Bucking under Acceleration, not fuel pump/filter

modulation · Post by **modulation** » Sat Sep 19, 2009 12:09 pm

modulation wrote:#1. I used a Fuel pressure gauge. Fuel Pressure is at factory Spec.
44PSI when fuel pump is primed, and 44PSI while cranking. Still won't start.

#2. I got extra intake manifold off craigslist. Blocked off all emissions stuff.
Use idle set screw to set idle. All new gasket, used torque wrench and FSM specs/directions to put intake manifold on.

Same problem as before I redid the intake manifold.

The last time I did a compression test the car would idle, just buck under acceleration.

I did a compression test again and looks like I need a new head gasket..

Cylinders 1,3 and 4 were all ~180psi.
Cylinder 2 was at 150 psi..

I had changed plugs a while ago too.
When I took them out to do compression test, cylinder #2's porcelain was black, all the other cylinders porcelain was still fairly white.

modulation · Post by **modulation** » Sun Sep 27, 2009 11:19 am

My friend and I finished the head-gasket job today. Didn't fire up at first, but after he messed with the dizzy for 10-20 minute, and then it fired up and ran great.

Still gotta get the timing 100% correct, and need to buy a timing light, but at least it's running again, first time in a month or so.

I'm also a moron cause if I would've changed my oil like 3 weeks ago when I first started having problems then I would have seen coolant in it and wouldn't have spent time troubleshooting stuff that wasn't bad.
(FPR, fuel pump, and intake manifold.)

Peace · Post by **Peace** » Thu Nov 12, 2009 4:54 am

Very interesting.
I got same problems on my RB25DET.
It seems to work fine cold. As it warms up tit is like 1 cylinder not working. from 2500 to 5000 RPM at 5000 everything becomes better and at 6000 the car runs as it should at 6000 =)
AFR readings was as you describe - lean. I've did some adustments to maf input signal so the mixture is not criticaly low and a car is running but still its like 1 cylinder out of order.

Tried to change everything already, Coils, spark plugs, CAS, tried switching to MAP(i had neccesary equipment) to ensure its not a MAF problem, i was adjusting fuel pressure from 2.3 Bar on idle to 3 bar on idle. Nothing works mixture jumps lean randomly and car fail to work good.

i got no visible leaks of oil or coolant. And no smoke from exhaust (white or black)