nhopa

I liven North of Phoenix, Az. In the last couple of days the temperature reached 114-115 degree F. When I try to start the car it just cranks but does not start. In the morning when temperature is down to about 90 F or lower it stars right of way and runs like a champ. What could cause the non-start? Thank you for your help.

Turbo X_J

What's missing fuel or spark? (this is posted in off topic btw)

dave1123

I'm thinkin' the IAT is out of range and the PCM doesn't like it.

nhopa

Hi Turbo X J and dave1123: Thank you for the quick response. Early morning today at temperature 88F the Jeep started right of way. I drove it about 10 miles without any problem. So I would say the Jeep had spark and fuel. At high temperature what would shut off and by what means? What is IAT stands for? Can it be changed or adjusted? Thank you.

Silentj

Intake Air Temperature

XJRed96

Intake Air Temperature sensor = IAT . it can be changed, it can't be adjusted. Does it start shortly after you've driven the Jeep for 20 minutes and shut it off?

dave1123

WAIT! forget that. My resistance chart for the IAT goes from -40*F to 238*F. Gotta be somethin' else. Maybe ask the IT guys if there's a temperature limit for the PCM function.

nhopa

Hi XJRed96:
If the Jeep starts the first time, after that it starts every time. It just something is preventing the engine firing up initially if the outside air temperature is too hot. Today we are down to about 107 F so that is cool.

dave1123

Just for jollies, try putting a gel freezer pack over the PCM the next time this happens and see if it starts. This is curious. During last the winter, we had one guy who had to use a hair drier to get it started.

XJRed96

alright more hypothetical. Say it starts in the morning around 9:00 on your way to work ambient temp 100. You get to work and boss sends you home early for good behavior, you get off around 4: and the temp is 117. Will it start after sitting for 6 hours or so?

Are your keys chipped? and do you routinely use the same ignition key always or are you known(like I am) to grab whatever key is available because you still haven't mastered the art of leaving your keys in the same spot every time you walk in the door?

nhopa

Hi dave1123 and XJRed96:
Yesterday morning at 6:30 AM I used the car to go to the pool, returned home about8:30 AM. Then I left the house 10:00 AM and 15 minutes later the Jeep died on me in an intersection. Called my wife to give me a tow home. 11:30 AM I hooked up the tow rope and started the Jeep, the SOB started so I disconnected the tow rope and drove across the street and parked in a parking lot. At this time the Jeep started running rough and died. This morning my wife drove me to the car and I drove it back home.
In the afternoon I took the IAT out of the manifold, hooked it up to an Ohm meter reading about5.6 KOhm and started heating the tip. The resistance rapidly dropped below 1 KOhm so I stopped the test. Conclusion is that the IAT is working properly. Next I checked for voltage on the computer end of the connector where one should see about 5 Volts coming from the computer. I only measured mVs. Started the Jeep with the same results. The Jeep ran about a minute than started running rough then died. Tomorrow morning while it is relatively cool I will start the motor and check for voltage. If there is no 5 Volts I would think that something is wrong with the PCM. Any thoughts on what is going on?

XJRed96

When was the last time that you did a full tune up? plugs wires cap rotor? You can try spraying the ignition down(with a misting spray bottle) when it's running right. If it begins to act up you know what you need to replace. Have you ever had any check engine lights while this was happening?

nhopa

Hi XJRed96:
Update to yesterdays tests. This morning I started the engine and read
5.18 V from the computer, the temperature was about 95 F. At 3 PM started the engine but it would not run, measured the voltage as 5.19 V and the temperature was about 112 F. Next I hooked up my code reader and was surprised to get the code P0113 "IAT sensor 1 circuit high input". Yesterday afternoon I measured 5.6 KOhm resistance for the sensor. From the internet I down loaded the sensor resistance chart and for about 113 F it gives a min. of 4,115 Ohms and a max. of 4,815 Ohms. At this point I do not know what the "high input" means. Does it refer to the resistance or the voltage being high? Tomorrow morning I will take the sensor out and measure the resistance and in the afternoon I will repeat the measurement. If I find the resistance too high and the engine not starting then I will replace the sensor input with a 3 or 4 KOhm resistor and see if that allows the engine run.

Turbo X_J

A low ambient temperature will result in a high signal voltage. Can you access live data and does the IAT show any value (like -30°F) when the engine will not start? As well when the engine will not start is it flooding with fuel?

HudsonN

Almost sounds like heat soak to me. The 00 and 01s are known for it.

Generally the jeep will start up and run fine until you turn it off, then the fuel in the rail will get really hot and vapor lock and prevent the jeep from starting until it cools back down.

If i were you i'd go get some heat tape and wrap it around your injectors and the rails and see if it helps. If it doesn't you're only out a few bucks and that'll help in the long run anyways.