87 s10 2.8 V6, timing off 20-30 deg - S-10 Forum
 
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post #1 of 32 Old 11-01-2009, 03:25 PM Thread Starter
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87 s10 2.8 V6, timing off 20-30 deg

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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post #2 of 32 Old 11-01-2009, 03:49 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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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post #3 of 32 Old 11-01-2009, 04:53 PM Thread Starter
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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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post #4 of 32 Old 11-01-2009, 06:54 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

Checked the EGR valve?


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post #5 of 32 Old 11-01-2009, 07:25 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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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post #6 of 32 Old 11-01-2009, 07:34 PM Thread Starter
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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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post #7 of 32 Old 11-01-2009, 07:37 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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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post #8 of 32 Old 11-01-2009, 07:40 PM Thread Starter
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Re: 87 s10 2.8 V6, timing off 20-30 deg

How do I check the EGR valve and what are the symptoms?
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post #9 of 32 Old 11-01-2009, 07:43 PM Thread Starter
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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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post #10 of 32 Old 11-01-2009, 07:47 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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



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post #11 of 32 Old 11-01-2009, 09:02 PM Thread Starter
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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.

Last edited by vetkaw63; 11-01-2009 at 09:04 PM.
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post #12 of 32 Old 02-22-2010, 10:53 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

Quote:
Originally Posted by The_Raven View Post
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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post #13 of 32 Old 03-14-2010, 07:03 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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Originally Posted by vetkaw63 View Post
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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post #14 of 32 Old 10-07-2011, 12:20 AM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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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post #15 of 32 Old 10-07-2011, 07:56 AM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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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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post #16 of 32 Old 10-09-2011, 01:06 AM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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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post #17 of 32 Old 10-10-2011, 12:31 AM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

yeah, i needa do mine soon. after putting in a new pickup coil in the dizzy i just kinda timed it by ear. im sure its off. =P
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post #18 of 32 Old 11-09-2011, 02:58 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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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post #19 of 32 Old 11-09-2011, 07:06 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

Whaat?

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post #20 of 32 Old 11-17-2011, 11:13 AM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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

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post #21 of 32 Old 11-26-2011, 06:33 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

it doesnt need the distributor! the distributor doesnt do much.. just controls EVERYTHING!
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post #22 of 32 Old 11-26-2011, 06:42 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

to check and see if your EGR diaphragm is working, pull the hose off and suck on it. you should see the plunger move. you shouldnt loose any suction while sucking on the hose.

i always tell people fix what you KNOW is wrong, then go from there.
if you fix what you know is wrong, 9x out of 10 it will fix the problem.
and if it doesnt fix the problem, its something that needed to be fixed anyways.

does it idle normal? or does it idle high? a vacuum or manifold leak can make engines pop under load due to making the mixture lean.

most common is funky spark plugs.. or cap and rotor, if your sparks intermediate and doesnt spark when its supposed to then fuel will build up inside of the combustion chamber, then the next time it comes around to fire it ignites a heaping load of fuel and gives a loud bang.
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post #23 of 32 Old 05-23-2013, 12:04 AM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

i tried timing mine today. i disconnected the wire and nothing changed no check engine light nothing
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post #24 of 32 Old 05-23-2013, 12:31 AM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

Ummm.... this thread first off is two years old.. second of all when u disconnect the tan wire under the passenger side carpet, it allows you to set the base timing.. which is 10* advanced for TBI engines. When you set the proper base timing, and put the wire back together, the computer now runs the timing wherever it is the most efficient for power and economy. Thats the simple explanation for what is happening haha.

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post #25 of 32 Old 05-30-2013, 04:29 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

Love this...distripor...
Quote:
Originally Posted by RobDog67 View Post
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
Gears...Actually almost 4 years old from the orignal post! This one just keeps coming back!



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post #26 of 32 Old 05-30-2013, 06:28 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

All hail the DISTRIPTOR

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post #27 of 32 Old 10-02-2013, 09:41 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

I have 1985 2.8 V6 w vacuum advance distributor. After engine rebuild lined up cam and crank gears properly w #1 at TDC and largest timing groove in crank pulley set at 0 degrees. In fact that's the only way the crank pulley would align on the crank so was a no brainer there. Installed brand new dizzy w rotor pointing at 6PM and she rotated into position at 7PM. All new wires and plugs. No other electronic controls are left attached to ignition system - just the standard, new 1985 ignition module. When it starts the timing mark is at near 30+ degrees BTDC. When I try to rotate dizzy clockwise to bring timing mark to 10 degrees BTDC the motor stalls and quits. I have rechecked that timing mark is at zero degrees when #1 piston is at TDC. Any ideas why the timing marks illuminates at 30 degrees and moving to 10 degrees kills engine?
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post #28 of 32 Old 10-02-2013, 11:51 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg


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post #29 of 32 Old 10-04-2013, 07:57 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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I have 1985 2.8 V6 w vacuum advance distributor. After engine rebuild lined up cam and crank gears properly w #1 at TDC and largest timing groove in crank pulley set at 0 degrees. In fact that's the only way the crank pulley would align on the crank so was a no brainer there. Installed brand new dizzy w rotor pointing at 6PM and she rotated into position at 7PM. All new wires and plugs. No other electronic controls are left attached to ignition system - just the standard, new 1985 ignition module. When it starts the timing mark is at near 30+ degrees BTDC. When I try to rotate dizzy clockwise to bring timing mark to 10 degrees BTDC the motor stalls and quits. I have rechecked that timing mark is at zero degrees when #1 piston is at TDC. Any ideas why the timing marks illuminates at 30 degrees and moving to 10 degrees kills engine?
FYI it wasn't anything to do with the dizzy. The dumba** who set the valve lash should be lashed for setting 3 cylindars badly. She purrs like a kitten now.
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post #30 of 32 Old 09-01-2015, 08:43 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

i hope this thread is still being monitored somewhat, i'm having trouble myself, ok, 87 model 2.8, pulled the motor because I thought the block was cracked, turns out it was the intake gasket by the dizzy, long story short, dropped the motor back in, timing trouble, finally got it back to 10* BTDC but now I read there is a mystery wire I have to unhook before I set my base timing, I've looked under the passenger side carpet and "under the heater box" as Chilton puts it, no luck, using a remote starter I can crack the butterflies open and it will run but as soon as I let the b/flies close it dies, what am I missing?

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post #31 of 32 Old 09-01-2015, 10:23 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

You're missing disconnecting the tan/black wire. It's in the passenger foot well, keep looking you will find it. The connector is a small black connector.

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post #32 of 32 Old 09-05-2015, 08:02 PM
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Re: 87 s10 2.8 V6, timing off 20-30 deg

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You're missing disconnecting the tan/black wire. It's in the passenger foot well, keep looking you will find it. The connector is a small black connector.
thank you sir, I finally found it, got timing set now, everything running smooth until I got in it and tried to put it in gear, having clutch problems now, on another thread now trying to get some ideas, thanks again

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