Random shut downs
 

Hello!

I own a Blazer k5 1990 5.7L for three years now, i got this strange problem from day one.. don't ask me why i write about this just now, anyway i'll try to keep it as short as possible.
95% of the time the engine runs like a Swiss clock, but in the other 5% i get one of these scenarios:

1. the engine shuts down with no warning ( like you've switched it off) usually in very low speed or when in parking
2. the engine begins to stutter, the rpm drops for a couple of times and then shuts down. recently it happens in almost every stoplight.

other than that the engine runs beautifully on open roads.
few things i can add to assist:
- the distributor is new and the ignition module.
- the exhaust seems to be plugged, I'll get to it asap.
- one more "clue", i think the timing is off, but i can't clear it because I'm unable to adjust the timing.. i can get my hand on a light gun but i don't understand the following picture

If the exhaust is restricted, I would get that fixed first before attempting to set the timing.

What part of the timing procedure do you not follow? Have you located the timing connector?

no. I'm having trouble locating that connector. that's exactly my problem.

a little update:
today the engine died on me in the middle of the road, it refused to start again.
it looked like the engine is in a middle of an earthquake while trying to start it again.
eventually i managed to get home, 2.5km from where i got stuck. it took me an hour and a half to do that.
any ideas where should i start? the engine starts with a lot of fighting involved but will only stay on for a second if i don't pump it with continues gas.

I would suggest pulling a spark plug, check to see if your timing mark is high or low on the electrode. That will tell you if you're close on your timing. Then check the condition of the plug, if its a certain color that will tell you a lot about what's going on inside the cylinder. If the electrode is wet, then you're getting fuel. After that check for spark, I just had a buddy of mine whose ignition module quit working while driving down the road in his K5. A couple buddies of mine had to go help him get it running. Pull plugs, it will tell you a lot about what's going on in there. Simply for a place to start.

You replaced the dizzy and didn't set your timing... :icon_fryingpan:

Manifold was probably flooded when you got stuck, hence it wouldn't start. Once it's that wet, it's a real biatch to get it to fire (even with the throttle blades wide open). With the timing off, it's even worse. :icon_doh:

The EST bypass wire is along the firewall between the ICM and the wiper motor. It's a single tan/blk wire and the disconnect plug you're looking for is black. You need to find the timing mark groove on the harmonic balancer and paint it with whiteout (or whatever).

Motor should be at operating temp to set timing. Unplug the tan wire and fire her up. To advance the dizzy, loosen the holddown bolt and rotate counter-clockwise. To retard, go clockwise. Goal is to get the timing mark groove into the widest valley on the timing plate (shark-tooth tab driver's side of engine under the water pump). 0* is the bottom of that valley. The first peak counter-clockwise is 2* advanced, next peak is 4* adv, etc..

It'll idle better being advanced with EST unplugged, but you'll get aweful detonation under load if you set it advanced. After it's at 0*, kill the engine and plug EST back in. Start engine and verify the timing is now advanced (not at 0*), indicating the ICM is doing the timing advance as it should.

WARNING: The ICM is grounded to the engine through the hold-down bolt unless you add a ground to the distributor (*smart*), and you will very quickly fry an ICM if it doesn't have a good ground. So.. don't loosen the bolt too much in order to rotate the dizzy with engine running.

I'm confused now, the est connector is in the engine compartment? i should look for it along the harness between the icm and the firewall?
yesterday i got the idea that the connector is inside. so... which one is it?

i hope to get my hands on a light gun by the end of the week in order to properly adjust timing. I've found the connector so that takes care of that.
but I've found something strange with the coil connections:
as you can see in the picture, there's a yellow wire with a connector on it that goes nowhere! keep in mind that the truck is running like this for years.
the other thing I've noticed in the other picture is that lonely two wires connector that just sits there..
oh and of course i started the truck this morning and it ran beautifully.. like yesterday nightmare never happened..
i really don't know where to begin or how to address this problem. i can't just buy new parts and replace the ones we suspect.

The wire that comes off the coil I believe is white and is for the tach signal.

The other two wire connector could be for the EGR solenoid which your truck may not have?...

i actually don't even know where's the egr valve should be located.
can it be related to my problem?