87 gmc sierra timing

[87gmcsierra]

Hello everyone i got a 87 gmc sierra with the 5.7 350 and was checkin the timing the other day because i could hear it pinging and it wasnt even on the scale it was off about a inch from it to the left , i tryed movin it a little to see if it would get to the mark but it would get way off wack do you think its 180out maybe?If i was to take the distributor out i would need to get the number 1 piston commin down from tdc right? any ez way to do this Thanks .

[Desert1957]

Hey

Just remember when you check timing on a "TBI" engine you must disconnect the wire under the brake booster. Its a little single wire with a black connector. If you need pics of mine I might be able to post them later this week.

Let me know...Desert

[87gmcsierra]

man thanks for reminding me i woulda forgot about that lol thanks man.

[rcbildr]

Check your harmonic balancer. A friend of mine had trouble timing his burb and discovered that his balancer was pretty much toast. The rubber ring was so far gone it allowed the outer ring of the balancer to shift and he could not get his timing set right until he got a new one.

[87gmcsierra]

ok cool man thanks but if i take distributor out does the first piston have to be uptop and just about to go back down to be on TDC?

[Blake_H]

Originally Posted by Desert1957

Hey

Just remember when you check timing on a "TBI" engine you must disconnect the wire under the brake booster. Its a little single wire with a black connector. If you need pics of mine I might be able to post them later this week.

Let me know...Desert

I would take a photo of that connector. We can't find the one for my '87.
Thanks,
Blake

[Desert1957]

Here it is , follow the white arrow. Brown wire with a black stripe..



Desert

[Blake_H]

Originally Posted by Desert1957

Here it is , follow the white arrow. Brown wire with a black stripe..



Desert

Desert, thank you very much. Will give it a try this weekend.

[Desert1957]

Originally Posted by 87gmcsierra

ok cool man thanks but if i take distributor out does the first piston have to be uptop and just about to go back down to be on TDC?

Originally Posted by Blake_H

Desert, thank you very much. Will give it a try this weekend.

Hope it works out for everyone, as far as removing the distributor , take the cap off , bump the engine around untill it lines up with something you can mark or any reference point, undo the hold down , unplug the harness, pull it out. when going back in just re-align the rotor to your original mark. find the wire in the picture unplug it , set the base timing , on a stock engine it might be 0 or even as little as 2 degrees. turn the engine off , plug the wire back in , start it up and verify the check engine light is off ( it will be on while setting the base timing)

Desert

[87gmcsierra]

i think my distributor might be 180out because i unpluged that and check it and the mark was right on the money but once i plug it back in the mark on the balancer is about a inch to the left from the scale , any advice on that is it 180 out or ?? could i run it with it unpluged? Thanks

[87gmcsierra]

bump

[Desert1957]

No , Its all good , you should have your "Base Timing" set with it unplugged. when you restart your engine (wire reconnected) the timing mark will run about an inch past the scale. this is about 15 to 20 degrees of timing. Its all controlled by the computer.

As far as the term "180 Degrees off" this can happen after the distributor is removed. Just remember the timing mark on the balancer comes up on the scale when number one piston is at top dead center and when number six is a TDC. so if you line the rotor up with number six when it should be on one , it will not start , sometimes backfire. Because your distributor is "180" degrees out of time.

Desert

PS: NEVER drive a "TPI" engine with that wire unplugged , you will have no power , bad mileage and many other problems.

[87gmcsierra]

cool man thanks i guess the timing is right on maybe my truck hates regular gas im try to put premium in it and see if the pining stops . Thanks man appericate it.

[Desert1957]

Wow , I didn't know the "pinging" problem is what you were trying to fix. If you have a detonation problem the first thing is to check is the timing. then the operation of your "EGR VALVE". If the vacum line has come off or is plugged. With the age of our trucks now chances are the valve itself is bad.

Desert

[87Bob]

Originally Posted by Blake_H

Desert, thank you very much. Will give it a try this weekend.

What does the wire control?

[87gmcsierra]

Originally Posted by Desert1957

Wow , I didn't know the "pinging" problem is what you were trying to fix. If you have a detonation problem the first thing is to check is the timing. then the operation of your "EGR VALVE". If the vacum line has come off or is plugged. With the age of our trucks now chances are the valve itself is bad.

Desert

when i got the truck the same egr valve was in it and it was unpluged cause i guess it wouldnt run with it pluged in so i bought a new one and pluged it in and it runs but if you drive it for a long time check engine light comes on and its egr lol i donno , it runs perfect i donno what its deal is, i guess 87 was first year for tbi and some other stuff wonder if maybe the computer is old and needs replaced.

[cableguy0]

The wire is the timing control. That distributor is basically locked out,theres no means to advance the timing mechanically. The timing advance and retard is done by the computer. If its not set at zero with the wire disconnected the computer will advance or retard the timing incorrectly because it doesnt have the ability to sense where the base timing is. It works off of the assumption that timing is set at 0. The tbi system is an extremely simple form of fuel injection and works really well when everything is functioning properly. Once your messing with a 23 year old truck theres bound to be something that isnt quite right. Things wear out and go bad thats part of life. Throwing parts at it for the hell of it isnt going to do you anygood. Did you look into egr passage in the intake? Chances are if the egr hasnt been functional for a long period of time the passages could be clogged up.

[Desert1957]

Originally Posted by cableguy0

The wire is the timing control. That distributor is basically locked out,theres no means to advance the timing mechanically. The timing advance and retard is done by the computer. If its not set at zero with the wire disconnected the computer will advance or retard the timing incorrectly because it doesnt have the ability to sense where the base timing is. It works off of the assumption that timing is set at 0. The tbi system is an extremely simple form of fuel injection and works really well when everything is functioning properly. Once your messing with a 23 year old truck theres bound to be something that isnt quite right. Things wear out and go bad thats part of life. Throwing parts at it for the hell of it isnt going to do you anygood. Did you look into egr passage in the intake? Chances are if the egr hasnt been functional for a long period of time the passages could be clogged up.

Yea! what he said.....

Desert

[87gmcsierra]

lol i unhooked the egr and it all went away and truck runs a million times better , which i guess egr passage is all carboned up , well atleast the one under intake

[87Bob]

Originally Posted by 87gmcsierra

lol i unhooked the egr and it all went away and truck runs a million times better , which i guess egr passage is all carboned up , well atleast the one under intake

If you unhoked the EGR valve and the problem went away. I suspect that the EGR valve is staying open because the coolant sensor is bad and it thinks the engine is cold and would naturally be running rich. It is giving the EGR valve vacumm when it is not supposed to.

[73chevyman]

you have what it's called spark knock put 93 in and it'll go away

[87gmcsierra]

Originally Posted by 73chevyman

you have what it's called spark knock put 93 in and it'll go away

put 93 in it before did nothing lol , egr vavle or passage is bad or clogged up just gona leave it unhooked screw it.