Runs Rough after Distributor Swap (Page 1/2)
CookesForChrist OCT 25, 04:10 PM
1986 Fiero SE 2.8L V6 4-Speed Manual

Just today, I very carefully replaced my Fiero's original (severely corroded) distributor with a new Spectra GM17 distributor. I did my best to line everything up in the same orientation as the old distributor, but I must have been off somewhere. I need some help!

The car started up no problem, but it idled a little rougher than usual. When I took it for a 20 minute drive on the highway, it seemed OK at higher speeds, however, whenever I drove at a lower speed, slowed down, or came to a stop, it got really, really rough. Whenever I stopped at a red light, it started hunting wildly from 600 to 1400 RPM and it sounded like it would stall. It did stall on me once when I finally parked it in my driveway.

I am thinking that the distributor is messing up the timing. Is that likely the case? Is this easy to solve? Do I try to spin the distributor a few degrees and see if the roughness goes away? How do I fine-tune this engine?

I would love to get some advice before trying anything else...

Thank you and God bless.

David

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fierosound OCT 25, 04:22 PM

quote
Originally posted by CookesForChrist:

I am thinking that the distributor is messing up the timing. Is that likely the case? Is this easy to solve? Do I try to spin the distributor a few degrees and see if the roughness goes away? How do I fine-tune this engine?



Use a timing light.
Pages 1-22 and 1-23 in the Haynes repair book.




I usually just connect to spark plug #1 and set to 10 degrees BTDC.


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[This message has been edited by fierosound (edited 10-25-2019).]

Gall757 OCT 25, 05:07 PM
Do not assume you got the plug wires in the right places. I have seen experts mess that up.....
CookesForChrist OCT 25, 09:32 PM
I don't have a timing light, so I will have to buy one and try that out. I'm not sure where those timing marks are. Hopefully I can find them.

I am sure the spark plug wires are all correct, but I will check that again also.

Thank you for your help. This Fiero Forum is a Godsend.
Gall757 OCT 26, 10:32 AM
A picture of V6 timing marks
CookesForChrist OCT 27, 03:14 PM
I purchased a timing light and I adjusted the timing to 10 degrees. It had been around 16 degrees, so obviously that was a problem!

However, I still have an issue.

It seems to be running smoothly when I am driving up over 60 km/h (35 mph). The RPMs are good and solid. Below this, it is a little rough - and it gets rougher the slower I go. And whenever I come to a stop, it stalls out after 10 or 20 seconds.

Any ideas?

Thanks!
Dennis LaGrua OCT 27, 04:34 PM
I would check out the spark plug wire location assignments again. It could also be an ignition module. Be advised that aftermarket modules do not work much of the time. Only the AC Delco modules seem to be able to take the high heat location and if you installed one did you use thermal grease? Are the heat shields back in place?

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fierosound OCT 27, 05:40 PM

quote
Originally posted by CookesForChrist:

...it is a little rough - and it gets rougher the slower I go. And whenever I come to a stop, it stalls out after 10 or 20 seconds.



Are there any error codes stored in the ECM?
http://www.fiero.nl/cgi-bin/main.cgi?ECMCodes

It sounds like you're saying it ran perfectly fine before you changed distributor.

That's why the emphasis is on timing, making sure plug wires are correct, and checking
anything that may have been disturbed or disconnected when changing distributor.

[This message has been edited by fierosound (edited 10-27-2019).]

CookesForChrist OCT 27, 06:54 PM
With the old (original) distributor, old spark plugs, and old plug wires, the engine was running OK, but not perfectly. It would hunt at idle and it seemed sluggish.

A few months back I had changed the EGR valve, which made it a little less sluggish.

Last week I replaced all the spark plugs and plug wires and made sure the engine ran, which it did. Then I changed out the distributor the same day.

After that, the hunting was worse than ever, and it was running REALLY rough. I thought this might just be a timing issue.

Now, just today I was able to set the timing at 10 degrees. (However, I have no idea what the timing was set at before I changed everything. Maybe it was at some "custom" setting?)

It still runs rough (though maybe slightly better than before I set the timing), and it is actually stalling when stopped for 10-20 seconds.

Is it possible that some other issue is now being exposed? Can this roughness be caused by the old ICM (ignition control module) and/or ignition coil (which are probably original)? Or is this definitely a problem with the new distributor?

I will note that there are NO engine codes present.
Patrick OCT 27, 07:47 PM

quote
Originally posted by CookesForChrist:

Now, just today I was able to set the timing at 10 degrees.



And you did this with the ALDL jumper in place?

[This message has been edited by Patrick (edited 10-27-2019).]