87 s10 2.8 V6, timing off 20-30 deg

vetkaw63 · 11-01-2009, 04:25 PM

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

The_Raven · 11-01-2009, 04:49 PM

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.

vetkaw63 · 11-01-2009, 05:53 PM

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

jtcfanof3 · 11-01-2009, 07:54 PM

Checked the EGR valve?

ddog800 · 11-01-2009, 08:25 PM

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.

vetkaw63 · 11-01-2009, 08:34 PM

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

jtcfanof3 · 11-01-2009, 08:37 PM

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.

vetkaw63 · 11-01-2009, 08:40 PM

How do I check the EGR valve and what are the symptoms?

vetkaw63 · 11-01-2009, 08:43 PM

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.

jtcfanof3 · 11-01-2009, 08:47 PM

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

vetkaw63 · 11-01-2009, 10:02 PM

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.

11-01-2009, 04:25 PM	#1
vetkaw63 Registered User Join Date: Aug 2008 Posts: 24 Location: User is: OffLine	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
	[Reply w/Quote]

11-01-2009, 04:49 PM	#2
The_Raven Registered User Age: 32 Join Date: Oct 2003 Posts: 1,039 Location: The Nest User is: OffLine	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.
	[Reply w/Quote]

11-01-2009, 05:53 PM	#3
vetkaw63 Registered User Join Date: Aug 2008 Posts: 24 Location: User is: OffLine	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
	[Reply w/Quote]

11-01-2009, 07:54 PM	#4
jtcfanof3 Busy at school Age: 33 Join Date: Aug 2005 Posts: 5,046 Location: On campus all the time practically!! User is: OffLine	Re: 87 s10 2.8 V6, timing off 20-30 deg Checked the EGR valve?
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11-01-2009, 08:25 PM	#5
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	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.
	[Reply w/Quote]

11-01-2009, 08:34 PM	#6
vetkaw63 Registered User Join Date: Aug 2008 Posts: 24 Location: User is: OffLine	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
	[Reply w/Quote]

11-01-2009, 08:37 PM	#7
jtcfanof3 Busy at school Age: 33 Join Date: Aug 2005 Posts: 5,046 Location: On campus all the time practically!! User is: OffLine	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.
	[Reply w/Quote]

11-01-2009, 08:40 PM	#8
vetkaw63 Registered User Join Date: Aug 2008 Posts: 24 Location: User is: OffLine	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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11-01-2009, 08:43 PM	#9
vetkaw63 Registered User Join Date: Aug 2008 Posts: 24 Location: User is: OffLine	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.
	[Reply w/Quote]

11-01-2009, 08:47 PM	#10
jtcfanof3 Busy at school Age: 33 Join Date: Aug 2005 Posts: 5,046 Location: On campus all the time practically!! User is: OffLine	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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11-01-2009, 10:02 PM	#11
vetkaw63 Registered User Join Date: Aug 2008 Posts: 24 Location: User is: OffLine	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 10:04 PM.
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