Jeep TJ hard starting

TMB

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Joined
Jan 20, 2020
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21
Location
South Carolina
Link to video ^^

What I have done:
Bought New battery
Checked alternator
Got autozone to test starter
Looked for parasitic leak (old aftermarket radio removed)


I don't know what else to do. On cold starts after sitting for 8 hours or so I need to hold the gas just for it to idle. Anyone know what could be wrong?
 
Remove and clean your battery connections with a battery post cleaner. Check the other ends of the battery cables for loose connections at the starter and engine block.
 
Link to video ^^

What I have done:
Bought New battery
Checked alternator
Got autozone to test starter
Looked for parasitic leak (old aftermarket radio removed)


I don't know what else to do. On cold starts after sitting for 8 hours or so I need to hold the gas just for it to idle. Anyone know what could be wrong?
If it starts right up (indicating the battery/starter is ok) but it just won't idle without holding your foot on the gas, that's a good sign your IAC (idle air controller) is dirty (most likely) or defective (less likely). The IAC is what provides all of the engine's air when the engine is at idle so when it sticks or won't open, the engine won't stay running unless you step on the gas a little to open the valve plate to give the engine enough air to run on.

Start the engine and with the engine at idle rpms, start spraying some throttle body cleaner into the throttle body. The engine will flood and then die from the cleaner filling the IAC area but that's ok just restart the engine and do it again. Don't be tempted to raise the rpms to stop the engine from dying as that would cause the cleaner to not pass through the IAC. I try to get 1/4 to 1/3 of a can through the IAC to assure myself it's clean.

Removing the IAC to clean it may seem like a good idea but that would mean you're not also getting the orifice (the part the IAC's plunger fits into) inside the throttle body clean as happens when you spray it into the throttle body while the engine is idling.
 
Remove and clean your battery connections with a battery post cleaner. Check the other ends of the battery cables for loose connections at the starter and engine block.
All connections are clean (enough) and tight. The battery posts were cleaned and tightened when I changed the battery as I do that when I change any battery.
 
If it starts right up (indicating the battery/starter is ok) but it just won't idle without holding your foot on the gas, that's a good sign your IAC (idle air controller) is dirty (most likely) or defective (less likely). The IAC is what provides all of the engine's air when the engine is at idle so when it sticks or won't open, the engine won't stay running unless you step on the gas a little to open the valve plate to give the engine enough air to run on.

Start the engine and with the engine at idle rpms, start spraying some throttle body cleaner into the throttle body. The engine will flood and then die from the cleaner filling the IAC area but that's ok just restart the engine and do it again. Don't be tempted to raise the rpms to stop the engine from dying as that would cause the cleaner to not pass through the IAC. I try to get 1/4 to 1/3 of a can through the IAC to assure myself it's clean.

Removing the IAC to clean it may seem like a good idea but that would mean you're not also getting the orifice (the part the IAC's plunger fits into) inside the throttle body clean as happens when you spray it into the throttle body while the engine is idling.
47E60462-0ABC-495D-AA5B-9C23E6B068C5.jpeg
E7EF8C59-2506-46E0-9B9E-BB80748540D8.jpeg

This is what the intake looks like seems decently clean to me I will buy a can and give it a spray down tho.
 
Those pics only show the TB, they're not showing what the hidden IAC plunger assembly looks like. Not to mention the inside of your TB looks absolutely GUNKED up. See that black on the inside of the valve plate?

IAC.jpg
 
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All connections are clean (enough) and tight. The battery posts were cleaned and tightened when I changed the battery as I do that when I change any battery.
In your video the engine was cranking very slow. I would remove and clean the connections again. If it doesn’t crank over faster have your battery load tested.
 
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I notice two abnormalities when you turn the ignition to start: The odometer goes blank and all gauges drops to zero. It looks as though the PCM is losing power with the ignition in the start position. Have you checked the odometer trip meter to see if it's resetting every time you start the engine?

I would begin by removing the entire battery wiring harness (connects to battery, PDC, alternator, starter, engine block, firewall). Clean all of the connections and ground points til they are shiny. There is also a ground harness from the driver side of the head to the firewall that needs to be checked.
 
I notice two abnormalities when you turn the ignition to start: The odometer goes blank and all gauges drops to zero. It looks as though the PCM is losing power with the ignition in the start position. Have you checked the odometer trip meter to see if it's resetting every time you start the engine?

I would begin by removing the entire battery wiring harness (connects to battery, PDC, alternator, starter, engine block, firewall). Clean all of the connections and ground points til they are shiny. There is also a ground harness from the driver side of the head to the firewall that needs to be checked.
The odometer trip is at 0.0 seems like that is occurring. I will clean all connectors throughly until shiny and clean the battery posts again and will report back. All my tools are at my work currently so I’ll have to wait till tomorrow.
 
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In your video the engine was cranking very slow. I would remove and clean the connections again. If it doesn’t crank over faster have your battery load tested.
I have gotten the battery load tested at autozone and the worker said that everything checked out.
 
A
Those pics only show the TB, they're not showing what the hidden IAC plunger assembly looks like. Not to mention the inside of your TB looks absolutely GUNKED up. See that black on the inside of the valve plate?

View attachment 136765
Ah I see now! Yes it looks very gunked I will buy a can and clean it off tomorrow and will report back.
 
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Cleaned out the throttle body and wiped up all access gunk.
Went to autozone and got the electrical system checked and everything checked out again.
Checked for a parasitic pull now that the old radio was out and there was no charge taken from the battery when off.

Started her up in the parking lot
and she started like a dream and idled perfect. No problems driving home from autozone and the problem seems to be fixed.

I will be checking battery voltages every time before I start the Jeep and after driving it to work for a week or so then when my new radio arrives I’ll check the voltage again. Hopefully the radio was the problem.

Thanks for all the help everyone!
 
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I notice two abnormalities when you turn the ignition to start: The odometer goes blank and all gauges drops to zero. It looks as though the PCM is losing power with the ignition in the start position. Have you checked the odometer trip meter to see if it's resetting every time you start the engine?

I would begin by removing the entire battery wiring harness (connects to battery, PDC, alternator, starter, engine block, firewall). Clean all of the connections and ground points til they are shiny. There is also a ground harness from the driver side of the head to the firewall that needs to be checked.
I cleaned all connections (hopefully all of them lol) and tightened the bolts today. Also wire brushed the ground contact points to make sure the ground wasn’t the problem.