Hesitation issues?

Well heres the story. Im having issues wit my XJ in terms of hesitation. (88, 4.0, 4wd, automatic tranny, 188,xxx miles) When i bought it it ran pretty good i got about a month ago from my brother. I noticed it would have a slight hesitation every now and then. Well now its worsening. So here is the symptoms...On accelertion from a stop i get a hesitation and feels like it wants to die out and then will come back to life, when im on the freeway (approx 60-65) i feel that it "sneezes", when i im trying to accelerate while going down the road it starts to sputter quite abit and sometimes ill let of the gas and then get on it again wont do it, usually if i ease into the throttle to try to get up to speed it wont sneeze or sputter. ive also noticed that sometimes it will die on me if im trying to back up OR making a hard turn WITHOUT my foot on the throttle, and its doing it intermittenly and pretty much in any weather condition. I replaced the spark plugs a while ago and they were full of soot (im running rich), and a couple of em had some carbon and oil deposits on em. i know that the valve seals are worn and i know that its burns a little oil in the morning. Off the top of my head thats all i can remember other symptoms. I dont have the money to just start throwin random parts at it since i dont make much and im going to college at the same time. I would like to know if anyone has had this problem or where would u recommend i start looking to fix the problem. Ill be glad to answer any questions you might have...No smart ass comments either.

No smart ass comments? Well, damn. I had the perfect one lined up.

My 89 was the same way when I purchased it. I cleaned the dirty throttle body and IAC and the issue went away. The pintle and seat of the IAC was quite dirty.

Glenn B said:

No smart ass comments? Well, damn. I had the perfect one lined up.

My 89 was the same way when I purchased it. I cleaned the dirty throttle body and IAC and the issue went away. The pintle and seat of the IAC was quite dirty.

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haha...well ill try that out and see what happens. ill keep yall updated.

Clean the TB and IAC port/pintle as Glen B suggested.

Also, test your TPS, adjust as necessary or replace and adjust. Don't forget you need to use an analog meter to test the TPS through its full range.

Well heres the deal. Yesterday i cleaned up my throttle body and sensor ports. The TB body wasnt as dirty as i thought and neither was the sensors. I noticed there was some corrosion in the connector of the IAC but i was able to clean it out. Only change i noticed was that it idled abit smoother and so far hasnt hesitated off a red light or stop sign but it does still have a hesitation under load when im about to pass someone. I also noticed at idle it feels like a slight misfire but it doesnt do it enough to throw the MIL on. So any ideas?

Last thing first: Renix engine management systems are strictly real-time info, there are no stored codes and there is no CEL or MIL light. There is only one light that could pop up, and that is a one-use only timer good for 60k miles to remind you to change the o2 sensor. A replacement will run you about $60 at the dealership. Most reach up under the dash, driver's side right knee area and unplug the timer. No more light, $60 saved. Just don't forget to change the o2 sensor every 60k miles.

You still need to check/adjust/test the TPS. For the AW4 automatic equipped vehicle the TPS has input to BOTH the engine management ECU and the transmission management TCU. If it is bad, not adjusted correctly, or has bad spots in its range of movement it will SCREW with you!

Unplug the 4-wire connector from the TPS; key ON, measure voltage between "A" positive and "D" negative. This value will be your "reference" voltage, so please write it down. Reference voltage is what the ECU or TCU is providing the sensor, supposedly 5.0 volts but seldom will you get that amount.

Ok, you now know your reference voltage value. Now, plug the 4-wire connector back in; key ON, measure the voltage between "B" positive and "D" negative--you have to back probe the connector to do this, use two small paper clips with one leg straight to slip into the back of the connector along the wire. This is the "output" voltage, and the value must be 83 percent of reference voltage. If it is not, loosen the two torx screws and adjust the TPS until it is that value. If you can't get it to adjust to that value, replace the TPS and start over.

Once you have the TPS correctly adjusted, check the output voltages through its full range of movement. This is where you need an analog--needle--type meter rather than a digital meter. When you move the throttle through its full range from closed to WOT you want to see a smooth sweep of the needle. Any hesitations/jumps indicates problems in the TPS and I guarantee you they will show up as problems in the engine or transmission's performance.

IF you have a super digital meter (read that as EXPENSIVE like a Fluke) then you can likely use that instead of the analog, but the lower price digital meters have to much buffering built in and they will mask many problems.

Good luck.

well this is the update on my hesitation issue. i tested the tps like you said but i made a dumb rookie mistake and tested the wrong connector which led me to believe that it was the tps. well i ended up replacing the tps (during the adjustment i realized the dumb mistake i made) i adjusted it. my hesitation was still there. i did all this at work and my mentor suggested i do a decarb. i did that and actually helped quite abit but didnt get rid of the hesitation. still under load it will hesitate. something i did notice that it tends to backfire through the intake when i snap the throttle. an idea my mentor gave me is to clean out my egr valve and port. im gonna try that and possibly even replace the egr while im at it.

1. Finish the tuneup by replacing plug wires, distributor cap, rotor, fuel filter. Don't want to chase your tail when the problem is related to tuneup stuff.

2. Test fuel pressure with a gauge at the fuel rail. At idle, you should be at 31 psi. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approx. 39 psi. Want to make sure that your fuel delivery isn't "weak".

birchlakeXJ said:

1. Finish the tuneup by replacing plug wires, distributor cap, rotor, fuel filter. Don't want to chase your tail when the problem is related to tuneup stuff.

2. Test fuel pressure with a gauge at the fuel rail. At idle, you should be at 31 psi. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approx. 39 psi. Want to make sure that your fuel delivery isn't "weak".

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This^^ next. Wouldn't hurt to refresh all your grounds either since the ones on the dipstick tube stud are for some major players as far as sensors go. Bad grounds do weird things to ECU readings from sensors that are variable grounding.............

Something I do on any old Renix Jeep I acquire or work on for someone else. RCBRC is the new acronym here. Refresh Connections Before Replacing Components. Unplug every connector I can find in the engine compartment, spray out both sides with a good contact cleaner, and plug it back in.You've already experienced this with one connector, right?

The cap, rotor, and fuel filter were replaced about a 2 years ago. but i guess it wouldnt hurt to refresh that. i replaced the spark plugs about 2 months ago. when i pulled the old ones out about 4 of em had sum oil on em and all of em were covered in soot...i did do a fuel psi test and i got if i remember correctly 33psi. but ill re-run the test to make sure...i have been contemplating on replacing the ground that goes to the dipstick...yeah when in put the new tps in i cleaned the connectors for that sensor. and about a month ago when i cleaned the tb i cleaned the IAC connector...now something i noticed one day was there is a connector hanging that looks like it broke off something. the connector is in the same loom as the o2 sensor. i did some research and found the knock sensor, and ect connectors come off that. but i see that the knock sensor is connected but looks like the wires are soldered on there. ill post a pic on here so you guys get a better idea of what im talking about.

Knock sensor won't be an issue. Please refresh the grounds at the dipstick tube stud now by removing them , scraping paint off the stud, cleaning the terminals real well and reinstallling. The ground wire that goes from the back of the head to the firewall: remove the bolt from the firewall, scrape the paint off from under it, clean the wire and reinstall. Better yet, replace that POS braided cable with a #4 wire.

It still wouldn't hurt to do the unplug, spray, and replug deal in the engine compartment. Take s15 minutes and eliminates the possibility of hidden problems.