I do the same thing (making it smaller) so I will run .042 as well.

 

Hey, I think your on the right track with, IAC valve. Lot of times they won't throw a code, Since you cleaned it out it might be the motor on it or wiring connector.

 

I reread your post, and here is my assumption. IAC valve. When it reads the 12 code it will eventually throw 32. Computer is telling it not to give vacuum to egr. Now you think you have a vacuum leak. Is this by sound? If it is, then your hearing control valve bypassing vacuum. Now for the idle screw. You should never have to adjust it. Its there so that the throttle doesn't shut completely closed. Now from latest post, you said it started running bad again. See if you got your 12 code back. As I reread your post, I realized that this is a week long post.
It really sounds like IAC valve, check for resistance, and voltage to the solinoid/motor. I think your "H" manual shows how to check.
Your egr sounds good. Cleaned ports and diaphram held Vacuum.
Your evp on the other hand, I don't know, remember this is what controls how much vacuum goes to egr. So how ever much voltage at a given time is how its controlled. There may be a diffence in evp's but not sure.
Anyhow, you needed a fuel pressure gauge. And a tune up. I hope I've helped.
Sure seems that all of this keeps you busy. I guess you stay out of trouble that way. Anyhow, good luck.

 

The only time I could get vacuum to the EGR valve was while I was driving. Then anytime I was just barely on the throttle, vacuum gradually eased up to 8 inches of mercury as the computer commanded the EGR valve to open. The idle speed should be set with the throttle stop screw, and once it has been set it's ok to leave it be, but if a previous owner moved it around any, it might be nice to get it where it should be. If the throttle stop is set for too little throttle, the idle air control valve will not have enough extra throw to idle the engine up higher during the test. It's such a pain to deal with problems such as these; best thing you can do is just keep testing and get everything set like it should be and see what happens.

 

I just changed the plugs and wires. The wires were in terrible shape. One of them I was able to "snap" in 1/2 as if breaking a twig. It looks like #8 and #3 weren't firing well because the plugs were considerably different then the others. The plug boot on #8 was kinda loose, and the #3 had the bad wire. They weren't routed very well either, the AIR system tubes are there and could easily burn the wire. I should of replaced this stuff awhile ago but too lazy and didn't care

It runs much better...but still not 100%. The other 6 plugs were kinda white...maybe its lean?? I'll compair them to my Haynes manual plug pictures. I also have an exhaust leak by the passanger side manifold area...

After cleaning the IAC it smoothed the idle out a lot. Previous to that, I could push the clutch in while driving and the idle would be all over the place, sometimes dropping down enough to kill the motor. Now the idle is much more stable and acceptable.

I've got to take it on a trip to maine on wed...the F-150 needs a little work and is hitting the dyno on tuesday...


As far as the EGR/EVP, I think the sensor and valve are fine. They're both definitely new. I think what the problem is, is that the shaft on the EVP sensor hangs too low before touching the closed EGR plunger. So that's causing the closed voltage to be low, and the open voltage to be low. Maybe I should put something on the EGR plunger (like a drop of solder?) to make the EVP shaft come up a little higher. Any opinions?

 

Fixing the exhaust leak will help too. As it's probably causing o2 sensor to read lean (if it's within limits it won't set the CEL), and the computer is trying to compensate.

 

A missfire would throw it rich due to the oxygen from the unburned intake charge. Unless the leak is pretty serious and there is good enough scavenging of the exhaust to pull air into the system, I wouldn't worry too much about a leak causing variation in the O2 content of the exhaust.

 

The exhaust leak isn't all that bad. I don't know where it's coming from yet, but just something to do with the passanger side manifold area. I'm not too concerned as of yet.