Stumbles With Acceleration
05-03-2013, 12:56 AM
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Year: 1988
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Stumbles With Acceleration
Sorry in advance for the bit of a read. You can skip to the last paragraph if you want to.
Hi, guys new to the forums not to Cherokees. I've owned over 30 Cherokees in the last 4 years. Buying them up from people willing to just give them up to the junkyard and repairing the ones I can and using parts off the other so unlucky ones to repair the salvageable ones.
Currently I'm working on a 88 2 door for my brother. Picked it off some young 17 year old country girl that pretty much destroyed the Jeep.
So far I've used another 96 2 door that was 2wd with a blown engine, stole the interior and every exterior panel off of that.
Three weeks ago I picked up a 95 4 door that was t-boned pretty good on the passenger side. It ran like a champ and drove damn good. I pulled the High Output motor, transmission, transfer case, axles, complete vehicle wiring harness, everything in the engine bay, fuel lines, fuel tank, dash, brake booster, steering column and HVAC box.
Got them installed in the 88, everything installed in the factory locations as if it came from the factory with all this. It fired right up first try. It idles right at 800 rpm in park and about 600 to 700 in gear and has all new vacuum lines, which eliminates the problem being a vacuum leak.
But anytime I step on the accelerator whether the Jeep be idling or driving 65 mph down the freeway it will stumble like it wants to die for what seems 2 to 3 seconds then it will take off like normal. I've kinda ran out of time to keep searching for the problem. That's why I came on here to ask for your guys help to help me pin point the problem.
Hi, guys new to the forums not to Cherokees. I've owned over 30 Cherokees in the last 4 years. Buying them up from people willing to just give them up to the junkyard and repairing the ones I can and using parts off the other so unlucky ones to repair the salvageable ones.
Currently I'm working on a 88 2 door for my brother. Picked it off some young 17 year old country girl that pretty much destroyed the Jeep.
So far I've used another 96 2 door that was 2wd with a blown engine, stole the interior and every exterior panel off of that.
Three weeks ago I picked up a 95 4 door that was t-boned pretty good on the passenger side. It ran like a champ and drove damn good. I pulled the High Output motor, transmission, transfer case, axles, complete vehicle wiring harness, everything in the engine bay, fuel lines, fuel tank, dash, brake booster, steering column and HVAC box.
Got them installed in the 88, everything installed in the factory locations as if it came from the factory with all this. It fired right up first try. It idles right at 800 rpm in park and about 600 to 700 in gear and has all new vacuum lines, which eliminates the problem being a vacuum leak.
But anytime I step on the accelerator whether the Jeep be idling or driving 65 mph down the freeway it will stumble like it wants to die for what seems 2 to 3 seconds then it will take off like normal. I've kinda ran out of time to keep searching for the problem. That's why I came on here to ask for your guys help to help me pin point the problem.
05-03-2013, 01:02 AM
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So you basically have an 88 shell with a 95 powertrain, right back to the fuel tank?
That stumble is likely the TPS. That's what tells the ECU you are accelerating so it can goose the fuel mix momentarily, like the old carb accelerator pumps used to do.
That stumble is likely the TPS. That's what tells the ECU you are accelerating so it can goose the fuel mix momentarily, like the old carb accelerator pumps used to do.
05-03-2013, 01:10 AM
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That stumble is likely the TPS. That's what tells the ECU you are accelerating
so it can goose the fuel mix momentarily, like the old carb accelerator pumps used to do.
so it can goose the fuel mix momentarily, like the old carb accelerator pumps used to do.
05-03-2013, 10:17 PM
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Well I installed a new TPS and did a tune up on it today and it still stumbles. I'm at a complete loss with this one.
05-04-2013, 03:43 AM
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Good fuel pressure? O2 sensor operating correctly?
Did you use a good quality TPS or a China cheapie? Might grab a DVM and check the output voltage while slowly opening the throttle by hand. (key on, engine off)
Did you use a good quality TPS or a China cheapie? Might grab a DVM and check the output voltage while slowly opening the throttle by hand. (key on, engine off)
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05-04-2013, 07:06 AM
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Test fuel pressure (with a gauge on the schrader valve on fuel rail). Gotta rule proper fuel delivery in or out before moving onto other things.
For a 95 engine, you should have 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Be SURE that the vacuum line leading to the regulator is pulling good vacuum and is not wet with raw fuel, as that would indicate a ruptured diaphragm in the regulator.
For a 95 engine, you should have 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Be SURE that the vacuum line leading to the regulator is pulling good vacuum and is not wet with raw fuel, as that would indicate a ruptured diaphragm in the regulator.
Last edited by tjwalker; 05-04-2013 at 07:10 AM.
05-04-2013, 03:54 PM
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Test fuel pressure (with a gauge on the schrader valve on fuel rail). Gotta rule proper fuel delivery in or out before moving onto other things.
For a 95 engine, you should have 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Be SURE that the vacuum line leading to the regulator is pulling good vacuum and is not wet with raw fuel, as that would indicate a ruptured diaphragm in the regulator.
For a 95 engine, you should have 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Be SURE that the vacuum line leading to the regulator is pulling good vacuum and is not wet with raw fuel, as that would indicate a ruptured diaphragm in the regulator.
I can't find my fuel pressure gauge, so I'll head out this evening and get a new one. I'll let you guys know later what the pressure is at.
Also another symptom its starting to have now is every now and again when it stumbles it will back fire through the intake.
05-04-2013, 04:36 PM
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Alright, so I found the problem and she runs like a beast now. Thanks everyone for your guy's help to try and pin point this.
And for those wondering what the problem was, I forgot and over looked the vacuum line going from the intake to the map sensor on the firewall. On the bottom of the line there was a crack about an inch long. Repaired the vacuum line and all my problems went away. Now to just get the cruise control to work and all will be good. Thanks again.
And for those wondering what the problem was, I forgot and over looked the vacuum line going from the intake to the map sensor on the firewall. On the bottom of the line there was a crack about an inch long. Repaired the vacuum line and all my problems went away. Now to just get the cruise control to work and all will be good. Thanks again.
05-04-2013, 07:43 PM
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