85 2M4 Misfire, help would be appreciated (Page 1/3)
Klyde7_2M4 OCT 04, 09:58 AM
I have been searching through the forums of this place on misfires for months, and no matter what I've done my car still misfires, it is an irratic misfire

The tach still bounces, I'm pretty sure it's when the missfires occur, not before, I've had the new icm tested and it passed

What I've done

Wires, plugs, cap, rotor, icm, pickup coil

Fuel pump, fuel filter

Timing

New 02 sensor

Also have played around with the plug gap

If I think of anything else I'll post
Klyde7_2M4 OCT 04, 09:59 AM
Just remembered more Important info

The car missfires during idle and trying to maintain speed, car shudders

Acceleration is 100% okay
Klyde7_2M4 OCT 04, 11:13 AM
Did have low fuel pressure from older pump, replaced pump, to a OEM pump and reads 90 psi (aware that is a **** ton and I know it should be around 9-13) that's just the pump with the ignition on, no idea how to test it with car running

Tested with a 20 psi gauge first, that completely blew it out of the water and it broke, put a nicer gauge on it and that's how I got the 90 psi (・o・)
Gall757 OCT 05, 05:10 PM
If you really are producing 90 psi with that pump, it's dangerous. Get another one.
Patrick OCT 05, 05:24 PM

quote
Originally posted by Gall757:

If you really are producing 90 psi with that pump, it's dangerous. Get another one.



Agreed. Trying to troubleshoot an engine issue while it's running 90 psi fuel pressure when it's supposed to be 9-13 psi is pointless... if not downright dangerous.

[This message has been edited by Patrick (edited 10-05-2021).]

buddycraigg OCT 08, 08:36 PM

quote
Originally posted by Patrick:

Agreed. Trying to troubleshoot an engine issue while it's running 90 psi fuel pressure when it's supposed to be 9-13 psi is pointless... if not downright dangerous.




I second that.
I am not talking to you when you have 90 PSI on a 4 cylinder engine.
NY_FIERO OCT 14, 03:12 PM
The year was 1998... i had a silver 2.5 with the isuzu 5 speed. I had the same symptoms.. I went to a junk-yeard... pulled the ecm from a buick (whatever it was) with a 2.5. Put it in and it ran flawlessly. It seems strange but true.. the buick was even an auto....

[This message has been edited by NY_FIERO (edited 10-14-2021).]

NY_FIERO OCT 14, 03:49 PM
And yes... resolve the fuel pressure issue first... are you certain you're not talking 9.0 lbs? not 90???
RWDPLZ OCT 14, 05:58 PM
Replace fuel pump with proper one, then replace coolant temp sensor for the ECM (there are 3, usually the one in the thermostat housing), and rebuild/clean the TBI.
Forrest OCT 18, 02:45 PM
Could it be a faulty fuel pressure regulator?
Get them on ebay...they are cheap. $20 as opposed to $87 from the parts stores.