2.5 TBI idles great but refuses to rev

[eaglescout526]

You know, I never thought of that but the CPS is more of a magnet than an electrical contact. Course I don't see any harm in removing the rust as I, and don't quote me on this, but I don't think rust has a lot of magnetic properties so it could be causing an issue.

[Dickinson County Comanche]

40 minutes ago, Dickinson County Comanche said:

I actually just tried to probe the CPS for the correct voltage and I got nothing. Could it be that the flywheel got a little bit rusty due to sitting out exposed when there was no transmission on it?

And when I say “nothing” I mean no voltage at all. It will still run with it reading 0 though

[eaglescout526]

Are you reading AC or DC voltage for the CPS?

[Dickinson County Comanche]

30 minutes ago, eaglescout526 said:

Are you reading AC or DC voltage for the CPS?

AC. I tried DC too with no avail.

[eaglescout526]

AC is the right way and you’re getting nothin on AC? And it’s still running? Damn that’s impressive. 

[Dickinson County Comanche]

4 minutes ago, eaglescout526 said:

AC is the right way and you’re getting nothin on AC? And it’s still running? Damn that’s impressive. 

Unless both of my multimeters are bad, yes

[eaglescout526]

Hmmmmmmmm kinda weird. If the flywheel is that badly rusted, it wouldn’t hurt to give it a good cleaning. 

[Dickinson County Comanche]

11 minutes ago, eaglescout526 said:

Hmmmmmmmm kinda weird. If the flywheel is that badly rusted, it wouldn’t hurt to give it a good cleaning. 

It doesn’t seem to be that rusty but I’ll still probably just go ahead and give it a clean to be on the safe side

[eaglescout526]

Woah! Is that a flex plate?

[Dickinson County Comanche]

1 hour ago, eaglescout526 said:

Woah! Is that a flex plate?

Yep. I’ve never seen a 2.5 with an auto except for this one. Cleaning it didn’t help, but I’m still sure it’s something to do with the CPS. I checked the CPS on my 89’ and it came back perfectly within spec so I almost wonder if maybe the CPS isn’t bad or positioned incorrectly. I’ll have to check in the morning and see

[Dickinson County Comanche]

I definitely think the CPS is mounted incorrectly now. I found a picture (after searching for one forever) of a XJ/MJ A904 and the CPS mounts on two spacers that I don’t have. The picture of the trans/transfer case is how mine is set up

[eaglescout526]

That will probably do it as well. I’m still amazed it is starting and running. Must be barely picking up the tone ring. 

[Ωhm]

Trigger wheel radial runout is 0.016 inch (0.40mm) using a dial indicator on the inner surface.

 

Check out page 77 or 2A-15

[Dickinson County Comanche]

It actually revs again! The CPS mustn’t been positioned correctly so after a quicky adjustment it actually revs again. Absolutely no power at idle-~1750 or so but after that it picks up and goes. Any ideas as to why it might do that? I know the EGR valve is no good so I’ll have to fix it eventually.

 

I also lost a tire on my test drive. Pour one out for the poor Walmart cheapo specials

[eaglescout526]

Does the ISA operate? Is the throttle all the way closed? My thoughts on crap idle is the ISA not being adjusted right.

 

As for the whole issues, I am glad it was just the CPS.

[Dickinson County Comanche]

2 minutes ago, eaglescout526 said:

Does the ISA operate? Is the throttle all the way closed? My thoughts on crap idle is the ISA not being adjusted right.

 

As for the whole issues, I am glad it was just the CPS.

I should have clarified better, it idles fine, just when you try to give it gas at idle-~1750 it runs like crap. If the ISA is the little stepper-motor thing that pushes the throttle plate open, it does function correctly.

[eaglescout526]

Ok, so we are still having high RPM issues.

[Dickinson County Comanche]

4 minutes ago, eaglescout526 said:

Ok, so we are still having high RPM issues.

Yes, but the ignition doesn’t blip out like before, so it’s not ignition. My guess is vaccum leaks screwing with the map sensor or maybe that bad EGR valve

[eaglescout526]

Entirely possible. EGR is se to open up upon the opening of throttle so we can move to replace the EGR. I’ll see if there is a testing procedure on the EGR solenoid. 

[Dickinson County Comanche]

4 minutes ago, eaglescout526 said:

Entirely possible. EGR is se to open up upon the opening of throttle so we can move to replace the EGR. I’ll see if there is a testing procedure on the EGR solenoid. 

The diaphragm on the EGR is totaled. I have an extra EGR solenoid to place in to see if it’s working or not

[eaglescout526]

Sounds like a plan. 

[Dickinson County Comanche]

Found out I’m not getting any voltage from the ECU to the O2 sensor. Wire checked out ok and the computer contacts looked good when I removed them so it might be a bad computer. I’ll have to research more before biting the bullet on a new computer though. 

[Dickinson County Comanche]

Checked voltage at the ECU. Nothing. 

[eaglescout526]

Perhaps the O2 heater relay? AMC was pretty adamant about the ECU being the absolute last thing to replace. 

[Dickinson County Comanche]

3 minutes ago, eaglescout526 said:

Perhaps the O2 heater relay? AMC was pretty adamant about the ECU being the absolute last thing to replace. 

O2 heater is getting 12v at the sensor. Unless something with the relay is bad, I’ll have to swap them around and see.