EGR and TPS questions.

[88 Fox GT]

Since I got the car I have always gotten code 33 (EGR not opening properly). I tried switching the EVP sensor and even cleaned out the EGR (which had lots of build up in it) but I still get code 33. So, I pulled of the vacuum line to see if there was any suction. I didn't feel anything. Is this normal or might this be causing my problem? All I know is that there is a vacuum line that runs from the intake to a solenoid on the passenger side shock tower and a vacuum line runs from there to the EGR. What is the purpose of that solenoid? What might be causing the problem here?

With my TPS, I stuck a volt meter on it to get it adjusted properly. I tested it with the key on and engine off. For some reason, I could not get the TPS to go below 1.25V. Does this mean the TPS is probably junk?

 

[HISSIN50]

All I know is that there is a vacuum line that runs from the intake to a solenoid on the passenger side shock tower and a vacuum line runs from there to the EGR. What is the purpose of that solenoid? What might be causing the problem here?

With my TPS, I stuck a volt meter on it to get it adjusted properly. I tested it with the key on and engine off. For some reason, I could not get the TPS to go below 1.25V. Does this mean the TPS is probably junk?

The solenoid gets constant vacuum. But you dont want manifold vac on the EGR, so the solenoid, which is computer controlled) acts like a door to allow the manifold vac to pass to the EGR when it is appropriate.

Did you slot the screw boss on the TPS? I had a recollection you did, but I might be thinking of someone else (I think you have mentioned this before in other theads, perhaps).

Good luck.

 

[HISSIN50]

Oh yeah, forgot to finish the thought. With the EGR, I would ensure all the vac lines are intact (no cracks, etc). You can test the EGR solenoid to see if it is energizing when it should (cruise situations).

Applying a little bit of vac to the EGR itself should cause an idling car to stall or idle horribly.
Jrichker has nice comprehensive posts on code 33 if you feel inclined to search his posts (or he will probably post the info in the morning).
Good luck.

 

[88 Fox GT]

The solenoid gets constant vacuum. But you dont want manifold vac on the EGR, so the solenoid, which is computer controlled) acts like a door to allow the manifold vac to pass to the EGR when it is appropriate.

Did you slot the screw boss on the TPS? I had a recollection you did, but I might be thinking of someone else (I think you have mentioned this before in other theads, perhaps).

Good luck.

Yep, I slotted them a little bit. Son of a bitch still doesn't want to go under 1.25. I might have to slot it more, but that just doesn't seem right.

 

[HISSIN50]

I would make sure the Vref is 5 volts and that the ground wire is solid. Not sure about why it is so far off (the base idle setting screw is not way out of whack, right?). Mine is set at 1.21 volts and works fine so I leave it. Anything more than ~25% out of spec should toss a code; otherwise the puter should zero out the TPS (baseline it).

Good luck.

 

[88 Fox GT]

Well, I think the TPS might be part of my whack idle. It will usually idle at like 1000-1200 (way too high), but when I lay into the throttle a little bit, it will then idle at like 1800 until I blip the throttle really quick to bring it back down to about 1000. Damn thing.

What was the spec on the idle set screw? I have a feeler gauge I can stick in there, if that's how I adjust it to spec.

 

[HISSIN50]

Here is a decent write up on doing it (there are several methods, but this seems to work pretty well). The feeler gauge method does not seem to be as common, and I think this way works better for people with IAC issues (which you dont have, but it might help lessen the duty cycle of the IAC, which might help).



Good luck.

 

[88 Fox GT]

Ok thanks man. I will give this a try tomorrow.

EDIT: What do you think is a good baseline to set the RPMs to with the screw? Should I get it as close to the stock as possible? Somewhere around 700 RPMs maybe?

 

[HISSIN50]

It is really up to you with that. I play around with different settings till I am happy or sick or messing with it.

When I am setting it, I like to get it to idle halfway decently with the IAC disconnected (so if the IAC clogs/goes south, I dont need it to idle). I can dial it down to about 700 RPM before the idle starts to degrade. But your lower limit will be different. And the condition and efficiency of the individual IAC has a lot to do with the setting, and that is different for everyone.

You really cant go wrong and this is not an exact science (If someone knew exactly how to dial the idle in on every EFI 302 stang, they would be LOADED. ).

MY two cents. Good luck.