I have no clue what's going on

Sorry it's long, but I have issues....

1997 Country 4.0 AW4 119k

Well, a couple of months ago it would act up some when I would accelerate - the Jeep would fall flat on its face - major hesitation, no power, etc. It would only last for a couple of seconds and then kick back in. It always seemed to happen in the morning when I was going to work and pulling out of my neighborhood - so I had driven approx a mile. It didn't happen every day though and really hasn't been doing it the last few weeks. Some suggestions on here were maybe TPS, but no solid answers. I haven't replaced anything yet....

I have an auto start installed on the Jeep and it's been cold the last few days here (rare for FL - mornings in the 20s), so I started the Jeep and let it run for about 10 min before I left for work. Well I accidentally hit the brake pedal when I got in which automatically shuts the vehicle off. When I went to restart w/ the key it wouldn't start!! It literally took me 6-7 tries of having to hold the key for a solid 10 seconds!!! (feels like a lifetime)

It also did it again today, but I hadn't used the auto start and I was just in the store for about 5 min and had been driving around for quite awhile before then,so it was definitely warmed up, etc.

The other thing I've noticed over the last few days is my temp gauge is doing it's own thing. It usually sits at 210, but I've noticed occasionally it'll quickly drop all the way down below 100 (like you shut the vehicle off) and sit there for 45 seconds or so and then slowly climb till a lil over 100 and then quickly shoot back up to 210. Then it'll fluctuate some between 190-210 area and eventually start the whole process all over again.

I also averaged 12.7 mpg last tank which is by far my worst. I usually average 14-14.5 which I still think is waaay too bad considering it's a stock vehicle w/ 235/75/15 tires, 2" budget boost, two core radiator, APN header & 2000 intake manifold (manifold was cracked which was my initial suspicion of poor mileage and I figured while I was doing that, I might as well do manifold & radiator). I also did O2 sensors, plugs, wires, rotor & cap about 10k ago and it is running Mobil 1 in engine, transfer case & both axles. I figure with all of that and proper inflation i should see around 16-17 city which is what my brother gets in his '00 w/ 199k and 31s!!! And that's with him just doing the math and not compensating for the 31s, so he's actually gettting better!!

Any ideas? I'm tempted to do a TPS & maybe CPS, but don't want to just throw money at stuff. Also, would either of those cause poor fuel economy???

sounds like cps to me.

Two different problems. Temp is the easiest. Thermostat bad or air in coolant system or temp sensor/connection. Dying on acceleration could be TPS.

I agree with winterbeater, I think you have more than one issue here.

1. Thermostat, air in system or an electrical problem most likely the coolant temp sensor or connection to it.

2. For the hesitation, definitely test your throttle position sensor. Your symptoms are classic for failure of that component.
Testing fuel pressure at the schrader valve on the fuel rail would never be a bad idea for this symptom as well.

3. The dying could possibly be a crank sensor issue. Test it to see where it falls in the spec range. Replace as necessary.

Crankshaft Position Sensor: (CPS/CKP) Failure Symptoms / Testing

*Both the fuel gauge and or voltage gauge may not work/display

*It is possible that you may see a No Bus on the odometer (on newer models only)

*You will have no spark. Fuel pressure may check out okay at the fuel rail, but fuel won’t get to the fuel injectors

*For 96 + newer, sometimes the OBDII code reader has trouble connecting to /reading codes. Crankshaft position sensor failure may or may not result in a check engine light/fault code.

*Crankshaft position sensors can be intermittent resulting in an abrupt misfire. "Thermal failure" is common. Thermal fail means that the sensor fails when engine gets hot, but works again when engine cools down. Be aware of this when testing, as if you have a sensor that suffers from thermal failure, it’s possible that it may test GOOD as soon as it cools down.
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CRANKSHAFT SENSOR TESTING PROCEDURE: 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.

2. Place an ohmmeter across terminals B and C. The terminals are identified as A-B-C looking into connector from left to right with the "notch" in the middle of the connector on your right. Ohmmeter should be set to 1K-to-10K scale for this test.

3. The meter reading should be open (infinite resistance). Replace sensor if LOW RESISTANCE

Question: Can't you test the TPS with a $3 digital volt/ohm meter on the 97XJ, rather than throwing on a new TPS? I'm asking from ignorance, as mine is a 90XJ, but it would seem that is should be testable and pehaps adjustable too?

Yes, any TPS can be tested. Testing is always the way to go before replacing a component. Meter and a manual will get you there. Joe, your 1990 TPS is adjustable, gonepostal's TPS on a 1997 is not adjustable.

Well good to know. I'll grab my manual and voltmeter tomorrow after work and mess around w/ CPS & TPS. I figured it was more than one issue, but they all started happening around the same time so I figured maybe they're somehow related. I'll post back on here w/ my results

Just a quick question. I have a background in alarm/security system installs. Did this problem occur directly after the remote start install? I have been out of the market for a few years and am not sure if your jeep has a transponder type key. If it does what type of bypass was used? If one was used and it is poorly installed then the truck is forgetting it has a key in it. With your description of the problems starting after "disabling" the remote start I suspect that the problem lies there. I hate to say it but many of the people in the aftermarket industry lack proper training or installation skills.

Test the coolant sensor while you're at it. If it's going bad, or has a wiring issue it will tell the computer the engine is cold. That will give you crappy mileage, rough running, and maybe hot start issues.

I'd bet it's your o2 sensor(s).

Well currently working on installing my overhead console and then will get to testing these sensors to try and fix these issues.

Questions regarding testing sensors - are specs in FSM or Haynes?? I saw the brief writeup by BirchlakeXJ regarding CPS, but not sure if it's the same for TPS & coolant. I've never actually tested a sensore before, but it's obviously not difficult - just never had the need till now.

Chris1968 - No, auto start installed last January. There is also no bypass system for the XJ (at least '97). Man that was a fun job though. Nothing like being 6'2" and trying to splice/solder 17 wires in under the steering console. My back hurt for 2 days. I have no idea what a shop would charge for that job, but it's gotta be good money.

Jeepster_259 - O2 sensors are a lil over year old. I believe they're Bosch? I bought them from Autozone - are they prone to failure rather quickly??

"Most" of the specs are in the FSM. Sometimes you need to read the "description", "testing", and "specification" sections to figure it out. A few of then aren't in there as they think the OBDII codes will tell you.

For the TPS, a analog ohmmeter is highly recommended because you could have dead spots along the throttle travel that a digital might hide.

It's funny how you younguns like to throw parts at a problem instead of troubleshooting :banghead:

First, pull the plugs and do a plug reading. This will tell you tons. If they are very white you are running too lean (may be caused by an air leak amoung other things). If they are brown to black, you are running too rich which may be caused by multiple things such as clogged air filter, bad MAP, bad TPS, bad O2, or clogged CAT. If it is one cylinder then suspect plug wire, plug, or leaky injector.

Second, use a vacuum gauge to check the manifold vacuum. The actual number varies by altitude and health of the engine, but it should be high.

Having said all of that, my bet is on the TPS.

I haven't thrown money at anything yet....

All of the parts I've replaced that I listed are over the course of the 18 months that I've owned the Jeep and it's b/c PO had no maintenance records of a 110k mile old vehicle, so I was just slowly getting the vehicle to a point where I knew everything had been done and when. I just basically did a thorough tune-up in my opinion.

gone postal said:

I haven't thrown money at anything yet....

All of the parts I've replaced that I listed are over the course of the 18 months that I've owned the Jeep and it's b/c PO had no maintenance records of a 110k mile old vehicle, so I was just slowly getting the vehicle to a point where I knew everything had been done and when. I just basically did a thorough tune-up in my opinion.

Click to expand...

You're testing parts now and asking the right questions. Sorry if it seems like we're picking on you, but some other people seem like they go nuts replacing parts that aren't bad.:cheers: