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2.8 v6. possible bad ecm? by bigdust80
Started on: 05-23-2015 04:44 PM
Replies: 16 (481 views)
Last post by: bigdust80 on 06-14-2015 11:04 AM
bigdust80
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Report this Post05-23-2015 04:44 PM Click Here to See the Profile for bigdust80Click Here to Email bigdust80Send a Private Message to bigdust80Edit/Delete MessageReply w/QuoteDirect Link to This Post
I've been up, down, all around my Fiero trying to get it running. I apparently can't get it running, ha. I've changed a ton of parts in my quest to get this damn car going.
Things I've done:
Timing was off by 3 teeth, so reset the gears to 0.
Changed out cam for a Melling MTC-5 w/ new lifter set
Had bent pushrods, so swapped pushrods out for comp cams ones
Installed comp cams 1.52 roller tip rockers
Went through ignition: cap, rotor, ign. coil, pu coil, module all new, replaced plugs between module and coil, coil and hot/ tach. tested ign and pu coil resistance with meter and also ignition test light; all good
New sensors: CTS, MAP, IAT, O2
New Starter
Resoldered ECM grounds and made sure they were tight on the tranny bolt they mount to
New fuel pump, filter, regulator, pintle injectors. Fuel pressure tested, goes to ~50 p.s.i. and slowly drains back down. Fuel pump comes on with key on. Deleted CSI
replaced cracked front manifold with a good one
New Dorman harmonic balance. Transferred the proper timing marks onto new one

Relocated battery up front w/ V8 Archie tray. Ran POS and NEG leads w/ 2/0 wire. Made ground straps w/ 2/0 wire and copper lugs from Batt to chassis and engine to chassis. One thing that has me concerned is if I crank on the starter a while, the starter starts dragging. Possible sign of a Voltage Drop?

After I did all this and got the engine back in, it was a little hard starting but ran for 5 minutes. I thought I had success because it ran great. I stepped out and revved the engine from the throttle body. As soon as I touched the throttle it died and I haven't been able to get it to crank since.

I'm wondering if it jumped time when I revved it? I pulled the cap today and checked between the rotor orientation and the 0 timing mark. I didn't get it exactly at 0, it was a little past. The rotor was just a little past the #1 point on the stator "star". So, I'm assuming timing is good. I still have the electronic timing set at 0 because I can't get the damn thing running long enough to balance 10 degrees adv between 1 & 4.

Since I've given the run down of what I've done so far, I'm curious if I have a bad ECM. I'm not getting any codes and I pulled the PROM to see if Code 52(I think?) came up and it did. I was careful to reseat it in the proper orientation. I checked all connections to ECM to see if I had corrosion issues or bad connections, seems fine. Will the ECM go bad and not throw any codes?

What do you fellas think?

One more thing, I just bought an OTC Compression Tester today and I just bought my wife a new laptop. I'm gonna take her old one over and use it for diagnostic work.

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Gall757
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Report this Post05-23-2015 05:13 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Disconnect the ECM at the Battery junction terminal. Wait a minute and re-connect. SES light on when you turn the key? Crank the starter and notice if the tach moves up to about 300.

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bigdust80
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Report this Post05-24-2015 11:04 AM Click Here to See the Profile for bigdust80Click Here to Email bigdust80Send a Private Message to bigdust80Edit/Delete MessageReply w/QuoteDirect Link to This Post
Reset the ECM multiple times through my troubleshooting. While cranking the tach ratchets up all the way until it pegs out. SES light comes on with key on. In diagnostic mode flashes code 12. That's the thing, everything looks good. But it's not, obviously. Could the ecm be bad and not have any obvious symptoms?

[This message has been edited by bigdust80 (edited 05-24-2015).]

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Gall757
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Report this Post05-24-2015 11:12 AM 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 bigdust80:
While cranking the tach ratchets up all the way until it pegs out.


What's that? Are you saying it goes up over 6000?
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bigdust80
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Report this Post05-24-2015 11:30 AM Click Here to See the Profile for bigdust80Click Here to Email bigdust80Send a Private Message to bigdust80Edit/Delete MessageReply w/QuoteDirect Link to This Post
Yeah, on cranking the tach rolls around until it pegs out. On each revolution of the starter it'll bounce roughly 100 RPM on the tach until it hits 7000. As of now, I have the tach filter bypassed, if that makes a difference.

[This message has been edited by bigdust80 (edited 05-24-2015).]

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Gall757
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Report this Post05-24-2015 12:20 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Well that's just weird. Maybe it has something to do with your ECM grounds repair, but I have no idea.

[This message has been edited by Gall757 (edited 05-24-2015).]

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bigdust80
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Report this Post05-24-2015 12:32 PM Click Here to See the Profile for bigdust80Click Here to Email bigdust80Send a Private Message to bigdust80Edit/Delete MessageReply w/QuoteDirect Link to This Post
My repair was better than it was. The grounds were cut and crappily butt spliced back together. I cut them back to good wire, soldered and then shrink tubed the splices. I then put the ring terminals securely back in place on the tranny bolt. I did a continuity test between the ecm case and the ground in the chassis by the ecm. Got a good strong tone. Do I need to do a continuity test from the grounds themselves where they plug into the harness to the chassis?
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Gall757
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Report this Post05-24-2015 12:47 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Don't think so, but was your car re-wired by a PO? Maybe some other things are not right. I would try to get the tach to show 200 - 300 rpm when cranking the starter, and go from there. That shows that the primary ignition is working.
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Report this Post05-24-2015 05:27 PM Click Here to See the Profile for bigdust80Click Here to Email bigdust80Send a Private Message to bigdust80Edit/Delete MessageReply w/QuoteDirect Link to This Post
The car wasn't rewired. They just cut the grounds when they rebuilt the engine.
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phonedawgz
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Report this Post05-24-2015 08:26 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Turning the crank clockwise stop at 10 deg btdc. Don't go backwards to get there because you want any slack in the timing chain to be on the correct side. Then as perfectly as you can alight the prongs and points inside the distributor. This will be close enough for starting the engine.

I would check for spark using an inline tester. This tells you if your spark plug is actually firing or not. It sounds like your primary is working since you are seeing something at the tach. Sounds like your tach is f'ed up btw.
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bigdust80
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Report this Post05-25-2015 08:15 AM Click Here to See the Profile for bigdust80Click Here to Email bigdust80Send a Private Message to bigdust80Edit/Delete MessageReply w/QuoteDirect Link to This Post
I checked for spark w/ an inline tester already. Tested straight off the coil and #1 cylinder. Lit up like a Christmas tree. Gonna do the other plugs later but my assumption is spark is good. Right now I'm leaning towards a stretched timing chain that jumped time, poor compression(which I don't think is the case) or bad ECM.

The reason i'm thinking it jumped time is after I got the engine installed and hooked up. I got it to crank and run for a few minutes. It ran well. Then I goosed the throttle a little and it died and I couldn't get it to crank. Thing is, how much slack does it take for it to be too loose. I checked the chain when I had the engine apart and it didn't seem too loose.

I'm planning on pulling the plugs and rolling the engine over to 0 by hand to check my timing.
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Dennis LaGrua
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Report this Post05-25-2015 08:50 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
ECM's do go bad but it is a rare occurrence. If the found that the timing was off by three teeth and you replaced none of the drive parts; the chance that they slipped again are probably high. A new timing chain at the minimum may help but if the gears were unevenly worn they could be part of the problem as well. Could the crankshaft be walking?

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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bigdust80
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Report this Post05-25-2015 11:10 AM Click Here to See the Profile for bigdust80Click Here to Email bigdust80Send a Private Message to bigdust80Edit/Delete MessageReply w/QuoteDirect Link to This Post
If I've found that the chain slipped, I'm gonna replace with a double roller setup and just eliminate the whole chain stretch issue. I hope the crank's not walking. The engine is supposed to be a fresh rebuild. It's fresh from what I can tell when I went into the engine. The block was bored .25mm over. I didn't look at the bottom end, though. I think the block was rebuilt by a local shop and they may have cheaped out and reused the original timing set. Hopefully I don't have any crank issues.
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bigdust80
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Report this Post06-13-2015 06:27 PM Click Here to See the Profile for bigdust80Click Here to Email bigdust80Send a Private Message to bigdust80Edit/Delete MessageReply w/QuoteDirect Link to This Post
Well, everyone, I got her running. Had slack in the timing chain. Changed out the timing set for a new cloyes one and it starts every time now. Thanks, everybody.
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Report this Post06-13-2015 08:35 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for the report. I guess the rebuild was not quite fresh enough...

[This message has been edited by Gall757 (edited 06-13-2015).]

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Dennis LaGrua
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Report this Post06-13-2015 08:45 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by bigdust80:

Well, everyone, I got her running. Had slack in the timing chain. Changed out the timing set for a new cloyes one and it starts every time now. Thanks, everybody.


Good job and glad to hear that the engine is running. When the timing chain goes loose, it is often accompanies by worn timing gears that can upset the timing. I suspect that's what happened.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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bigdust80
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Report this Post06-14-2015 11:04 AM Click Here to See the Profile for bigdust80Click Here to Email bigdust80Send a Private Message to bigdust80Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:

Thanks for the report. I guess the rebuild was not quite fresh enough...



I think it was a halfhearted rebuild. I'm thinking the previous owner sent the block out got it punched and rebuilt it himself using the old parts. Hopefully it'll stay running until I can put a real engine in it.
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