Map Sensor? Timing? Vacuum Routing? Help!

[karenjim]

How much do you know about timing an engine? For the past couple of days, my husband has advanced and retarded the timing and hasn’t been able to get it right…. If that’s even the problem, in the first place!

Let me start at the beginning...

We have a 1988 Chevy Astro 4.3L...... My husband changed the head gasket and the intake manifold gasket on the van. They were in some REALLY bad shape (surprisingly, however, the head wasn't warped!) Anyway, he mistakenly had not marked the vacuum lines and put it all back together as best as he could remember.

Then, he realized while trying to start it, that he had seated the distributer shaft in at least 180 degrees off. With the help of a fellow mechanic, he got the shaft in properly and adjusted the rocker arms enough so that the van would start and drive. But the vacuum lines were incorrectly routed or leaking somewhere (sometimes surged) and the timing still needed a little more adjusting. So he rerouted the vacuum lines and drove the van, gradually advancing and retarding the timing as needed. But it still drove like crap wanting to stall and sometimes not wanting to restart back up.

The next day, he read some suggestions online and removed the vacuum line from the MAP sensor. The van idled fine (much better than before), until he put it in gear. Then it ran just as bad. We got another sensor from the junk yard and replaced it... no change (unless it getting worse is a sign). He’s found that if he unplugs the MAP sensor vacuum, it makes it idle better, but when trying to drive, it wants to overflow the gasoline and just about flood itself out. We tested the MAP sensor at AutoZone and they said that it was fine. Perhaps it has to do with the connections to it? Vacuum lines all have been tested too for cracks and clogging.

He is getting so frustrated. His transmission is also controlled by this and it doesn’t want to shift out of 2nd gear because it doesn’t think that he is needing it to. It stalls just about every time he takes his foot off the gas peddle and sometimes doesn’t want to start back up for awhile. He basically coasts to stops and puts it in Neutral when needed, but driving is becoming a challenge as it doesn’t like going over 25 miles per hour. He can’t think of anything else to try and he’s entered into an area that he knows nothing about…. Vacuum lines and timing.

Last night I put $15.00 into his tank, which gave him a little more than 5 gallons. That should have covered him for at least 2 days at work. But he was running out of gas on his way home because his engine was dumping so much into it trying to stay started. Do you have any suggestions? Could timing or vacuum lines cause this? I am running out of suggestions for him to try. And he is pulling his hair out about ready to blow the thing up!

We need help. Let me know if you can think of anything that we have not. Thanks in advance. I just hope someone can give him some input that I have not been able to give this time.

[CD Smalley]

Is he disconnecting the EST wire when he is trying to set the timing?

[karenjim]

EST Wire?

I'm not sure. What is that? He drives with the doghouse off and turns the distributer to advance or retard it. Can you tell me what this wire is? I don't imagine he knows about it either. Thanks.

[CD Smalley]

I believe it should be a brown and tan single wire. It should have a weather pack connector in it. This connector MUST be disconnected to set the base timing at IDLE. If you do not do this, the computer is controlling the timing. That's why he's having problems getting it set and keeping the van running.

I'm not sure where it is located on your van. But it should be readily available with the doghouse off.

Again, this wire MUST be disconnected when you are setting the timing and it MUST be done at IDLE! If you do not do this, the computer will advance/retard the timing as it sees fit regardless of where you turn the distributor.