Jeep randomly stalling if gas isn't being pressed

WhoIsThis

WhoIsThis

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May 16, 2020
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Homestead, FL
First off, hello! This is my first post so sorry if anything is incorrect. It’s incredible how many forum posts I’ve come across with the same issue...My Jeep will stall at idle randomly unless I’m holding the accelerator down. When I let off it either idles perfect for a bit then stalls or will stall as soon as I let off. Sometimes it will drop to 300-400 rpms and surge back up to normal idle on its own. It even idled all by itself for an hour yesterday when I was testing it after taking it for a drive. I bought this Jeep a couple weeks back and the guy said someone had left the acc on so the battery was dead. I’ve since then replaced the battery. All I’ve gotten from different posts is that it could be a mountain of things, I’m going to post videos just in case someone notices something before I start replacing and throwing money at everything that’s mentioned.

I’ve already removed the throttle body and cleaned it out including the IAC. The TPS seemed to have been replaced already. Also no CELs are being stored.

Here are the videos. Thank you!

 
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Welcome,

All good info and if you're new to Jeeps and TJ's one of the first rules I learned years ago is to stick with OEM or original parts suppliers for any of the sensors including the throttle sensor so see what you have on there. The 2 most likely causes at this point it the IAC or the TPS.
 
Are the battery terminals shiny clean? Are all the connections tight and secure? If they aren't secure, they could easily cause the engine to sputter or stall due to intermittent loss of electrical power.

If not, dissolve any built up corrosion (it looks like a white cancer) on the terminals with a mixture of baking soda and water. Then take steel wool or emery cloth, disassemble the battery terminals, and make any contacting surfaces shiny. Also check the ground on the body and the engine and shine them up as well. The engine ground is notorious for causing issues. Also check and clean the cable terminal going to the alternator.

You may also want to have the alternator tested. Any auto parts store generally does free testing. Low voltage will cause many issues, including but not limited to stalling at idle.
 
The two first suspects I'd have for the engine's inability to idle smoothly would be a dirty IAC or a low nearly dead battery. The alternator REQUIRES a good solid 12 volts from the battery for its exciter circuit so it can generate power to charge the battery. The days of being able to run with a low or dead battery once the engine is started are pretty much over for most cars and for all Jeeps newer than (guessing) the early 90's during the YJ Wrangler days. Even dirty corroded or loose battery connections can cause that problem so physically disconnect both battery leads and wire brush the battery posts and the connectors until they're bright and shiny clean and see if that fixes the problem. Very often that is the only fix needed.

The second suspect, which is a VERY common cause of an idle problem where the engine won't run unless the gas pedal is held down is a dirty Idle Air Controller. Note that because it's dirty doesn't mean it needs to be replaced. Get an aerosol can of Throttle Body Cleaner and after removing the air intake tube from the top of the throttle body, start the engine. Have a helper work the gas pedal for you while you do the next step. Spray the cleaner into the TB while the engine is running at idle rpms. The IAC will ONLY suck the cleaner in through itself when the engine is at idle rpms so keep them at idle as much as possible, spray only when it's idling. If you spray while the engines are up off idle, no cleaner will pass through the IAC. The IAC is the engine's sole source of air at idle rpms so if it can't get enough air through the IAC when idling the engine will die. Eventually, if enough of the cleaner passes through the IAC at idle rpms, the engine should start idling ok.

Either of those two would be my co-suspects.

The other suspect would be a bad upstream O2 sensor but I'd only suspect that if the engine idles ok when cold but the idle goes bad as you describe once the engine has started to warm up. The computer only starts referring to the upstream O2 sensor to set the air/fuel ratio once the engine starts getting warm. When the engine is cold it doesn't look at the O2 sensor(s) at all.
 
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Thank you for the fast replies. I have already cleaned the battery terminals they’re super shiny. I’ve already removed the whole throttle body and cleaned it out including the IAC socket and the IAC itself. I will try with the method Jerry suggested when I get home. I’ll also go ahead and check the wiring to the battery.

After driving it around it usually doesn’t stall if I let it idle. The stalling happens when it hasn’t been driven, like every morning when I wake up which is how I got the videos. My girlfriend drove it a whole week to work without stalling but I had told her to not even let it idle in the morning. That has been the longest it’s gone without stalling.

Also forgot to mention sometimes there’s a very loud screeching noise when it does stall while moving or slightly accelerating. It hurts my soul every time.
 
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WhoIsThis said:
Thank you for the fast replies. I have a wire brush coming in
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A battery brush for $4 or so makes quick work of that job, it includes a male brush for the connectors and female for the battery posts.

P.S. A bad Throttle Position Sensor can cause a bad idle and some aftermarket TPS sensors will cause problems. Since yours appears to have been replaced, I wonder if the previous owner installed a cheap store brand which cause problems. Where sensors are concerned I try to stick with Mopar or the OME brand.

battery brush.jpg
 
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Jerry Bransford said:
A battery brush for $4 or so makes quick work of that job, it includes a male brush for the connectors and female for the battery posts.

P.S. A bad Throttle Position Sensor can cause a bad idle and some aftermarket TPS sensors will cause problems. Since yours appears to have been replaced, I wonder if the previous owner installed a cheap store brand which cause problems. Where sensors are concerned I try to stick with Mopar or the OME brand.

View attachment 161808
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I edited my comment right now, I found a wire brush from my dremel, the battery terminals are now as shiny as they will ever be.
 
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So I got home cleaned the terminals and went to go turn it on to clean the IAC and it stalled, now the catch this time is it’s not turning back on 🤦‍♂️. I couldn’t catch it on video but before this video it turned on, screeched and turned off.
 
WhoIsThis said:
So I got home cleaned the terminals and went to go turn it on to clean the IAC and it stalled, now the catch this time is it’s not turning back on 🤦‍♂️
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What's the voltage on the battery posts without the engine running? Next measure the battery voltage on the battery posts while a helper has the ignition switch turned to and held at the start position? If the battery voltage drops off when the ignition switch is in the start position you have a bad battery.
 
Jerry Bransford said:
What's the voltage on the battery posts without the engine running? Next measure the battery voltage on the battery posts while a helper has the ignition switch turned to and held at the start position? If the battery voltage drops off when the ignition switch is in the start position you have a bad battery.
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Just checked it’s reading at a little after 12 volts, when the ignition is turned to start it doesn’t drop at all.
 
WhoIsThis said:
Just checked it’s reading at a little after 12 volts, when the ignition is turned to start it doesn’t drop at all.
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See if that voltage stays high like that when measuring on the battery connections themselves with the ignition switch in the Start position, this time not on the battery posts.

If the battery voltage remains high on the battery connections while the switch is in the Start position I'd guess either your starter or ignition actuator switch has gone bad. Is the starter getting +12v at its heavy/large connector while the ignition switch is in the Start position? If not I'd suspect the ignition actuator switch.
 
Jerry Bransford said:
See if that voltage stays high like that when measuring on the battery connections themselves with the ignition switch in the Start position, this time not on the battery posts.

If the battery voltage remains high on the battery connections while the switch is in the Start position I'd guess either your starter or ignition actuator switch has gone bad. Is the starter getting +12v at its heavy/large connector while the ignition switch is in the Start position? If not I'd suspect the ignition actuator switch.
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It drops very very very slightly to 12 from right above 12. The CEL also turns on and then off every time I try turning the jeep on.
 
Jerry Bransford said:
See if that voltage stays high like that when measuring on the battery connections themselves with the ignition switch in the Start position, this time not on the battery posts.

If the battery voltage remains high on the battery connections while the switch is in the Start position I'd guess either your starter or ignition actuator switch has gone bad. Is the starter getting +12v at its heavy/large connector while the ignition switch is in the Start position? If not I'd suspect the ignition actuator switch.
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All the voltage is checking out, how would the actuator cause stalling?

I’m pretty sure it’s bad as well because sometimes I’m able to remove my key while the car is on. What would be a good replacement?
 
After doing a bit of research on the actuator it seems like I should be looking into a replacement, any recommendations would be great. My only confusion is that if it were bad wouldn’t it also turn off even if I was giving it gas? Also here’s more video lol.
 
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DazzelingGemJeepGirl said:
I need to know that too! Which 3 sensors? I reviewed entire thread and can't figure out which 3 sensors I should replace. Ugh, felt so close to the answer and felt relief to finally have an answer. Ugh, bummer!
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Possibly oxygen sensors? Newer 6-cylinder models (2000-2006) have four, 1997-1999 have three if I recall correctly. 4-cylinder models only have two.

Could potentially also be throttle body sensor, Manifold Air Pressure (MAP) sensor, and Intake Air Temperature (IAT) or Manifold Air Temperature (MAT) sensor. (Older models have a MAT, newer models have an IAT. I think the change occurred in 2003 but I don't know for sure. The terms are sometimes used interchangeably, so whatever a catalog like RockAuto lists should work.)
 
DazzelingGemJeepGirl said:
I need to know that too! Which 3 sensors? I reviewed entire thread and can't figure out which 3 sensors I should replace. Ugh, felt so close to the answer and felt relief to finally have an answer. Ugh, bummer!
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First...start a new thread and explain what your problem is and tell us more about your Jeep.

If you're having idle problems check out the resources section and follow the instructions for cleaning your IAC.

-Mac
 
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