91' Cherokee, please somebody help me

Guys, I have 91' XJ 4.0 litre, auto transmission. Something strange happens when I try to accelerate. Engine comes to about 2000 and some more RPM and then stalls or looses breath. Then, after I pass maybe to 2500 it accelerates like rocket. Strange thing. Few weeks ago I posted this question here but no answer. Since then, new fuel pressure regulator was installed, new spark plugs and wires, distributor cap... etc. Nothing better. I've noticed that it happens more with warm engine, less with cold. Can it be something with crankshaft position sensor? This one I haven't pulled out yet, it's very hard to reach down there. Car has exactly 200 000 kilometres (about 124 000 miles) and catalysator is still original, is it too much? Please I will really appreciate your help, you are my only hope. I live in part of Europe where only few Cherokees are around and no chance to ask anybody something serious about Jeep. Thanks. Davie

Reply to
Davey
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Davey did pass the time by typing:

The CPS sensor is a major pain to get at. IF you ever have to I did a short write-up.

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Your pushing it's limit but usually if it cloggs up your engine simply will not accelerate no matter what. It will feel like your dragging a ton of lead.

no-start or engine cut-out is usually due to a failing CPS sensor.

What your explaining is a shift problem. Good acceleration past that RPM tells me the engine is probably fine. I'd be looking at the kickdown cable to the transmission and the trasmission itself. I suspect the bands for first gear may be out of adjustment. How long has it been since you changed the transmission fluid and filter?

Reply to
DougW

I was planning to do this one of those days. Question is how to drain converter too? I don't know what brand of oil is inside so it would be better to drain it all, I think. Trans fluid filter I can get only from USA and it will take time - I've never removed this before, can I wash and blow this filter with compressed air? For this shifting matter, Jeep is in same gear when problem occurs, I mean, for example, in first gear it comes to as I said till about 2000 and some more, then "hole" in power and after 2400 it goes like hell. Still in same gear. After it shifts in another gear - thing continues. Sometimes it accelerates without problem and usually when engine is still colder.

Reply to
Davey

For your stalling problem, have you checked or replaced your throttle position senson? I think your 91 has a HO engine and the throttle position sensor is not adjustble. You can meter the readings to test it. As for your trans filter, it's a fine metal screen and you can use brake or carb cleaner to clean it. Just make sure it's dry before reusing. I don't think you can drain the converter, just change the fluid twice and you'll have gotten most of it.

JoBo

Reply to
Jo Bo

I would first be suspecting a dirty connection on the TPS or a worn one. I would take off the TPS plug and clean it (the plug and socket) with a contact cleaner spray. WD40 will do in a pinch, but isn't the best.

The TPS can be checked with a meter as well. You can use resistance and watch if it gets higher smoothly as the throttle opens on 2 of the pins and watch it get lower on the other pin. (3 pin plug I think with one common) You can leave it plugged in with the key just 'on' but the engine off and check the voltage by backfeeding the plug. Same deal, 2 pins will get higher and the other one with center will get lower. It needs to rise or lower smoothly ranging from 0.02V to 4.8V.

Second I would be thinking fuel filter. It is on the frame rail back by the tank.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Davey wrote:

Reply to
Mike Romain

Davey did pass the time by typing:

You can't drain the torque converter wihout removing it from the transmission so there will always be some old transmission fluid in the system. The filter screen (at least on my ZJ) is metal and can be cleaned in solvent and dried. I don't know if your filter can be cleaned or not. The brand of transmission fluid doesn't matter, what matters is the specifications on that fluid. ATF+3 is what you need.

This is worth a read:

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Your describing a tranny problem similar to "delayed up-shift" or "slips on

1-2 up-shift" Apart from old fluid the following can be causes.

- valve body faulty

- solenoid faulty

- electronic control problem

- throttle cable out of adjustment

- shift cable out of adjustment

Shift cable is the easiest to look at. On your throttle body there is a link that runs down to the tranny. with the engine off, move the throttle full open then closed. there shouldn't be any slack in the kick-down link. IF there is, look on the link, there should be a little button you can press in. Press that in and take the slack out of the cable. After you do this, run the throttle full open again. There shouldn't be any binding.

Reply to
DougW

Reply to
Davey

Hah, seems like it's much better now. What I did? Just like you guys told me (some of those things). First, I cleaned plugs for TPS and the other one (I think it's for cold start, just nearby). Then, in meantime, tranny oil. Transmission sump was very clean, even magnets were only little black. But after oil change, Jeep runs more and more smoothly (?!) Is it possible that something was wrong with oil? Maybe would be nice to "wash"one more time with fresh oil just because some of old oil was still in converter?

Reply to
Davey

Davey did pass the time by typing:

It's entirely possible the tranny fluid had broken down or adsorbed water from years of heat/cool cycles. Tranny fluid is not oil. If your going to abbreviate it use "ATF" Automatic Transmission Fluid.

Cleaning sensor plugs will have a gradual effect as the Jeeps computer (ECU) and the transmission computer (TCU) slowly adjust back to normal operation ranges.

Did you clean out the Idle Air Passage (IAP)? THat will also help smooth out idle.

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Reply to
DougW

Reply to
Davey

Davey did pass the time by typing:

Exactly,

That connection is a solinoid that adjusts the flow of air and sets your idle. The internal passages get crud and dirt buildup that keeps the little pintle from moving smoothly. If you take the solinoid off do not.. do not.. pull the pintle out, that will kill it.

That's why it is easier to just spray some cleaner through the slot.

Reply to
DougW

On Sat, 18 Dec 2004 22:39:41 UTC "DougW" wrote:

Same advice goes for turning the igniton on while it's out - that sucker will shoot the length of a garage. I did get one back together

- once - but it's a fight and you have to know what you are doing. Picking nits, it isn't a solenoid but a stepper motor.

If the throttle body is pretty dirty and you can see caking in the idle bypass port you would be better off pulling the IAC and cleaning the pintle (cone shaped tip) and the shaft. Use a small amount of grease like the spray on white lithium grease on the shaft after it dries. Then, before you put it back on, take a tooth brush and solvent to clean the port the IAC came out of really well. That sucker will gum up so badly the IAC can't seat and you really can't clean it from the top. I've got the older Renix system, but I'm pretty sure that the Mopar tb has the same setup. There should be a hole from the top surface of the tb, probably a quarter of the way around from the IAC. If so, it will be about a 1/4 inch hole running straight down to the manifold. At the bottom of the tb there will be a cover over a needle valve. You shouldn't have to touch the needle valve unless that hole is plugged solid like mine was when I got the truck. If it's plugged and doesn't open up with cleaner from the top, you'll have to pull the needle valve (count the turns it takes to screw it all the way down, then take it out. Put it back to the same position when you are done). Mine had a cap over the valve that had to be pried off with an ice pick. Use a 16-18 guage solid copper wire and tb cleaner to get the passage clean then replace the needle valve. That's a minimum idle air flow setting and on my older truck it made a lot of difference in the idle and low RPM/light load performance. You may not have the minimum flow port in your 91, but it's something to look for. A gummed up IAC/bypass setup will cause all sorts of surges and hesitation under light to moderate acceleration.

I'm pretty sure they remove the EGR valve in the 91, but if it has one that could also be causing problems if it's caked up.

Reply to
Will Honea

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