AZ89MJ

I hate to bring up this issue as it seems like there are 10 posts a day on this subject but I am so frustrated with it.

89 comanche converted from 2wd to 4wd
Automatic transmission
New fuel pump and filter
New cap and rotor plugs and wires
Cleaned all connectors and grounds
Added beefy monster cable 4 gauge ground from valve cover to the body and to the negative terminal.... Figured over kill would help eliminate any issues with the grounds
Cleaned throttle body
New water pump
All vacuum lines appear to be in decent shape
New air filter

Now for my issue.... Jeep has a miss when driving but it is only when at 1/8 to 1/4 throttle. It happens at any speed and in any gear. Also has a high idle on start up. So I went through and did cruisers tps adjustment. The ground wire on tps was around 1 ohm of resistance so I spliced and soldered in another wire and went straight to the negative terminal on the battery. That brought the resistance down to .4 ohms.... Not sure if that was the best way to do it but it brought the resistance down and I didn't have to mess with the nasty wiring harnnes on the fire wall. Adjusted the the tps to .834 volts on the output side but I still have the high idle and the miss while driving. Tried adjusting the tps down to bring the idle down but no matter where I put it it still has the high idle and the miss will move around a little bit to a different throttle range. Tps has a smooth sweep of voltage throughout it. I even went and bought a new tps to rule out the sensor it's self. Now is where it gets weird.... If I unplug the 3 wire tps connector it idles normal... Maybe a tad bit high but not too bad and also the miss goes away while driving. The fact that it does good with it unplugged is driving me crazy!!! What should I look at next?

DFlintstone

I'm gonna pretend you didn't just say unplugging the TPS "Fixes" it.

I'd make double sure there are no vacuum leaks. Besides the below, there is about 10 feet of line back, then forward allong the right fender to the vacuum ball behind the bumper, and the ball its-self.

Do you have AC, or "platinum" plugs? Willl it miss if you just hold the RPM's up a bit?

Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep.

AZ89MJ

None of my jeeps have front bumpers so the ball gets relocated to the engine bay... It has the vacuum line to it but no line in the out side of it. Would that be suspect? And where does the line that I have missing even go to?

Plugs are Copper auto lite or ac brand can't remember which tho.

I've gone through 2 cans of throttle body cleaner looking for vacuum leaks.

I changed out the old stock injectors and put in the yellow ford ones and all the o rings were good and lubed with Vaseline. They are used from a junk yard and I had them in my old cherokee before the engine blew up and were working fine when it ran. They were pulled and sat inside the blown cherokee with no doors on it for about 6 months before I put them in the comanche so there is a chance they might be clogged? The thing is it idles fine and revs up fine while not moving. It only does it while moving and at the same cruising rpm in any gear. If I give it more gas its fine. Would unpluging the TPS really mask bad injectors?

DFlintstone

I can't answer all of your questions. I did finally try this one. First I checked for leaking, then with the coil wire carefully grounded, cranked it.

Also, Is the color of the porcilin on the plugs even? All looking nice and gapped to .035?

cruiser54

Have you done the sensor ground test? Other sensors besides the TPS are on that circuit.

DFlintstone

On my 90 that small line goes into the dash to control the heater/AC vents. I guess if I had cruse it would do that as well. When you "stab" your foot, vacuum crashes. That "ball" is a buffer to continue operating vacuum controlled systems while you are "getten jolly" .

OH, and, your your fourth can, be sure to hit the engine side of the injectors. I use starting fluid. Something that burns well/evaporates quick works for me. LITTLE SHOTS!!, (3)

DFlintstone

And rule this one out..>

There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage and it will be pig-rich. (black smoke, fouled black plugs).