97 J30 still sluggish AFTER KS replacement -- what's next?

[Pogophil]

My dad's 97 J30 is still sluggish, even after the KS replacement. I'm looking for next steps.

The history: the car was sluggish when recently purchased. OBD2 gave the knock sensor code, so we planned on replacing KS to fix the problem. We replaced the KS, the code went away, but sluggishness remained.

We're using 93 octane fuel, so I don't think the ECU should be retarding timing to rob power. I also replaced plugs specifically with stock NGK plugs to avoid any problems. No other codes exist.

Here's what I'm thinking would be next:1) fuel injectors2) MAS3) fuel pump4) compression test

Can anyone assist? Thanks in advance!

[driverdriver]

Welcome to NICO!!!

Is the knock sensor still kicking out a code?

[yodawill2000]

He said the Code went away.

I would clean the MAF itself AND its connectorfirst.Cheap and easy.Be sure and use ZERO residue contact cleaner to clean the MAF thermistor.

[Pogophil]

No knock sensor code anymore, after changing it. I made sure to check to ensure the code went away.

I'll clean the MAS and connector, and I'll repost.

[elwesso]

Next place I would check is fuel pressure. SHould be around 40PSI at ALL Times. Tee it in so you can watch the gauge while you drive.

[NismoChi]

Well, i would suggest you to check the timing using a timing light, since you purchase the car not too long ago, may be someone did a timing belt job incorrectly. I am getting a feeling that it is more of a ignition problem than a fuel problem, bad coils or bad power transistor are pretty common on nissan cars.Just think of one more thing, When was the last time you replace you fuel filter?
Modified by NismoChi at 12:31 AM 7/29/2007

[Pogophil]

Ok, to summarize what has been recommended so far:

1) MAS air flow sensor2) Fuel pressure3) Timing, ignition coils, fuel filter

I cleaned the MAS with a good electrical cleaner. I took it apart and cleaned liberally in several places, including the actual sensor, the connector, and the inside of the piece on the side of the MAS. When I put it back together, the car died several times -- it wouldn't start! Finally we got it running, but it stumbled quite a bit. I'm getting a P0100 code (MAS). Could I have killed my MAS by cleaning it with electrical cleaner?? I didn't have any problems with it before. I've used the same electrical cleaner on my Lexus with great results.

Regarding the t fitting on the fuel rail - is there a write-up on that? I do have a fuel pressure gauge, but I'd need a write-up to complete this job.

Similarly, I have a timing light. Is there a write-up on checking timing on the J30? (Or perhaps on the 300ZX?)

Thanks in advance.
Modified by Pogophil at 2:53 PM 7/29/2007

[Pogophil]

Ok, whew....

There were three prongs going from the MAS to the connector that I pulled out (four small screws hold this piece on the side). I noticed there wasn't a good connection when I put it back in, so I bent the three prongs upward to ensure a tight connection -- all was fixed.

No more stuttering, no more P0100 MAS code, and for now, no more sluggishness! (Or, at least, it's now tolerable.)

{{Edit: the sluggishness is still very noticeable with the A/C on, but tolerable otherwise.}}

A big thanks to all who posted here!

Now, onto my other issues, ABS and the Bose stereo....
Modified by Pogophil at 6:16 PM 7/29/2007