• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Hot engine misfiring when started

T

TruebloodVA

NAXJA Forum User
Location
Virginia
Sometimes, not always, my 2001 XJ will misfire very badly for about 5-20 seconds upon starting. It usually happens when the engine is very hot, like after highway driving for hours, then will go away and it acts like nothing ever happened. Check engine light will come on during misfire, and the reading says that cylinder 3 is misfiring. I have replaced all fuel injectors, spark plugs, and the ignition coil. Nothing has worked so far. My mechanic said I might have a "weak cylinder" which i really hope is not the case bc I don't have the time or money right now and don't plan on overhauling this thing for at least a few years. Might even replace the engine eventually. Any ideas would be greatly appreciated (especially ones that involve cheap solutions).
 
TruebloodVA said:
Sometimes, not always, my 2001 XJ will misfire very badly for about 5-20 seconds upon starting. It usually happens when the engine is very hot, like after highway driving for hours, then will go away and it acts like nothing ever happened. Check engine light will come on during misfire, and the reading says that cylinder 3 is misfiring. I have replaced all fuel injectors, spark plugs, and the ignition coil. Nothing has worked so far. My mechanic said I might have a "weak cylinder" which i really hope is not the case bc I don't have the time or money right now and don't plan on overhauling this thing for at least a few years. Might even replace the engine eventually. Any ideas would be greatly appreciated (especially ones that involve cheap solutions).
Click to expand...

If you do a search on this forum you will find that this is a common problem on the 99-01 4.0L.
The problem is called HEAT SOAK where the fuel injectors on cylinders 3&4 will soak up the heat and the fuel inside will perculate due to the heat. When the engine is started it takes 15-45 seconds before the cooler fuel will cool down the fuel injector.
Some solutions are to apply thermal insulation the the bottom of the intake manifold, wrap the fuel injector in thermal reflective insulation, wrap the fuel rail in thermal reflective insulation.....
 
The good news is it's only occasional, and not the result of something going bad. (Doesn't make you feel any better, does it?)

There was a factory recall on the 00/01s to add a heat shield on the intake manifold. Not sure if the '99-down jeeps were affected. Adding that might help if you don't already have it.
There was somebody who made a heat shield to go between the intake and the pre-cats on the '00. That's also supposed to help. I think the thread was in street and performance.
 
What you describe is definitely classic "heat soak". The 00-01 are the most susceptible to it.

Two pretty popular remedies for persistent cases of this malady include installing a timer on the e-fan which keeps it running for a predetermined amount of time when you turn off the engine. Some also install some louvers into the hood. Both of these techniques aim at reducing engine temps and engine bay temps. SEARCH for more information and threads on this.
 
Had the same problem for years. The TSB didn't do squat and I overdid it, by wrapping the whole fuel rail and putting down a full heat shield under the manifold. I tried vents but that didn't do a thing except create a heat show at red lights. I finally was able to tackle the bitch by installing a timer like Birchlakexj mentioned. Mine's set for 2.5 minutes after shutdown. The fan will run, blowing cool air on the problematic area and prevent the gas from vaporizing. Worked like a charm since and I only had the misfire once on a very hot day. Used to get it every time I went for a drive and restarted it shortly after.
 
tbburg said:
There was a factory recall on the 00/01s to add a heat shield on the intake manifold. [/qwuote]
That TSB for the heatshield on the top of the manifold is not related to the misfire condition. It is to prevent debris from gathering where the shield goes and causing a fire.

The TSB for the misfire puts a heatshield on the injector #3.
Click to expand...
 
Man, Awesome info. Thank you for your time and input. I'll definitely look into the e-fan and heat shields. Really appreciate it. Thanks again.
 
You must log in or register to reply here.

Similar threads

N
New Engine is Hard to Start
Replies
0
Views
34
NGThomas
N
M
Oil pressure question
2
Replies
26
Views
3K
Money_Pit_Incoming
M
W
No Spark
Replies
6
Views
1K
Runnin'OnEmpty
R
A
Long crank when engine warm
Replies
15
Views
3K
aquaman788
A
H
Another heat soak thread
2
Replies
22
Views
3K
Unclewolverine
U
Back
Top