Schokkie

I'm having a problem with my 88.
When hot the car almost doent want to rev beyond idle.
The car starts and idles fine 700 RPM), also when hot.
When in park i can rev it normaly after start. But under load it won't rev. even when put in park again.
When cold the car runs and revs fine. It happens when the engine runs hot. In my idea it is heat related and electric.
Fuel Pressure in "on" around 44 PSI, in run around 35PSI.
No error codes.
I am out of ideas.
Anyone can help with this issue?


Things i have done already:
Replaced spark plug, wires, distributor rotor, coil and ICM.
Replaced injectors to Bosch Gen III 22lbs. (was lucas).
Replaced O2
Replaced ECM for a known good one.
All to no effect.

Kevova

Check MAF sensor and relays. If you still have a cat conv it could be restricted. You could drop exhaust in front of converter and see if it improves.

THE 383 admiral

35psi. simply put. is not really enough pressure. at this point. you have a clogged filter OR a weak pump.
And you appear to be on a misguided parts replacement. without diagnostics.

Schokkie

Thanks for the quick reply.
My cat is empty (bought this way).
Engine is stock.
Other things i forgot to mention:
TPS is 0,7% @idle and goes up to 90% @WOT.
With Winaldl MAF output seems fine. (@1000RPM around 10 g/s)
ECT and IAT are good, temps are correct.


New pump is on its way.
I noticed it didnt hold pressure, its drops immediatly after 2 seconds in "on".
Car starts in 4 - 5 seconds.
When hot starting is difficult.

Schokkie

Ignition @6 deg.

Schokkie

Plug wires are new and org. AC Delco.
I even put the 2 and 3 cylinder cables in front of the distributor as the FSM says.

THE 383 admiral

Hold. ON. again. diagnostics!!! if your pressure drops Immediately. on a OE fuel pump system. this indicates you have a bad FP regulator. a weak pump. will not drop the pressure. the OE fuel system. has a check ball/valve it would typically maintain pressure for hours.

Schokkie

I tested the fuel pressure regulator.
I pulled the vacuum line, no fuel coming out and almost no gas smell.
When the car runs i get 35PSI pressure and when i pull the FPR vacuum it goes up to 45PSI.
So the fuel pressure regulator should be oke right?
I think the check valve in the pump is broken and because i have around 35PSI when running i am replacing it anyway.

THE 383 admiral

Unlikely. but possible the fuel pump. check valve has failed.

antfarmer2

Might be the pulsater or the hose to replace it or the sock.

Schokkie

I will check this tomorrow.

Kevova

This is all when condition occurs: If you have a spark tester I would check to be sure there is adequite spark going plugs. How does MAF respond with throttle. What does O2 sensor read and cross counts? INT/BLM ? If you unplug regulator how does engine run with 44psi?

THE 383 admiral

these are great suggestions. 35lbs is to low. there is a problem at fuel level. especially. Schokkie mentioned> "in run around 35PSI". does this represent below 35??

Kevova

If lack of fuel volume or pressure is the issue; the O2 and INT/BLN will indicate lean condition. If running engine at 44psi corrects condition then the fuel system. I would agree it's all fuel system. But his concern is only when hot so I would look at a few things first. OP has winaldl and a fuel pressure gauge...spark tester? poor or weak spark tends to happen as ignition heats up. My suggestions should only take a few minutes after car starts acting up.

Schokkie

indeed good sugestions i will see what i can check tomorrow.
I dont have a spark tester, only a timing light.


Could low fuel pressure really be the culprit?
The problen occurs even when i slightly touch the gas pedal.
I can only drive in @idle.
Anything off idle and the cars tries to die.
I cant even peddle it.

Schokkie

I can use Winaldl.
BUt when i connect the cable (with 10K installed) the revs go up to 1200.
Without the 10K i get no data.
Winaldl doesnt give me results in the tables.
I can only see live data and error codes.


I dont have any lean conditions shown in the error codes.
BLM stays around 128 but i will check tomorrow.

Schokkie

I also have this problem when i disconnect the MAF so the car is in limp home mode.


Does disconnecting the EST wire test/prove anything?

Kevova

Disconnecting timing connector takes away advance, and on some cars ecm will go into "set timing mode" which can effect Idle speed. Was anything done or happen prior to this condition? Can you clarify how car runs cold? is it driveable?

Schokkie

Update.


I tested the car again this morning and the problem also occurs when cold, i was mistaken.


I took the vacuum off the FPR and problem still exists so it should not be a fuel problem right? also i dont have black smoke from the exhaust.


I put back the old distributor cap/coil --> no effect.


I removed the fuel pump and the check valve is broken. I can blow trough the pump from both sides. Pulsator looks oke, no cracks or anything.

THE 383 admiral

OK. now you are validating with diagnostics. the check valve. only HOLDS pressure. I can assure you!!! it is NOT needed. high performance pumps. do not have a check valve. however they are much stronger pumps. producing more volume. this would change the way you start. it would REquire. instant keyon. to start. after the prime shot. there is NO pressure. once started a GOOD pump. will maintain the regulated pressure. your pump is weak!! I have installed. check valve free pumps in my last 3 cars.