Running bad, need help!
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Running bad, need help!
I have a 1989 Cherokee. When driving easy it does good. But when I push down good on gas pedal it starts spitting and sputtering and back firing. It will only do this when pushing down on gas shifting in to running gear. It will not shift up until I let off gas then drives good. Any idea?
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Thanks for the quick response. I have checked the fuel filter and fuel pump and both are good. I can stop, then punch it and it will run fine until it starts to shift into over drive. If I just putt around in it, it never acts up.
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Joined: May 2009
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Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
Sounds like a TPS that needs tested.
Will it do the same thing in park? If so, I would do a fuel pressure test too, hook it up and while watching the gauge give it some throttle, see what your fuel pressure does.
Will it do the same thing in park? If so, I would do a fuel pressure test too, hook it up and while watching the gauge give it some throttle, see what your fuel pressure does.
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I have also changed TPS and had the fuel pressure checked. It reads 30 psi at idle. While in park if I push gas down quick it bogs down. But if I ease on the gas it does fine. But why would it only do the bad spitting, sputtering, and back fire while shifting into over drive and not the other gears?
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And ever time I stop and get gas it will start running rough right after I crank it back. Then does dead and will not start back unless I pour gas down breather directly into motor. And it takes forever to crank on any given day. Could fuel pressure regulator cause anything like this?
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Joined: May 2009
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Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
Fuel pressure sounds OK.
What was the input voltage of the TPS, and what was it adjusted to?
When is the last time its had a tuneup, and what parts were changed?
Is it running rich?
A video would really help, I know what youre trying to describe, but a video would be 1000 words.
Try letting the fuel pump run a couple times before you start it...
MPI system fuel pressure is maintaine d at 214 kP a31 psi) when the pump is operating and vacuum is supplied to the fuel pressure regulator. If vacuum is not supplied to th e pressure regulator, because of a broken or clogged vacuum line, fuel pressure will be 55-69 kP a (8-10 psi) higher.
When is the last time its had a tuneup, and what parts were changed?
Is it running rich?
A video would really help, I know what youre trying to describe, but a video would be 1000 words.
Try letting the fuel pump run a couple times before you start it...
Last edited by 89Laredo; Dec 1, 2011 at 11:45 PM.
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Thread Starter
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I will have to get a ohm meter and check voltage. Do you know what it should read? I have owned jeep since February and have not done complete tune up yet. Have changed the coil, distributor cap, rotary button, fuel filter, oil filter, air filter, TPS, CPS, and plug wires. Have you ever heard of a Jeep having the same problem as mine? And if so what was the main cause?
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Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
The tps on a renix isnt just plug in and forget. It needs to be adjusted.
This could be the cause of your problem, but until it is eliminated we dont have much to work on. Ill post a writeup on how to test/adjust it in a minute.
Bogging out could be caused by alot of things. Bad MAP sensor, Bad TPS, Rich mixture from any number of problems, fuel pressure, injector problems, etc.
I would change the oxygen sensor too, theyre supposed to be done around every 100k.
Your starting problem at the gas station sounds almost like heatsoak (minus having to add fuel), which is not a common problem with renix.
Like I said, let the fuel pump run a couple times before you start it and see if that helps.
This could be the cause of your problem, but until it is eliminated we dont have much to work on. Ill post a writeup on how to test/adjust it in a minute.
Bogging out could be caused by alot of things. Bad MAP sensor, Bad TPS, Rich mixture from any number of problems, fuel pressure, injector problems, etc.
I would change the oxygen sensor too, theyre supposed to be done around every 100k.
Your starting problem at the gas station sounds almost like heatsoak (minus having to add fuel), which is not a common problem with renix.
Like I said, let the fuel pump run a couple times before you start it and see if that helps.
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Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
Yes, but I dont really think its your problem.
TPS
TPS
Originally Posted by 5-90
The RENIX TPS output is not an absolute, neither are absolute resistance readings necessary in the TPS proper.
TPS output voltage should be 17% of input voltage, I will invariably use the manual transmission test outlined in the FSM (1990 FSM p. 8D-33.) This works on vehicles with the AW4 as well, and I consider it to be more reliable than the procedure for the automatic - since the automatic uses the "transmission side" to test, and the automatic TPS is two sensors in one body, a "good" test on the transmission side is not necessarily a "good" test on the engine side. And the engine side is more important.
Begin by measuring the input voltage to the TPS, between pins A and B on the three-pole cnx. Should be ~5.0VDC (experience shows that 5.0VDC +/- 0.5VDC is about right, so 4.5-5.5VDC. It's a regulated supply, and regulators do deteriorate with age.)
Calculate 17% of the input voltage. For correct 5.0VDC, that would be 0.85VDC. For, say, 4.83VDC, that becomes 4.83 x 0.17 = 0.8211VDC. (Yes, use a digital voltmeter, unless you're very experienced with an analogue and have one known to be reliable. It's that important.)
Backprobe pins B and C (positive lead in C) and read output voltage at closed throttle. Loosen the two screws, adjust to reach the figure calculated earlier (17% of input.) Hold the TPS in place (usually, pressing with your thumb will do) and tighten the screws to retain the adjustment. I like to dab a bit of fingernail enamel on these screw threads as an ersatz threadlocker - it has a few advantages:
- It's actually less strong than even LocTite #222, so you don't risk snapping off the screws
- It's just as waterproof.
- It does a better job of coating the threads.
- It may be "gently broken" to allow for adjustment, and will retain the screws without needing to reapply.
- You have a longer initial work time.
However, it is vital that you not use a fixed value for calibration - it is only 0.85VDC nominal output if the reference voltage signal supplied is 5.0VDC! A reference voltage of 4.5-5.5VDC is considered "acceptable," I'd start thinking about a replacement ECU below 4.25VDC.
For a function test of the TPS, an analogue ohmmeter is required. Absolute resistance values are not necessary, nor are they given.
What you do is you disconnect the three-wire plug, connect in to the TPS side for pins A & C or B & C, and then slowly and smoothly sweep the wiper arm on the sensor. The resistance reading should vary smoothly as you move the wiper arm - adjust your ohmmeter range setting until you get a reading that makes sense and varies with the position of the wiper arm. You can not use the typical DMM for this test, as a DMM has buffer circuits inbuilt into it that will work to stabilise a reading - and cause a delay in showing a reading change. Analogue ohmmeters do not have buffer circuits, and respond instantly (to demonstrate, set a DMM and an analogue multimeter to the 200VAC range, and connect both to a house outlet. You'll probably see the needle on the analogue waver slightly, while the digital tends to "seek." The analogue response is instant - and knowing this is the first step toward using an analogue multimeter correctly for diagnosis and troubleshooting. I've been using them for thirty-odd years, so I've gotten used to it. I ignore it if I don't need to know, and process it if I do. I've never gotten rid of my analogue, so I have an analogue and a digital handy.)
TO MAKE BACKPROBE PINS:
- Go to your wife's/girlfriend's/SO's/mother's sewing kit.
- Find the two longest, heaviest straight pins in there (quilting pins are good, hatpins are better.)
- Ask for them nicely. (If you end up having to, just go to the craft store and pick up a packet.)
- With a stone (like you'd use to sharpen a blade,) blunt the point of the pins. You want to round it off nicely with no burrs - the lack of burrs will help to preserve insulation and seals. You should be able to press the tip against your skin without penetrating.
The pins slide in the backside of the connector alongside the wire, so you can take a reading without disconnecting (which sometimes eliminates the possibility of taking a useful reading.)
Backprobe pins may also be purchased at electronic supply houses, but they're cheaper to make and easy enough, and you can make a dozen or so for less than what purchasing two would cost. Just don't let the metal bits touch once you've got them inserted - I've made a set and found heat shrink small enough (in various colours) to have a set of a dozen or so that are colour-coded - I used floral pins (about 2m/m thick, about 3" long) and left the 3/4" or so nearest the point uncovered. The heat shrink was cut short enough and located so that I can attach a small crocodile clip or a five-way test lead clip directly to the pin shaft, but the rest of the exposed metal is covered
TPS output voltage should be 17% of input voltage, I will invariably use the manual transmission test outlined in the FSM (1990 FSM p. 8D-33.) This works on vehicles with the AW4 as well, and I consider it to be more reliable than the procedure for the automatic - since the automatic uses the "transmission side" to test, and the automatic TPS is two sensors in one body, a "good" test on the transmission side is not necessarily a "good" test on the engine side. And the engine side is more important.
Begin by measuring the input voltage to the TPS, between pins A and B on the three-pole cnx. Should be ~5.0VDC (experience shows that 5.0VDC +/- 0.5VDC is about right, so 4.5-5.5VDC. It's a regulated supply, and regulators do deteriorate with age.)
Calculate 17% of the input voltage. For correct 5.0VDC, that would be 0.85VDC. For, say, 4.83VDC, that becomes 4.83 x 0.17 = 0.8211VDC. (Yes, use a digital voltmeter, unless you're very experienced with an analogue and have one known to be reliable. It's that important.)
Backprobe pins B and C (positive lead in C) and read output voltage at closed throttle. Loosen the two screws, adjust to reach the figure calculated earlier (17% of input.) Hold the TPS in place (usually, pressing with your thumb will do) and tighten the screws to retain the adjustment. I like to dab a bit of fingernail enamel on these screw threads as an ersatz threadlocker - it has a few advantages:
- It's actually less strong than even LocTite #222, so you don't risk snapping off the screws
- It's just as waterproof.
- It does a better job of coating the threads.
- It may be "gently broken" to allow for adjustment, and will retain the screws without needing to reapply.
- You have a longer initial work time.
However, it is vital that you not use a fixed value for calibration - it is only 0.85VDC nominal output if the reference voltage signal supplied is 5.0VDC! A reference voltage of 4.5-5.5VDC is considered "acceptable," I'd start thinking about a replacement ECU below 4.25VDC.
For a function test of the TPS, an analogue ohmmeter is required. Absolute resistance values are not necessary, nor are they given.
What you do is you disconnect the three-wire plug, connect in to the TPS side for pins A & C or B & C, and then slowly and smoothly sweep the wiper arm on the sensor. The resistance reading should vary smoothly as you move the wiper arm - adjust your ohmmeter range setting until you get a reading that makes sense and varies with the position of the wiper arm. You can not use the typical DMM for this test, as a DMM has buffer circuits inbuilt into it that will work to stabilise a reading - and cause a delay in showing a reading change. Analogue ohmmeters do not have buffer circuits, and respond instantly (to demonstrate, set a DMM and an analogue multimeter to the 200VAC range, and connect both to a house outlet. You'll probably see the needle on the analogue waver slightly, while the digital tends to "seek." The analogue response is instant - and knowing this is the first step toward using an analogue multimeter correctly for diagnosis and troubleshooting. I've been using them for thirty-odd years, so I've gotten used to it. I ignore it if I don't need to know, and process it if I do. I've never gotten rid of my analogue, so I have an analogue and a digital handy.)
TO MAKE BACKPROBE PINS:
- Go to your wife's/girlfriend's/SO's/mother's sewing kit.
- Find the two longest, heaviest straight pins in there (quilting pins are good, hatpins are better.)
- Ask for them nicely. (If you end up having to, just go to the craft store and pick up a packet.)
- With a stone (like you'd use to sharpen a blade,) blunt the point of the pins. You want to round it off nicely with no burrs - the lack of burrs will help to preserve insulation and seals. You should be able to press the tip against your skin without penetrating.
The pins slide in the backside of the connector alongside the wire, so you can take a reading without disconnecting (which sometimes eliminates the possibility of taking a useful reading.)
Backprobe pins may also be purchased at electronic supply houses, but they're cheaper to make and easy enough, and you can make a dozen or so for less than what purchasing two would cost. Just don't let the metal bits touch once you've got them inserted - I've made a set and found heat shrink small enough (in various colours) to have a set of a dozen or so that are colour-coded - I used floral pins (about 2m/m thick, about 3" long) and left the 3/4" or so nearest the point uncovered. The heat shrink was cut short enough and located so that I can attach a small crocodile clip or a five-way test lead clip directly to the pin shaft, but the rest of the exposed metal is covered
