2004 Grand Cherokee lagging/bucking under acceleration - Page 2 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > WJ Grand Cherokee Forum > 2004 Grand Cherokee lagging/bucking under acceleration

End of Summer Sale, 20% OFF!2007 - 2011 Jeep JK Long Arm Lift KitsIntroducing MONSTALINER™ UV Permanent DIY Roll On Bed Line

Reply
Unread 12-23-2013, 10:44 PM   #16
Leatherman
Registered User
2004 WJ 
 
Join Date: Dec 2013
Posts: 12
Today I did the following:

1. Reinstalled the coil rail after measuring its impedances, but did NOT replace it. Since I couldn't really tell anything by trying to measure it, I am not yet eliminating it from the suspect list. Went out for a test drive. No change - same problem remains.

2. While on the test drive, once the problem began, shifted into neutral and rev'ed the engine slowly up to around 5000rpm. It sounded good all the way up (under no load of course).

3. Replaced the MAP sensor. Went for a test drive. No change.

4. Removed the transmission pan and replaced the filter and fluid. Went for a test drive. Problem still there, but is seemed to act a little different in the way it lagged... maybe my imagination. I don't yet have the fluid set at the right level anyway, will recheck / re-level tomorrow. The transmission theory is still on the list... for now.

5. Called a couple of muffler shops and talked about the catalytic converters. One guy offers a free diag check, so I'll probably take it in after Christmas. The other guy's shop was being expanded, and so he is shutdown for a month. Since he can't do any business, I felt like he was shooting straight with me. He asked about the symptoms in detail, then concluded that he didn't think it was the cats. The main things that seemed to convince him of this were that it runs fine for the first minute or two after starting, and that it can rev high (and move a lot of air volume without issue) at any time. What do you guys think of this? This second guy also suggested that I watch the manifold vacuum while running and make sure it drops smoothly with increasing throttle. Clogging in the exhaust, he said, would cause manifold pressure to not drop as much with throttle.

Leatherman is offline   Reply With Quote
Unread 12-24-2013, 03:09 AM   #17
86cj74.2L
Web Wheeler
 
86cj74.2L's Avatar
2004 WJ 
 
Join Date: Jul 2006
Location: Stouchsburg, PA
Posts: 6,667
If you have 4.0l. Checking the resistance on the secondary is easy for the coils. There are two spark plugs per ignition coil. Put a meter lead in each spark plug hole of rack coil.

That resistance reading will be your secondary measurement.
86cj74.2L is offline   Reply With Quote
Unread 12-24-2013, 04:06 AM   #18
WJDaddyTrick
Registered User
2000 WJ 
 
Join Date: Feb 2013
Location: Kent, England
Posts: 23
I've been suffering with a similar issue to this for a while and had gone round testing everything as you have. I run on LPG for most of the time and she runs great on it without the fault, its only a problem when running from cold on petrol.

I took it in for a LPG setup and was he couldn't get the mixture correct.
When we looked at it on petrol the fuel meters were wracked up to full.
We corrected this and angine ran fine. We set the LPG and all was sweet...... Until.

I took the battery off to charge it over night and fuel meters have set themselves up the shot again when I put the battery back on.

I know the problem with mine, it's running bl**dy rich. Just can't figure how to fix it long term, for now I live with it.

Symptoms and work around.
Cold start. Idle ok. gentle acceleration, spits and splutters. Hard acceleration, accelerates ok.

I switch to LPG and it runs fine.

When hot. Runs ok. ( because O2 sensor it's active at temperature)

Try restarting it when at temperature.
Check the long term fuel meters with obd tool
Get the fuel ratio emotions checked.

Hope this helps.
WJDaddyTrick is offline   Reply With Quote
Unread 12-24-2013, 05:22 AM   #19
MadderThanMax
Registered User
2001  
 
Join Date: Oct 2011
Location: Glasgow, Scotland
Posts: 1,659
Wait.. go back to the coil pack..

On another car... this was a common failing. Try this and see what happens. put the coil pack/rail in the oven and heat until hot. (DO NOT MELT!!) Then remove and spray liberally with WD4O or similar (Must be water/moisture resistant!!) Then smear in silicone grease - a fine coating on all over and reconnect and report back.

On the "Other" car what was happening was due to the heat build up on the coil pack off the engine, the plastic would crack and allow in moisture thus creating lumpy running which was worse when cold and because your car is OBD2 and auto the TCM is trying to learn what driving style therefore jumping in/out of gear.

I don't think your trans is the issue here...
MadderThanMax is offline   Reply With Quote
Unread 12-24-2013, 01:01 PM   #20
Stono-see-um
Registered User
1984 FSJ Wagoneer 
 
Join Date: Dec 2013
Location: Charleston, SC
Posts: 1
Have you cleaned your throttle body? Cheap and easy, and everyone should do it.
Stono-see-um is offline   Reply With Quote
Unread 12-24-2013, 01:44 PM   #21
creepingdeath94
Registered User
2000 WJ 
 
Join Date: Sep 2010
Location: port saint lucie
Posts: 147
I just read this thread today and just wanted to verify something. Is this bucking/misfire issue only after its warmed up and at interstate speed only? Does it do it at all at lower speeds under 60 mph? Also, have you been able to get it up to interstate speed and check this cold? I assume you have to drive a bit to the interstate and its warmed up by then?
creepingdeath94 is offline   Reply With Quote
Unread 12-24-2013, 03:45 PM   #22
86cj74.2L
Web Wheeler
 
86cj74.2L's Avatar
2004 WJ 
 
Join Date: Jul 2006
Location: Stouchsburg, PA
Posts: 6,667
I'm still thinking its a coil braking down under load and misfiring.
86cj74.2L is offline   Reply With Quote
Unread 12-24-2013, 03:55 PM   #23
blackcar87
Registered User
1994 XJ Cherokee 
 
Join Date: Sep 2008
Location: Montgomery, AL
Posts: 158
X2 on the clogged cat. I have experienced the same prob as you with other cars. ssshhhh, I cut mine off of the XJ!
__________________
1994 Cherokee country, 3 inch aal, 17x7 Jeep Libery wheels, 245/75/17' BFG's, yakima rack
2004 Grand Cherokee Freedom Edition 4.7 HO ebc dimpled/slotted rotors, green stuff pads, Bilstein shocks

"Do you know about Tyler Durden?"
blackcar87 is offline   Reply With Quote
Unread 12-24-2013, 04:47 PM   #24
86cj74.2L
Web Wheeler
 
86cj74.2L's Avatar
2004 WJ 
 
Join Date: Jul 2006
Location: Stouchsburg, PA
Posts: 6,667
To test for a clogged cat.

Remove a upstreem O2 sensor. Thread in a fitting you can connect a pressure gauge to. I believe its a 14mm spark plug thread.

Start engine and at idle see what psi you have. Compare to others on the Internet. I think around 5psi and above at idle is a bad reading.
86cj74.2L is offline   Reply With Quote
Unread 12-24-2013, 04:54 PM   #25
86cj74.2L
Web Wheeler
 
86cj74.2L's Avatar
2004 WJ 
 
Join Date: Jul 2006
Location: Stouchsburg, PA
Posts: 6,667
Here is something I think I'm going to buy just to have.

My 4runner has 256,000 on it with original CAT, my Saturn SL1 has 206,000 on it with original CAT also.
image-1885366128.jpg

86cj74.2L is offline   Reply With Quote
Unread 12-25-2013, 07:15 PM   #26
Leatherman
Registered User
2004 WJ 
 
Join Date: Dec 2013
Posts: 12
Hey all, Thanks for the great feedback. Once I get past some Christmas stuff with family, I'm going to try all this.

I like the pressure tester and tip about doing it through the upstream O2 sensor hole. I think I will order one too. If I do, I will post back what I measure. The quote was $700 bucks to do all three cats, so it is not something I would do without being certain.

I also hear you about not dismissing the coil rail. Good tips on baking out the one I have and a new one is about $100 bucks at O'Reilys. So at some point soon I will come back to that.

To answer Creepingdeath94: I do have a home location that limits my ability to open it up much in the first bit - congested until the interstate about 2 miles away. I need to park it over by the interstate and let it sit then start and go immediately. I do know that the problem occurs at various speeds. And I "think" is that it does not have the problem for the first couple of minutes after starting. I will try to test more and get more info on this for you.

Also to Stono-see-um: I have not (yet) cleaned the throttle body. I thought that the $100 cleaning that the shop did (see my first post) was supposed to cover the throttle body, manifold and injectors. But I have no real way to verify that they really did anything. If I take the plastic intake plenum off, I can see that it is wiped clean down to the throttle valve, then black south of there if I flip it open. (see pic) What do you suggest I do to clean it good? Do you unbolt it from the manifold and clean it off the car?
open-throttle.jpg  
Leatherman is offline   Reply With Quote
Unread 12-26-2013, 01:01 AM   #27
DevinB
Registered User
1993 YJ Wrangler 
 
Join Date: Mar 2006
Location: Utah
Posts: 138
Quote:
Originally Posted by Leatherman View Post
I like the pressure tester and tip about doing it through the upstream O2 sensor hole. I think I will order one too. If I do, I will post back what I measure. The quote was $700 bucks to do all three cats, so it is not something I would do without being certain.
I was worried about having to replace them all as well. My muffler shop (personal friends as well as avid jeepers) narrowed it down to the one furthest downstream, so they replaced that one and I've been good ever since. Good luck with everything you try and I hope you find the culprit soon.
DevinB is offline   Reply With Quote
Unread 12-26-2013, 03:04 AM   #28
MadderThanMax
Registered User
2001  
 
Join Date: Oct 2011
Location: Glasgow, Scotland
Posts: 1,659
You unbolt that from the manifold. Use Cab cleaner aerosol until spotless then lubricate the butterfly with some 3 in 1 light oil.and work. It will relearn once reinstalled. There should be no black on it at all. held up to the light ther should be a very thin line of light around the butterfly when closed.
MadderThanMax is offline   Reply With Quote
Unread 12-26-2013, 10:40 AM   #29
GlocksandJeeps
Registered User
2000 WJ 
 
Join Date: Dec 2013
Location: Prescott, Arizona
Posts: 4
x3 on the cat. On mine, it was when the rattling stopped the real issues began.
GlocksandJeeps is offline   Reply With Quote
Unread 12-28-2013, 10:27 PM   #30
Leatherman
Registered User
2004 WJ 
 
Join Date: Dec 2013
Posts: 12
Hey all. Today I took the Jeep to a muffler shop and they said that the catalytic converters tested fine. I appreciated the honesty of their "we don't want to sell you something you don't need". But am not 100%. They did the test "thermally". The car was warm from the drive over (~6 miles) and was idling in the parking lot during the test.

From what I could tell, the guy pointed a laser temperature sensor at the pipe, just above, then just below each cat. I don't understand the physics of it, but the temperature measures from below the cat were approximately 80 degrees higher than the temperature measures from above the same cat. Why it is hotter further from the engine, I don't grasp right offhand... need to read up on that sometime. Anyway, he said that 50 degrees or greater indicated no problem.

Meanwhile, I ordered the pressure tester that 86cj74.2L suggested above, and will give it a check myself when it arrives. I wonder if I can drive it with this gauge taped to my windshield? I suppose there would be a missing O2 signal since I'd be measuring through the O2 hole, but it still might be interesting. Should I replace the O2 sensors while I'm in there?

I didn't get to the throttle clean-out yet. As I drove it to the muffler shop today, I stayed very gentle on the gas and repeatedly had the softer, longer-lasting laggings that I described earlier (as opposed to jerking). With me holding the pedal exactly constant on a steady incline, it felt as if I let off the gas halfway, held it there for a period, (sometimes many seconds), then resumed. There is no slipping, RPM's drop during these lagging periods.

Frustrating. I might end up going back to an auto shop or dealer on this. Seems like if I had a good computer readout of all the sensors and systems while I was driving I could see the problem.
Leatherman is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.