I've never had a true "heat soak" problem on any of the the 4.0s I have or have had.

I live in Arkansas where it is hot (110+ degrees) and humid all the time unless it is snowing. Then it is cold and humid.

I think someone has an underlying problem.

Coolant getting into the cylinders from a cracked 2000-01 0331 head, or any cracked head/blown head gasket, will cause a misfire and throw codes that will simulate heat soak.

Doing the "poor man's prime" on a substandard fuel pump will help cut down on excessive crank times. But the pump should really be replaced under those circumstances.

I had a '97 4.0 Grand last year that would stutter around for a while after a long crank time. I replaced the fuel pump and the problem was solved. Smooth as silk after that.

 

My 2001 has done this to varying degrees for the past couple of years. I'm not sure if its the increased ethanol in fuel these days, aging of other engine components, or what. I have a couple of injectors wrapped. I'm sure its not the head on the 2001, because I replaced it. My 1997 had a problem with long crank time on a warm engine. Replaced the fuel pump and it fires up very fast 100% of the time.

 

I have a timer on my electric fan. I have it set for about 3.5 minutes. So if I'm going to turn off the Jeep for a few minutes and run in the store, or get gas, I hit a button and that starts the e-fan. It has helped,but it's not 100% gone. I have also wrapped my injectors and everything else I could. I really think if I had a hood vent or functional cowl hood it would solve it altogether. The hot air would have somewhere to go, and would not be trapped in the engine compartment. I am going to bring pictures of a cowl hood that a member on the forum built himself to a body shop and see if they can build it for me.

 

I experience the same heat soak issues with my 2000 Cherokee, I am assuming the head is fine since it has over 200K on it. I have wrapped the injectors and fuel rail, heat shield is still installed. If the two catalytic converters are the cause of the heat, is there an after market exhaust header that could be swapped in. Not sure if this would cause other issues with O2 sensors....

 

I have the same problem on my 2000 4.0. Only if I shut the car off after engine comes to temp and turn it back on while the engine is still hot. I've gotten very good at timing it so my CEL won't come back on and I can pass emissions.

 

There are headers available for the '00-'01 XJs, but they do not replace the precats. They bolt in above the precats in place of the stock exhaust manifold. They have holes for the upper O2 sensors and don't displace your lower O2 sensors at all. The only problem you have with the O2 sensors is that installing a header can sometimes cause them to fail because "stuff" on them burns off during break-in and fouls the sensors. Then you just replace them.

I doubt a header would solve your heat issue. I had my header and downpipe ceramic coated to help with heat management and to liven up the exhaust, but I have the EPA version without the precats. I'm not sure I would coat or wrap a cat, because that seems like it would cook it, especially if it's getting mature in years.

Have you looked into hood vents? I suspect part of the heat soak problem is that the heat has nowhere to go under that broad, flat hood. If you give the heat a chimney, maybe it won't sit there cooking your injectors.

 

I have just fixed my heatsoak issue. My jeep was originally from up north and I ended up moving down to Florida. needless to say, to fix any issue we have to go back to mechanics 101. I spent alot of time, money and research on this thing trying to fix it.

Over the weekend The jeep did something ive never had happen before, The jeep slightly over heated, and The coolant in the reservoir bottle litterally boiled/bubbled likea pot on a hot stove, and there was a serious smell of electrical burning, oh and the jeep decided to pour out smoke.

After bringing it to my mechcanic and spending a few hours doing some more research as to what caused this. AllData.com became our best friend.
Start with the ignition system since that is where the issue actually starts. You have multiple sensors in the ignition system. MAPS, TPS, CMP and another one I cant think of right now....
For me because I moved down to Florida I was in a completely different elevation and environment this was the reason for my heat soak. If your MAPS sensor has been in the vehicle since day one it will get used to the environment it "lives" in. So first things first change the MAPS sensor out, the next one that I changed out was the Camshaft Position Sensor.

The codes were then cleared and ive put at least a 100 miles on the xj. Testing the vehicle out where it normally has its heatsoak issue, and I have not had an issue arise yet..

Hopefully this all makes sense and works for you like it did for me, PLUS the sensors are super cheap!

Goodluck!

 

 

Just installed a set of new 4 hole injector (off Amazon) as I thought 300,000ks wasn't a bad innings for the old single hole injectors it was made with
Replaced and cleared the pcm/ecu in the usual way
Jeep is relearning the cold start but wow hot start heatsoak issues that I've never experience with the old metal injectors
Hot start turn off and restart immediate no issue but as time moves on the starting cycle goes from instant start to a number of crank rotations to fire
For me it has to be the plastic body injectors
As I switch back to the originals and the problem disappears
The fuel rail is hot to touch so are the injectors
My XJ is a 96 the last of the non recirculating EFI systems with no pressure regulator on the the rail
I suspect this is one reason jeep went to the recirculating Fuel rail for cooling purposes
Reading some of the replies heat shielding 1-3 makes sense has the end injectors will fill first on a non recirculating EFI rail leaving 1-3 with a gasey mess
I will experiment and post what I find
Me Iam a retired mechanic did my time on Jeeps and owned 2 XJ's, 1 ZJ and 1 WJ
Never had heat Soak here in NZ

 

Heat soak was (is) a problem inherent in 1999 - 2004 4.0 engines.

What specific 4-hole fuel injectors did you buy?

 

These fellas
Seems to have to be popular choice
On you tube seem to promote these generic type for fuel savings and effincency increases
Think I might refit my old ones

 

https://www.predisiness.com/index.ph...ucts_id=709048

P2A198s. A $3.00 injector.

Don't think it's a heat soak issue...

If you want to upgrade go with Bosch.

Or refurb your old ones.

Either way I think you're looking at 100-120 bucks.

BTW I went with 12 hole. No real good reason. One of mine was dead (ohms out of spec, so I new I needed at least one new one). 2 others had physical damage (falling apart), but they were still working.

 

Holy cow, a recent thread with a problem exactly like mine. Sorry for such a new user account, I have been on other forums a long time. I recently did the same as you:

I have a 1996 XJ with 170,000 miles or so. I was getting some intermittent rough idles and rough starts and such and decided that maybe some new injectors were due. I started the research and figured since I'm replacing them, I might as well upgrade them like I do for any other parts. So I ordered some 4 hole injectors from K suspension fab. The link will be at the end. They are remanufactured and were plug and play. I did the swap, cleaned all the ports up and all that, seemed great. Jeep started up well, ran a little rich for a bit as it adjusted, but all seemed well. Then we took a trip. We live in Colorado and drove to the Great Sand dunes using I25 and some mountain passes. We took our XJ and our JKUR and headed out. About 1.5hrs down the road, check engine light popped up and then started flashing. It was on a big hill and the jeep seemed ilke it lost all of it's power. (girlfriend was driving and called me). I told her we need to stop driving it and see whats up. we pulled into a near autozone to get codes read, misfires on cylinder 1 and the fix was carbon cleaning according to them (nope). We reset the computer with the old battery cable touching trick and it ran fine until we found a camping spot in the mountains on a cool evening. Next day driving, no check engine light, but heat soak (from my experience it seemed this way at least from modified cars in my garage) wouldn't allow the jeep up a very small obstacle in 4wd. put it in 4-lo to get up the obstacle and pulled over, popped the hood and let it cool, fine afterwards.

All this to say that I think I have the same issue, I think the plastic bodies of the new injectors are allowing the heat soak issue to present itself. I never had any issues like this before the injectors.

Now I will note one other thing here. I recently swapped my dummy cluster for a gauges cluster and went to change the sensors and the darn temp sensor snapped off at the threads. So in the interim I have attached a new sensor and just let it rest in the same area on the block (thinking I'll tap it into a new spot). I don't think this is relevant but the temperature on the gauge does get pretty high.

Link: https://www.ksuspensionfab.com/store...XJ%2FMJ.html#/

I want to swap my old injectors back in with some new o-rings and see if the problem goes away, based on what you said it will.

 

Why not switch #1 with #6 and see if the issue follows? If so, get K fab to give you a new injector.

Also check the the resistance, may show something.

 

Maybe wouldn't be a bad idea to check fuel pressure either.