What's wrong with this !@#$% thing?

[mieth]

1989 Jeep Cherokee with 4.0L inline 6 cyl and auto transmission.
After starting the engine revs to about 2500 RPM and will not ramp back down. Same thing when driving, except there's an extreme amount of spitting and sputtering if you try to accelerate, you have really stomp on the gas just to get the thing moving. It runs okay if all you need to do is 25 mph.
After reading quite a few posts I decided that I'd buy a throttle position sensor and some throttle body cleaner. Tonight I was going to replace it, but didn't because of further observations. There is an opening next to the throttle body inlet behind the idle speed stepper motor and there was an extreme amount of suction happening here. If I blocked this opening the idle would drop to what I'd say is normal. Because of this I'm skeptical that the TPS would help me. I had replaced that idle speed stepper motor about a year ago at around $100. Could it be bad again? Also my crummy Haynes manual says "After you have replaced the ISA motor, have it adjusted by a dealer service department." Is this absolutely necessary? How would they adjust it?
I would really appreciate any and all comments. This Jeep is becoming dangerous to drive!!

Thanks,
Kyle

[Saudade]

If you mean on the inside of the throttle body (next to the fuel rail) and towards the firewall, that's supposed to connect to the Manifold Absolute Pressure (MAP) sensor. The MAP sensor is located on a bracket on the top, center of the firewall. It has an electrical connector and a vacuum line. The vacuum line connects to the throttle body. The line is a small diameter hard plastic tube that is easy to break.

[mieth]

No, that isn't it. What I'm speaking about is a ½" rectangular opening next to the throttle body opening. You have to remove the flexible air duct that runs from the air filter housing to the throttle body to see it. I'd say it is in the 8 o'clock position relative to the opening. I'd post a picture if I knew how...

[mieth]

Her is a picture (hopefully)

[capt. apathy]

that is the inlet that is controlled by the idle-air stepper motor. take out the motor and clean it and the port it goes into (wd-40 & a small nylon brush works wel, and adds a little lube),and check the electrical conections.
it sounds like the idle-air stepper motor is stuck, or possibly has a bad electrical conection that doesn't let it control the air flow.

[mieth]

Okay, here's where I'm at with this problem:
I tried cleaning the ISA motor w/o success, so I shelled out $87 for another new one (I had replaced this part about a year ago). This ISA motor came with instructions on how to initially adjust by pushing in the spring-loaded sleeve and turning the pintle head until 1 1/8". Last time I replaced the ISA there were no instructions and I just bolted it on. I took and adjusted my old ISA like the directions said to and now the idle is normal. WhoHoooo!! $87 saved!

But wait, it still runs extremely poor like it did before the idle went crazy.
There isn't any power and you have to floor the gas just to get it moving. You have to constantly floor it to keep it moving. There is a lot of spitting and sputtering going on. Here are some further observations: There is a lot of oil in the air filter and consequently in the flexible hose running from air filter box to the throttle body. The vacuum line running from the throttle body to the MAP sensor is clear and unblocked. Most of the vacuum lines (hard plastic) around the throttle body/fuel rail area have been replaced. Also spark plugs, plug wires, distributor/rotor were replaced.
Comments/suggestions/ideas?

Thanks

[thinmints]

have you replaced the catalytic converter yet? may want to go that route next

[mieth]

Actually the exhaust system is one more thing I need to fix on this vehicle. The exhaust pipe is corroded/broken in front of the catalytic converter, so the cat converter isn't even being used right now.

I'm not sure what to do here, I don't have the $$$ to just start throwing parts at this thing.

Any further ideas/suggestions would be appreciated.

[Saudade]

Thanks for the clarification on the leak, and congrats on fixing it (so far).

So the idle speed is OK now. Does it idle smoothly? If you rev the engine (in Park), slowly, does it build RPM smoothly? If you give it the quick shot, does it still rev smoothly, or does it sputter, pop, kick, etc.?

I'm assuming you never replaced the TPS, did you take the old one off?

[mieth]

It idled a little rough, and would build up RPM kind of smoothly when reved slowly, but spits, sputters and pops with the quick shot. Today I bit the bullet and replaced the Throttle Position Sensor, but the upper bolt, made of aluminum I think, broke off. I had to remove the throttle body so I could drill out the broken bolt. I retapped that hole and mounted the TPS. I replaced the fuel filter. It now runs much better, but still spits and sputters during acceleration. The power still isn't there during acceleration. Once at cruising speed it seems to run okay, whereas before I had to keep flooring it to maintain speed.
Does it seem that the TPS is not adjusted properly. I just bolted it on. Do I need to have the TPS adjusted by a shop that can hook up a diagnostic computer?
I'm almost there...
Thanks for all you suggestions so far everybody.

[mieth]

The on-going saga continues:
FYI: 1989 Jeep Cherokee 4.0L inline 6 cylinder
In addition to all the problems listed above, the Jeep also needed a new exhaust system. I replaced the front exhaust pipe, catalytic converter, muffler, tailpipe. Now it's quieter but it actually runs worse! So I adjusted the TPS output voltage like the factory service manual states to, still no difference. I also replaced the oxygen sensor and still no difference.
Here are the main symptom:
1) Starts hard, but idles relatively good once started.
2) Can steadily slowly ramp up RPMs in park and it doesn't miss a beat.
3) Acceleration is extremely poor. I have to floor it just to get it moving and to maintain speed (it maintained cruising speed better before I did all this work yesterday). Theres a lot of spitting and sputtering going on.

Does anyone know hot to get the computer codes on this rig. I've tried the "on, off" thing, but that isn't working. I read in the Haynes model to jumper some pins on the diagnostic port, but they say that this is for the V6 engine, not the I-6.


Any comments/ideas/suggested are appreciated.

[kablemd]

sorry to hear about your problems with your jeep. I now know that I am not the only one with the same exact problems. if you have any sucess with this problem tell me what you did to fix it.

[mieth]

Okay, believe it or not, problem is solved!!
I replaced the fuel pump, and while doing so I found out that the fuel sending unit was broke. One of the lines (I think it a vent or something like that) also has the fuel pump bracket welded on it. This thing was all loose and stuff. Thinking this wouldn't be a big deal, I replaced the fuel pump anyways. The Jeep ran awesome for about 60 miles, then the thing wouldn't start. I took the fuel pump/sending unit out again and the loose pipe caused the fuel hose from sending unit to fuel pump to pop off. Because this sending unit costs about $200 and wasn't available in a local salvage yard, I decided to glue it back in. I used my Dremel tool to clean up the area and used JB Weld to fix it back into position. It worked well, but there was just a bit too much sag. So I got some epoxy putty and used that too. The unit was rock solid and the Jeep has been running swell ever since.