Sputtering?

For a while now, when I turn off the car (2001 XJ 4x4 4.0L) when it's hot, then restart it, it sputters for a minute or two, just idle-ing below 1000 so it's just jumpy, and sputtery. Today, after starting it while hot, I let it idle for a minute, like always to let it figure itself out, and the sputtering never stopped. I started driving home, opened the throttle wide open, it started sputtering like it was out of gas, or almost like it wanted to go into 4th or 5th and just kept retrying but couldn't reach it, then I let off and it was driving fine, tried it a few more times and it did the same thing... still, when I come to a stop it idles low and jumpy. Recently I replaced the spark plugs, thinking it could be misfiring, and I topped off the transmission fluid today also, as the trans fluid has had a slow drip.

My thoughts, it could be a clogged fuel filter, fuel pressure regulator, or weak fuel pump. I'm hoping someone could give me more of a solid reason or educated guess.

Someone help? :tears:

There is a known "heat soak" problem that can occur on your vintage when starting up a hot engine. Not uncommon.

As for your other symptom, can we assume that there is no check engine light? Fuel delivery can be verified pretty simply by installing a fuel pressure gauge on the schrader valve on the fuel rail. For an 01, you want 49.2 psi, plus or minus 5 psi.

Cleaning the idle air control and throttle body is never a bad idea as they get carboned up over time and miles and can lead to varied goofy symptoms.

birchlakeXJ said:

There is a known "heat soak" problem that can occur on your vintage when starting up a hot engine. Not uncommon.

As for your other symptom, can we assume that there is no check engine light? Fuel delivery can be verified pretty simply by installing a fuel pressure gauge on the schrader valve on the fuel rail. For an 01, you want 49.2 psi, plus or minus 5 psi.

Cleaning the idle air control and throttle body is never a bad idea as they get carboned up over time and miles and can lead to varied goofy symptoms.

Click to expand...

How do you clean the IAC? I have a very similar problem with my 2001 XJ. It will run fine. I shut it off. Turn it back on few minutes later and it has terrible terrible idle and The exgaust smells like a old farm truck. If I put it in gear and drive it just chugs and jerks and about dies till I let off the gas. I have to sit for a few minutes before ir calms down

CodyJames said:

How do you clean the IAC? I have a very similar problem with my 2001 XJ. It will run fine. I shut it off. Turn it back on few minutes later and it has terrible terrible idle and The exgaust smells like a old farm truck. If I put it in gear and drive it just chugs and jerks and about dies till I let off the gas. I have to sit for a few minutes before ir calms down

Click to expand...

Quick and dirty test for heat soak--drive the vehicle and get it good and warmed up. Park the vehicle, shut off the engine, open the hood and let it cool for about 30 minutes. Start the engine. If the symptoms are GONE or substantially mitigated, you have heat soak.

To answer your question, remove the IAC from the throttle body (TB), clean the end of the IAC pintle, clean the TB paying particular attention to the IAC port on the TB. Use TB safe aerosol cleaner, toothbrush, cotton swabs. DO NOT BE ROUGH with the IAC's pintle or you will be buying a new IAC.

The IAC is a stepper motor that responds to extend/retract commands from the PCM to control the idle speed of the engine. Dirty port or pintle and things turn hinky quick.

joe_peters said:

Quick and dirty test for heat soak--drive the vehicle and get it good and warmed up. Park the vehicle, shut off the engine, open the hood and let it cool for about 30 minutes. Start the engine. If the symptoms are GONE or substantially mitigated, you have heat soak.

To answer your question, remove the IAC from the throttle body (TB), clean the end of the IAC pintle, clean the TB paying particular attention to the IAC port on the TB. Use TB safe aerosol cleaner, toothbrush, cotton swabs. DO NOT BE ROUGH with the IAC's pintle or you will be buying a new IAC.

The IAC is a stepper motor that responds to extend/retract commands from the PCM to control the idle speed of the engine. Dirty port or pintle and things turn hinky quick.

Click to expand...

And actually, this IAC cleaning procedure, along with throttle body cleaning, should be considered normal maintenance just like spark plugs and the like.

cruiser54 said:

And actually, this IAC cleaning procedure, along with throttle body cleaning, should be considered normal maintenance just like spark plugs and the like.

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Agree--at a MINIMUM every two years.

joe_peters said:

Quick and dirty test for heat soak--drive the vehicle and get it good and warmed up. Park the vehicle, shut off the engine, open the hood and let it cool for about 30 minutes. Start the engine. If the symptoms are GONE or substantially mitigated, you have heat soak.

To answer your question, remove the IAC from the throttle body (TB), clean the end of the IAC pintle, clean the TB paying particular attention to the IAC port on the TB. Use TB safe aerosol cleaner, toothbrush, cotton swabs. DO NOT BE ROUGH with the IAC's pintle or you will be buying a new IAC.

The IAC is a stepper motor that responds to extend/retract commands from the PCM to control the idle speed of the engine. Dirty port or pintle and things turn hinky quick.

Click to expand...

Heat soak is essentially the fuel vaporizing in the fuel rail. IIRC there was a TSB to install a heat shield to help negate the problem, but I can't say how well it worked as I never had it done on mine. I installed a switch on my fan and just turned it on for about 30/40 seconds before I started it. That would blow the heat from under the hood and helped greatly.