Stumbling on hot start

[casm]

2000 Limited, 4.0, NP242, currently in need of a wash.

Here's the problem: sometimes, after stopping for a few minutes with the engine at normal temperature, I'll restart the vehicle and have a really bad stumble that feels like the timing's off. Power surges under acceleration, rough idle, sometimes you can make it misfire if you stomp the accelerator.

It looks like this may be linked to coolant temperature. If I park with the needle on the coolant temperature gauge at 210degF, switch off, and come back a few minutes later, the gauge will be reading above that - usually at or just a hair over the first mark past 210; this leads me to believe that heat from the engine block is transferring back into the coolant. If I let it idle until the temperature is back at 210degF, there's no problem. This is only an issue if the temperature's above 210 when starting.

I'm thinking that the block and/or radiator coolant temperature sensors are having issues, but was wondering if anyone else might have any ideas. The XJ runs fine otherwise, has good coolant (still green after nine months in there), and isn't exhibiting any other odd behaviour.

 

[Seamoose]

I have a 2000 xj , same problem and from what I have read, in 2000 jeep redisigned intake manifold.. there was a possibility of a fire so they added a heat shield (tinfoil looking thing).. well this has caused problems with the #3 injector causing it to miss..I have read on here where there is a fix throught the dealer, I havent taken mine in becuase hasnt bothered me enough (yet)

not sure if helps or not...

 

[casm]

I have a 2000 xj , same problem and from what I have read, in 2000 jeep redisigned intake manifold.. there was a possibility of a fire so they added a heat shield (tinfoil looking thing).. well this has caused problems with the #3 injector causing it to miss..I have read on here where there is a fix throught the dealer, I havent taken mine in becuase hasnt bothered me enough (yet)

not sure if helps or not...

Good point. I should've mentioned that the recall's been performed and (apparently) the #3 injector fix applied as well. I take this with a grain of salt, though, because it was done before I owned the Jeep.

 

[87manche]

call a jeep dealer with your VIN number THey can verify if it was repaired under the recall.

 

[Ben H]

my 2000 does the same when its a little to hot. i just turn it off and start it up. that usually takes care of it. I wonder if it is just the 2000's?

 

[casm]

call a jeep dealer with your VIN number THey can verify if it was repaired under the recall.

This is how I verified it had been done.

 

[techno1154]

My '96 also does the same thing. I cannot find the problem no matter where I look. The only thing I can contribute it to is fuel evaporating in the fuel line and or cousing air bubbles. I think the under hood tempeture get higher after the engine is shut down helped by the the heat sheild under the hood. In addition, the new fuel injection system do not have the return line to the fuel tank. That means all the fuel in the line have to pass through the injectors including the air (if that is what it is). With little or no fuel in the line the engine will stumble until is has the right amount of fuel. How to fix it? I do not know.
This just my theory.

 

[Bent]

I take it there is no check engine light? I have had a similar problem, especially at higher altitudes and warmer weather. I've only been able to pull a code a couple of times and that also has been during the summer. Each time it says that there is a misfiring injector, several of them one time(very high, very hot). I get the same symptoms once in a while that does not set off the engine light, usually only last no more than a minute. This never happens on a cold start and is most common when restarting after ~10 minutes. The only condition existing each time would be high temperature in the engine compartment. I have been meaning to put an insulating wrap on the fuel line where it passes by the exhaust.

 

[Ben H]

so insulation of the fuel line might fix it. What about hood vents to disapate heat faster?

 

[casm]

I take it there is no check engine light?

None whatsoever, and no stored codes either. In fact, any time I have tried to pull a code on this there's never been one.

I have had a similar problem, especially at higher altitudes and warmer weather.

Odd - I've had it happen even after parking in relatively cool weather. FWIW, altitude doesn't seem to be a component since it happens here (c. 850ft.) or up in the hills (c. 4000ft.).

I get the same symptoms once in a while that does not set off the engine light, usually only last no more than a minute. This never happens on a cold start and is most common when restarting after ~10 minutes.

Yup, this fits exactly the pattern I'm seeing.

The only condition existing each time would be high temperature in the engine compartment. I have been meaning to put an insulating wrap on the fuel line where it passes by the exhaust.

Hm, not a bad idea. I've got some free time today so will swing by Kragen and grab some. Cheers!

 

[Bent]

Hm, not a bad idea. I've got some free time today so will swing by Kragen and grab some. Cheers!

They won't have it, you'll have to try an auto parts store.

 

[casm]

They won't have it, you'll have to try an auto parts store.

Heh, between the local Pep Boys and Autozone - I'll take Kragen.

 

[spcustoms]

Hey ever get this prob fixed? im havin the same thing...

 

[Ben H]

Hey ever get this prob fixed? im havin the same thing...

I had the injectors wrapped with the foil from the dealership. No help. Installed some hood louvers, still no help. I tried to wrap the injector rail with my own shroud, and that was a failure. I have just learned to live with it. It only happens if the vehichle has been run for a while and is nice and hot, then turn it off for about 5 minutes. It sucks but hey what can you do.:tear:

 

[spcustoms]

yea.. I just bought a harbor frieght scanner and erase the misfire codes when they come up, im gunna change the plugs, maybe get a new coil rail and if that doesnt stop it, im gunna park the jeep in the city with the keys in the ignition...

 

[YMMV]

I have the same prob with my 00 as well. All the recalls have been done. I even swapped plugs and mins still does it. It doesnt do it as much now with the new plugs. When it does happened, I always get a misfire code for cylinder #6. I have checked the injector pulse and made sure there were no cracked or arching on my coil packs. Still stumped.

 

[parkeruph]

one thing that might help is to turn on the ign switch and wait for all lights and bells to go out (giving the computer time to read everything) That works on my 2000, at least wait for eng light to go out. Hard to remember to do that every time but mine reminds me when I forget by missing on 2. It's worth the few seconds wait. Hope this helps your's

 

[spcustoms]

hmm ill try that

 

[techno1154]

one thing that might help is to turn on the ign switch and wait for all lights and bells to go out (giving the computer time to read everything) That works on my 2000, at least wait for eng light to go out. Hard to remember to do that every time but mine reminds me when I forget by missing on 2. It's worth the few seconds wait. Hope this helps your's

I tried that. It did not help. I am stumped. I have not seriously tried to find the source of the problem; chaulked it up to a minor iritation. However, it could be serious if this happpens when you are in a cross road with incoming traffic.:doh: I wil try to have one if my electric fans run for a few minutes after I shut the engine down. I first have to get a 12 volt timer.

 

[Ben H]

If you guys are getting codes then there is something else up. Misfire on six seems like a faulty CPS. I wouldnt go dropping money on a new ignition rail just yet. What is the exact code for misfire on 6? Interesting...

Here is the underlying problem...It is just a heat soak problem related to all 2000's with the thinner 0331 head. It happens to all of us with 2000's but you shouldnt be pulling codes on this. It should happen only if you run it for a while then turn it off for 5 to 10 minutes and then try to restart. (at least that is what I have found when reading about it).