Howdy!

I have a 2001 4.0L Cherokee, automatic trans, 116,000 miles. It's basically stock because I'm lame...

THE PROBLEM: This problem only occurs if it is hot outside (90+ degrees), and if the engine is still hot (180+ degrees or so) from a previous drive. I'll turn it on, and it starts to shudder and gasp, almost like it is about to stall out. But five seconds after I get it moving, the shuddering goes away and it purrs like a kitten. The jeep never overheats. I do not experience any shuddering once driving, not even stopped at a light. I thought maybe this was linked to dying AC (which would coincidentally be used on these hot days) but I just replaced AC/dryer due to worn out barings and the shuddering problem upon a hot start still remains. When this shuddering does occur it seems to be getting worse and worse, not in length of time, just in magnitude.

These have all been replaced recently and I don't see them as being the culprit:
96,000mi water pump
100,000mi coil pack
105,000mi serpentine belt
115,950mi AC compressor/dryer
haven't replaced battery but it seems decent
key turns over and jeep starts up just fine, but then it shudders

Again, this only happens if it's both hot outside and the engine is already hot. So far, consensus is that I just need new spark plugs, and since I bought it and put on 26,000mi, I have not replaced the spark plugs.

I should also note that the jeep was driven for a substantial period of time (about 5 months) over this past winter with the main fan unplugged yet concealed because of a crooked mechanic. I never noticed because I never used the AC over winter. But as spring hit my barings of the AC were obviously shot and whining. I finally replaced the AC the other day and now it no longer whines.

So I guess my question is, does the new spark plug theory make sense if this only occurs on hot days with a hot engine?

I'm not mechanically inclined so please break things down to dummy-level. Thanks!

Lauren

 

Search "Heat Soak". I had the same problem with my 2000 XJ. There is a factory recall write-up, that puts a small peice of hose to block the manifolds heat exchange to injector #3.

 

Yup, i think you're right. Based on what I just read, it sounds like Heat Soak. Seems like people offer a bunch of different solutions, though... I wonder which is best.

Is that "small piece of hose" you are referring to synonymous with "ignition wire shield?" This answer seemed to be the most official:

"1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
Date: 09/05/03 (supercedes 1802702 dated 09/06/02)
Model Year(s): 1999-2004

Description: NOTE: This bulletin applies to vehicles equipped with a 4.0L engine. This bulletin involves the installation of a fuel injector insulator sleeve.

Details: Customers may describe a 20 to 30 second rough idle following the restart of a heat soaked engine. This condition may be most noticeable when the engine is restarted following a prior 10 to 20 minute heatsoak in hot ambient conditions of approximately 32 C (90ºF) or higher. This condition may be consistent with short city stop-and-go driving trips and can be aggravated by the use of fuel with a high ethanol content. Depending upon various conditions a MIL may occur due to DTC P0303 - Cylinder #3 Misfire.

This condition may be caused by heat from the exhaust manifold that following engine shut down migrates to the area around injector #3 and causes fuel vapor to form within the injector. This in turn may cause a momentary misfire of cylinder #3 until the fuel vapor is cleared of injector #3. The insulator sleeve lowers the injector #3 temperature to a point below which the fuel will not normally vaporize.

If vehicle exhibits a rough idle, and if a misfire of cylinder #3 is observed following a 10 to 20 minute hot soak, perform the Repair Procedure.

Parts required:
56028371AA Ignition Wire Shield"

 

Here's a related issue of heat soak from the other thread: https://www.cherokeeforum.com/f2/200...o-i-fix-59457/

 

The peice of hose is to put around the #3 injector. I'll try to find the write up I used.

 

Sorry, I couldn't find the write up.

 

That's ok, I think I'm good. Thanks so much for your help!

 

What octane gas are you running? Are you using ethanol added fuel? If you are then you're problem is the ethanol evaporating in the fuel rail causing "bubbles" because cherokees use a returnless fuel system. The easier fix is to start running 87 octane or other fuel with no ethanol added. I did this with mine after speaking with my mechanic and it solved my problem. My jeep would shudder like you explained after a long drive then letting it sit and starting back up. Our jeeps just don't dig ethanol. Try it ill bet it stops. Hope this helps

 

Umm, not sure... bottle says "Everclear - 190 proof"


just kidding...


But actually, I don't know ethanol content. I just get the regular cheap gas out here from Conoco, I'll look when I go to fill up on my way home tonight.

 

The cheap gas is usually the one with ethanol. Just run straight 87 octane unleaded and take the hit at the pump. I'd be shocked if it didn't solve the problem