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Discussion Starter #1
Hi,
I have a big problem. My truck started missfiring about 6 months ago. 2 weeks ago it started sputtering and spitting up through the TB. I checked the MAP voltage and it was correct. I checked the timing. My timing was off 20-30 deg. I replaced the timing chain. It is still off the same amount. I am checking it with an inductive timing light connected to num. 1 (front P/S). My service book says to cut the engine control switch. Where is this and what does it look like. What else should I do.
What size bolt holds the dis clamp? How do you get to it? It is almost impossible.
Do you guys have any other suggestions?
Thanks,
Mike
 

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The connector you're looking for is located in the passenger footwell, sometimes covered by the carpet/floor mat. It is a black connector, that has a tan/black wire in each side. Disconnect this wire and you will be able to see the base timing.

It's not unusal to see the ignition timing off by 20 to 30 degrees when this wire is still connected. The ECM will control the timing with that wire connected. When it is disconnected the timing advance is controled strictly by the ICM (Ignition Control Module) located on the base of the dizzy.
 

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Discussion Starter #3
Thanks,
I set the timing, it was only off by 12 degs. It is still sputtering constantly under load. At idle, and free revving, it runs fine.

The cap and rotor are shot. I have them but, have not replaced them yet. Do you think this could be the problem?
Spark plugs are about 5 years old but, still look ok.
After cap and rotor, what should I be looking at next?

There is a little vacuum line going to a little brass looking thing in the back side of the air cleaner. What is that?

I'm desperate. I have a new car but, I am afraid I will hit another deer soon. I have hit 3 in the last year.
Thanks,
Mike
 

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Checked the EGR valve?
 

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Man, a bad cap and rotor can cause just the sort of problems you're having, I'd change them out and go from there. I had a bad cap a few years ago cause allll sorts of firing issues. Changed it out and it was running like a charm.
 

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Discussion Starter #6
No I haven't checked the egr yet. I heard that was a real bitch. I'd like to shoot all GM engineers. That engine bay is realy tight for such a tiny little engine. I'll try checking that after I replace the cap.
I barely got the timing set. That dissy hold down bolt was a real Bi**h!
Thanks guys
 

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Eh it's not that tight, I meen we drop in V8's all the time!
Nah, it's an easy check, just make sure it is closed at idle, you can check it by opening the diaphram with your fingers. It may be stuck open. You can always remove it and block it off.
 

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Discussion Starter #9
Guess I was thinking and typing while you were posting. I'm not sure where it is located or what it looks like on the 2.8. I have only worked on old school V8's.
 

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On the back side of the intake you will see this:

 

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Discussion Starter #11 (Edited)
The EGR appears not to be stuck. I don't know if it actually opens though. I don't know if it is getting vacuum and opens. The diaphram could be ripped.
 

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The connector you're looking for is located in the passenger footwell, sometimes covered by the carpet/floor mat. It is a black connector, that has a tan/black wire in each side. Disconnect this wire and you will be able to see the base timing.

It's not unusal to see the ignition timing off by 20 to 30 degrees when this wire is still connected. The ECM will control the timing with that wire connected. When it is disconnected the timing advance is controled strictly by the ICM (Ignition Control Module) located on the base of the dizzy.

hey will this also work on the 4.3
 

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No I haven't checked the egr yet. I heard that was a real bitch. I'd like to shoot all GM engineers. That engine bay is realy tight for such a tiny little engine. I'll try checking that after I replace the cap.
I barely got the timing set. That dissy hold down bolt was a real Bi**h!
Thanks guys
Did you ever find the problem? My 86 S-15 2.8L does the same thing but mine has had the, ready for this, EGR, oxygen sensor, coolant sensor, distributor, cap, rotor, plugs, wires and fuel pump replaced and I just rebuilt the TB with a rebuild kit.. Seems to run great cold for the first couple miles then it starts missing out on acceleration and sometimes even backfires through the TB. The timing is set at the 10 degrees, with the timing wire unhooked while setting and at normal operating temp.
 

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Great old thread, the Haynes manual does not talk about disconnecting this wire nor where it is located. It only refers to the sticker under the hood. Some one painted over my sticker. Going to try this tomorrow.
 

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Great old thread, the Haynes manual does not talk about disconnecting this wire nor where it is located. It only refers to the sticker under the hood. Some one painted over my sticker. Going to try this tomorrow.

the chiltons manual mentions it
 

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Timed my engine as per the thread discussion. Awesome, great throttle response now! Not like driving my Tahoe but now it can get out of its own way :)
 

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Hello i'm having problems with my 87 s10 2.8l i'm trying to bypass the computer from the distriptor i lower my truck so i took out half the stuff that was in the way now truck started sputtering and spitting any help would be great tks
 

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Whaat?
 

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^^^^^^ Um, like huh????
Ditto Raven.
 
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