Absolutely. But the problem is an old fuddy-duddy thinking his years of working in his own shop makes him the absolute authority on anything automotive related.

He's giving bad advice.

rrich IS right in saying that you shouldn't just apply a band-aid to a broken leg - but he's WRONG in assuming that this particular case is anything more than exactly what it sounds like.

It's not as if this is a new problem. It is, in fact, at LEAST 12 years old, maybe slightly older even.

Chrysler investigated the issue and discovered the problem. They issued a TSB on how to eliminate the issue, and those who have followed that TSB have reported that the problem did indeed go away.

If what rrich is saying is true, then in EVERY CASE where someone wrapped the injectors with heat shielding, there was a miraculous stroke of luck where their fuel pressure regulator suddenly repaired itself and started working properly.

But rrich denies conventional wisdom and common sense and chooses to wear HIS tin foil on his head - apparently there's a "great idiot conspiracy" that's out to get him and the rest of the very few "truly intelligent" species of human out there.

Meanwhile, rrich will over diagnose while we get right to the source of the problem and fix it.

And I'm ok with him thinking I'm an idiot. MY Jeep runs perfectly. MY fuel pump and pressure regulator work perfectly. MY injectors are staying nice and cool. MY proof is in my pudding, and rrich REFUSES to believe he can be wrong.

 

My 2000 cherokee does the same thing. About once or twice per summer it misfires on a couple of cylinders, I just reset the code and move on. No harm no foul, as my 3 year old daughter would say "No Biggie."

 

When I was completely new to the net..2000, one of the first things I did was e-mail a bartender lady I saw almost every day. The content involved "rock"......and I think "love" was mentioned.

Well, since then I've figured out I'm not "magically disconnected", Partly , because the word "muffin", was in there as well.

The point is, we are all here, sitting in the same room, looking eye to eye. There is no barrier or disconnect. I'm sitting right here. ICU

There was a learning curve there for me. Without mentioning any names, it's just good to recognize some people need to learn a bit to fit in. (as if we where siting together on a bench).

Then tar and feathers were invented.

 

Dude, you crack me up all the time

 

If at the beginning of this thread we were all sitting in the same room looking eyeball to eyeball at each other, by post #100 or so, half of us would be dead and the other half in jail........................... ......over a freakin' XJ and egos.

 

I would like to add my recent experience to this thread. I have a 2001 and have recently had the heat soak problem since the temps have been about 90-101 here in MI. I found this thread this morning, and after reading everything went down to the local Chrysler parts counter and asked their take on it. The nice guy at the counter printed me off a TSB that was different from the TSB mentioned earlier.

As TylerSpyler mentioned a couple pages ago:

Number: 18-039-03

Date: Nov. 14, 2003

Subject: Rough Idle due to high ambient or Hot soak Temps.

Overview: This Bulletin involves selectively erasing and reprogramming the PCM with new software.

Models: 2000-2001 (xj) Cherokee Domestic

Symptom/condition: The customer 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 10 to 20 minute heat soak in hot ambient conditions of approximately 90* 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 high ethanol content.

The new software lowers the temperature threshold used to determine when the engine cooling fans are turned on. The cooling fans will cycle more often.

Diagnosis and repair follow for the tech, but my fingers would bleed...

Time allowance: Reprogram PCM: 0.7 Hours


I read through this and approached the Service Manager for a quote...

He quoted me $150 for the service, and explained that he might have to download some extra software or some bull*****. I didn't bite. It may work just fine, but it isn't worth the money to me. FWIW, They didn't have any record of the other TSB on file, so I am guessing this one must have superseded that.

TylerSpyler sounds like he got better service.

I should add that the parts guy printed me a recall (#B06) for an Intake Manifold Debris Shield. I had heard this mentioned before on this thread and it seems it is to prevent a buildup of leaves and other flammable rubbish on the exhaust manifold. My 2001 XJ had this installed. For those not familiar to these; It is a silver flame resistant mat about 1/2" thick or so, that is fit on top of the intake/exhaust manifold and contours around the fuel injectors and is held in place by the fuel injector wire harness and a couple of the head studs on the driver side.

As for me, I will run down to the local parts store and pick up some heat resistant spark plug boot isolators, and cut them to fit around #3 fuel injector. They aren't that expensive and worked pretty well for me on past projects. Temp is right at 100* today, so I will post back for the good of the forum on their effectiveness.

Just figured I would add my $.02
Hope it helps somebody.

 

So.....would you suggest synthetic tar or dino? Should I add some Lucas to make it extra clingy?

 

i just logged on and checked the current TSB's for 01'.


the TSB for the sleeve is stilll there
TSB:18-031-03

 

Keep in mind that Jeep is to make money, so their fix is going to be the cheapest as possible, as the next TSB shows that now there is much bigger charge to reprogram PCM to run fans more often.

 

Fair enough. Didn't have the computer in front of me.
All I know is the talking head behind the counter said that was the only one he could find...

 

I spent a few hours at my dealership last week, looking at factory service manuals and parts catalogs - both in book printed form and computerized.
It seems that the heat soak problem is not just recent occurrence, it dates as far back as the Renix systems.
Until 1995 the fuel pressure regulator was up top on the fuel rail. They did not use dual pre-cats under the manifold like some believe. Normal running fuel pressure should be 31 lbs with vacuum connected, 8-10 psi higher when vacuum disconnected (or engine off.) Key on, engine off the rail pressure SHOULD BE 39-41 psi. Measuring the pressure after it starts misses the problem.

In 1996 a few 4.0's were made with dual pre-cats, but in very limited production. On those the fuel pressure regulator was moved to the fuel tank. It was mounted on top of the tank, but inside the tank itself as an integral part of the fuel pump, unlike later ones. IF you can find a replacement you are lucky, they are rare and expensive. Fuel pressure was increased to 48-49 psi.
Fortunately not very many were made. The pressure was increased to 48-49 lbs on those - and the regulator no longer used vacuum. All the rest of the '96 4.0's were still the older type like the '95's. Most likely it was Jeep testing to see how they worked. Very little factory information is available on those.

The next year, '97, the dual pre-cats became more popular but still very limited production. The states with the tighter emissions laws got those. The backwards states did not get them till 98 and some not until '99.
By 2000 ALL the 4.0's had the dual pre-cats, the pressure regulator on top of the tank mounted pump and the DIS Ignition system, and fuel pressure was 49-51 psi!


You can look at the aftermarket exhaust mfgr's - they don't offer a dual pre-cat system for the 96's because the dual cats are so rare. And the bends look slightly different.

Not one factory service manual said anything about injector heat shields, gum wrappers, or tinfoil wraps for the injectors. Not one showed one factory wrapped.

There is no question that the fuel in the rail gets too hot and turns to vapor. By the factory increasing the fuel pressure that 10 psi or so seems to have avoided the problem. 50 psi is a very common pressure for lots of injected vehicles.

Have you ever looked INSIDE one of the pre-cats? Inside is only a platinum screen, similar to a hunk of window screen. You can see right through it. It's purpose is to give any escaped HC or CO a place to burn. The DIS Ignition helps to ignite it, as it not only fires on the compression stroke but also on the “backside.”

To check to see that the pre-cats are working, use what someone referred to it as an “exotic tool” - an infra-red thermometer. They should run about 100 degrees HOTTER at the outlet than the inlet. Same with the big main cat - 100 degrees HOTTER out than in.

But as I said all along - if the pressure in the rail is too low, the fuel will vaporize. If there's a defective part like a FPR you can ignore it if you like.

You cannot measure it if the engine is running - even if you do tape the pressure gauge to the windshield.

Funny there's a new heat soak thread - yo yo - the same guy that can't measure pressure is now saying to measure the fuel pressure!


If you want your electric fan to come on sooner than the factory setting - find the temperature sender in the thermostat housing.

Put a 1000 OHM resistor between the 2 wires - in parallel with the sender. That sensor is what tells the computer to turn on the electric fan. By paralleling it with 1000 OHMS, the turn-on temp is lowered by 10-15 degrees. Much cheaper and easier than reprogramming.

Or buy the data link to connect to your laptop or PC and program it yourself. It's not rocket science. But if you don't understand a simple fuel pressure gauge get someone else to do it.

 

Well written Rrich. (could have left out the gum wrappers). YES! Key on, up to 96, 41 max...I hadn't put together just key on is the same as no vacuum.

There might be middle ground here. The vaporizing temp goes down with pressure. Siting, the pressure goes down, while the temp goes up there. So there is a balance. If that 2000 actually DID sit there at it's 49 lbs or whatever, it might not go to vapor. Protecting the injectors from the heat is one part, having the pressure is the other. There's a balance. The injectors and the lines getting toasted on one side, and the check valve, regulator and injectors holding pressure on the other side. (Very Zen?)
On my 84 Tempo, the fan runs after it is turned off. Cheater!