Turbo X_J

While it certainly wouldn't hurt, if the IAT is going out of spec and sends bad data to the PCM when hot, wrapping the injectors won't fix it.

nhopa

Hi XJRed96, Turbo X J and HudsonN:
Thank you for the responses. Since my last reply I got the engine code P0113, "IAT sensor 1 circuit high input".
I checked out the sensor and it's resistance is in range at various temperatures. Also the computer out put is about 5.18 V which is also in speck. So what is this "high input" means?
I changed the spark plugs about 2 years ago but I put only about 10K miles on the car. On my 2001 Jeep Cherokee I do not see any distributor cap I think the firing is controlled by the computer.
The car started last Thursday I drove it about 6 miles then it died. So this could not be caused by vapor lock.


P.S. Yesterday I changed out the rod ends and put in 3 new Moog rod ends.
Now I can take the Jeep for wheel alignment. The "Brake Plus" shop told me they can't do alignment until the rod ends and the lower control arms are replaced. I took out one of the lower control arm and found that there was nothing wrong with the bushings. It is hard to find honest people anymore.

CFreeman

Hello Sir. I saw your post all all the responses you have been getting. I own a 1995 Jeep Cherokee. My buddy owns a 1998 Jeep Cherokee. We both have been experiencing similar problems-except we are in So Calif.-our Jeeps cut off when we are off-road and climbing, usually in compound low. Anyhow, we see the engine and transmission heating up and then our vehicle(s) die. After 30-45 minutes of cooling they start up and run fine. We have checked the fuel pressure which was good. The last time it happened to me my vehicle indicated a Code 32 which was a heat senor to the transmission or a solenoid in the transmission.
Bottom line, we are very interested if you find a diagnosis.

XJRed96

I wasn't paying attention to year necessarily. I forgot you have the coil pack and not a distributor. thats my bad.

I would replace the IAT. they aren't too expensive and it seems like a logical place to start.They certainly fail enough to know it's a problem part even if the sensor is acting up momentarily it's enough to trip the computer up. Everything you have described sounds like an IAT. you have certainly done enough testing to prove that the circuit is ok, and unless it's an ECM checking out you have pretty much proven that it's gotta be a faulty reading from the sensor. One way you could check the ecm is with an inexpensive tool called an IAT sensor. Sometimes after all the basic testing you just gotta throw a part at it. (not always but at this point in your diagnostics it's called for)

circuit High is tripping because the computer is getting back over 5.0 Volts. likely caused by an unexpected drop in resistance from the sensor. one thing you could try next time it wont start is unplugging the sensor and trying to get it to start that way. it might take a couple tries and it may not run as efficiently as it normally would but the computer SHOULD default to a base setting and you should be able to make it to wherever you may need to be.(the MIL will illuminate when you do this)...

And now that I say that it has me thinking that the MIL could have been illuminated because you unplugged the sensor to test it while the key was on. So I guess I took you full circle on that one and didn't get you anything.one thing you can do to prevent this is to back probe the connector while leaving it plugged in this will require a small conductive pin of sorts. (a very thin paper clip)

nhopa

Hi XJRed96 and CFreeman:
Thank you for your comments. I was driving home this morning after making a couple of stops. At one of the red light the engine started to sputter and it died. I thought, here we go again, except the temperature was around 90 degree F. So I tried to start the engine and it did start and I got home without further problem. So what ever give me the problem was very intermittent. To take the possible sensor problem out of picture I will remove the computer connection and solder a 4.7KOhm resistor to the computer plug. I also changed out the air filter which was pretty dirty (my bad). I will keep you informed.

dave1123

A 4.7K ohm resistor is going to have your PCM thinking the air temp is around 110*F. You're better off with a 10K ohm resistor for a 70*F reading.

XJRed96

i wouldn't start cutting up the harness like that for a test if you can avoid it. if anything just solder some small pins to the resistor and plug them into the connector on the harness.

nhopa

Hi XJRed96 and dave1123:
The average temperature this time of the year in the greater Phoenix area is about 105-110 degree F. This is the reason I picked the 4.7 KOhm resistor but it is easy to change it to a 10 KOhm one since I put pins into the Computer harness sockets. Thank you for the suggestions.
When the engine stalls it happens after a few miles of drive, so it can not be due to vapor lock in the fuel line. On the other hand when the engine just cranking it could either be due to no spark or no fuel flow. I don't see how these two problems can be caused by the IAT sensor being bad. The DTC codes should be indicating if the problem is either with the Ignition System or with the Fuel and Air Metering, but I get no code indication.

CFreeman

nhopa; I told you my friend and I were experiencing similar issues. I changed out some of the sensors and test drove my jeep this weekend; and No problems...it did not stall.
First, I cleaned the throttle body and Throttle body position sensor (TPS). This sensor was filthy. Next I replaced the Intake Air Temperature Sensor (IAT). I noticed the old one also had carbon on it. Then I changed the Crank Position Sensor (CPS)-it was covered with a gunk. I also put in a new air filter.
My test drive was during the day (about 90 degrees). I drove up to big Bear mountain, from 1,500 foot elevation to 6,000 foot elevation. My engine temp got to 220-225 (could have gotten as high as 230) when climbing up the mountain. My engine did not stall.
I have one more test next Saturday-an off road trip with a steep climb.
Hope this helps.

Jeep Driver

Interesting that none of you considered the fuel pump relay.

nhopa

Hi CFreeman:
Thank you for the tips. I drove the car for the past two days with temperatures in the high 90s with no problem. Tomorrow we expect about 107 F. I disconnected the IAT sensor and put in a 10 KOhm resistor to the computer also replaced the inlet air filter. The CPS was replaced last year because it stopped working. I will check the TPS to see if it needs cleaning. Will keep the forum posted.

nhopa

Update: This morning I drove the Jeep, stopped some places, no problem, temperature around 88 F. About 1 o'clock with temperature around 108-110 F the engine would not start. I kept pushing the gas pedal and the engine finally started going. I kept the RPM around 2500 for about two minutes the I let off on the gas and the engine died. It would not start after that. Obviously why I was applying the gas pedal I had fuel and spark. I left the key in the ignition and I could hear the fuel pump going. I checked the appropriate fuses, everything was OK. So why is this darn thing quits when it is so hot?

Turbo X_J

Test and if defective replace the TPS.
http://www.rockauto.com/en/moreinfo....sn=380&jsn=380

Jeep Driver

Swap the fuel pump relay.

dave1123

Just as a point of reference, I looked my engine sensor data while it was running today with my Actron scanner and with air temperature at 68* and the engine fully warm, the IAT was reading 154*. Engine temp at 212*. That tells me the engine heat is soaking the intake manifold pretty good. Maybe the TPS is acting weird when it gets hot.