I went back to the garage to read the chilton book again. It says to install the TPS with the pigtail facing toward the IAC. I was confused enough before getting into this deal... I have to wonder if it doesn't make a difference which way it's oriented?

 

I have the Haynes.

 

I'm at a total loss now...

I tested each wire on each component for continuity from the component to the source, and all were good. I tested vacuum again, and all was good. I tested valve movement with external vacuum, it was good. I have no leaks or blockage in the exhaust tube.

I found a site called fordfuelinjection.com which is info from Ford about their electronics, and it had some great info. It said to short pin 33 on the EGR solenoid to ground to see if the system is working. Pin 33 is the left one as you look at the solenoid from the front of the truck. That gives the solenoid full voltage and opens the EGR valve completely, proving wiring, vacuum, and valve movement - I did that, and it stalled the truck.

From there, I thought maybe the old sensor that I shaved down a bit might be causing the codes again - tried the new one and stalled the truck again, but still get the 33 code. With the old sensor that I modified, I could fluctuate between low voltage and movement not detected, but couldn't get a sweet spot in between where it didn't cause a code. Not to mention the truck still goes through phases of running good and running like crap.

The ford guys say that the coolant temp sensor will cause poor performance, and of course the throttle position sensor can cause poor performance too. They should throw their own codes though...

So what the hell am I to do now? Could the computer have a glitch causing it not to read the sensor input, should I start testing the TPS and ECT or other sensors, or am I missing something obvious?

 

Back for round 2...

I also read a blog from a guy who had gone through about the same deal as I have, only on a mustang 5.0. He finally found that the intake orifice was totally blocked. He knocked the junk out, and all was well.

So, I decided to take the valve off one last time, and take another look. Awhile back, I thought I had cleaned the intake orifice - it was built up around the edge of the hole and about 50-60% blocked. I scraped all of that crud out, and didn't look any further.

Well... I looked again, with my head laying on the battery and a flashlight in the hole - it was blocked up severly (closer to 90%) up in there about an inch or so past the edge. That far inside such a small hole, it's hard to get that stuff loose without losing some on the inside. I did the best I could to pull it out, but was sure that some bits had gotten into the intake. Got 'er done, back to a round hole, and put it all back together.

I decided to fire up the motor to burn off any crud that fell inside, and the funky smoke went rolling out the exhaust pipe. I let it run for awhile (it was dead cold by this time) until it came up to normal temp. I got in and goosed it a couple of times, and it made a little cloud behind the truck. A couple of more gooses, and it was back to normal exhaust.

I got under the hood again, and watching with a flashlight, I could see the valve open as I pulled on the throttle lever. I guess these are all good signs - since it's getting late and I have to get up early in the morning, I didn't go for a drive. The trip to work tomorrow should tell the true story.

I'm still open to any suggestions for other places to look just in case this doesn't do it, but hopefully that was finally the solution to this nightmare.

 

That sounds like it may be it, but so did all the other stuff you did. Maybe the air being blocked off wouldn't give the EGR the extra push it needed to give proper sensor readings. I hope that does it for you.

 

I hope so too!!! I'm almost afraid to drive it tomorrow, for fear that I'll be on suicide watch!

Seriously, though - I just can't come up with any other ideas, aside from throwing irrelevant parts at it. That's the problem with this, you start running out of reasonable solutions and start wasting time and money on stupid guesswork.

I guess in theory, if the orifice was blocked that bad, it could lead the valve to stay closed, which would allow it to just get caked full of junk. I feel pretty silly thinking that I cleared it out but didn't look deep enough to actually do the job right.

If that cures it, I don't feel too bad about the parts - the valve was definitely trash, and the solenoid was shot too. The sensor was probably good, but I replaced it in a last resort Hail Mary. There again, ran out of reasonable ideas and jumped to conclusions. Vac lines and fittings are cheap, and a couple were definitely getting hard and cracked, so no waste there either.

If the damned thing runs right tomorrow, it'll be worth all of the frustration. One thing's for sure - I've learned a lot from this (mostly thanks to you), I've gotten some good exercise for my brain, and I've gotten much more familiar with the ole' truck.

If it doesn't run right, I'm about ready for an EGR delete kit!

 

Seriously. Emissions be damned if this doesn't work; you've done your fair share for the environment by this point.

This post is starting to feel watching Lost.... I just want answers damit!

Good luck; hope it works.

 

Didn't work... the truck drove like crap all the way to work!

 

I might have stumbled onto something tonight, but I have no idea what it means...

I was pretty much staring under the hood of the truck, thinking that I might just see something that I'd missed before. Behind the EGR solenoid, there are 2 smaller solenoids. Until tonight I had no idea what they were. I did notice, though, that the front one looked strange.

I climbed up to get a better look, and the bottom vacuum line was not connected. There are two lines with a double fitting like on the EGR solenoid, and the bottom one was twisted toward the front of the truck, totally missing the port.

I plugged it in, checked the one behind it (it was connected) and started the truck. Didn't drive it, but let it idle and gave it some gas for awhile. Sure feels like it smoothed things out - at least returned full vacuum by having it connected. When I checked vacuum before, I didn't even mess with those, because I had no idea what the hell they were and didn't want to mess anything up.

So now I'm wondering - what the hell are those things for? The chilton manual points them out in a diagram as TAB (front one) and TAD (rear one) but doesn't tell a whole lot about them, aside from being bypass and diverter solenoids for the smog pump? I guess that means something, probably a system that's related to or interacts with the EGR system?

Looking through the code definitions, there are codes for the thermactor air system (I think that's the right name) - why wouldn't it display a code if it wasn't even getting vacuum?

Any ideas, theory, explanation of what this thing is all about, etc. would be much appreciated!

 

I think you stumbled upon something that may help. For one thing, that vacuum leak (if it was leaking) wouldn't help the running condition. Then, the thermactor does close to the same thing the EGR does, except with fresh air. While the EGR uses exhaust to reduce emissions, the thermactor uses fresh air. So with one solenoid not working the emissions would be higher than expected. But I think you would have gotten a different code other than EGR movement not detected, even if you didn't get a TAB/TAD code. Maybe the computer relates higher emissions with an EGR code.