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  DOHC: Replaced ICM, immediately backfired, won't start?

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DOHC: Replaced ICM, immediately backfired, won't start? by Squeaky
Started on: 07-03-2015 10:07 PM
Replies: 5 (113 views)
Last post by: Fieroking on 07-07-2015 02:06 AM
Squeaky
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Report this Post07-03-2015 10:07 PM Click Here to See the Profile for SqueakyClick Here to Email SqueakySend a Private Message to SqueakyEdit/Delete MessageReply w/QuoteDirect Link to This Post
http://www.fiero.nl/forum/Forum2/HTML/135555.html

This is a continuation of the above thread. To summarize; car wouldn't stay running at idle so after performing a scan my scanner diagnosed a faulty ICM.
After installing the new ICM I tried starting the car and it turned over briefly before letting out a huge "BANG", now it won't start up at all, it will just crank instead.
Before I installed the new ICM it didn't do this, it would idle for a bit and then stall but at least then it would restart. Now it doesn't seem to want to, any ideas?
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tesmith66
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Report this Post07-04-2015 07:36 AM Click Here to See the Profile for tesmith66Send a Private Message to tesmith66Edit/Delete MessageReply w/QuoteDirect Link to This Post
Are the plug wires on correctly? Does it go back to running the way it did before the new ICM if you put the old one back on?

Check your wiring. If you did the swap, go back and look at ALL of your wiring. If you bought it or the harness, good luck. You're gonna have to go wire by wire.

------------------
1986 SE Aero coupe.

3.4 DOHC swap is complete and running, now just have to finish the rest of the car...

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Joseph Upson
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Report this Post07-04-2015 09:46 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post
If your scanner is capable, look at the value for all of your readable sensors with ignition on to make sure all sensors are being read and processed by the ECM. If something is missing from the data output to scanner you'll have your answer.

I'm assuming you used the EPROM from the old computer, if you didn't that can be the problem. If you did, again that can be the problem as it is tied into the circuitry of the ECM so you may have a bad EPROM and or ECM so you need a fresh ECM and PROM.



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phonedawgz
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Report this Post07-04-2015 10:51 AM 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
A backfire through the throttle body can take out the MAF, IAT and MAP. Check the values of those while scanning to see if they look right.

The backfire was most likely caused by the plug wires being put on incorrectly.

What code did you get that made you suspect your ICM?

[This message has been edited by phonedawgz (edited 07-04-2015).]

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Joseph Upson
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Report this Post07-04-2015 11:19 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Squeaky:

Update:

I successfully connected the scanner and was able to perform a scan yesterday evening. I couldn't load the bin file for the 3.4 DOHC so I tried the scan again after loading a 3.1l bin file.
As expected it indicated that I was running rich however it also came up that my electronic spark control module was faulty, placed another one on order, just awaiting it's arrival.

Keep you folks posted!



Went back and found that in your initial thread.

You need to explain in detail what you've done and where you are right now. Don't replace parts on a whim, test them first. You should never have bothered your fuel pump without first confirming a problem with fuel pressure.

The injectors for the 3.4 DOHC are specific for that motor due to the spray pattern of 4 ports angled in a manner that directs two at each intake runner in the head although others will work.

Sounds like you have a wiring problem, or a code mask and ECM mismatch. At this point I believe it best that you start from scratch by properly programming the correct code mask into the chip. If you can't do that, don't do anything else until you correct the cause that is preventing you from doing so.

Afterwards you should be able to connect with Tunerpro. If you can't find out why as that program will tell you everything you need to know about the state of your sensors and whether or not they are working properly, or at all.

If you accomplish the above; proper code mask programmed in the chip with the correct ECM, connectivity with Tunerpro and proof of properly reading sensors, it should run normally.

If it doesn't, get a multimeter and back probe your ECM pinouts to their respective assignments and make sure you don't have anything connected backwards and that you don't have missing grounds, or grounds that are in the wrong place.

[This message has been edited by Joseph Upson (edited 07-04-2015).]

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Fieroking
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Report this Post07-07-2015 02:06 AM Click Here to See the Profile for FierokingClick Here to visit Fieroking's HomePageClick Here to Email FierokingSend a Private Message to FierokingEdit/Delete MessageReply w/QuoteDirect Link to This Post
Try the old ICM to see if the engine will run. Did you get the correct ICM the one for the DOHC is different.

Joe Sokol

------------------
85 SE Daily driver with a 3.4 DOHC OBD II
88 Formula/GT 4.9 Allante Intake (My Baby)
www.fieroking.com

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