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93 XJ Country Stalls While Cold

S

StoneX

NAXJA Forum User
Location
Chicago IL
My 93 XJ randomly stalls while idling or right before stopping at low speed. It usually runs fine on warmer days and can stall several times on colder days. It restarts without problem and it seems to run all right after engine warms up. The idle speed is a little bit above 750. Not sure if that's normal.

There is a code 17. I've replaced coolant temperature sensor with no avail. After disconnecting the battery the code is still there. The temperature reading from the console is low so it can be a malfunctioning thermostat but I don't think it causes stalling.

I also replaced the idle air control motor but the problem is still there. And there doesn't seem to be any vacuum leak.

What would be the next to do? Replace the MAP sensor? Or the TPS sensor? Any idea?

It comes with a 6-cylinder engine and automatic transmission.
 
Last edited:
Code 17--engine cold too long.

Cold engine = richer mixture = lower idle (leaner mixture = higher idle).

1. Replace your thermostat. I only install and only recommend the Stant SuperStat Premium 195 degree thermostat for the XJ 4.0 engine.

2. Your idle should be 700~750 RPM after 20 minutes of operation--full operating temperature (assuming you are reaching full operating temperature). Manual trans in neutral, automatic trans in DRIVE (you need a friend in the driver's seat with their foot on the service brake pedal, don't rely on the parking brake).

3. Did you clean the throttle body and IAC air passage with a throttle body safe aerosol cleaner, or did you just change the IAC?

I would say you need to change the thermostat first and see if you can get the engine up to 205-210 range on the gauge.

After you get the engine running at the right temperature, shut the engine off. Disconnect BOTH battery cables from the battery's terminals, then hold the cable ends together for about 15~30 seconds to clear the PCM's memory. Hook your cables back up and the code should be cleared.
 
Thanks joe_peters. I know code 17 may be indicative of a bad thermostat. But is it possible that the coolant temperature sending unit (not the coolant temperature sensor) is not accurate which makes the temperature reading low? I'm getting 20+ MPG on highway so does this imply the coolant temperature is fine since lower coolant temperature makes MPG higher?

Also is this the reason that it stalls or there's something else going wrong?

I didn't quite clean the throttle body and IAC air passage because they look clean enough to me and there is no carbon/oil buildup that can be potentially clogging.

I'll try replacing the thermostat since it should be cheap also easy hopefully.


joe_peters said:
Code 17--engine cold too long.

Cold engine = richer mixture = lower idle (leaner mixture = higher idle).

1. Replace your thermostat. I only install and only recommend the Stant SuperStat Premium 195 degree thermostat for the XJ 4.0 engine.

2. Your idle should be 700~750 RPM after 20 minutes of operation--full operating temperature (assuming you are reaching full operating temperature). Manual trans in neutral, automatic trans in DRIVE (you need a friend in the driver's seat with their foot on the service brake pedal, don't rely on the parking brake).

3. Did you clean the throttle body and IAC air passage with a throttle body safe aerosol cleaner, or did you just change the IAC?

I would say you need to change the thermostat first and see if you can get the engine up to 205-210 range on the gauge.

After you get the engine running at the right temperature, shut the engine off. Disconnect BOTH battery cables from the battery's terminals, then hold the cable ends together for about 15~30 seconds to clear the PCM's memory. Hook your cables back up and the code should be cleared.
Click to expand...
 
StoneX said:
. The temperature reading from the console is low so it can be a malfunctioning thermostat but I don't think it causes stalling..
Click to expand...

What does the coolant temp gauge read? You should be around 200-210 for the Jeep 4.0 when engine is fully warmed up. BTW, cooler temperatures does NOT mean more MPG. Just the opposite actually. Your engine is designed to run at the 200-210 range and that is where you get the best efficiency.

If you have a low coolant temp reading along with the code 17, get a new thermostat in there. I like stats from JEEP and also the Stant Superstat. 195 degree only.

The stalling issue may not be related to the code. It is possible you have more than one thing going on.

The best strategy is always to chase the code and get that resolved and THEN see where you are at with any remaining symptoms.
 
Last edited:
I would do the thermostat first, and clear the code.

After that, when the engine is hitting the 205~210 range, check and see if the code returns.

You are correct that the code 17 could be related to the CTS on your 93. After the thermostat if the code returns testing the CTS would be the next step.
 
It reads about 100 (quarter of full range) for the past years but the MPG seems to fine so I suppose it's a bad coolant temperature sending unit (not the sensor which sends signal to ECU) and didn't do anything about it.

Anyway I think I'll follow you guys' suggestion on replacing the thermostat.


birchlakeXJ said:
What does the coolant temp gauge read? You should be around 200-210 for the Jeep 4.0 when engine is fully warmed up. BTW, cooler temperatures does NOT mean more MPG. Just the opposite actually. Your engine is designed to run at the 200-210 range and that is where you get the best efficiency.

If you have a low coolant temp reading along with the code 17, get a new thermostat in there. I like stats from JEEP and also the Stant Superstat. 195 degree only.

The stalling issue may not be related to the code. It is possible you have more than one thing going on.

The best strategy is always to chase the code and get that resolved and THEN see where you are at with any remaining symptoms.
Click to expand...
 
Code 17 was somehow cleared after several days of driving. The CTS is new. But the car still stalls, mostly before stopping or while running at low speed. This usually occurs within 15 minutes of startup and after that it seems to run fine. This is opposite to what "thermal failure" of CPS/CKP is causing so could it be related?

I saw some post about o2 sensor causing stalling so disconnected it but it didn't do the trick.

I just received a new thermostat and will put it in this weekend. Anything else I should take a look at?


joe_peters said:
I would do the thermostat first, and clear the code.

After that, when the engine is hitting the 205~210 range, check and see if the code returns.

You are correct that the code 17 could be related to the CTS on your 93. After the thermostat if the code returns testing the CTS would be the next step.
Click to expand...
 
StoneX said:
But the car still stalls, mostly before stopping or while running at low speed. This usually occurs within 15 minutes of startup and after that it seems to run fine.

Anything else I should take a look at?
Click to expand...

A marginal battery could be in play. If you have a battery that is weak, it still could be strong enough to start the engine but weak enough to create a stall, until the alternator charges it back up enough to stop the stalling symptom. I've actually seen this before.

If I were you, I would definitely LOAD TEST your battery. Most parts stores will do this for you for free in the hopes that you'll buy a new battery from them if you need one.

Sure there are other possibilities but life starts with electrons and I'd sure want to verify a solid electrical system before moving onto other more complex possibilities.

Keep us posted!
 
The battery was actually just replaced as the old one looked weak after several stalls and restarts. Is it possibly because the firing circuit is somehow short-circuited which causes the battery to drain?


birchlakeXJ said:
A marginal battery could be in play. If you have a battery that is weak, it still could be strong enough to start the engine but weak enough to create a stall, until the alternator charges it back up enough to stop the stalling symptom. I've actually seen this before.

If I were you, I would definitely LOAD TEST your battery. Most parts stores will do this for you for free in the hopes that you'll buy a new battery from them if you need one.

Sure there are other possibilities but life starts with electrons and I'd sure want to verify a solid electrical system before moving onto other more complex possibilities.

Keep us posted!
Click to expand...
 
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