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Old 11-11-2011, 08:33 PM   #1
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Acceleration issues

My 97 tj has been doing something weird lately. Kinda hard to explain but I'll do my best. It seems like when I'm accelerating the gas gives out for just a millisecond. It does it two or three times, back to back in a matter of 4 or 5 seconds. It's mainly when I'm going up a hill. Usually happens in 3rd gear but that might just be a coincidence. Anybody know what this could be? And if so how do I fix it? Just don't want it to give out for good one day and shut off on me.

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Old 11-11-2011, 10:21 PM   #2
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Misfire maybe???

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Old 11-11-2011, 11:38 PM   #3
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Quote:
Originally Posted by zsimpson View Post
My 97 tj has been doing something weird lately. Kinda hard to explain but I'll do my best. It seems like when I'm accelerating the gas gives out for just a millisecond. It does it two or three times, back to back in a matter of 4 or 5 seconds. It's mainly when I'm going up a hill. Usually happens in 3rd gear but that might just be a coincidence. Anybody know what this could be? And if so how do I fix it? Just don't want it to give out for good one day and shut off on me.
so you're on the throttle and the power drops off then surges back on? and it does this 2-3 times over 4-5 seconds? could be maf not reading right.
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Old 11-11-2011, 11:53 PM   #4
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I thought that too but he says it only does it for a millisecond.
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Old 11-11-2011, 11:58 PM   #5
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i didn't take millisecond to literal. if it really was i doubt anyone would notice it.
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Old 11-12-2011, 12:00 AM   #6
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I know, I just figured he meant really quick.
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Old 11-12-2011, 12:27 AM   #7
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at what rpm
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Old 11-12-2011, 01:52 AM   #8
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Originally Posted by coors
at what rpm
Sorry guys, didnt know I had any responses! And it doesn't always happen within the same range of rpm's, I'd have to say about 1500-2000 range though if I had to say one. Havnt looked at it exact, but I'll look at it closer tomorrow while I'm driving.
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Old 11-12-2011, 01:54 AM   #9
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Quote:
Originally Posted by 6InARowMakesItGo

so you're on the throttle and the power drops off then surges back on? and it does this 2-3 times over 4-5 seconds? could be maf not reading right.
Maf? I assume your talking about some kind of computer system, but I have no idea what maf is lol. Could someone explain?
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Old 11-12-2011, 01:56 AM   #10
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Originally Posted by zsimpson View Post
Maf? I assume your talking about some kind of computer system, but I have no idea what maf is lol. Could someone explain?
sorry mass air flow sensor. they have really sensitive detectors. do you by chance have an aftermarket air intake?
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Old 11-12-2011, 01:59 AM   #11
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Quote:
Originally Posted by 6InARowMakesItGo

sorry mass air flow sensor. they have really sensitive detectors. do you by chance have an aftermarket air intake?
Naw my intake is 100 percent stock. The weird thing is it just started doing this about two weeks ago? I've never had a problem with it before.
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Old 11-12-2011, 02:01 AM   #12
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I have a similar problem, but mine occurs in 1st or 2nd and at 1600 rpms. It has gotten worse and jerks when the accelerator is depressed, but stops when I let off the gas. However, this problem is not every day. BTW, I've had the o1 and o2 sensors replaced.
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Old 11-12-2011, 02:12 AM   #13
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Originally Posted by Heather0017
I have a similar problem, but mine occurs in 1st or 2nd and at 1600 rpms. It has gotten worse and jerks when the accelerator is depressed, but stops when I let off the gas. However, this problem is not every day. BTW, I've had the o1 and o2 sensors replaced.
Sounds exactly what mines doing. A mild jerking motion while I'm on the gas. Could you explain to me what an o1 and o2 sensor does so I can figure out if this is the root of my problem? Or could anyone?
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Old 11-12-2011, 02:26 AM   #14
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Sounds like what mine did when it needed the TPS (Throttle Position Sensor) replaced. Has yours thrown any codes or had the check engine light come on? Mine did sometimes when that would happen. It's very easy to change and inexpensive. Search some threads here for TPS. I changed mine about a year ago and haven't had a problem since. Also wouldn't hurt to clean out your throttle body and IAC while you're at it.
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Old 11-12-2011, 02:57 AM   #15
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thing is a tps should throw a code, although not always.

an o2 sensor is an oxygen sensor in the exhaust. an o1 sensor doesn't exist.
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Old 11-12-2011, 03:00 AM   #16
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Originally Posted by zsimpson View Post
Naw my intake is 100 percent stock. The weird thing is it just started doing this about two weeks ago? I've never had a problem with it before.
the reason i ask is sometimes those aftermarket filters require a special stuff to clean them. that stuff soaks through the filter and gumms up the works. it messes up the mass air flow sensor and throttle body sometimes.

the easiest thing for you to do would be check and clean those first then test it. there have been some other possibilities mentioned but they cost money to fix. try the free things first then report back.
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Old 11-12-2011, 03:50 AM   #17
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My 04 TJ 4cyl used to do that, I traded it in on an 03 Rubicon that also does it from time to time. I found that I could shut mine off then start it again and the problem would go away for a while. The last few times it happened I flogged the crap out of my Jeep running at higher rpms, and I haven't had any issues now for a couple of months. I don't know what causes it, or why beating on my Jeep helped it, but if I had to guess I'd venture that some kind of sensor was fouled out and that a bit of spirited driving cleaned it off somehow?? Neither of my Jeeps threw a CEL or any codes.
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Old 11-12-2011, 03:56 AM   #18
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Quote:
Originally Posted by 6InARowMakesItGo

the reason i ask is sometimes those aftermarket filters require a special stuff to clean them. that stuff soaks through the filter and gumms up the works. it messes up the mass air flow sensor and throttle body sometimes.

the easiest thing for you to do would be check and clean those first then test it. there have been some other possibilities mentioned but they cost money to fix. try the free things first then report back.
I don't think TJ's have mass airflow sensors. Mine doesn't. It has a MAP sensor that goes by vacuum. It's never given me a problem, so I've never changed it. I have a 4.0l, so I can't speak for the 4cyl engines, but I figure they are the same.
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Old 11-12-2011, 04:03 AM   #19
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Quote:
Originally Posted by necromancer_tat
My 04 TJ 4cyl used to do that, I traded it in on an 03 Rubicon that also does it from time to time. I found that I could shut mine off then start it again and the problem would go away for a while. The last few times it happened I flogged the crap out of my Jeep running at higher rpms, and I haven't had any issues now for a couple of months. I don't know what causes it, or why beating on my Jeep helped it, but if I had to guess I'd venture that some kind of sensor was fouled out and that a bit of spirited driving cleaned it off somehow?? Neither of my Jeeps threw a CEL or any codes.
This sounds like what mine did also. It didn't throw a code for the longest time. I thought it was just something dirty in the TB. I kept cleaning it. Just turning it off then back on would seem to help it. After reading on this forum and others I was leaning towards the TPS being the problem, then it finally threw the code. I think it's P0123, I'd have to look it up to be sure. Once you see how they are made, you'll realize why they don't last forever.
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Old 11-12-2011, 04:06 AM   #20
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I don't think TJ's have mass airflow sensors. Mine doesn't. It has a MAP sensor that goes by vacuum. It's never given me a problem, so I've never changed it. I have a 4.0l, so I can't speak for the 4cyl engines, but I figure they are the same.
yea i think your right its called a MAP sensor. other vehicles with the 4.0 are the same. i can't speak on the 4 cyl either. everything about the MAF or MAP in this thread is likely useless anyway because the op has a stock air cleaner.
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Old 11-12-2011, 08:14 AM   #21
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Quote:
Originally Posted by HarryJeepGuy
Sounds like what mine did when it needed the TPS (Throttle Position Sensor) replaced. Has yours thrown any codes or had the check engine light come on? Mine did sometimes when that would happen. It's very easy to change and inexpensive. Search some threads here for TPS. I changed mine about a year ago and haven't had a problem since. Also wouldn't hurt to clean out your throttle body and IAC while you're at it.
Alright sounds good. Thanks for the info man. I'll get started on it asap and see if that helps anything.
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Old 11-12-2011, 08:15 AM   #22
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Quote:
Originally Posted by 6InARowMakesItGo
thing is a tps should throw a code, although not always.

an o2 sensor is an oxygen sensor in the exhaust. an o1 sensor doesn't exist.
Lol yea I didn't think I had ever heard of an o1 sensor before. Thanks bro!
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Old 11-12-2011, 08:46 AM   #23
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And no guys, I've never got any codes, and I couldn't account for the check engine light being on because it's always on lol
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Old 11-12-2011, 08:54 AM   #24
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Quote:
Originally Posted by HarryJeepGuy View Post
I don't think TJ's have mass airflow sensors. Mine doesn't. It has a MAP sensor that goes by vacuum. It's never given me a problem, so I've never changed it. I have a 4.0l, so I can't speak for the 4cyl engines, but I figure they are the same.
I'm pretty sure that all TJs are MAP based (no map). Possible causes include spark plugs fouled or too big a gap, TPS not working correctly, bad o2 sensors, bad map sensor, or maybe the coil pack.
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Old 11-12-2011, 12:50 PM   #25
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Quote:
Originally Posted by zsimpson
And no guys, I've never got any codes, and I couldn't account for the check engine light being on because it's always on lol
I think the "Key Trick" works on 97's. If your CEL is on you probably have a code. With your Jeep parked and off, turn your key in the ignition from off to on (the position before start, don't start it) 3 times fast, leaving it in the on position at the end of the third. Watch your odometer, it will show you a code(s) if you have any. Then you can look the code up on the net or ask us here. This works for most TJ's, I know there is a year or two in there somewhere that it doesn't.
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Old 11-12-2011, 02:22 PM   #26
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Quote:
Originally Posted by HarryJeepGuy

I think the "Key Trick" works on 97's. If your CEL is on you probably have a code. With your Jeep parked and off, turn your key in the ignition from off to on (the position before start, don't start it) 3 times fast, leaving it in the on position at the end of the third. Watch your odometer, it will show you a code(s) if you have any. Then you can look the code up on the net or ask us here. This works for most TJ's, I know there is a year or two in there somewhere that it doesn't.
It worked. My code says 12-11-21-21-21-55. What does this mean?
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Old 11-12-2011, 09:00 PM   #27
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Diagnostic Trouble (Error) Code Descriptions:

11* No crank reference signal detected during engine cranking.
11** Intermittent loss of either camshaft or crankshaft position sensor. CKP sensor target windows
have too much variation.
12* Direct battery input to PCM was disconnected within the last 50 Key-on cycles.
13** No difference recognized between the engine MAP reading and the barometric (atmosphere)
pressure reading from start-up.
14** MAP sensor input above or below acceptable voltage. 5 volt output to MAP sensor open.
15** No vehicle speed sensor signal detected during road load conditions.
17** Engine did not reach operating temperature within acceptable limits. Engine does not reach
20║ F. within 5 minutes with a vehicle speed signal.
21** Upstream oxygen sensor response slower than minimum required switching frequency.
Upstream oxygen sensor heating element circuit malfunction. Downstream oxygen sensor
heating element circuit malfunction. Downstream oxygen sensor input voltage maintained above
the normal operating range. Oxygen sensor voltage too low, tested after cold start. (Upstream or
Downstream) Left oxygen sensor input voltage maintained above the normal operating
temperature.
22** Engine coolant temperature sensor above or below acceptable voltage.
23** Intake air temperature sensor input above or below acceptable voltage.
24** Throttle position sensor input above or below acceptable voltage. TPS signal does not correlate
to MAP sensor.
25** A shorted or open condition detected in one or more of the idle air control motor circuits. Actual
idle speed does not equal target idle speed.
27** Injector #3, and/or 4, and/or 5, and/or 6 output driver does not respond properly to the control
signal.
31** An open or shorted condition detected in the A/C clutch relay circuit. Insufficient or excessive
vapor flow detected during evaporative emission system operation.
33* An open or shorted condition detected in the duty cycle purge solenoid circuit.
34* An open or shorted condition detected in the Speed Control vacuum or vent solenoid circuits.
Speed control switch input below the minimum acceptable voltage.
37** Relationship between engine speed and vehicle speed indicates no torque converter clutch
engagement. An open or shorted condition detected in the torque converter part throttle unlock
solenoid control circuit. Incorrect input state detected for the Park/Neutral switch. Auto only.
41*** An open or shorted condition in the generator field control circuit.
42* An open or shorted condition detected in the auto shutdown relay circuit. An open condition
detected in the ASD relay output circuit. An open or shorted condition detected in the fuel pump
relay control circuit. An open circuit between PCM and fuel gauge sending unit. Circuit shorted to
voltage between PCM and fuel gauge sending unit. No movement of fuel level sender detected.
43* Peak primary circuit current not achieved with maximum dwell time
43** Misfire detected in one or more cylinders 1 thru 6. (4 and 6 cyls.)
44** Battery temperature sensor in voltage above or below acceptable range.
46*** Battery voltage sense input above target charging voltage during engine operation.
47*** Battery voltage sense input below target charging during engine operation. Also, no significant
change detected in battery voltage during active test of generator output circuit.
51** A lean air/fuel mixture has been indicated by an abnormally rich correction factor.
52** A rich air/fuel mixture has been indicated by an abnormally rich correction factor.
53** PCM Internal fault condition detected.
54** No camshaft signal detected during engine cranking.
55* Completion of fault code display on Check Engine lamp.
63* Unsuccessful attempt to write to an EEPROM location by the PCM.
64** Catalyst efficiency below required level. (Same as code 72)
65* Power steering high pressure seen at high speed. (2.5L only)
72** Catalyst efficiency below required level. (Same as code 64)
77* Malfunction detected with poser feed to speed control servo solenoids.

* = This DTC will not cause the Check Engine Lamp (MIL) to illuminate. However, if another problem causes the MIL to illuminate, and this code is identified when you display all of the codes, at least you will know what it means.

** = The Check Engine Lamp (MIL) will illuminate during engine operation if this DTC is recorded.

*** = Generator Lamp will also be illuminated if this DTC is recorded.

Source: 1997 Jeep Wrangler Factory Service Manual; Group 25, Emission Control Systems.
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Old 11-12-2011, 09:00 PM   #28
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Looks like you need some new sensors.
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Old 11-12-2011, 09:23 PM   #29
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Thanks for posting those trouble codes!
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Old 11-12-2011, 09:31 PM   #30
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I'm adding this to my list. I have the same issues. Would cleaning the maf/map with carburator cleaner help?

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