xj stall/stumble when trying to accelerate

[simonm]

i did clear the code i has not came back yet
i sit normal that i was able to start the truck without a map sensor?i forgot to plug it and it did similar symptom when it won'T start when hot but the truck was cold. i was able to keep it from stalling by giving it gasfor a second or 2 and then it idled perfectly i didn'T try moving it like that because the garage door was closed (the exhaust hose was on the tailpipe don'T worry).

i'll check the sensor you've told me after dinner and come back with the data

thank a lot for your help

p.s. does it have to be an analog voltmeter to check the tps?

 

[Ecomike]

Yes, analog. You are looking for a smooth change in voltage as you move the TPS from idle to WOT, power on, engine off. That can only be seen with an analog (needle) meter. If the needle jumps at any point, that is a bad spot on the TPS!!! Also verify the idle TPS voltage again versus the FSM spec!

There is a B+ relay under the hood that keeps the ECU alive long enough after turning the engine off to set the IACV for idle air flow on restart. If that relay is bad it will be hard to start, starved for air, or too much air.

I do not understand this?

"i sit normal that i was able to start the truck without a map sensor?i forgot to plug it and it did similar symptom when it won'T start when hot but the truck was cold."

 

[simonm]

yesterday i had unpluged the map sensor this morning i went to start the truck it had a hard time starting but it finally started and idled fine when i opened then hood the map sensor wasn't plugged but the engine was running fine(it was cold) i was asking if thiswas normal.

 

[Ecomike]

Yes, IIRC it will start and idle with out the MAP (or the TPS), but try to give it gas and it will backfire badly with out the MAP data.

 

[simonm]

the cts show 2.88volt at idle (engine at operating temp) and 1195ohm at around 80C
the iat at same engine condition is showing 4780ohm 1.62 volt intake was hotish to the touch(under 60C but over30)

tps was receiving 0.8volt at idle wich is ok according to fsm

and i donT' understand how to get live data from the o2 sensor

thank you for your help
p.s. well it does back fire a little when i give it gas when it is hot and stalling

 

[Dragonslayer]

I second testing the TPS again. Basically, it is a carbon potentiometer and eventually the
wiper or the carbon will wear out.

Test it with an analog ohmmeter. Turn the TPS manually slowly and smoothly. The needle on the ohmmeter should sweep smoothly. If the needle on the ohmmeter should bounce,
pause, jiggle, etc. - then the TPS is bad.

 

[simonm]

i've tested the tps this afternoon and it was smooth going up and down i didn't test the resistance i tested the voltage. i tested it 3 time to make sure i was slow enough and smooth enough.

 

[simonm]

i now have a code 24 check tps wiring (or tps out of range from a different website), after retesting the TPS it flashes this code twice( tried 3 time to make sure i wasn't missing a flash)

So i tested the wire continuity ,ground to pin 4, signal to pin 22 and power to pin 6 all wire had continuity and less then 1 ohm(lowest possible reading when in continuity mode if there is a resistance)

 

[Ecomike]

Starting to sound like a wiring problem, the worst kind, a buried set of wires with damaged insulation somewhere, or a bad ECU. The ECU on a 94, IIRC, controls the alternator voltage regulation, and you have high voltage sensor errors, so watch for that possible issue!!!!

You fixed the grounds, but have had two separate sensor error codes at one time or another, unless your sensor testing confused the computer? Did you test sensors with the engine running, or power on engine off?

Interesting that it never threw an error code for the missing MAP sensor when you forgot to reconnect it?

Be sure the check the connectors them selves, ECU and sensors, check for loose connections, tighten any that have gotten loose (like closing up a female end by closing the gap with fine needle nose pliers), clean any that are dirty!!!!!!!

So far this one is a puzzle, wandering gremlin.

 

[simonm]

i think it is too
but all the wire have continuity to the ecu and low resistance
all the ecu pin are clean and the sensor pin are clean too

i'll recheck the sensor tomorrow

i tested them with engine off key on except for the map and tps that i tested with the engine on to know if it was giving me a volt reading that is in the fsm range
after the check engine gave me code 24 i tried resetting the ecu but it kept coming back. so i think i might be the tps that died.

how should i test the o2 sensor i haven'T found anywhere

p.s. the truck backfire when releasing the gas when hot only small gargle like backfire.

p.s.s. when i shut it down it make bubble sound but the coolant is clean and doesn'T smell exhaaust, the oil is clean and the exhaust isn't smoking any color that would indicate blown head gasket. could it be burping since the radiator was changed recently.

thank you for your help

 

[Ecomike]

Here is a thread I started a while back on how to test Jeep O2 sensors.

http://www.naxja.org/forum/showthread.php?t=1012701&highlight=oxygen+sensor+test

 

[Goose_XJ88]

Sorry to hijack your thread, but I'm having a similar problem with the stumbling/stalling except mine happens when cold and accelerating or decelerating at low rpms, and idle sometimes. but as soon as the engine warms up to 150* or so i don't have any problems. I have an 88 and have swapped tps with a buddy's parts rig and still have the problem.

 

[simonm]

i've solved the problem it was a broken ground wire in the splice to the right of the map sensor(from the driver pov) it wasn't totally broken but when hot it would disturb the signal and cause the engine to shut down

thank you all for you help

 

[Ecomike]

Sorry to hijack your thread, but I'm having a similar problem with the stumbling/stalling except mine happens when cold and accelerating or decelerating at low rpms, and idle sometimes. but as soon as the engine warms up to 150* or so i don't have any problems. I have an 88 and have swapped tps with a buddy's parts rig and still have the problem.

Seems to be temperature related. So check the IAT and the CTS, Coolant, and Intake Air Temp sensors, see if the meet the factory FSM specs for resistance, power off ohms test, while cold, and hot. Measure the sensor temperature and resistance at the same time, check the FSM tables to see if they are a close match. Also check the O2 sensor heater, ohms test, should be about 8 ohms IIRC, and check the O2 sensor heater +12 volts feed to the O2 sensor (power on) to see if the heater in the sensor is getting 12 volts. What year is your jeep?