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85 2M4 Misfire, help would be appreciated by Klyde7_2M4
Started on: 10-04-2021 09:58 AM
Replies: 22 (194 views)
Last post by: buddycraigg on 10-23-2021 11:11 PM
Klyde7_2M4
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Report this Post10-04-2021 09:58 AM Click Here to See the Profile for Klyde7_2M4Click Here to Email Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
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
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Klyde7_2M4
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Report this Post10-04-2021 09:59 AM Click Here to See the Profile for Klyde7_2M4Click Here to Email Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post

Klyde7_2M4

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Member since Jul 2021
Just remembered more Important info

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

Acceleration is 100% okay
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Klyde7_2M4
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Report this Post10-04-2021 11:13 AM Click Here to See the Profile for Klyde7_2M4Click Here to Email Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
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・)
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Gall757
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Report this Post10-05-2021 05:10 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
If you really are producing 90 psi with that pump, it's dangerous. Get another one.
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Patrick
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Report this Post10-05-2021 05:24 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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).]

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buddycraigg
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Report this Post10-08-2021 08:36 PM Click Here to See the Profile for buddycraiggClick Here to Email buddycraiggSend a Private Message to buddycraiggEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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.
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NY_FIERO
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Report this Post10-14-2021 03:12 PM Click Here to See the Profile for NY_FIEROClick Here to visit NY_FIERO's HomePageClick Here to Email NY_FIEROSend a Private Message to NY_FIEROEdit/Delete MessageReply w/QuoteDirect Link to This Post
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).]

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NY_FIERO
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Report this Post10-14-2021 03:49 PM Click Here to See the Profile for NY_FIEROClick Here to visit NY_FIERO's HomePageClick Here to Email NY_FIEROSend a Private Message to NY_FIEROEdit/Delete MessageReply w/QuoteDirect Link to This Post
And yes... resolve the fuel pressure issue first... are you certain you're not talking 9.0 lbs? not 90???
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RWDPLZ
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Report this Post10-14-2021 05:58 PM Click Here to See the Profile for RWDPLZClick Here to visit RWDPLZ's HomePageSend a Private Message to RWDPLZEdit/Delete MessageReply w/QuoteDirect Link to This Post
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.
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Forrest
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Report this Post10-18-2021 02:45 PM Click Here to See the Profile for ForrestClick Here to Email ForrestSend a Private Message to ForrestEdit/Delete MessageReply w/QuoteDirect Link to This Post
Could it be a faulty fuel pressure regulator?
Get them on ebay...they are cheap. $20 as opposed to $87 from the parts stores.
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Patrick
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Report this Post10-18-2021 03:28 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Forrest:

Could it be a faulty fuel pressure regulator?


Completely eliminating/plugging the fuel return wouldn't result in a duke fuel pump creating 90 psi of pressure. Something's wacky, but I suspect it isn't the regulator.

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Klyde7_2M4
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Report this Post10-18-2021 03:42 PM Click Here to See the Profile for Klyde7_2M4Click Here to Email Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
So I've replaced the fuel pump, did that yesterday, car is running a little better, not as rich, but still shudders could it be the ecm? I've tested for codes and it doesn't give out 55 whose to say that's supposed to work though lol

What ecm options do I have? Is there any aftermarket ones or better coded ecms than the OEM? Or will I have to get a remanufactured one?

Also thinking about rebuilding the throttle body, a hose died in the tank and had tube gunk in the old sock, could that have messed with the tbi?
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Gall757
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Report this Post10-18-2021 03:48 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
The ECM is probably fine. It's not smart enough to make a Fiero shudder.
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Klyde7_2M4
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Report this Post10-18-2021 03:53 PM Click Here to See the Profile for Klyde7_2M4Click Here to Email Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
More I can add

The car is missing on not any specific cylinder, it's erratic and across the entire engine checked the spark plugs and none of them were fouled or wet
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Patrick
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Report this Post10-18-2021 04:11 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Klyde7_2M4:

I've tested for codes and it doesn't give out 55


Perhaps more importantly, does it give a Code 12?

 
quote
Originally posted by Klyde7_2M4:

What I've done... Timing


Gotta ask... With the ALDL jumper in place?

[This message has been edited by Patrick (edited 10-18-2021).]

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Klyde7_2M4
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Report this Post10-18-2021 04:19 PM Click Here to See the Profile for Klyde7_2M4Click Here to Email Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
Yes it gives code 12, does the jumper have to be in place to correct timing, I thought 85's are done manually

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Gall757
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Report this Post10-18-2021 06:53 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Klyde7_2M4:

Yes it gives code 12, does the jumper have to be in place to correct timing, I thought 85's are done manually


Timing is done manually with the jumper in place.
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Klyde7_2M4
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Report this Post10-18-2021 07:59 PM Click Here to See the Profile for Klyde7_2M4Click Here to Email Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
Would be resetting the ecm after not do anything if I didn't use the jumper?
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Gall757
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Report this Post10-18-2021 08:15 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
If the timing is set without the jumper, there is nothing the computer can do to overcome the error.
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buddycraigg
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Report this Post10-18-2021 08:16 PM Click Here to See the Profile for buddycraiggClick Here to Email buddycraiggSend a Private Message to buddycraiggEdit/Delete MessageReply w/QuoteDirect Link to This Post
you have to set the base timing by adjusting the distributor when the aldl jumped.
the ECM controls the timing advancement after that.
REsetting the ECM won't do anything if the base timing wasn't set correctly in the first place.
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Klyde7_2M4
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Report this Post10-18-2021 08:30 PM Click Here to See the Profile for Klyde7_2M4Click Here to Email Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
Okay, I'll do that next, I'll keep y'all posted
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Klyde7_2M4
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Report this Post10-23-2021 09:00 PM Click Here to See the Profile for Klyde7_2M4Click Here to Email Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
Did the timing correctly, running a ton better, still shudders, timing is between 8-10 degrees since I live in a high altitude
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buddycraigg
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Report this Post10-23-2021 11:11 PM Click Here to See the Profile for buddycraiggClick Here to Email buddycraiggSend a Private Message to buddycraiggEdit/Delete MessageReply w/QuoteDirect Link to This Post
give a little more detail now that you have the timing set correctly.
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