Scooterpookin

Hey yall 1999 cherokee sport 2wd
First crank of the day starts right up. I'll drive to the grocery store come back 10 minutes later and it cranks but doesn't start, if I sit for about 15 minutes and try it again cranks on the first try. Sometimes it cranks multiple times and then doesn't but it seems if I wait it eventually starts up. I've already checked my grounds clean them up I've replaced the crankshaft position sensor. And I've also checked my relays for the click and for resistance. I hear the fuel pump when I turn the key to on and I get fuel out when I test the Schrader valve. I haven't done a tune-up on it yet but I plan to just looking to see if I can get it fixed now before the parts get here.

Scooterpookin

It happened again today twice. I timed myself and as long as I don't crank within 30 minutes it cranks up just fine. Seems like it has to be some other sensor. Check engine light has been on since I bought the jeep just recently made it my everyday. So I wonder how long it's been like this. Gonna get the code read tomorrow at the parts store.

jessenator

Could be heat soak. Where are you at? hot climate?

I put on one of those insulator kits. Like $50 on ebay. Worth every penny. I'd check all the avenues other members might suggest before you start flinging presidents at the problem, though.

Scooterpookin

Yea I live in FL usually in the 90s everyday, what about an air intake problem sometimes at idle the rpms don't want to stay put bumping up and down.

thinking about it now it could be heat soak, I should mention my jeep is missing electric fan which could ex plain it

EZEARL

Have you ever cleaned the throttle body and IAC? See post #6 in the link below:
https://www.cherokeeforum.com/f2/jee...s-idle-245907/

Scooterpookin

I need to do that too, ezearl

jessenator

What was the engine code you mentioned? I'm curious about that—missed that part of your post when I relied initially.

fb97xj1

Heat soaked injectors, or even an overheated crank sensor would be my guess. Like said, what was the engine code?

Turbo X_J

Turbo X_J

Any codes?
What's the fuel pressure in psi?

Scooterpookin

so i picked up an electric fan from the junkyard and plugged it in, turns on when I run the AC. I was thinking of a time delay relay to let the fan run for a minute or 2 to help with heat soak. Bought new intake sensors.
I got oriellys to read the code but he didnt tell me code numbers just low battery and ambient temp sensor. We went back in and he looked up two sensors IAT sensor I believe? Cleaning the throttle body today. I started leaving the hood popped in between short trips and so far I haven't had starting problems so I definitely think there was probably some heat soaking going on.

also does the on off on off on with the keys trick work with 1999 Jeep Cherokee for reading the codes yourself?

Both of these pop up when i search IAT sensor

jessenator

With OBD-II vehicles I just use a reader on the OBD port. I don't want to bother with the dash light readings, even if it exists, which I'm not sure does on the XJ (I've read that the TJ did still do that). I picked up a bluetooth reader for maybe $20 on amazon and it's worked fine for me.

If they're not telling you the actual numbers, next time go take it to another big box store who does it for free and have them give you the numbers. All my stores actually aren't allowed to tell you what to do, just the code and what the code name is. As good as OBDII is, the codes can also be symptomatic of other issues. e.g. a P0420 catalyst code isn't always that the cat is bad, could be you've got exhaust leaks, etc.

A bad ambient temp sensor though could throw off your PCM's fuel/air mix a bit. The temp determines O2 density and without an accurate reading will give you mixture issues, but not necessarily starting issues.

How old is your battery? if it's fairly new I'd borrow a multimeter and check the output of the alternator. A battery cell check might not be remiss either.