2003 Jeep Liberty Stalling from air starvation.

Tiny
03LIBERTYJEEPGUY
  • MEMBER
  • 2003 JEEP LIBERTY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 48,000 MILES
My Jeep has developed an unusual set of symptoms over the last 3 weeks. Primarily, it stalls a lot. About every 2 minutes (roughly, and not consistently) it stalls. If I'm at idle, it quits. If I'm driving, it picks right back up and drives like normal for a bit. Sometimes, the gages don't even dip, there's just a quick grab.

Ok, now the background. I moved the Jeep to Minnesota from Hawaii. No problems in Hawaii. Before shipping, I did a basic tuneup (oil, filters, spark plugs). When I did this, I replaced the stock filter for a K&N. I also replaced a small section of vacuum hose that had a big crack along the bottom of it. This hose came down from the throttle body and T'd into a line coming from the purge solenoid (80% sure that's what the thing mounted off the relay box is that clicks sometimes.)

For the first several weeks, there were no engine codes. I hooked it up to an OBDII reader and verified there were no codes. There were 4 lights flashing on the reader: O2, CAT, EVA, HTR. Now, I get an engine light when I start the Jeep, until it does it's first stall, then the light check engine light goes away.

When my wife picked the Jeep up from the shipper, they drove it up to the pickup area, turned it off, and it wouldn't start again. All the stall symptoms started about a week after this. The shipper had a couple guys look at the Jeep and mess with it until they could get it started. Ever since, the alarm system hasn't worked the same. Not sure if the pickup from the shipper is important, but you never know.

Lasts week, I changed out the K&N for a paper filter to see if there was any change. It went a whole day of driving without stalling, but then went back to stalling again. I disconnected the battery, cycled the key, and let it sit overnight to reset the computer. I started it up the next day and started getting incredible gas mileage, though it was still stalling. Gas mileage in Hawaii was 13.4 avg over 4 years. Gas mileage went up after fixing vacuum leak, to about 16 mpg. Ever since resetting the computer, it's been averaging over 18.5 mpg.

After resetting the computer and driving it for a couple days, I took the airbox off and visually inspected the throttlebody. I started the Jeep and watched and noticed the throttle plate wasn't moving to adjust the throttle plate and the idle. So, I think the engine is starving of air because the IAC isn't working and the throttle plate stays closed for some reason. With the vacuum leak, it could have been drawing air in through the vacuum line via the suction drawn behind the throttle plate. With the vacuum leak fixed, there's no source of air. That means the problem could have existed in Hawaii and been part of the gas mileage problem.

But, I'm not ready to change out the IAC. It makes sense that some signal may not be telling it to open.

So, I took the Jeep to hook up an OBDII reader again with the check engine light in, and it returned a code 0601 checksum code, again with the same 4 flashing indicators (O2, EVA, HTR, CAT.)

When I had the airbox off and was watching it idle, about halfway between the time I would restart it and the time it would stall, there was a clicking that would start. I traced it to a thing that has 2 vacuum lines and an electrical connection to/from it. I believe it's a purge solenoid related to the emissions system. So, once it starts clicking audibly (about 2 clicks per second), the Jeep soon stalls.

I've been to the forums, but most help there is "Replace your PCM and see what happens." I don't like the "replace some expensive part and see what happens" style of troubleshooting that happens all to often - even at dealerships. So, I'm hoping for some insight into this complicated picture of electronics, emissions, vacuum lines, sensors, etc. That can relate these symptoms to a common component.

Thanks for your time. Jason
Do you
have the same problem?
Yes
No
Saturday, July 25th, 2009 AT 1:10 PM

13 Replies

Tiny
MERLIN2021
  • EXPERT
DTC P0601: PCM INTERNAL CONTROLLER FAILURE Monitored & Set Conditions Circuit is monitored with ignition on. DTC will set if PCM senses internal checksum for software failed and does not match calculated value. Possible Causes PCM Internal Or SPI Testing The PCM is reporting internal errors, view repair to continue. If PCM is reporting internal errors, replace PCM. Program the new PCM. See PROGRAMMING. NOTE: For circuit identification and wiring diagram, see WIRING DIAGRAMS. In testing procedure, alpha/numeric character in parenthesis, i.E. (K4), designates circuit. After each repair procedure has been completed, reconnect all components. Perform POWERTRAIN VERIFICATION TEST VER-1 under VERIFICATION TESTS to ensure system is functioning properly.
POWERTRAIN VERIFICATION TEST VER-1 1. Inspect vehicle to ensure all engine components are properly installed connected. Reassemble and reconnect components as necessary. Inspect the engine oil for contamination. If oil contamination is suspected, change the oil and filter. If repair procedure did not include replacing PCM, or PCM has been replaced and has already been programmed, go to next step. If PCM has been replaced but has not been programmed, program PCM and clear DTCs. The correct VIN and mileage must be programmed or a DTC will set in the ABS and Air Bag modules. In addition, if the vehicle is equipped with Sentry Key Immobilizer Module (SKIM), Secret Key data must be updated to enable start. For ABS and Air Bag systems enter correct VIN and Mileage in PCM. Erase codes in ABS and Air Bag modules. For SKIM theft alarm connect DRBIII(R) to data link connector. Go to Theft Alarm, SKIM, Misc. And place SKIM in secured access mode, by using the appropriate PIN code for this vehicle. Select Update the Secret Key data. Data will be transferred from SKIM to PCM. See PROGRAMMING. After PCM has been programmed, go to next step. 2. Attempt to start engine. If the conditions cannot be duplicated, clear all DTCs. Is the vehicle still unable to start and/or are there any DTCs or symptoms remaining? If no, test is complete. If yes, check for any related technical service bulletins that apply to symptom. If repaired DTC has reset, proceed to appropriate DTC test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS. If necessary, go to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom. NOTE: If replacing the PCM, the correct vehicle mileage and Vehicle Identification Number (VIN) must be programmed into PCM to prevent DTCs from being stored in Controller Anti-Lock Brake (CAB) module and Air Bag Control Module (ACM). If replacing PCM and vehicle is equipped with a Smart Key Immobilizer Module (SKIM), secret key data must also be updated to enable engine starting.
You can try checking the connectors at the PCM for bent or pushed out pins, and PCM grounds.
Was this
answer
helpful?
Yes
No
+1
Sunday, July 26th, 2009 AT 8:33 AM
Tiny
03LIBERTYJEEPGUY
  • MEMBER
So. Replace the PCM?

Ok. You're validating that there isn't likely to be something else wrong that's causing the PCM error? It sounds like that's what the code is saying.

Thanks for posting the detailed info on the 0601 error. Hopefully it's related to the stalling problem. I only recently started getting the code, but it's been stalling for weeks.

Could it be that something else is causing the stalling, which has resulted in the internal checksum error? And it still doesn't make sense that it goes away as soon as it stalls the first time after starting.

In fact, I tested it last night by starting the Jeep - verified I had check engine light - checked the code, it was 0601 - covered the throttle body to cut off air and stall the Jeep. It stalled. I restarted it and the check engine light was out.

I'm glad I didn't go and replace the IAC. I took resistance readings on it and got 53 ohms from outside pin to outside pin. I also got 53 ohms between the two inside pins. Any other combination resulted in OL. However, the signals coming to the IAC didn't make sense. The pin resistance combination didn't match. I got 23K ohms from pin 1 to pin 3, and same from pin 2 to pin 4. Going outside to outside, like on the IAC, resulted in OL.

Without any reference on correct readings, I don't know how else to verify the IAC is working other than visually. It drives out, but I could not get it to drive in.

I'll start looking for a PCM. I just want to eliminate other (cheaper) possibilities first.

Thanks for the reply. Jason.
Was this
answer
helpful?
Yes
No
Sunday, July 26th, 2009 AT 9:44 AM
Tiny
MERLIN2021
  • EXPERT
You can try checking the connectors at the PCM for bent or pushed out pins, and PCM grounds.
Was this
answer
helpful?
Yes
No
Tuesday, July 28th, 2009 AT 2:41 AM
Tiny
03LIBERTYJEEPGUY
  • MEMBER
I checked all the wires I could get to. There's a bunch in the loom that are wrapped pretty good, but anything accessible I checked. Everything going into the PCM looks good.

I messed with the Jeep some more last night. When I unconnect the vacuum line that I fixed and leave it unconnected then there's no check engine light when I start the Jeep. It doesn't stall. It just seems to run fine. So, the PCM still appears to be working. I just don't understand it.
Was this
answer
helpful?
Yes
No
-1
Tuesday, July 28th, 2009 AT 5:27 AM
Tiny
MERLIN2021
  • EXPERT
May be helpful to know what vacuum line supplies vacuum to? If there is an electrical connector on the same location? Any chance of a picture? Or try hooking up the vac, and unplugging the electrical part. See what codes come up then.
Was this
answer
helpful?
Yes
No
Tuesday, July 28th, 2009 AT 5:16 PM
Tiny
03LIBERTYJEEPGUY
  • MEMBER
It's the vacuum line that comes down from the throttle body and T's into the bottom line from the purge solenoid.

The purge solenoid has 2 vacuum lines and an electrical connector.

When I leave all vacuum lines plugged in, but disconnect electrical connector, Jeep still stalls.

When I reconnect electrical connector but disconnect bottom vacuum line, letting more air get to throttle body, then the Jeep runs fine with no codes. No engine light. No stumbles. Just runs.

So for some reason, it runs fine with a vacuum leak, with air getting sucked into throttle body, but will stall and get PCM code if I fix vacuum leak.

Just doesn't make sense.


http://www.2carpros.com/forum/automotive_pictures/387567_IMG_3177_1.jpg


Purge Solenoid. Part of the emissions system. The vacuum line that had the leak I fixed T'd into the bottom one on this solenoid.


http://www.2carpros.com/forum/automotive_pictures/387567_IMG_3178_1.jpg


This is the section of hose I replaced. When I found the leak, the hose piece that was there was split lengthwise and wrapped around the two connections. Now that I've fixed the vacuum leak, the Jeep gets great gas mileage but I have this stalling problem.


http://www.2carpros.com/forum/automotive_pictures/387567_IMG_3179_1.jpg


This is where the line goes into the throttle body. When I disconnect it, the Jeep runs fine, idles a tad high, sucks a LOT of air in through here, but runs fine with no codes.


http://www.2carpros.com/forum/automotive_pictures/387567_IMG_3180_1.jpg


Picture of Purge Solenoid in foreground and line going to T with section of hose I replaced.
Was this
answer
helpful?
Yes
No
+1
Tuesday, July 28th, 2009 AT 6:14 PM
Tiny
MERLIN2021
  • EXPERT
Check to see if the solinoid holds vacuum, and the same for the check valve in the vac line to brake booster, also check booster and check valve there.
Was this
answer
helpful?
Yes
No
Tuesday, July 28th, 2009 AT 7:07 PM
Tiny
03LIBERTYJEEPGUY
  • MEMBER
Ok. I hadn't thought of that.

Do you have a recommendation on how to check those?

As soon as I disconnect anything to check, it will lose vacuum. I don't have any kind of vacuum tester.

I didn't realize there were check valves in the system.

Now that I think about it, when the Jeep stalls out, or I shut it off, there's a hissing sound - like it's losing its vacuum - for about 2 to 3 seconds. I can't identify where it's drawing in the air, but it sounds like it's breaking vacuum through the air intake. I thought that might be normal.

Hmmm. Ok. I'll see if I can figure out how to test those check valves and the solenoid.
Was this
answer
helpful?
Yes
No
Tuesday, July 28th, 2009 AT 7:34 PM
Tiny
MERLIN2021
  • EXPERT
Buy a vacuum tester, it has a gauge and pump handle, attach it to the piece being tested and pump, watch gauge, if it drops, or fails to pump up, the part leaks! Tester is only about 20.00 dollars.
Was this
answer
helpful?
Yes
No
Wednesday, July 29th, 2009 AT 2:34 PM
Tiny
03LIBERTYJEEPGUY
  • MEMBER
Sweet. I'll do that. Give me a couple days to get the tester and get that done. I'll let you know what I find out as soon as I do.

Thanks again. Jason
Was this
answer
helpful?
Yes
No
Wednesday, July 29th, 2009 AT 4:50 PM
Tiny
MERLIN2021
  • EXPERT
I will be checkin in.
Was this
answer
helpful?
Yes
No
Thursday, July 30th, 2009 AT 2:10 PM
Tiny
03LIBERTYJEEPGUY
  • MEMBER
Well, I bought a vacuum gage. They didn't have anything with a handle. They had a gage with different fittings that can check vacuum and compression.

So, my indications when I hooked it into the line I fixed the vacuum leak on (connected to the purge solenoid and the throttle body) were this:
Initially, vacuum comes up to the middle of the green band (18/19 inches) and is steady. Once purge solenoid starts clicking, vacuum drops to the bottom of the green band (15/16 inches). Then right before the engine stalls, the vacuum goes away.

Looking closer at the purge solenoid and the fuel system, all this may be a fuel problem. I just don't understand why it would tend to stall more when I come off the gas or am at idle for a bit.

Talking to my wife, the shipping company tried to start the Jeep over and over for about a half hour before they finally put gas in it. After that, it started right up. So, it was out of gas and the fuel pump comes on every time the key is turned to the on/start position - which was a bunch of times over the half hour.

I'm thinking about dropping the gas tank and taking a look. Before I do, I want to figure out if it's possible to have a fuel pump problem with no fuel pump codes.

I'll be looking at the Jeep more again this coming week.

Thanks again for your help and patience. If you've had any epiphany's, please let me know. Thanks, Jason
Was this
answer
helpful?
Yes
No
Saturday, August 15th, 2009 AT 10:09 PM
Tiny
MERLIN2021
  • EXPERT
Fuel pressure test it before you drop the tank, on Jeep the regulator is in the tank on the pump too. At idle the IAC(idle air control) can be a problem, it's bolted to the throttle body.
Was this
answer
helpful?
Yes
No
Monday, August 17th, 2009 AT 2:48 AM

Please login or register to post a reply.

Recommended Guides