Hi everyone,

I've got a Jeep Cherokee XJ 94 Sport 4L Auto and have a strange cold start issue. Car doesn't start in the cold morning or when car sits for around 6h. If it starts or i run for a little (~20 minutes) , then it will crank without problem all day after 3~4h sitting, after ~5H it starts to struggle again but still kinda of ok until impossible to start if longer, sometimes I can't start at all my Jeep as perhaps forcing to much cracking..

strangely sometimes even in the morning it starts perfect for few seconds then dies and after that, impossible to restart! Giving few gas helps sometimes to start, but would start really roughly giving gas until it idle properly by itself after 30 seconds assisting gas (with very bad idling). Once idling kick in it runs ok and needs to warm up 20 min. Right after everything turns to normal but still need to drive around half an hour to not have the problem, and start perfect all day..


I tried /changed almost everything and even been to few mechanics who refused to be involved on my car!!!

To list just a few this is what i replaced brand new:
6 new injectors,
new fuel pump,
new throttle position sensor,
deep clean idler air control,
deep cleaned throttle unit,
filter,
new starter motor,
checked vacuum if any leaks, n
idler pulley,
spark plugs,
new distributor cap,
new spark plug cables,
new fuel pressure regulator,
new battery,
Checked​ all the relays, fuses ...

I also freshly changed my engine oil with new oil filter.



If anyone can help me and beat this impossible issue I would be really thankful

Thanks

 

You test the coolant temp sensor?

 

Check your grounds. ALL of them. Especially the one to the PCM or anything grounded to the block that might be temperature sensitive.

 

Haven't as got the wrong part, going to try this Tomorrow!

Thanks!

 

What is your fuel pressure at idle?
What I said your fuel pressure at with key on, engine off?
What is your fuel pressure at, after sitting for 4-5 hours, vehicle turned off?

 

The coolant temp sensor...the one in the t-stat housing has incredible control over fuel mixtures...cool makes it rich and warm or hot makes it lean. Since you have a separate sender for the gauge in a 94 you have no idea what the coolant temp sensor is reading..easiest way to see if its your issue is to disconnect it in the morning when its cold...it sends a failsafe rich mixture...if it starts right up then thats your problem...you will set a check engine light

 

Changed with a brand new temperature sensor didn't work too!! That is driving me crazy...

PS: I already had tried to disconnect and didn't work neither, I was able to start but always with the exact same problem (forcing, giving gas and very bad idling until ok) as explained on my first post

 

Yes just replaced with a brand new still doesn't work...

 

Replaced with a brand new sensor but didn't work...

 

What brand of parts are you using? Mopar sensors? Champion spark plugs?

Looking at your list, if you are just throwing parts at it & not diagnosing the problem, you missed afew parts in your list.

- ignition rotor.
- you didn't mention what your sparkplugs are gapped at.
- how old is your fuel?
- when you replaced your battery & starter, did you clean both sides of the terminals? Where it mounts to the battery & where it mounts to the starter? How corroded are your cables? Even the inside of your starting cables.

- do you plan on renting a fuel pressure tester gauge and sharing your findings with fuel pressure?

 

Check the wires at the pigtail to the distributor pick up coil (the round flat sensor under the distributor cap). You may have replaced your sensors but you will need to back probe your map, tps, coolant and air temp sensors. This will let you see what the ecu is seeing.

 

Thanks for your help..

if I could diagnostic as easy as you say I wouldn't come here asking help or "just throwing part at it"... Also almost all of them have been recommended for mechanics, not me.

Everything listed no exception is brand new a week old including battery, terminal are brand new too when changed the battery ! fresh new fuel two days ago (as car still runs when I can crank it) new spark plugs Champion pre gapped and anyway been running for the same brand without problem for years.. it is definitely not the sparkplugs.

As explained the car runs perfect and cranks perfect once engine is warmed up and when problem comes and I can start in cold morning (with lot of effort), needs to give gas and start with very rough idle missing fire and need to force gas, then after 5 min forcing with gas it suddenly idles ok by itself doesn't die and I let it warning up. After it strangely can start the car without problem immediately and during the day too if it doesn't sit too long.

I checked yesterday the cables, wires, and did a parasitic draw test voltage, fuses are ok, relays are ok, including resistance. Checked too yesterday the coolant temperature sensor throttle position sensor, voltage, resistance on plugs, also changed yesterday a brand new coolant temperature sensor.

I did changed the ignition cap or rotor brand new as well

 

I hate to suggest yet another load in the parts cannon here, but there is a problem that someone else had and solved with a new PCM/Computer.. the cold weather caused the jeep to fail to crank, intermittent... I ran into the same behavior and happened to be replacing my PCM anyway (P.O. had the wrong part number) and that did solve the same problem for me as well. If you turn the ignition to "ON" but not start, you should hear the fuel pump prime. In this odd error case, the fuel pump would NOT prime at this point for me.
NOTE -- This is specific to the 96 and earlier Jeeps with the fat black vented PCM rather than the newer slim silver/chrome style PCM.

I'd do the fuel pressure testing FIRST, along with the wiring checks. If you have corrosion in the battery cables, new terminals won't help. If your cables are original, I'd replace those first before committing to a high price component like the PCM. If you can find a cheap one, maybe snag it regardless just so you have one even if it's not the problem.

 

Thanks for your suggestions I didn't think of this too..

However I might have found the problem!...
Testing it...

 

Ok guys!!

I think everyone gonna hate me right now..

Something I didn't think of was the crankshaft sensor !

So ran to get that part and jump under my Jeep to get that part.

Untill....


One bloody bolt dropped IN the bell housing!!!!🤦🤦🤦

Yes I told ya... I can feel you hate me all rights now for my stupidity!!👎🍅🍅🍅

​​​so big challenge started trying to get that bloody freaking bolt with magnet deep in there and no chance! Tried three different ones and made even one... No The chance!

So unscrew the bottom part ( thanks Jeep of making this part to access on the crankshaft) and BOoOm, my bolt was sitting there and showing me it it would have been impossible to get him even with an Harry Potter stick magnet or if I had to turn the car half second I would have destroyed everything 🙃

BIG LESSON TO LEARN here .. for the ones who needs to change their crankshaft sensor, there is a plastic protection that comes on top, even if this plastic falls off when you get the old part PUT IT BACK STRAIGHT AWAY to NOT drop anything in there...

I have read MANY people doing that same stupid mistake as to get there it quite tricky even tho if the part is two simple bolts...

Well eventually after all this efforts I felt immediately something different in my nice Jeep but still need to confirm
so I might fixed the problem!!!

Waiting tomorrow cold morning to check!!

Please pray for me 😅

Thanks anyway in advance for all of you guys for giving precious helps and also to Cherokeeforum.com🙏🙏🙏