Georgia Fiero Club Forum

All Things Fiero => Tech Tips, Tech Questions => Topic started by: Plastic Fantastic on March 27, 2020, 11:51:25 pm

Title: Backfiring
Post by: Plastic Fantastic on March 27, 2020, 11:51:25 pm

Help.. I have a 85 GT , on any given day I can hop in , cranks right up and runs great for 45-- 60 minutes. Stop at a store , come back attempt to start but it doesn't want to. When I do get it started it runs bad for half a mile , backfires and dies. You can smell the in burnt gas. Any ideas? I can replace parts but not good with diagnostics. Thanks.

Title: Re: Backfiring
Post by: GTRS Fiero on March 27, 2020, 11:53:56 pm

Have you checked the ICM?

Title: Re: Backfiring
Post by: Plastic Fantastic on March 28, 2020, 12:46:49 am

Not yet I read a post earlier that referenced the ICM and that prompted me to post. I will Google the location in engine bay and how to test it.

Title: Re: Backfiring
Post by: TopNotch on March 28, 2020, 09:10:22 am

The ICM is in the distributor. The best way to test it is to take it to a parts store with a tester.
But before you do all that, you should check your trouble codes. There might be a clue about your problem. See this page (http://www.fiero.nl/cgi-bin/main.cgi?ECMCodes) for info on how to check them. Note: your ALDL connector may be upside down from what is shown on that page.

Title: Re: Backfiring
Post by: Fierofool on March 28, 2020, 09:13:49 am

It's the black plastic electronic component inside the distributor.  When replacing it, one should discard the clear thermal grease that comes with it and use a white or silver thermal grease that can be purchased in small tubes at some auto parts stores or computer and electronics stores.  Smear a coating of it on the metal plate on the bottom of the ICM and install it. 

Raw gas smell could also be caused by the Coolant Temperature Sensor located on the end of the engine just above the water pump.  It tells the computer how it needs to adjust the air/fuel mixture.  If it fails it can cause the mixture to be very rich. 

Title: Re: Backfiring
Post by: Plastic Fantastic on March 28, 2020, 11:18:14 am

Thanks everyone for the information. Plan on checking it all out and will report back.

Title: Re: Backfiring
Post by: Plastic Fantastic on May 10, 2020, 09:32:08 am

Update. Went straight to the coolant temperature sensor reached in to remove the connector and it just fell off , the connector housing on the sensor was broken , I just plugged the connector straight to the sensor , fired it up and drove 45 miles , stopped four times , cranked right up with no gas smell. Haven't got to replacing the sensor yet , but I will. Thanks to all in the Fiero community.

Title: Re: Backfiring
Post by: GTRS Fiero on May 10, 2020, 09:36:00 am

Glad it's working.

Title: Re: Backfiring
Post by: Roger on May 10, 2020, 02:08:00 pm

I guess you mean the sensor beneath the fill neck?

Title: Re: Backfiring
Post by: Plastic Fantastic on May 11, 2020, 06:26:06 am

Yes. At the fill neck.

Title: Re: Backfiring
Post by: Fierofool on May 11, 2020, 08:41:54 am

PlasticFantastic, you may have told me before and if you did, I don't remember.  Where are you located?