Pennock's Fiero Forum
  Technical Discussion & Questions
  85 2M4 Misfire, help would be appreciated

Post New Topic  Post A Reply
Email This Page to Someone! | Printable Version


next newest topic | next oldest topic
85 2M4 Misfire, help would be appreciated by Klyde7_2M4
Started on: 10-04-2021 09:58 AM
Replies: 22 (281 views)
Last post by: buddycraigg on 10-23-2021 11:11 PM
Klyde7_2M4
Junior Member
Posts: 9
From: Utah
Registered: Jul 2021


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-04-2021 09:58 AM Click Here to See the Profile for 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
IP: Logged
PFF
System Bot
Klyde7_2M4
Junior Member
Posts: 9
From: Utah
Registered: Jul 2021


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-04-2021 09:59 AM Click Here to See the Profile for Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post
Just remembered more Important info

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

Acceleration is 100% okay
IP: Logged
Klyde7_2M4
Junior Member
Posts: 9
From: Utah
Registered: Jul 2021


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-04-2021 11:13 AM Click Here to See the Profile for Klyde7_2M4Send a Private Message to Klyde7_2M4Edit/Delete MessageReply w/QuoteDirect Link to This Post

Klyde7_2M4

9 posts
Member since Jul 2021
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・)
IP: Logged
Gall757
Member
Posts: 10938
From: Holland, MI
Registered: Jun 2010


Feedback score: N/A
Leave feedback





Total ratings: 90
Rate this member

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.
IP: Logged
Patrick
Member
Posts: 36240
From: Vancouver, British Columbia, Canada
Registered: Apr 99


Feedback score: (1)
Leave feedback





Total ratings: 458
Rate this member

Report this Post10-05-2021 05:24 PM Click Here to See the Profile for 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).]

IP: Logged
buddycraigg
Member
Posts: 13588
From: kansas city, mo
Registered: Jul 2002


Feedback score: (5)
Leave feedback





Total ratings: 478
Rate this member

Report this Post10-08-2021 08:36 PM Click Here to See the Profile for 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.
IP: Logged
NY_FIERO
Member
Posts: 1554
From: mexico NY
Registered: May 2002


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-14-2021 03:12 PM Click Here to See the Profile for NY_FIEROClick Here to visit NY_FIERO's HomePageSend 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).]

IP: Logged
NY_FIERO
Member
Posts: 1554
From: mexico NY
Registered: May 2002


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-14-2021 03:49 PM Click Here to See the Profile for NY_FIEROClick Here to visit NY_FIERO's HomePageSend a Private Message to NY_FIEROEdit/Delete MessageReply w/QuoteDirect Link to This Post

NY_FIERO

1554 posts
Member since May 2002
And yes... resolve the fuel pressure issue first... are you certain you're not talking 9.0 lbs? not 90???
IP: Logged
RWDPLZ
Member
Posts: 15010
From: Michigan
Registered: May 2002


Feedback score:    (11)
Leave feedback





Total ratings: 304
Rate this member

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.
IP: Logged
Forrest
Member
Posts: 101
From: Seabrook TX
Registered: Sep 2019


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-18-2021 02:45 PM Click Here to See the Profile for 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.
IP: Logged
Patrick
Member
Posts: 36240
From: Vancouver, British Columbia, Canada
Registered: Apr 99


Feedback score: (1)
Leave feedback





Total ratings: 458
Rate this member

Report this Post10-18-2021 03:28 PM Click Here to See the Profile for 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.

IP: Logged
PFF
System Bot
Klyde7_2M4
Junior Member
Posts: 9
From: Utah
Registered: Jul 2021


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-18-2021 03:42 PM Click Here to See the Profile for 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?
IP: Logged
Gall757
Member
Posts: 10938
From: Holland, MI
Registered: Jun 2010


Feedback score: N/A
Leave feedback





Total ratings: 90
Rate this member

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.
IP: Logged
Klyde7_2M4
Junior Member
Posts: 9
From: Utah
Registered: Jul 2021


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-18-2021 03:53 PM Click Here to See the Profile for 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
IP: Logged
Patrick
Member
Posts: 36240
From: Vancouver, British Columbia, Canada
Registered: Apr 99


Feedback score: (1)
Leave feedback





Total ratings: 458
Rate this member

Report this Post10-18-2021 04:11 PM Click Here to See the Profile for 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).]

IP: Logged
Klyde7_2M4
Junior Member
Posts: 9
From: Utah
Registered: Jul 2021


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-18-2021 04:19 PM Click Here to See the Profile for 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

IP: Logged
Gall757
Member
Posts: 10938
From: Holland, MI
Registered: Jun 2010


Feedback score: N/A
Leave feedback





Total ratings: 90
Rate this member

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.
IP: Logged
Klyde7_2M4
Junior Member
Posts: 9
From: Utah
Registered: Jul 2021


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-18-2021 07:59 PM Click Here to See the Profile for 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?
IP: Logged
Gall757
Member
Posts: 10938
From: Holland, MI
Registered: Jun 2010


Feedback score: N/A
Leave feedback





Total ratings: 90
Rate this member

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.
IP: Logged
buddycraigg
Member
Posts: 13588
From: kansas city, mo
Registered: Jul 2002


Feedback score: (5)
Leave feedback





Total ratings: 478
Rate this member

Report this Post10-18-2021 08:16 PM Click Here to See the Profile for 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.
IP: Logged
Klyde7_2M4
Junior Member
Posts: 9
From: Utah
Registered: Jul 2021


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-18-2021 08:30 PM Click Here to See the Profile for 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
IP: Logged
PFF
System Bot
Klyde7_2M4
Junior Member
Posts: 9
From: Utah
Registered: Jul 2021


Feedback score: N/A
Leave feedback

Rate this member

Report this Post10-23-2021 09:00 PM Click Here to See the Profile for 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
IP: Logged
buddycraigg
Member
Posts: 13588
From: kansas city, mo
Registered: Jul 2002


Feedback score: (5)
Leave feedback





Total ratings: 478
Rate this member

Report this Post10-23-2021 11:11 PM Click Here to See the Profile for 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.
IP: Logged

next newest topic | next oldest topic

All times are ET (US)

Post New Topic  Post A Reply
Hop to:

Contact Us | Back To Main Page

Advertizing on PFF | Fiero Parts Vendors
PFF Merchandise | Fiero Gallery | Ogre's Cave
Real-Time Chat | Fiero Related Auctions on eBay



Copyright (c) 1999, C. Pennock