. Any input would help!

Thanks

[robomatic12]

I can't believe it runs on only 2 cylinders, I've seen it running on 4 and it isn't happy at all.

Have you checked all connectors for corrosion anyways even with a new harness, if not protected they can corrode quickly? In particular the injector, coilpack and PTU connectors.

Do you have the series 1 ptu with the silver heatsink on the back?

[EM.TT]

I know thats what I said when I started it! But it's a newer PTU. The harness for the PTU looks older than the rest of the main harness so im thinking maybe that's my next step but im not sure. I have the old ptu that came with the motor, should I swap them out or would that not do anything?

[robomatic12]

The PTU conversion subharness is a common problem for corrosion, try wiggling it with the engine running and see if some cylinders pick up.

Mine was bad, a couple times if I went over a bump too fast it would jiggle it and a cylinder would drop off. I solved this by soldering the subharness together eliminating the old style connectors that belonged to the older series PTU. Perhaps this could be your issue too

[Ace2cool]

I gotta see a video of a V6 running on 2 cylinders. I would suspect either the PTU or the CAS, FWIW though.

[EM.TT]

So I just put a new PTU and sub harness in and it did help, but only for a few seconds. I started it and it ran normal or on at least five cylinders for a couple seconds then cut back to two... Im so confused! What would adjusting the CAS do? In this situation.

[robomatic12]

It would be more of a case of checking out the CAS with the procedures found in the 300zx service manual, or checking with a known good CAS from a running Z.

[EM.TT]

Ok, Ill give that a shot. Is it possible that I have bad injectors even thought they all tested out good?

[EM.TT]

Could this be from the timing belt? installed wrong?

[robomatic12]

It is possible that the injectors are stuck closed, but the actual electrical part of the injector is okay.

Timing belt being off would not cause cylinders not to fire, well as long as it has not slipped and damaged valves.

Check your fuel pressure after the fuel filter. Pull all the spark plugs and check if they are wet or not

[Chattzx]

I gotta see a video of a V6 running on 2 cylinders. I would suspect either the PTU or the CAS, FWIW though.

Haha you beat me to it Ace, I gotta see this thing running on 2 cylinders. I've seen a VG run on 4 and it was not a happy sound.

[EM.TT]

I would've taken a video for you guys but I got the damn thing running! It turns out some of the 555's were testing good but not flowing so I just swapped out my fuel rails and put the oem set in and it fired right up. But now I have another quesiton...

The first couple days it was running at like 13 psi according the the factory gauge, but now when I boost it stays right at ten (which is where it's supposed to be..?) and it whines almost like a super charger. Any Ideas? Boost leak? I haven't investigated the problem much but I just wanted to get a second opinion

[robomatic12]

If it's making more of a whistling noise than normal under boost suspect a boost leak for sure.

[EM.TT]

Ok, what does it sound like ( if it sounds any different) when a turbo goes bad? or what happens?

[robomatic12]

They can make all different noises when they fail, they can be a strange noise almost a whine when boosting, or a squeel if there is metal to metal contact. If the seals are gone they will blow blue smoke out the exhaust. You may not be getting any boost, or a low amount of boost.

Why do you think the turbos are blown?

[EM.TT]

Well for one thing they match the supercharger whine and loss of power.. and I could spin the tires just rolling on the throttle in first and now I can't. Is there a way to find out which one it is? one that doesn't involve an engine stand would ben nice lol

[NolimitZ32]

Pull the downturns/downpipes off and see if one of them feels stiff or has too much play.