'89 XJ - High Idle, high NOx (vehicle is in california)

BulletMaker · Jan 12, 2014

So I'm back visiting the folks working on bailing my wife's cherokee out of here, she already paid california road taxes on it this year, it just needs to pass smog so I can drive it out of the state (without getting harassed by the local politzei).

I did some work on it last time I was down here, including cleaning out the throttle body, refreshing some of the connectors, and after cleaning the TB, the idle went high and usually sits around 2K.

Stuff done so far:

Cleaned TB, Cleaned IAT, Cleaned IAC, checked/replaced vacuum lines.

After this I started checking all the grounds, and right now from the B-wire (TPS disconnected) I'm getting 41Ohms. Greaaaaat...

BulletMaker · Jan 12, 2014

Ok, I put in new #4 cable that goes from - battery terminal, to the engine (scrubbed the stud, and the two little wires with a wire brush, brake cleaner, and then finished up with contact cleaner/preservative) and then ran another #4 from there to the chassis ground connector (bolt on the firewall) where the braid normally connects.

No change. Ideas?

I'm going to go try: http://www.naxja.org/forum/showthread.php?t=1072534

BulletMaker · Jan 12, 2014

ok so here are my results per cruiser's faq:
(also, NP231 TC automatic AW4 trans)
Engine Test (this is the issue)
A-B voltage -4.88V
B-C voltage is -.629V (seems low, should be -.82V)

Transmission Test (so far this isn't an issue)
A-D voltage -4.08V
B-D voltage is -.8V (seems low, should be -3.38V)

BulletMaker · Jan 12, 2014

Ooooookaaaayyy... so this is interesting, one of the things I noticed while cleaning out the throttle body was the butterly wasn't closing 100%, I figured 'eh whatever right? So while I was checking the TPS for dead spots, I noticed that the bracket that stops the throttle when all the way down was slightly bent, and had plier marks on it. I took a look at my jeep (sitting about 10 feet away) and noticed it was dead straight. Hummm

So I pulled out my pliers and bent it back straight and checked it with a square (yea, that's how I roll). For Shits and giggles I fired it up, funny now it idles at a perfect 600-700 RPM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

WTF!#@*(!@#)!(@$U!

So one thing I determined that wasn't really spelled out in Cruiser's FAQ on renix debugging is that the voltage gets higher with more throttle. (and yes I do have a deadspot, just a hair before MAX throttle BFD, not going to monkey with it) however the output voltage is now even lower on the TPS.

I'm going to go do a driveability test and see what shakes out. It would be interesting to note if the PO (more likely some shady mechanic) made this "fix".

cruiser54 · Jan 12, 2014

BulletMaker said:
Ooooookaaaayyy... so this is interesting, one of the things I noticed while cleaning out the throttle body was the butterly wasn't closing 100%, I figured 'eh whatever right? So while I was checking the TPS for dead spots, I noticed that the bracket that stops the throttle when all the way down was slightly bent, and had plier marks on it. I took a look at my jeep (sitting about 10 feet away) and noticed it was dead straight. Hummm

So I pulled out my pliers and bent it back straight and checked it with a square (yea, that's how I roll). For Shits and giggles I fired it up, funny now it idles at a perfect 600-700 RPM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

WTF!#@*(!@#)!(@$U!

So one thing I determined that wasn't really spelled out in Cruiser's FAQ on renix debugging is that the voltage gets higher with more throttle. (and yes I do have a deadspot, just a hair before MAX throttle BFD, not going to monkey with it) however the output voltage is now even lower on the TPS.

I'm going to go do a driveability test and see what shakes out. It would be interesting to note if the PO (more likely some shady mechanic) made this "fix".

Post 14:

Rare, but it happens.

Cruiser’s Renix Throttle Body Butterfly Adjustment

Okay. Let's start from scratch. First off, that's not an idle adjustment screw. It's a throttle butterfly stop screw. It's purpose is to allow the butterfly to be as close to completely closed as it can be without binding or wearing into the throttle body. It was never intended to be adjusted in the field. But, Uncle Bob didn’t know that, did he?

Engine off. Back off the butterfly stop screw with a 3/32” allen wrench until the butterfly is completely closed. Now. turn the screw in until the FAINTEST movement of the butterfly opening is detected. This can be done more easily with the throttle body removed. If you remove the throttle body, be sure to replace the gasket underneath it after thoroughly cleaning the old one off.

Revised 07/07/2012

Now, readjust your TPS if you're confident the throttle butterfly is not gonna eat into the soft body.

BulletMaker · Jan 13, 2014

I used some .002" shims in the gap until they just grabbed like a feeler gauge. I just bent the throttle stop arm back to where it was supposed to be, and that solved the problem. So the gap is now .002" or less (both sides).

Even though the TPS is reading lower than your spec sheet says, driveability is quite good, I think acceleration may be even better than on mine.

I'm kinda thinking that some dumb wrench spinner just tweaked it to make "the problem" go away, rather than actually fixing the vehicle at some point in the past, and the fact that I fixed the vacuum system (first thing) then cleaned and replaced much of the electric system (cleaned grounds, put in new grounding cables #4's) with new clean parts (also pulled and cleaned power distribution relay) so my fixes obviated the PO's mechanic fixes, and actually his fix created my problem.

Anyways, the big issue now is the master cylinder/brake system is absolutely horrible, and I happen to have a recently pulled late model XJ booster/MC/Prop Valve that I'm going to try to wedge in there tonight.

'89 XJ - High Idle, high NOx (vehicle is in california)

BulletMaker

NAXJA Forum User

BulletMaker

NAXJA Forum User

BulletMaker

NAXJA Forum User

BulletMaker

NAXJA Forum User

cruiser54

NAXJA Forum User

BulletMaker

NAXJA Forum User

Similar threads