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WJ Fan 04-18-2012 10:33 PM

02 Overland- rough running at speed
 
OK- I feel like I have come to the oracle at Delphi... but here it goes

Took a risk and bought a 2002 Overland with engine issues (including check engine light) for a song (a "match" to the current 2002 Overland creampuff so his/hers if I can get the engine sorted out). 165K, trans replaced by dealer at 95K, no leaks, otherwise fine.

Story from prior owner was misfire code on cyl #6, beginning about two weeks after an overheating incident. Mechanic at dealership said "no way, don't touch it, 4.7 HO goes v bad when over heated- dark mutterings about valve sleeves popping out, partially re-seating, and about shot thrust bearing. Local general mechanic that I trust suggested possibility of shot coil over #6. Noodled price for the '02 down so low that I took the risk. When I picked it up, I found out that owner had continued running it with the misfire (x 2 months or so).

Local boy mechanic won the prize- #6 coil no spark, replaced for $25 or so, no exhaust gases in radiator, cylinder compression varies from 75 - 125 pounds depending on cylinder, but #6 within range of others.

Idle seemed pretty good now, about 625 or so, would run up to 3K pretty smooth also, but take it out on the road and it would cough and choke at speed unless I kicked the accelerator. Ran various additives (Techron etc) presuming it was fouled injector/carbon build up somewhere.

Swapped the copper champion plugs that had been in for 60K or so (now with huge gaps) for NGK Iridiums, but still ran rough at speed or under load unless I hit the pedal- and then it roars just like my other '02 overland that runs like a top. No problem kicking the wounded one up to 80MPH. Old plugs were otherwise fine, prior owner had swapped out #6 Average MPG running about 15, despite my needing to put a foot into it periodically to over come the rough running at speed. If I set the cruse control at highway speed, it runs really rough.

Reading on this and other forums, I now suspect O2 sensors or clogged cat converters from the prior owner running excess hydrocarbons down the pipe.

Unplugged the battery, no check engine when I ran it yesterday, but the check engine light was baaack when I fired it up this AM.

The local mechanic is pulling the codes today.

Q#1- A set of 4 O2 sensors run a minimum of $200+. Is there a reliable way or an amateur like me to test which of any of these need to be swapped out?

Q#2- the Haynes book just does not cut it in my opinion- can anyone recommend something better?

Q#3- What else should I have in the "differential diagnosis" for this 4.7HO?

Very many thanks to all who have contributed to similar threads, and thanks in advance to any who may advise on this one.

2005JGC 04-19-2012 01:52 AM

Re: 02 Overland- rough running at speed
 
typically, if you had a plugged cat you your engine would fall on its face when you stomped on it. What are the codes being pulled now?

ONLY ONLY ONLY use mopar sensors, sorry, this will add to the cost but if your going to replace o2 sensors make them mopar or dont replace them. Ultimately I am sure there is a time and a place to replace O2 sensors without dtc's but if they are not throwing any dtc's then they are operating in their parameters and I wouldn't personally waste the money at this point in time.

As for service information, you can purchase an alldata.com subscription for like 20-25 bucks per year (per car, kinda steep I know), its nice having information at your fingertips, to be quite honest, I couldn't find the compression spec ANYWHERE on dealerconnect for an 04 4.7l even using the search feature, it kept bringing me back to engine specs page where it was NOT listed, but alldata had the spec for me. I am sure you can find a cd based version of the service information on ebay, or the paper service manuals.

75-125lbs is really low, if for nothing more this would lead me to believe there is either cylinder integrity issues OR a plugged cat could in theory cause a low pressure test. The compression test spec is 140-180psi with no more than 25% variance and your under in all your cylinders and also beyond 25% variance. How did you perform your pressure test?

WJ Fan 04-19-2012 09:30 AM

Re: 02 Overland- rough running at speed
 
Thanks for the feedback.

I agree that the acceleration is not consistent with plugged Cat converter, and from what I read it bypasses O2 sensor PCM control ("open circuit"?), hence the thesis concerning O2 sensors- but I am probably over thinking this (see below)

Compression done with a threaded in-type gauge, but this is the first time I have done this and certainly may not have performed correctly.

Thanks for info on what compression to expect. At 165K on the engine, my most important decision at this point is whether to rebuild/replace with rebuilt, swap in a junkyard 4.7HO, or just nurture the one that is in there at present. As you probably know, the HO is sort of a rare and expensive hothouse flower, but I understand that switching to the standard 4.7 would require new harness and PCM.

Local mechanic tells me today that the only code is misfire on #6, but also that the cylinder numbers for the code are NOT the firing order, so I have been focusing on cylinder #7, not #6. Same mistake made by prior owner. I guess both myself and prior owner can chalk that misunderstanding up to the Haynes book.

I got the memo about the O2 sensor vendors from reading prior boards. Appreciate your reinforcing that.

Local mechanic is swapping coils to see if that addresses the #6 issue.

20-25 bucks per year is cheap if it is a good resource. Again, thanks. Particularly given that I have taken on restoration/maintenance of three WJs. I am hoping that by training myself up on the care and maintenance of these, I can save myself a lot of grief over having to maintain different used 4x4 trucks. For example 2 of the three have had the notorious ground wire failure in the door. Easy fix once you know the problem. Same for those pesky front speakers that rot in the sun. Now if I could only figure out why the center panel shifter illumination is intermittent on the '99... Already pulled and cleaned the contacts in the center console between the seats.

Again, thank you for your time and assistance.

01grand 04-19-2012 01:50 PM

Re: 02 Overland- rough running at speed
 
I don't mean to discredit anybody, 2005JGC has been INVALUABLE to this forum, and I'm sure has helped many users save lots of money. However, mopar doesn't make all of their own parts, ie. their spark plugs are champion, and for the WJ, the O2 sensors are Denso. While the dealer is a great way to know you are getting good parts, if you know who makes the OE part you can often find it cheaper elsewhere. I have been running OE Denso O2 sensors from rockauto.com for 3 months now with no problems, and have noticed a slight increase in MPG (old ones were also throwing a code for slow heat up time). I did take a slight risk by trusting the site when they said denso was OE, but when I pulled out the old sensors it was confirmed, they said "DENSO" right on them.

TJXJWJ 04-19-2012 02:09 PM

Re: 02 Overland- rough running at speed
 
Quote:

Originally Posted by 01grand (Post 615823)
I don't mean to discredit anybody, 2005JGC has been INVALUABLE to this forum, and I'm sure has helped many users save lots of money. However, mopar doesn't make all of their own parts, ie. their spark plugs are champion, and for the WJ, the O2 sensors are Denso. While the dealer is a great way to know you are getting good parts, if you know who makes the OE part you can often find it cheaper elsewhere. I have been running OE Denso O2 sensors from rockauto.com for 3 months now with no problems, and have noticed a slight increase in MPG (old ones were also throwing a code for slow heat up time). I did take a slight risk by trusting the site when they said denso was OE, but when I pulled out the old sensors it was confirmed, they said "DENSO" right on them.

^ Smart....very smart. You're like a Magnavox. That's my new nickname for you...hahahhaha.

Like Magnavox said, 2005JGC is the chiz when it comes to technical stuff like this.

...and the real reason I chimed in was to agree that Haynes sux. Everytime I buy a new ride, I budget in $100 extra to buy the factory service manual. To me, they are like the bible. Everything you need to know is in there. They aren't cheap, but I can't tell you how many times they've paid for themselves in my experience. I like the actual manuals...paper, so I can flip through it on the work bench, like I know what I'm doing. Nothing beats having a step by step on every possible part on your vehicle.

01grand 04-19-2012 02:13 PM

Re: 02 Overland- rough running at speed
 
Quote:

Originally Posted by TJXJWJ (Post 615836)
^ Smart....very smart. You're like a Magnavox. That's my new nickname for you...hahahhaha.

Great, I can only imagine where this will go.......:lol:

Service manuals are definitely a great tool, haynes or chiltons are ok, but nothing beats the factory manual.

Frango100 04-19-2012 03:02 PM

Re: 02 Overland- rough running at speed
 
I also bought the 2004 factory manual on CD and it has been very valuable over the past years. I also downloaded the same, for free, for models 1999-2004, eventhough there are some minor differences with the manual i bought.
But is seems that its not available for free anymore, at least not on that site where i downloaded it from.
And yes, MOPAR doesn't make the parts, they only buy them from selected manufactures and increase the price by a factor 2.:mad: I agree with 01Grand that if you know which brand is installed, you could also buy it directly from that brand for a lot less.

WJ Fan 04-19-2012 05:21 PM

Re: 02 Overland- rough running at speed
 
Quote:

Originally Posted by 01grand (Post 615823)
I don't mean to discredit anybody, 2005JGC has been INVALUABLE to this forum, and I'm sure has helped many users save lots of money. However, mopar doesn't make all of their own parts, ie. their spark plugs are champion, and for the WJ, the O2 sensors are Denso. While the dealer is a great way to know you are getting good parts, if you know who makes the OE part you can often find it cheaper elsewhere. I have been running OE Denso O2 sensors from rockauto.com for 3 months now with no problems, and have noticed a slight increase in MPG (old ones were also throwing a code for slow heat up time). I did take a slight risk by trusting the site when they said denso was OE, but when I pulled out the old sensors it was confirmed, they said "DENSO" right on them.

RE: Denso vs Mopar for O2 sensors- also read that previously, understood. But not Bosch, right? I am all about being cheap so long as quality does not suffer- see prior RE: trolling for used parts on ebay and craigslist. Local Jeep dealership cannot seem to get with the program regarding parts pricing- I only go there for common Mopar fluids and small stuff (which they usually need until tomorrow to get in...). In contrast, Steve White Motors in NC is really hungry for on-line sales and will often give me deeply discounted prices- relative to Mopar list.

WJ Fan 04-19-2012 05:27 PM

Re: 02 Overland- rough running at speed
 
Quote:

Originally Posted by Frango100 (Post 615862)
I also bought the 2004 factory manual on CD and it has been very valuable over the past years. I also downloaded the same, for free, for models 1999-2004, eventhough there are some minor differences with the manual i bought.
But is seems that its not available for free anymore, at least not on that site where i downloaded it from.
And yes, MOPAR doesn't make the parts, they only buy them from selected manufactures and increase the price by a factor 2.:mad: I agree with 01Grand that if you know which brand is installed, you could also buy it directly from that brand for a lot less.

RE: Factory manual on CD, I saw those on ebay, was not sure if they were the right thing to do, hence the open ended question. Now I have two good source suggestions, one for specs and the other for how to. Looking over the shoulder of the local Jeep dealership parts guy when he was on an "official" terminal, I noticed that Jeep has flagged tech tips that they provide to the dealerships based on what part is being pulled up, sort of like what google does with their targeted ads. Would love to get access to that! But these boards and forums seem like a pretty good substitute- probably even better. Which is another way of saying "thanks for the suggestions folks"!

WJ Fan 04-19-2012 05:31 PM

Re: 02 Overland- rough running at speed
 
RE: Factory download manual- does this source look legit?

http://www.tradebit.com/filedetail.p...erokee-factory

WJ Fan 04-19-2012 05:52 PM

Re: 02 Overland- rough running at speed
 
Quote:

Originally Posted by Frango100 (Post 615862)
I also bought the 2004 factory manual on CD and it has been very valuable over the past years. I also downloaded the same, for free, for models 1999-2004, eventhough there are some minor differences with the manual i bought.
But is seems that its not available for free anymore, at least not on that site where i downloaded it from.
And yes, MOPAR doesn't make the parts, they only buy them from selected manufactures and increase the price by a factor 2.:mad: I agree with 01Grand that if you know which brand is installed, you could also buy it directly from that brand for a lot less.

obrigado Frango.

Enjoy Brazil a lot. As a nation, this may be your century to finally move to a central role on the world stage. Atlanta has a local embassy and Brazilian/American chamber of commerce. Also enjoy Portugal. We breed Lusitano horses, and our top mare was imported in utero by Interagro farms.

FlyinRyan 04-19-2012 06:05 PM

Re: 02 Overland- rough running at speed
 
Have you done the key dance? What codes are you getting specifically?

The reason why I ask, is because if the PS pump has gone bad previously- it's a WJ, of course it has- and the fluid got everywhere, there is a VERY good chance it seeped into the front O2 sensor connectors. This will completely freak out the O2 sensors, dumping fuel and making the truck run like garbage. Stomping on the gas will throw the truck into open loop, eliminating O2 feedback, thus eliminating the rough running.I had an '02 myself and this problem reared its ugly head on a 1200 mile road trip, about 50 miles in. The dealer was USELESS because of the modifications I had (simply did not have time to troubleshoot myself), this sort of problem really made me want to rip my hair out.

It may seem unrelated as you mention the overheating, but heres some food for thought.....The '02+ has a hydraulic fan that is driven by the PS pump....if the PS leaked over time, it would slow or stop the fan from working, leading to the overheating.....

I dont know the tolerances for cranking compression for a 4.7, but 75-125 sounds pretty low.


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