low/rough idle cherokee, need help
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
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Model: Cherokee
Okay so I have properly soldered all sensor to ground wires and also spliced in another ground aswell. The problem is still there, rough low idle and almost stalling when letting off gas.
But I tested my cps today and I got about 200 ohms through it but when I check the voltage (ac) when cranking motor over it won't even register, but It will measure about 500 microvolts.
I am using a good quality fluke multimeter too
I though the motor will not even run if the cps is bad or not making voltage?!?
But I tested my cps today and I got about 200 ohms through it but when I check the voltage (ac) when cranking motor over it won't even register, but It will measure about 500 microvolts.
I am using a good quality fluke multimeter too
I though the motor will not even run if the cps is bad or not making voltage?!?
Last edited by noraayrrek; Apr 25, 2015 at 01:58 PM.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
[QUOTE=noraayrrek;3079067]Okay so I have properly soldered all sensor to ground wires and also spliced in another ground aswell. The problem is still there, rough low idle and almost stalling when letting off gas.
But I tested my cps today and I got about 200 ohms through it but when I check the voltage (ac) when cranking motor over it won't even register, but It will measure about 500 microvolts.
500 ac millivolts is the proper output while cranking with CPS unplugged.
I am using a good quality fluke multimeter too
I though the motor will not even run if the cps is bad?!?
See above
But I tested my cps today and I got about 200 ohms through it but when I check the voltage (ac) when cranking motor over it won't even register, but It will measure about 500 microvolts.
500 ac millivolts is the proper output while cranking with CPS unplugged.
I am using a good quality fluke multimeter too
I though the motor will not even run if the cps is bad?!?
See above
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Joined: May 2014
Posts: 63
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Model: Cherokee
Okay
Checked fuel pressure today 31psi at idle, so that's good.
Where should the torx screw on the side of the tb be set?
I think I may find a scanner to read the computer and see what it's saying.
Open loop or closed loop, see what my O2 is saying
The jeep runs good when it's cold, but once it warms up it runs rough almost a miss and low Idle, the first line on the rpm gauge and its very jumpy not smooth at all
Checked fuel pressure today 31psi at idle, so that's good.
Where should the torx screw on the side of the tb be set?
I think I may find a scanner to read the computer and see what it's saying.
Open loop or closed loop, see what my O2 is saying
The jeep runs good when it's cold, but once it warms up it runs rough almost a miss and low Idle, the first line on the rpm gauge and its very jumpy not smooth at all
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Joined: Aug 2011
Posts: 43,971
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Reread your first post. Vacuum is only 12?
CRUISER’S VACUUM TEST FOR EXHAUST RESTRICTION
Your vacuum gauge should come with an instruction booklet outlining the procedure. Hook the vacuum gauge up to a source on the intake manifold. Start the engine and note the vacuum reading. Usually 17 to 21 inches of vacuum. Throttle the engine up to 2,000 to 2,500 RPM for 20 seconds or so and the vacuum reading should stabilize to the same reading you got at idle. Let the throttle snap shut. The vacuum reading should shoot up about 5 inches of vacuum higher for a second and then come quickly down to the original reading. If the vacuum reading stays high and comes down slowly with jerky needle movements, you have an exhaust restriction.
CRUISER’S VACUUM TEST FOR EXHAUST RESTRICTION
Your vacuum gauge should come with an instruction booklet outlining the procedure. Hook the vacuum gauge up to a source on the intake manifold. Start the engine and note the vacuum reading. Usually 17 to 21 inches of vacuum. Throttle the engine up to 2,000 to 2,500 RPM for 20 seconds or so and the vacuum reading should stabilize to the same reading you got at idle. Let the throttle snap shut. The vacuum reading should shoot up about 5 inches of vacuum higher for a second and then come quickly down to the original reading. If the vacuum reading stays high and comes down slowly with jerky needle movements, you have an exhaust restriction.
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i do not think my exhaust could be plugged up because my cat fell off so I temporally put in a spool peice.
Okay so today put the old injectors back in no change, so I reinstalled the new 703s
Pulled plugs and they are black so I am over fueling Not sure what is causing it tho
Reset tps to the 17% of the input voltage 4.86v so I set it to .8v (that's as high as I can go)
When driving around it almost stalls at when I stop then catches it self and raises to the 450-500 rpm
Okay so today put the old injectors back in no change, so I reinstalled the new 703s
Pulled plugs and they are black so I am over fueling Not sure what is causing it tho
Reset tps to the 17% of the input voltage 4.86v so I set it to .8v (that's as high as I can go)
When driving around it almost stalls at when I stop then catches it self and raises to the 450-500 rpm
Last edited by noraayrrek; Apr 26, 2015 at 08:08 PM.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
i do not think my exhaust could be plugged up because my cat fell off so I temporally put in a spool peice.
Okay so today put the old injectors back in no change, so I reinstalled the new 703s
Pulled plugs and they are black so I am over fueling Not sure what is causing it tho
Reset tps to the 17% of the input voltage 4.86v so I set it to .8v (that's as high as I can go)
When driving around it almost stalls at when I stop then catches it self and raises to the 450-500 rpm
Okay so today put the old injectors back in no change, so I reinstalled the new 703s
Pulled plugs and they are black so I am over fueling Not sure what is causing it tho
Reset tps to the 17% of the input voltage 4.86v so I set it to .8v (that's as high as I can go)
When driving around it almost stalls at when I stop then catches it self and raises to the 450-500 rpm
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Posts: 63
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Model: Cherokee
When I start the engine (cold) it idles around 8-900 rpm until it warms up, but it's still jumpy and rough, I have made a little you tube vid of the rpm gauge wile driving so u can see it. When I finish uploading it I'll post the link
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i have just put a brand new block in it, the old engine had excessive blow by and was worn out, it idled low and rough as well not quite as bad as it does now though
so here are the list of new parts and i have tested to confirm they are good
brand new engine block (timing set cruisers way) last 1/4 of the rotor passing post 1 when on the "0" mark
coil
distributor
cap
rotar
plugs gaped to .35
wires
new injectors 703s
New map tested ok and no leaks
iac tested ok 450ohlms
tps tested ok and set .8v
cts tested ok 250 ohms
cps .5v and 230 ohms
o2 Bosch ( supply tested good, 14v,5v,0.2ohms)
egr removed and blockoff plate installed(vac lines blocked too)
Cat is removed
fuel pressure tested good 31 and 40
Charcoal canister has been removed
tried swapping computer with a friends no differance.........do not recommend anyone trying this it is such a pain in the ***
tb is clean
no vac leaks and its only pulling about 13 inches at idle I think this is due to the low idle
Sensor ground circuit has been re soldered and an Extra ground has been been spliced into hire harness and grounded to firewall. .2ohms restance
Dip stick tube is shiny and an extra 4ga wire added to body aswell
so it idles around 450-500 rpm once it warms up, when i come to a stop sign it almost stalls, it will do this if you play with the throttle when its idling as well.
i am sure i am missing somethings i have triet
please send some suggestions my way
Edited
Here is the link, maybe this will shed some light
http://youtu.be/2bbVqYLGP-k
Last edited by noraayrrek; Apr 29, 2015 at 01:47 AM.
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Model: Cherokee
My jeep is an auto
Is there any other test I can try. I don't really want to spend money on another tps if mine is fine
Last edited by noraayrrek; Apr 27, 2015 at 12:27 PM.
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Model: Cherokee
So today I put a peice of rubber vac hose on the tps tap to allow me to get my .83volts, no change in idle
I also decided to unplug some sensors, and I found if unplug the mat sensor and the cts sensor my idle increases to 650-700, but the jeep has no power limp mode I am guessing
So my question is when those are unplugged what does it cause the computer to do?
I also decided to unplug some sensors, and I found if unplug the mat sensor and the cts sensor my idle increases to 650-700, but the jeep has no power limp mode I am guessing
So my question is when those are unplugged what does it cause the computer to do?