hesitation at partial throttle

[littlebill86]

i have completed the entire ground refresh. i added a new firwalll to engine ground as well as a new chassis to battery ground. i got the resistance in the ground circuit down to .5 ohms. still have the same issues. any other sensors i need to check?

 

[cruiser54]

Pull the cap and look at it and the rotor. also pull a plug and see what it looks like.

This is never a bad idea:

Renix Jeep ICU/Coil contact refreshing
　
　
The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future.
The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner and some fine sandpaper.
Squeeze the springy contacts closer together with some needlenose pliers. Bolt the coil back on to the ICU.
While you’re right there, unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier.
I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.
　
Revised 04-04-2013

 

[littlebill86]

would a coolant temp sensor or air intake temp sensor cause my isues?

 

[cruiser54]

Maybe. They can be tested. do the coil ICU testing.

 

[Ecomike]

Temporarily disconnect the O2 sensor and see if the problem goes away.

Did you use a new TPS sensor?

Hmm, is time to try my first suggestion?

 

[littlebill86]

tried the o2 sensor early in the game man, thanks. no change when unplugged

 

[cruiser54]

tried the o2 sensor early in the game man, thanks. no change when unplugged

Do the refreshing FIRST.

 

[Ecomike]

tried the o2 sensor early in the game man, thanks. no change when unplugged

Sorry I meant my second suggestion in that post that you never answered?

"Did you use a new TPS sensor?"

 

[cruiser54]

Refresh first. Takes 1/2 hour. Whine later if it doesn't fix it.

 

[littlebill86]

Yes it has a new tps new cts ground refresh has been done. we spent all day checking it out. all i have left to do is dig into the fuel pump and fuel filter. the only reason i say that is that i did a plug check and they show that it has a lean condition. i had the intake tube.off and got a pretty good lean backfire through the throttle body. i will keep this post active and let you guys know how it goes thanks for all of your help.

 

[Gunter]

i am in the exact same hell!! fixed and cleaned every ground and made a few as well. made one for the alternator as i had alt problems but it is all fixed.
anyways
my jeep wont hold a steady speed with out sputtering exploding balls of fire out the back.
everything that was lost due to ground issues has been fixed, and the full on functionality is all back. just cant hold a steady speed and it kills my fuel economy.
thinking of just replacing the distributor entirely as it is just 4 dollars more than the cam sensor and the reman dist includes the sensor!!

 

[Gunter]

i should add--
o2 sensor changed
cps sensor changed
tps changed
distributor and tps disconnected and made no difference

also when i was cleaning grounds, i had one day of this engine running really good and strong.

 

[8Mud]

The Cam position sensor in the distributor doesn't do much if anything in my experience. In the Renix it has a different function than in the HO motors. In the HO motors it is critical, in the Renix not so much.

You said you disconnected the TPS and it made no difference? The TPS is necessary and important, it controls much of the timing for your motor, among other things.

Look behind the TPS, there is a little "L" shaped arm on the back. Make sure the "L" is under the arm (half hook) connected to the throttle plate axle and the "L" shaped arm on the TPS moves when you work the throttle by hand. It is possible to mount the TPS wrong, with the "L" on the top of the throttle plate arm (or hook).

Better than half the time the problem isn't in the sensor, you can change them forever and never find the problem. The information has to get from the sensor to the ECU and has to travel through wires and connectors to get there. You can set up the TPS perfect, if the info never makes it to the ECU (or is corrupted on the way), it is useless. Swapping out sensors hoping to get lucky may not be the best way to find the solution.

With the motor running, push on the "L" in the back of the TPS with a small screw driver (without moving the throttle), something should happen, in all likelihood the engine will idle up.

 

[Gunter]

on mine i took the sensor off and moved the arm and it made the engine slow down just a little and nothing else. i left it plugged in while i did that. so yeah the tps connected or not makes little difference. so this MAY be corroded/damaged wiring then? i wonder if the wires are damaged where they connect to the ECU.

 

[cruiser54]

In for some fun?

Ever done the connector and relay connection refreshing?

That's super easy to do.

The eCU connector refreshing is a bit of a bear though. But at least you'd know it's not the problem.

Click on the link below and see #3 and 9.
http://www.cherokeeforum.com/f51/cruiser54s-mostly-renix-tips-153657/

 

[Ecomike]

Is the distributor properly indexed? If it is off one tooth it may be sparking the wrong cylinder. Is there side to side play in the shaft ( a bad bearing). You may need to do a compression test, and leak down test for a burned exhaust valve at some point. Also, make sure the vacuum line from the throttle body to the MAP sensor is air tight!

i am in the exact same hell!! fixed and cleaned every ground and made a few as well. made one for the alternator as i had alt problems but it is all fixed.
anyways
my jeep wont hold a steady speed with out sputtering exploding balls of fire out the back.
everything that was lost due to ground issues has been fixed, and the full on functionality is all back. just cant hold a steady speed and it kills my fuel economy.
thinking of just replacing the distributor entirely as it is just 4 dollars more than the cam sensor and the reman dist includes the sensor!!

 

[Ecomike]

i should add--
o2 sensor changed
cps sensor changed
tps changed
distributor and tps disconnected and made no difference

also when i was cleaning grounds, i had one day of this engine running really good and strong.

If the TPS is NEW (not used-new from a JY), then the TPS wiring connection/signal back to the ECU may be bad from the results you have so far. But indexing on the Dizzy is another item to be sure about. If it worked perfectly one day, then not the next, that does not sound like a burned exhaust valve. Sounds like a loose dirty connection TPS to the ECU or damaged O2 wiring that got too close to the exhaust manifold? You may have an intermittent short from chaffed wiring that moves around and partially shorts to ground through dirt-humidity-burned or cut insulation anywhere in the harness.

 

[Gunter]

thanks Mike
the engine works fine. most of the time it is not perfect but i can live with it for now. sometimes it runs perfectly and runs really strong, tons of power.
before the part where it cuts out and runs like crud, it runs good. and once you move the throttle beyond that range it works good too. it just will not so far, keep a steady speed with out popping out the exhaust and horrible fuel economy.
i am confident i have a good engine. no noises or lack of power to guide me to think otherwise. the timing works right most of the time, so i am reasonable sure the timing is right on. if the dist was off one tooth could it cause it to fire with an open exhaust valve as the CPU tries do the advance as the engine speeds increase? if i had a old skool engine with no electronics i would say this engine acts like the timing advance has a problem , like the static timing was set wrong and as it advances it goes to crap and wont run right. i should set number one at tdc and see where the rotor is pointing i think.

 

[Gunter]

my truck has 265 K on it, it certainly COULD have a replacement engine and it is not unheard of for people to put distributor in with one tooth off or even 180 off .

 

[Ecomike]

thanks Mike
the engine works fine. most of the time it is not perfect but i can live with it for now. sometimes it runs perfectly and runs really strong, tons of power.
before the part where it cuts out and runs like crud, it runs good. and once you move the throttle beyond that range it works good too. it just will not so far, keep a steady speed with out popping out the exhaust and horrible fuel economy.
i am confident i have a good engine. no noises or lack of power to guide me to think otherwise. the timing works right most of the time, so i am reasonable sure the timing is right on. if the dist was off one tooth could it cause it to fire with an open exhaust valve as the CPU tries do the advance as the engine speeds increase? if i had a old skool engine with no electronics i would say this engine acts like the timing advance has a problem , like the static timing was set wrong and as it advances it goes to crap and wont run right. i should set number one at tdc and see where the rotor is pointing i think.

If it is off one tooth it can some times fire the spark to the wrong cylinder because the rotor is too close to another cylinder, and thus fuel hits the hot exhaust pipe and pops, I think. I had a recent problem with mine that was similar and it was a bad rotor and cap, and dirty plugs. It really sounds like a bad TPS, but I think you covered that already. How old is the distributor? Mine started throwing oil up inside the cap at around 230,000 miles.

This part is really puzzling: "it just will not so far, keep a steady speed with out popping out the exhaust and horrible fuel economy." Is there a crack and leak in the exhaust near the O2 sensor?