Thread: Misfire or stumble at high RPM

^^^^ his problem was the maf,if you read all the posts
http://www.sr20-forum.com/turbo/17129-problems-full-throttle-3rd-gear-6500-7000-rpm.html#post229054

Thanks though,I will try the coil too,I have spares here.

Yes, I think it was the loose ground wires that connect to the intake manifold, including the MAF.
I forgot I tightened that down at the same time I swapped coils between my N/A and turbo car.
Still swapped and both are running fine.
Must have been the loose ground wires.

You can check the resistance on the coil.
Should be 1 Ohm terminal 1 to 2
Should be 10 kOhms terminal 1 to 3
Terminal 1 is on the left, Terminal 2 on the right, when looking at coil connector with locking tab on top.
Terminal 3 is coil wire connector.
If it's heat related, you may have to check this hot / when it's running bad.

Power transistor test is too complicated to post as text, lol.

Swapped a known good maf...no change
known good coil ...no change
My dizzy was leaking a little oil...changed that...no difference




I have replaced the PTU before on this car it was getting hot and quitting.It even tested good...I just changed it because I was out of options at the time.
I am really thinking this is a fuel issue now.
I noticed that the FP gauge(which is new,too) is fluctuating by like 5psi.
It is fine when I first start the car and ok for a while.
It seems like it does this when the car is acting up.

It is just like when you run out of gas...Almost like the fuel pump cant keep up??
Is it possible that the FP has lost some of its capability,or it is getting hot?
It seems like this problem started happenning with lower fuel.Now it does it on a full tank,too.I thought it was maybe the pickup in the tank or something.

I have also read about voltage probs with fuel pumps,and addind a relay to them.Could that be the cause of the fluctuatig pressure?
I guess today I will pull the fuel pump again ,and see if there is something obvious there....

This sux..I can drive the car anywhere at a normal cruise,but cant rev it out.
This is getting real frustrating.

You said the problem went away with new plugs.
Were the plugs you removed fouled?
How long did it run good with new plugs?
Was it just a coincidence and the real cause is a bit intermittent?

Did you check the ground for the MAF?

You said you were going to put a new cap/rotor on - did you?
If not, remove it and check the contacts.

How about all connections to/from battery and alternator?

Couldn't hurt to do this:
http://www.sr20-forum.com/general-sr20/18000-nismo-afpr-leaking-vac-minor-fix.html

Is your intake piping mounted well, particularly the MAF?

If you re-fueled and got a tank of really bad/dirty gas, maybe it plugged the filter, even though it was new(er).

Like you mentioned, maybe the fuel pump wiring/connections are bad, or the pump is failing.

Well,I got this car after it sat for 6 years,so I had to clean the tank and replace the fuelpump before the swap.I changed the fuel filter again after 2500 miles.So I started having these stumbles when the gas was low.I figured I was maybe having a pickup issue or something.
Eventually it got to doing it with a full tank.
Yesterday,I pulled the pump out again,and the sock was packed full of doo-dooI cleaned it out again.The part where the sock filter sits in the bracket was nasty again.Inch thick of crud.
It seems to have helped ,I guess I need to change the fuel filter again,and plan on doing a tank cleaning a couple more times.

Thanks for the help,I will keep updating as things happen.
Today I filled up took a 50 mile trip with no problems,although I only revved it hard a couple times.
It runs flawless,no misses,perfect idle,etc,aside from the weird stumble up top hat has surfaced.