pmXJ01

So whenever it's warm out I start having issues with what I assume is heat soak. I notice that it might happen more often if I run my a/c. I'll start it up, starts fine, drive for a while and then shut off. I'll run in to the store or whatever, come out and start the jeep. If it stays running it sounds like it is running on about one cylinder. This has happened 2 or three times now. I was able to get it going and it had no power but finally got enough fuel to it to start running ok. I'm assuming the cool fuel finally cools down the injector or something.

The last time this happended was a couple I days ago. I got 4 codes:
Multiple cylinder misfire
Cylinder 1 misfire
Cylinder 2 misfire
And throttle position sensor error of some sort. (don't remember exactly what it was right off)

The first time this happened it threw a cyl 3 misfire code. I put a piece of metel under injector 3 as a heat shield.

So what advice do you guys have to help with this issue to make for a reliable driver in the summer? Sell it?

Thanks



Oh, 2001 Jeep Cherokee sport 4.0 automatic 4x4

mikeoc1

I was able to cure my bad heat soak issue by wrapping #3 and #4 injectors with some heavy heat wrap and secured it with some zip ties. That helped, I eventually replaced the cat converter and muffler, as it was the original with 160k miles. After the new cat, and wrapping the injectors I have yet to have heat soak since. and No codes. I have seen some wrap all of the injectors.

pmXJ01

What kind I heavy heat wrap did you use? Where can I get it? I wouldn't be surprised if a new cat set up would help. I have got A cat code once before. I just don't want to start dumping much money into it as I might just sell it. I already have another truck and a company truck starting mid july with my new job. A new double cat set up is like 400 bucks or something like that. I don't want to invest more money into it than it will be worth if I sold it.

I'll try more heat wrap first. Wish I could wire the electric fan in a timer or something easy. Thanks for the input

Parsnip

Its throwing misfire codes and a tps code....id check the tps

mikeoc1

The heat wrap came from a local auto parts store. all of them have it. You can use the heat tape and wrap a bunch of it, or I used the a heat sheild sheath and just cut sections off. Go to the autoparts store and see what they have and use your imagination...Mine never threw a TPS code. So you might want to look into that. As for the cat, I only replaced the cat in the tail pipe, not the two little cats on the down pipe.

rrich

Check the fuel pressure at the rail when it acts up - downstream from the pressure regulator. A weak/hot regulator can do it.

If you had decent pressure when restarting, any vapor from heat in or around the injector would shoot out into the cylinder the first time it opens. Sounds like the pressure is too low at first - regulator or pump.

Check pressure before and after the regulator.
Low on the pump side - bad pump.
Pump side good, rail side low - replace regulator.

Check the steel fuel lines underneath to make sure they are not too close to the exhaust.

99.99999% of all the Cherokees don't have the heat wrapped injectors, nor do they need them.

Wrapping only does like the cat in the cat box - covers it up. It will get worse until it totally quits unless you find and cure the problem.

the buddmang

There are two tsb's from jeep about this issue. Heat wrap is NOT a cover up.

There are LOTS of cherokees and grands that have a heat shield to prevent the fuel injectors from getting too hot and vaporizing the fuel that is in the injector/rail.

There is another tsb regarding a hotsoak misfire relating to the valves having deposits. The intake/exhaust valves are designed to spin in their seat to keep them clean, this only happens after 3000rpm. If you never go above this rpm, deposits can build and cause misfire issues that are hard to track. Jeep's solution for this is to do a top end engine clean service and advise customers to occasionally accelerate past 3000rpm.

rrich

LOTS OF THEM?
How many? 100? 200?
Out of the hundreds of thousands of 4.0's made through the years, what is the percentage? Why wasn't it used on all new 4.0's?

Why didn't Jeep wrap them it on all the later years? Surely they would have known about it in the early injected years and avoided the problem. TSB's would be a retrofit.
Not just Cherokees, but TJ's as well.

If the fuel had become vapor in the rail, when the very first injector opened would let all the vapor out into that cylinder - if there was pressure behind it - vapor is much thinner than liquid. -- Basic physics - (oops, another recent post said physics doesn't apply to JEEPS - was that you?)

But of course if the pressure wasn't there, it wouldn't blow the vapor out.

If you are not capable of using a simple pressure gauge, then wrap it. You might also want to hose the engine down with cold water when you know it will act up too.
And - the obvious - glue a pyramid on the roof to keep away the evil spirits.
Years ago the ignorant "fix" was clothespins on the fuel hose.

The pressure gauge - the Schrader valve measures in the rail, you have to Tee into the fuel line to see pump pressure.
Not even close to rocket science.

Internet bull like that doesn't work out here in the desert where it gets warm. Today was cool, only 105.

Parsnip

^best reply ever.
Im still sticking with tps as being the culprit...if there were too much heat causing fuel vapor it would affect all cylinders not just a few...but as you said pressure is another factor... i dunno i just feel a hunch the tps might be off a bit...

And physics applies everywhere even in Jeeps. Logic however does not

Kalali

Back to the OP's issue, if it were my Jeep, I would clear all the codes and insulate the no. 3 and 4 injectors using a heat wrap.
Do your regular (driving) routine and report back.

djb383

I do believe rrich is spot on....and no one says it more eloquent. Could it have something to do with the heat off those mini-cats, the late models have?

the buddmang

Its not internet bull. TSB # 18-031-03:

This shield:


How bout you pop the hood on any 4.0 newer than 2000 and tell me how many of those shields you find.

Just because its not on your jeep, or on any of your buddies...doesnt mean it isnt on others.

This "percentage" stuff is bogus, theres no way to track who has had the tsb performed by the dealership, by their own independent shop or by themselves. The part is available over the counter. Guess you could call jeep and find out how many they sold if youre feeling that froggy...

Parsnip

Yet again though, heat would effect more then just 2 points/cylinders/injectors

the buddmang

Get your temp guage out next time your engine is hot, there are hot spots.

The shield fix is (IIRC) directed towards misfires occuring on cyl 3/4 after a hot soak. The other tsb I mentioned is for misfires occuring on cyl 6 after a hot soak. Both tsb's are for 0331 head'ed 4.0l's, regardless of platform.....

the buddmang

FWIW, Im just regurgitating info from the tsb's as well as my personal experience working on customers vehicles over the years...

If you want to question my advice, or think its a tinfoil hat, talk with the OEM engineers that came up with the fix. They make a LOT more money than I do....