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1987 2.5l Fiero engine misfire (Possible ECM Failure?) by jacob5485
Started on: 09-05-2014 02:27 PM
Replies: 15 (590 views)
Last post by: theogre on 09-07-2014 12:19 PM
jacob5485
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Report this Post09-05-2014 02:27 PM Click Here to See the Profile for jacob5485Send a Private Message to jacob5485Edit/Delete MessageReply w/QuoteDirect Link to This Post
[img]I have a 1987 2.5l Fiero with just over 117,xxx miles. Bought back in July 2014. When I bought the car it had a high idle (1,400rpm) figured it was a vacuum leak so didn't think much of it. It also had an oil leak from the oil cap,there was oil around spark plug holes 1 and 2. So I took an engine block degreaser sprayer that hooks up to air compressor to clean (uses minimal amount of cleaning product). It had the high idle before I cleaned but after I was done it had a very distinct miss throughout all rpm's.

At first it wouldn't run with the idle where it was and someone had already removed safety cap, I turned it up till I could get it to run so I could move it. I figured I might have ruined a sensor so I ordered all new ones (CODE 22 MAP sensor and CODE 42 engine misfire) were present.

I replaced:
All Vacuum Lines,
Throttle Position Sensor (TPS),
Air Charge Temp. Sensor,
Spark Plugs + Wires,
Engine Crankshaft Position Sensor,
Ignition Module (old one was tested bad, new tested good),
Both Ignition Coils replaced (4,1 coil pack had no resistance),
Idle Air Control Valve (IAC),
EGR Valve + Gasket,
MAP Sensor,
Coolant Temp. Sensor,
Replaced the ALL Throttle Body Gaskets and cleaned carburetor and injector + Gaskets,

No more CODE 22.

I have good fuel pressure so I don't think it is fuel related but not sure. I am leaning towards it being electrical related. I downloaded the 1987 Service Manual and have tested CODE 42 diagnostics with OHM Meter but not sure if I did it right (pictures). Can't tell if module switches like it states? Could I possibly have a bad ECM? Or my paths CKT 423 be grounded, CKT 424 be open?

PLEASE HELP!
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jacob5485
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Report this Post09-05-2014 03:08 PM Click Here to See the Profile for jacob5485Send a Private Message to jacob5485Edit/Delete MessageReply w/QuoteDirect Link to This Post
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Gall757
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Report this Post09-05-2014 04:01 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Welcome to the Forum!

After reading your post I can't figure out what the problem is.....is it running now?
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jacob5485
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Report this Post09-05-2014 08:42 PM Click Here to See the Profile for jacob5485Send a Private Message to jacob5485Edit/Delete MessageReply w/QuoteDirect Link to This Post
Yes, the vehicle does run but if it is cold and you give it a little throttle in drive it stalls. But if it is warm it won't stall unless you put your foot to the floor at a stop.
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Gall757
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Report this Post09-05-2014 09:05 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 jacob5485:

At first it wouldn't run with the idle where it was and someone had already removed safety cap, I turned it up till I could get it to run so I could move it.


This adjustment may cause problems with the computer.

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theogre
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Report this Post09-06-2014 10:31 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
See my Cave, DIS Ignition

If missing PIM shield can short out the PIM.

DTC 42 is NOT misfire. 42 is "Electronic Spark Timing" and often engine won't misfire to get the DTC.

What plugs? Some plugs doesn't work well or hate DIS.

DTC 42 can be problem from PIM main ground to engine
also See my Cave, Ground "Myth" notes

DTC 42 could be ECM...
If ECM is bad or not, See my Cave, ECM Heat

42 could be TSB for PROM but rarely happens but Is mostly other problems. See my Cave, PROM TSB notes

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jacob5485
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Report this Post09-06-2014 11:14 AM Click Here to See the Profile for jacob5485Send a Private Message to jacob5485Edit/Delete MessageReply w/QuoteDirect Link to This Post
Thank you theogre, when I replaced my ignition module/coils I know there wasn't a galvanized plate between them. Do you think that is what would be causing the misfire?
Is the ground for the ignition module on the outside or where the bolts come through to secure the coils?
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theogre
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Report this Post09-06-2014 03:22 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yes, missing shield can cause this, fires, etc.

DIS PIM ground is black wire between PIM and Trans bell housing bolt.

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jacob5485
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Report this Post09-06-2014 04:55 PM Click Here to See the Profile for jacob5485Send a Private Message to jacob5485Edit/Delete MessageReply w/QuoteDirect Link to This Post
Ok, I made a shield out of .030 galvanized metal. I know it should be .018 thicker but it was all I could find. So I reinstalled it and put dielectric grease on all connectors + shield like stated in the Cave article. It still has a misfire and am still getting CODE 42. I checked and rechecked all grounds and they are good. My wires and plugs are both Autolite and were new 200 miles ago, along with Duralast coils.

I remember readings an article about pulling spark plug wires while engine is running to see which cylinder has misfire. So I did that and noticed cylinder 3 wire does not arc the distance the other cylinder wires did (about 1 inch). Is it better to have a smaller arc vs. larger arc?
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Report this Post09-06-2014 06:50 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you damage the PIM w/o the shield... Damage to coil pins often won't show.

Missing PIM shield can/will cause coil pins to bend inside of PIM.

You can try get a store to test the PIM.
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jacob5485
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Report this Post09-06-2014 07:56 PM Click Here to See the Profile for jacob5485Send a Private Message to jacob5485Edit/Delete MessageReply w/QuoteDirect Link to This Post
I will have module tested tomorrow. What about the spark arcing?
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Report this Post09-06-2014 11:06 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
spark arcing? Where?
something is way wrong. Damage PIM likely won't help that.

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jacob5485
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Report this Post09-07-2014 09:43 AM Click Here to See the Profile for jacob5485Send a Private Message to jacob5485Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
I remember readings an article about pulling spark plug wires while engine is running to see which cylinder has misfire. So I did that and noticed cylinder 3 wire does not arc the distance the other cylinder wires did (about 1 inch). Is it better to have a smaller arc vs. larger arc?
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Gall757
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Report this Post09-07-2014 10:17 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Pulling spark plug wires while the engine is running will likely damage your ICM (PIM).

[This message has been edited by Gall757 (edited 09-07-2014).]

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jacob5485
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Report this Post09-07-2014 11:16 AM Click Here to See the Profile for jacob5485Send a Private Message to jacob5485Edit/Delete MessageReply w/QuoteDirect Link to This Post
I am fully aware of the damage and the ignition module tested good at Autozone.

Can you answer my question that I have about the arcing?
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Report this Post09-07-2014 12:19 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by jacob5485:
I am fully aware of the damage and the ignition module tested good at Autozone.

Can you answer my question that I have about the arcing?

Is a fairly useless test. PIM/ICM does not like this. DIS coils generate ~2x power vs HEI will quickly fry messing w/ wire, dead wires or plugs, etc.

Switch coils and see if that move w/ coil. or good used coil to replace 3/2 (upper) coil.
If not then maybe return wires or plugs under warranty or...
Switch new wire to any used wire. 1 at a time for 3 and 2.
Switch new plugs to any used plugs.

Again, ECM does not know when and most time doesn't trip DTC 42 for coil, plug or plugwires are bad.
Bad ECM or PIM, wires to them, iffy power/ground to either, etc can cause 42.
Example PIM gets power thru c500, ECM fuse, and ignition switch. PIM Ground to bolt close to PIM on PIM or Trans bell w/ stud top bolt. (1 OE tray bolt has stud top and Many FWD uses this.)
Iffy ECM or PIM or wires between two can cause 42.

[This message has been edited by theogre (edited 09-07-2014).]

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