Another J30 Stalling Post! Help!

[BrazilianJitz]

I recently sold a '93 J30t to someone after owning it a very short time. I drove the car only twice and didn't have any problems with it. Car has 140k miles on it. The car stalls after at least 30 minutes of driving at red lights or stop signs. It will start right back up but have to keep giving it a little gas so it won't stall again. No check engine light and only stored issue is the knock sensor. Here is one thing I have noticed that is different with other cases and that is the car will not rev past 4k rpms wether its warm or cold. Runs and drives great up until it gets really warmed up. I have already replace the ect sensor and cleaned off the maf sensor and the throttle bodies. There are already a million threads about cars with similar problems but none have the limiter on the revs like this car and it seems everyone just starts replacing sensors until the problem is fixed. Anyone have any ideas of what to do next. He said he took it to a mechanic and said it needs a fuel pump but that doesn't seem to fit. Any help will be appreciated thanks guys.

[yodawill2000]

First off
Welcome to NICO !!!!

There are several things that can cause the stalling but not getting past 4K is quite odd.
The knock sensor is ignored after 3K so we can eliminate that.
Has the Fuel filter been replaced ?
If I recall there is three stages of flow from the fuel pump.
If the FPU is defective it might cause this.
I would think 4k is when the FPU is in WOT mode. (Highest fuel pressure).
Only way to rule out fuel is to T off a fuel pressure gauge and see if its within spec.

In case you don't have the FSM here is the link to download.
http://www.nicoclub.com/FSM/J30

[driverdriver]

Could be either fuel pump sending unit or revolution sensor (does the transmission shift?).

Have you pulled codes yet? It will help in diagnosing the problem.

There is a "sticky" on the forum, that explains how to do this.

[BrazilianJitz]

Only code on the ecu is the knock sensor. I didnt think it would be the fuel pump since it works fine for 30 minutes before acting up. My next guess on the car would be the IACV. I am gonna take it off an clean it out and see if it helps at all. I can also do a fuel pressure check on it next time I am able to work on the car.

[yodawill2000]

"car will not rev past 4k rpms wether its warm or cold"

That's what made me ponder the pump.

A crack in the knock sensor will work fine till it heats up and the crack opens up.
Common on the J's.

[devis]

I had the same problem. Warm or cold it would die at full stops. It would start back up without an issue though and be good for a while. No trouble codes from ECU.

Not exactly sure what fixed it... It was about time for a smog, the guy who I took it to get it smoged said there were multiple issues with it. So I took it to Mr Kim, my friend's mechanic, who's also a test and repair station. He did things... fluids mostly... and I remember he also changed the spark plugs. No idea what he did in detail, but not only did he make it pass smog, he eliminated that very issue as well. When I first brought it in he said he'd make it pass but I'd better think about selling it soon. After he worked on it he tells me to hang on to it.
I'll ask next time I see him.