Puzzled . . .

[anupaum]

Ok, with the new intake adapter and the repairs to my intercooler I managed to get everything to fit. When I fired up the truck it sprang to life without trouble, but now I can't get the idle to drop below 2 500 rpm.

TPS settings are normal. Warm-up is normal, but my O2 sensor is reporting an extremely rich condition. If I go into the fuel table and back the fuel down, nothing happens, and that is VERY strange because it SHOULD be responsive.

I can't find a vacuum leak, but it's REALLY hard to hear anything because the engine is so loud. I've got all of my fittings on tightly and if I check each joint nothing happens to the idle speed.

Now, I AM using the Mustang throttle body that Dave sent me. It's got this weird idle stop thing that has no adjustment because it comes from the bottom. The engine responds to pedal, but simply won't go below 2 500 rpm.

*** edit ***

Also, in the midst of all this trouble I noticed that my interior fan was stuck on one speed. I tried adjusting it, but nothing happened. Then, all of a sudden, it went "poof!" and filled the cab with a cloud of smoke. The smoke dissipated, and while the fan still works, it only works on full blast. It's likely that I blew the rheostat that controls fan speed, but why?

After tighting everything up again, I checked the vacuum gauage. It's reading 20 inches of vacuum, which is normal, and when I take the truck out for a spin it goes into boost nicely. I just can't get the idle down!

***end edit***

Any ideas?

 

[TireIron]

What does the mustang TB use for an IAC? does it use the same type that the ranger had? does it even use one?

Also does the TP sensor run in the same voltage ranger as the ranger one? if not you will need to recalibrate the megasquirt to run with those values.

 

[anupaum]

What does the mustang TB use for an IAC? does it use the same type that the ranger had? does it even use one?

It's got an IAC. I was using it on the stock Ranger throttle body and swapped it over. I thought that maybe I'd installed it backwards, but I changed its position and it doesn't matter. Also, if I unplug it, the idle doesn't change.

Also does the TP sensor run in the same voltage ranger as the ranger one? if not you will need to recalibrate the megasquirt to run with those values.

I don't know if it does or not, but when I've got Megatune up and running, the TPS values for idle are in the high 40's, and wide open is something above 250.

I'm really stumped with this, and my sweetheart is getting IMPATIENT!

 

[anupaum]

One more tidbit of info . . .

When I take the truck downhill, I can feel the injector cut-out occur. The engine feels like it's dying, then there's a surge when the injectors come back on. Now, it's NORMAL for the injectors to cut out at no load when the TPS value is below 60, but it's unusual for the truck to feel like it's bogging.

Is this a strange problem, or what?

If I had a vacuum leak, I shouldn't be getting 19 - 20 inches of vacuum at the 2 500 rpm idle, nor would I expect the truck to go into full boost.

I thought that maybe my IAC valve had gone wonky, but swapping it didn't help, and pulling the electrical plug for the IAC does NOTHING to the idle.

This is VERY strange!

 

[Sevensecondsuv]

Not many people here have megasquirt experience. I'd recomend asking over at www.turboford.net. Those guys are boosted 2.3 junkies and many of them have extensive megasquirt experience as well as mustang throttle body swap experience.

 

[BlackBII]

If the throttle plate is closed, and the IAC isn't letting air in...it's gotta be getting in somehow!

Have you tried the carb cleaner/propane method to look for vac. leaks?

 

[anupaum]

If the throttle plate is closed, and the IAC isn't letting air in...it's gotta be getting in somehow!

That's why I initially suspected the IAC valve. It seems strange, though, that it would suddenly fail when it had been working fine on the older throttle body.

Have you tried the carb cleaner/propane method to look for vac. leaks?

The first thing I'm going to do is "paint" all of my intercooler tubing joints with soapy water to see if any of them are leaking. Then, I'll do the WD 40 technique on the blower manifold, the intake manifold and my adapter. That's my task for this afternoon, as soon as I've picked my boys up from school.

 

[anupaum]

Not many people here have megasquirt experience. I'd recomend asking over at www.turboford.net. Those guys are boosted 2.3 junkies and many of them have extensive megasquirt experience as well as mustang throttle body swap experience.

I'm not convinced that my problem involves Megasquirt. I've been running that computer for over two years now, and it's worked flawlessly. The only thing that's different now is that I've swapped the intercooler tubing, the new blower manifolds and the throttle body.

I'll peek over at turboford and see if anyone can offer advice. Thank you!

 

[anupaum]

Ok, I've now tried the WD 40 and soapy water techniques. I can't find any leaks. Nothing is different when I spray WD 40 around any of the joints, and I get no bubbles when I use soapy water, either.

It would be a shame to abandon the project when I've come this far, but thoughts of that nature have been dangling dangerously in my subconscious . . .

 

[TireIron]

Grab a volt meter and check the TPS values for the heck of it. The ranger runs from I believe it was 0-5 volts through its sweep with no dead spots.

Also the bypass valve is opening up properly right? and it opens to the full 1" that the hose is? If the bypass was sticking closed I could see it forcing more air into the engine than it would be used to causing some pressure that shouldn't be there. Where is your vacuum reading from (before the S/C or after it)?

 

[anupaum]

Grab a volt meter and check the TPS values for the heck of it. The ranger runs from I believe it was 0-5 volts through its sweep with no dead spots.

Megasquirt only uses the TPS signal for overrun and injector shut off for flooding under cranking conditions. The TPS count should range between 30 and 250, and mine is right in there.

Also the bypass valve is opening up properly right? and it opens to the full 1" that the hose is? If the bypass was sticking closed I could see it forcing more air into the engine than it would be used to causing some pressure that shouldn't be there. Where is your vacuum reading from (before the S/C or after it)?

That's possible, because the bypass valve sits just beneath the intercooler tubing and may not open or close properly when the hood is shut. However, when I first hooked up the blower (how many years ago was that now?) I didn't HAVE a bypass valve installed and I don't remember the idle being this high.

My vacuum readings come from the manifold tree, which is AFTER the blower.

 

[anupaum]

Ok, I went over to TurboFord to get some advice. One of the guys there told me that there's an adjusting screw on the bottom of this throttle body. You can see it in this image, which is on the top because my throttle body happens to install upside down:

So, I cranked it down and lost about 500 rpm, which is progress, but it still isn't enough. Now, I had a misunderstanding about this particular throttle body because I didn't think it actually HAD an adjustment for idle speed. The reason is evident in THIS photo:

This is exactly how Dave sent it to me, and I really wish he was still around. However, I'm sure that between all of our collective experience we'll get to the bottom of this problem!

Does this look stock to any of you? Should I just cut the offending stud off and use the screw to adjust my idle?

***edit***

By the way, I double checked the actuation of my bypass valve. It opens and closes properly--at least, as long as the hood is up!

Also, here's a photo that shows my new intake manifold adapter:

***end edit***

robert

 

[Davis]

I'd just trim it down a bit and then reinstall it. see how it runs, and then trim it down a bit more if needed. or you could install a new screw.

 

[TireIron]

How does the throttle plate sit? is it closed completely or is the pin keeping it held open too much? If the pin is keeping open then definitly try trimming it down a little, and then some more if needed. I'll look around to see if i can find some pictures of a mustang TB. What year range is that from?

also you could just get a new screw that is a bit longer and screw it in so you can have more adjustability from it.

 

[anupaum]

How does the throttle plate sit? is it closed completely or is the pin keeping it held open too much? If the pin is keeping open then definitly try trimming it down a little, and then some more if needed. I'll look around to see if i can find some pictures of a mustang TB. What year range is that from?

I don't know if it's being held open too much. I tightened it down as much as I could, but I can still see a gap around the throttle plate when I hold it up to a light. So, how closed is closed?

I wish I could tell you what year range it's from, but I have no idea. It was Dave's throttle body.

also you could just get a new screw that is a bit longer and screw it in so you can have more adjustability from it.

That would involve drilling and tapping . . . My tool set is rather, uh, limited. If you saw what I've been working with you'd be astonished that I've managed to accomplish as much as I have!

robert