05 WK 4.7L Misfire - no PCM codes

05_WK_NH · 09-07-2008, 11:15 AM

I recently purchased a 2005 Jeep Grand Cherokee Laredo, 4.7 L V8 to replace my 01 WJ that had 150k on it and very few problems. I have had an issue with the 05 since the day I picked it up that the local Jeep dealership has been unable to fix. I am new to this forum, and hope that someone can shed some light on this issue.

The issue is a surging or hesitation that is most noticeable at engine speed of 1200-1700 RPM as a low frequency surging (1-2 times per second) when driving in 4th or 5th gear on uphill grade at 40-45 mph, partial throttle. The hesitation is present at higher engine speeds and in other gears, but the entire vehicle surges forward most noticeably at low rpms. It feels like an engine misfire, but the ECM is not showing any codes.

So far the spark plugs have been replaced with OEM champions, chamber cleaning performed, TPS sensor replaced, ECM flashed / reprogrammed, heads removed and valves replaced and ground, and torque converter replaced. None of these actions has changed the symptoms. Please help! This is a very nice vehicle otherwise, but I am quickly loosing confidence in the local Jeep's service dept.

merlinTec · 09-07-2008, 11:25 AM

Hi
Have they done a cylinder leak test? Also disconnect the air con conpressor and try it.
Regards,
Merlin

05_WK_NH · 09-07-2008, 11:07 PM

I did a compression test and found 115 +- 10 psi for all cylinders. The dealership did a leakdown test and based on that decided to replace all of the valves.

merlinTec · 09-08-2008, 01:23 AM

Hi
Ok let me know how you get on with the air con disconnected. If still there I would do a leak test again to see if it’s rings.

05_WK_NH · 09-09-2008, 10:13 PM

Hi
I disconnected the AC compressor and no difference. I did notice that the pulley and clutch fan had a lot of play and will be replacing the water pump tomorrow. After that I am going to try O2 sensors and MAP. Any other suggestions? The spark plugs are coated with a fine white powder as if the engine is running lean...?

**dmcanally** · 09-10-2008, 01:46 AM

I just picked up a 06 WK today... (getting rid of my YJ) so I am afraid that I don't know too much about the WK yet, but the WK doesn't have a rotary distributer correct? If so please feel free to correct me. I assume it has a timing module type firing system controlled by the computer. Have you checked the modules that connect onto the spark plugs?

merlinTec · 09-10-2008, 11:53 AM

Hi
If they have flashed the PCM there should be a label under the hood can you give me the number off that label as there is a flash for the PCM for 02 sensor so just want to check you have the latest software. Should be 56044551AM (two wheel drive) or 56044552AN (four wheel drive)
Regards,
Merlin

kiesha · 09-11-2008, 06:40 AM

hi there, i have same issue with my 06 wk 4.7 limited but i though it's normal.
my warranty will expire soon should i take it to jeep to have a look or i can still drive and don't worry about it.
Please advice.
regards

05_WK_NH · 09-11-2008, 01:34 PM

merlinTec,
There are 2 labels on the PCM. The original label is 56044515AE, and there is a software update 56044552AJ. Is the P/N you gave an update from the flash that was already performed? Thanks

merlinTec · 09-11-2008, 02:04 PM

Hi
Yes 56044552AJ is well out of date goes to AL, AM, then to 56044552AN. When was your update done? perhaps they didn't update the label? Best to give them a call I think.
Regards,
Merlin

kiesha · 09-12-2008, 03:53 AM

is this issue covered by limited warranty.
thanks

juanowk05 · 02-15-2009, 07:59 AM

Hi Merlintec i have a problem with my WK, the Cel iluminate for a dtc 2096, which is "Post Catalyst Fuel Trim System Too Lean Bank 1" i changed the O2 sensor for a new oem one, and still have the same problem, the dealer check for electronics problem, and check for leaks and nothing, do you know if exist any tsb o new firmware update for the pcm, the engine is 4.7 V8 Laredo 2005, and if exist what would be the number for asking.

Thanks, Juan

merlinTec · 02-15-2009, 11:20 AM

Hi
There are TSB for upstream 02 sensors and another for cat efficiency so I would make sure it’s at the latest software level first. Is there running problems? There is also possible exhaust leak (crack welds) and possible contaminated fuel/ water in fuel issues.
Regards,
Merlin

alexr40 · 03-02-2009, 12:52 PM

mine does the same.

at idle it feels like a small misfire.. like a little vibration.. the RPM needle stay steady tho. but feels funny sometimes... mostly happens when cold start.

i dont know what is it. when driving slowly it kinds of jump

slaught1 · 04-21-2009, 09:49 AM

Hey 05_WK_NH,

Did you ever figure out the heistation problem with your WK

Your seems to be very similar to mine, but I have the 5.7 liter Hemi.

I think there are two issues, One with the transmission and one with
the hesitation at low RPM that seems like a misfire.

I was trying where to go next?

09-07-2008, 11:25 AM	#2
merlinTec Registered User Join Date: Jul 2007 Location: England Posts: 2,944 Profile Gallery Classifieds My Jeeps	Hi Have they done a cylinder leak test? Also disconnect the air con conpressor and try it. Regards, Merlin __________________ UK Chrysler Jeep Master Tec.

09-08-2008, 01:23 AM	#4
merlinTec Registered User Join Date: Jul 2007 Location: England Posts: 2,944 Profile Gallery Classifieds My Jeeps	Hi Ok let me know how you get on with the air con disconnected. If still there I would do a leak test again to see if it’s rings. __________________ UK Chrysler Jeep Master Tec.

09-10-2008, 11:53 AM	#7
merlinTec Registered User Join Date: Jul 2007 Location: England Posts: 2,944 Profile Gallery Classifieds My Jeeps	Hi If they have flashed the PCM there should be a label under the hood can you give me the number off that label as there is a flash for the PCM for 02 sensor so just want to check you have the latest software. Should be 56044551AM (two wheel drive) or 56044552AN (four wheel drive) Regards, Merlin __________________ UK Chrysler Jeep Master Tec. Last edited by merlinTec; 09-11-2008 at 01:58 PM..

09-11-2008, 02:04 PM	#10
merlinTec Registered User Join Date: Jul 2007 Location: England Posts: 2,944 Profile Gallery Classifieds My Jeeps	Hi Yes 56044552AJ is well out of date goes to AL, AM, then to 56044552AN. When was your update done? perhaps they didn't update the label? Best to give them a call I think. Regards, Merlin __________________ UK Chrysler Jeep Master Tec.

02-15-2009, 11:20 AM	#13
merlinTec Registered User Join Date: Jul 2007 Location: England Posts: 2,944 Profile Gallery Classifieds My Jeeps	Hi There are TSB for upstream 02 sensors and another for cat efficiency so I would make sure it’s at the latest software level first. Is there running problems? There is also possible exhaust leak (crack welds) and possible contaminated fuel/ water in fuel issues. Regards, Merlin __________________ UK Chrysler Jeep Master Tec.

02-15-2009, 07:59 AM	#12
juanowk05 Registered User Join Date: Sep 2008 Location: Perú Posts: 8 Profile Gallery Classifieds My Jeeps	Hi Merlintec i have a problem with my WK, the Cel iluminate for a dtc 2096, which is "Post Catalyst Fuel Trim System Too Lean Bank 1" i changed the O2 sensor for a new oem one, and still have the same problem, the dealer check for electronics problem, and check for leaks and nothing, do you know if exist any tsb o new firmware update for the pcm, the engine is 4.7 V8 Laredo 2005, and if exist what would be the number for asking. Thanks, Juan

04-21-2009, 09:49 AM	#15
slaught1 Registered User Join Date: Apr 2009 Location: NC Posts: 1 Profile Gallery Classifieds My Jeeps	05 WK 4.7L Misfire - no PCM codes Hey 05_WK_NH, Did you ever figure out the heistation problem with your WK Your seems to be very similar to mine, but I have the 5.7 liter Hemi. I think there are two issues, One with the transmission and one with the hesitation at low RPM that seems like a misfire. I was trying where to go next?