EFI - Vacuum Lines - 1990 302
 

New post, same problem. I posted this some weeks ago where I changed my plugs, wires, and filters, then miserably failed an air-care test. Well as I reposted, I had been a little careless when installing the plugs and cracked the porcelain insulator on 1 (or more) plugs. I since replaced ALL the NGK's with Bosch plugs (I blamed it on the NGK's, but that was wrong). So now it runs well, but won't idle. It "hunts" if you know what I mean. If I come to a stop, it will stall unless I put it in neutral. In neutral it will stall if I turn the steering wheel. If I put ANY load on the engine in neutral, it will stall. So I figure that when I changed the plugs I have knocked or broken or undone a vacuum hose or some other EFI mechanism. If I hold the pedal at 800-900 RPM, no problems, but that is wrong. I can't find or see any problems.

Anybody have or know of a schematic of the EFI system and vacuum hose routing to troubleshoot this goof-up?

As always, thanks in advance.

phil

It should be on a sticker under the hood. Either on the air intake box or the along the front somewhere.

I replaced all the hard plastic vacuum lines...
 

with rubber tubing a couple of years ago. It eliminated a bunch of problems, and it's run a lot better ever since.

My hose diagram is hard to read where they put it. A digital camera helps a lot. If you do not have one a MityVac vacuum tester is about $30 then you will know all the vacuum systems are correct. Then you did not mention pulling codes?

Check and then re-check your spark plug wires. From what you have said (changing spark plugs twice and all) I'd bet you connected the spark plug wires wrong and messed up your firing order.

What was the results of the emissions check? High hydrocarbons, high NOX, etc?

It could be a vacuum line, check them as well.

Ask your tranny shop if they removed the upper intake in order to lift the motor to change the rear main seal. If so, they probably created an intake leak.

Above all, Stop just replacing parts in the hopes of fixing it. diagnose the problem, test the suspect part, and then replace it if necessary.

vac lines
 

Try looking at the red vac lines on top of the motor they are made out of a hard composite material and can crack with out it being visable my truck would stall at every light once I changed mine on my 93 bronco no problem it has run fine since.

It wasn't the vacuum line(s) afterall
 

Thanks for the insight, but as it turns out, my fuel pressure regulator AND Oxygen senser weren't working. The engine was constantly flooding. All is well now.