'01 2.5L TJ hesitates/bucks at 2000RPM, running out of things to replace

[cmmartin86]

I need help/ideas. I have a 5-speed, 4cyl, 2.5L Wrangler TJ (01), and I installed a Eaton m45 Supercharger on it. I am having a consistent hesitation every time -- 100% of the time -- I accelerate and hit 2000RPM. I can push through it, and the jeep will run perfectly fine again. It is solely at 2000RPM that this hesitation occurs. Also, the smell of fuel accompanies this hesitation. P0301 Cylinder 1 misfire code is thrown.

I have replaced just about everything I can think of, and I'm running out of things to test. I don't really want to take it in because I know they will charge a lot, but if that's the last resort.

List of replaced:
Crankshaft Sensor
TPS
02 sensors
IAC
Radiator
Checked/cleaned fuel pump and filter
IAT
Air Filter
Ignition Coil
Spark Plugs and Wires
Cap and Rotor
Checked exhaust valve rotation
Compression Test
New Fuel Injectors
Checked Fuel Pressure (50 psi) -- no leaks
Vacuum Pressure (no leaks)
Ran seafoam through
Clock Spring (yes it's real)
Drained gas tank and have only used Premium

I'm considering changing the distributor and ECU next, but would rather find the problem before dropping a couple hundred on these.

Suggestions?

Thanks

 

[Bounty__Hunter]

Welcome to the Z.

What mods have you done to get more fuel into the cylinders?

 

[cmmartin86]

It has a manifold and adapter plate from rimmer engineering. An aftermarket high flow fuel rail(not sure what brand it was used). Ford Racing 30lb Injectors. Had the gas tank out a week ago and replaced both strainers and cleaned.Stock fuel filter. To control the injectors I am using a split second fuel/timing calibrator. It is not perfect yet but very close. Havent had a chance to take it and get it dyno tuned yet. Just to make sure it was not the fuel timing calibrator doing it i took it out and returned it back to stock and it was still missing at 2000rpm exactly. I have tried running rich, lean, exactly stoich. It acts the same either way. I also have a wide band O2 monitor installed to monitor during tuning and left it hooked up, it goes a hair lean 2000rpm but not enough to cause what it is doing. I have had a fuel pressure gauge hooked up to the rail to monitor pressure and it stays very close to 50PSI.

 

[C Wills]

New to the Site. I'm having the same problem with my 98 sahara when I first start it up. Mines usually hesitates around 2000 rpm also. I can drive through it also, but, I don't have a supercharger in my jeep. I changed the injectors, but that didn't fix my problem. Wanted to know if it was a big job to drop the tank to change the fuel filter?

 

[cmmartin86]

New to the Site. I'm having the same problem with my 98 sahara when I first start it up. Mines usually hesitates around 2000 rpm also. I can drive through it also, but, I don't have a supercharger in my jeep. I changed the injectors, but that didn't fix my problem. Wanted to know if it was a big job to drop the tank to change the fuel filter?

Before you do that(more than likely that is not your problem). Unplug your upstream O2 sensor and go drive it. If it dose not happen, then that is your problem. Usually this is what is going out. Let me know if this does not fix it and well go from there. Cheers Chris

 

[C Wills]

Ok thank. I'll try when I get home from work .

 

[Icelia]

In my earlier life as an auto mechanic, I remember encountering a bad distributor timing advance mechanism.
It caused the engine to buck and hesitate at specific throttle speed.
Check to see that it advanced smoothly, and for wear on the bushings. ( you can do this by taking the cap off and then advancing the rotor by hand.
-Ezra

 

[cmmartin86]

Yea I found my problem, but yours won't be the same. My O2 map was off so I got a piggyback ecu to remap them. Hardly the problem you are having. To your question about the gas tank. No it is not that hard to drop. Unscrew the 7 screws around the gas cap. Then remover the 7 or 8 bolts supporting the gas tank skid( but be carfull dropout it the gas line and emissions air lines are attached to the top and you could break one if you are not careful). The emissions just have a nipple fitting but the gas has a little connect that you have to squeeze to remove. I would suggest doing this when you are out of gas( makes it lighter). I'm not sure what you are expecting his filter to look like, but it referee to by thE FSM as a strainer not a filter and looks kind of like a Maxie pad. There is not real way for it to get clogged.

 

[C Wills]

Thanks bro. I did what you said and it didn't hesitate. I drove once around the block. Usually it would've done it before I left my block. I'm going to change the oxygen sensor sometime this week.

 

[luis]

I need help/ideas. I have a 5-speed, 4cyl, 2.5L Wrangler TJ (01), and I installed a Eaton m45 Supercharger on it. I am having a consistent hesitation every time -- 100% of the time -- I accelerate and hit 2000RPM. I can push through it, and the jeep will run perfectly fine again. It is solely at 2000RPM that this hesitation occurs. Also, the smell of fuel accompanies this hesitation. P0301 Cylinder 1 misfire code is thrown.

I have replaced just about everything I can think of, and I'm running out of things to test. I don't really want to take it in because I know they will charge a lot, but if that's the last resort.

List of replaced:
Crankshaft Sensor
TPS
02 sensors
IAC
Radiator
Checked/cleaned fuel pump and filter
IAT
Air Filter
Ignition Coil
Spark Plugs and Wires
Cap and Rotor
Checked exhaust valve rotation
Compression Test
New Fuel Injectors
Checked Fuel Pressure (50 psi) -- no leaks
Vacuum Pressure (no leaks)
Ran seafoam through
Clock Spring (yes it's real)
Drained gas tank and have only used Premium

I'm considering changing the distributor and ECU next, but would rather find the problem before dropping a couple hundred on these.

Suggestions?

Thanks

I know its out if topic. But how do u like the supercharger? How much did the mod cost u? With installation and labor and miscellaneous parts? Sorry I don't wana jack your thread but I just wana know cuz I have the 2.5 aswell but I have the 97 tj

 

[cmmartin86]

I know its out if topic. But how do u like the supercharger? How much did the mod cost u? With installation and labor and miscellaneous parts? Sorry I don't wana jack your thread but I just wana know cuz I have the 2.5 aswell but I have the 97 tj

As far as power, probably bumped it up to what's 4.0 is stock. As far as cost, probably around 2,500 for everything. All out cool factor, priceless:shades:. Just kidding I did it pretty much just to see if I could do it, as is pretty much every reason people do the things they do to jeeps. That's why we have them and drive them. In the end it would have been cheaper to sell the jeep and buy a 4.0 but that would not have been any fun.

 

[luis]

As far as power, probably bumped it up to what's 4.0 is stock. As far as cost, probably around 2,500 for everything. All out cool factor, priceless:shades:. Just kidding I did it pretty much just to see if I could do it, as is pretty much every reason people do the things they do to jeeps. That's why we have them and drive them. In the end it would have been cheaper to sell the jeep and buy a 4.0 but that would not have been any fun.

Ya its cool to experiment with power stuff. Where did u get yours? Iv been wanting to super chargeb mine. I like my jeep so selling it and simple getting another isn't an option.

 

[mouse53]

I have the same problem. Ours is a 97 TJ with the 2.5 and 5spd, otherwise stock. Ran fine until about 2-3 weeks ago. Check engine came on said " intermittent CPS or C something, said it was either the crank sensor or the cam sensor which is in the distributor I believe. I remember changing from the auto to stick and when I installed the sensor on the bellhousing, it didn't really feel right, but it ran good. Well when this all started, I checked those bolts and they were the wrong ones, ( should M7 ). I installed the right bolts codes checked out OK and ran OK for about a week. Now runs like crap, hesitates, almost like water in the gas. No check engine light though. Since this is my wife's daily driver, and if the wife isn't happy ( well you know the rest ) I would really like to get it running right. Haven't seen any concrete answers yet.

 

[cmmartin86]

I have a few more questions for you mouse. Can you be a little for specific about the occurrence of the hesitation. What I mean is, what are the conditions it happens in(i.e, idle, rpm, vehicle speed, engine hot or cold, right away or takes a minute, a certain throttle position) every little detail helps. Also what do you mean by went from stick to auto? As in you changed out the transmission and added a clutch pedal?

Ya its cool to experiment with power stuff. Where did u get yours? Iv been wanting to super chargeb mine. I like my jeep so selling it and simple getting another isn't an option.

I found a used rimmer kit that came with an Eaton roots type blower and a modified intake manifold, but these are few and far between. I believe if you were going to start from scratch a turbo would be much easier and cheaper. Also you would be able to put an inter-cooler in there as opposed to the supercharger.

 

[mouse53]

Thats strange, I know I sent a response last night, but don't see it. I changed the trans from the auto that took a crap to a 5spd, found the whole set-up on CL for a couple of bills complete with the ECU, flywheel, pedals master and slave, etc. I didn't know about the CPS and had to retrieve from the old trans. Trans was 21 spline and t-case was 23, so had to change that. TJ has run fine up until a few weeks ago then started this hesitating and bucking kind of like water in the gas. It seems to happen when it gets warm and leaving a stop sign or signal at about 1500-2000 rpm. Once you get in 3rd, it runs good. I've seen several others here at the forums with similar problems and don't want to change a bunch of parts needlessly. It is a 97 TJ has a 2.5 with about 90,000 mi, small 5spd AX, stock t-case, stock height.

Rich

 

[luis]

Thats strange, I know I sent a response last night, but don't see it. I changed the trans from the auto that took a crap to a 5spd, found the whole set-up on CL for a couple of bills complete with the ECU, flywheel, pedals master and slave, etc. I didn't know about the CPS and had to retrieve from the old trans. Trans was 21 spline and t-case was 23, so had to change that. TJ has run fine up until a few weeks ago then started this hesitating and bucking kind of like water in the gas. It seems to happen when it gets warm and leaving a stop sign or signal at about 1500-2000 rpm. Once you get in 3rd, it runs good. I've seen several others here at the forums with similar problems and don't want to change a bunch of parts needlessly. It is a 97 TJ has a 2.5 with about 90,000 mi, small 5spd AX, stock t-case, stock height.

Rich

I'm no expert but it shouldn't matter what type of trans u have cuz the sensor monitors the crank shaft and not the transmission. But I'm only using what seems reasonable. I may be wrong. If it ran fine after the swap and it just started maybe the sensor took a dumb or there is another issue

 

[mouse53]

Well when it first did this hesitation thing, the " Check Engine Light "came on. I borrowed a code reader and it said intermittent signal from the CPS. So I checked it and it was loose, I tightened the bolts. If I remember right, if the sensor isn't working, the Jeep will not start. I started it up checked the codes, no codes, so I cleared it. Ran ok for about a day, now it is hesitating again, but no check engine light. I don't mind replacing a sensor, If that is whats wrong, but they aren't cheap. No sense replacing parts that aren't broke. I know what type of trans makes no difference as the same sensor works for both and I put the 5spd in 3 years ago.

 

[cmmartin86]

Well if it takes it a minute to start hesitating then it is more than likely a sensor(not water in the gas, or a fuel related issue). What is happening is for the first couple of minutes the ecu is running in open loop and running just off stored data in the ecu. If I can remember correctly it starts to read off the O2's, IAT, and temp sensor when it goes into closed loop. So if unplugging the O2's didn't work I would find a scanner that can read live data and have somebody drive it while you monitor the live data and see if anything looks out of the ordinary when it hits closed loop. Just so you are not guessing on which sensor is bad.

 

[mouse53]

Thanks for the info cmmartin86, I will try that tomorrow. I found some more information on testing the sensors with a volt/ohm meter on JeepForum.com also. Hope to get this solved soon.

 

[mouse53]

Well tried everything, had wife drive the TJ while I monitored the code reader, still got a P0320 distributor / speed control/ cps. So I pulled the sensor and found some of the wires were cracked in two right where it plugs into wiring loom. Replaced the sensor and it runs better than it ever has. I couldn't see any cracks until I had the sensor on the bench with a magnifier lens and did a continuity check. Hope you guys get yours fixed as easily. Now for the leaking seal.