Tell me if these readings make any sense

[sal_park]

left field suggestion: how are your VANOS seals ?

http://www.beisansystems.com/products.html

after reading up on this I'm 99.9% sure mine are shot and need replacing. The reason I suggest this as a possible reason is that the VANOS piston should be energised / under pressure when the engine is below 3k, but if your seals are worn out it won't be and hence the engine will react differently (less torque etc), possibly causing your problem.

just a guess though...


sal_park

[whiskychaser]

Apologies for the late response. I agree that the pump can deliver around 70psi but it doesnt operate at that. Bentleys says you are looking for 51psi with the fuel pump jumpered ie. engine not running so there is no vacuum. When the engine is running the vacuum on the FPR reduces the pressure. So yes you are looking at about 43 psi.
The quick pressure loss obviously isnt good and needs addressing. But IMHO you have the correct pressure when the engine is running and thats when you are experiencing the problem
I think you originally said it was deceleration to idle hesitation and wonder if you would clarify what exactly happens?

[BennyM]

Apologies for the late response. I agree that the pump can deliver around 70psi but it doesnt operate at that. Bentleys says you are looking for 51psi with the fuel pump jumpered ie. engine not running so there is no vacuum. When the engine is running the vacuum on the FPR reduces the pressure. So yes you are looking at about 43 psi.
The quick pressure loss obviously isnt good and needs addressing. But IMHO you have the correct pressure when the engine is running and thats when you are experiencing the problem
I think you originally said it was deceleration to idle hesitation and wonder if you would clarify what exactly happens?

While that contradicts what Ross was saying, it does make sense. FPR seems fine except for the leaking part. So, I guess we'll know for sure how bad the it is once I put the new one in.

To clarify, when the engine is hot and the DME switches over to closed loop mode, I get a 1222 code. The engine behavior is pretty solid at idle and when given gas. The only real problem is that it runs rich and when the engine is DECELERATING from higher RPMS, it will just about die. RPMs drop to 500 or 600 and then it spikes to 1500 and then down to 700 and then up to 900 and then finally resting at about 800. This only happens when it's hot and when I let off the throttle. It's instantaneous too. It's not like it gradually gets worse as the temp increases, it's like a switch flips and suddenly that transition back to idle is very unstable.

Thus my conclusion is that the closed loop mode is unachievable right now. So, so far I've replaced vacuum hoses, seals, o-rings, and will soon be doing the sensors.

Thanks for your help.
BennyM

All of this ties into my original post on the issue:
http://www.bimmernut.com/forum/showthread.php?t=41790

[whiskychaser]

A bit of bedtime reading for you :-):
http://www.lambdapower.co.uk/diagnos...c_index.asp#q2
http://minimopar.knizefamily.net/fuelsystem.html