Jeep Commander Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
21 Posts
Discussion Starter #1 (Edited)
So not sure what is going on with this 07 XK 4.7 V8... but here is my problem...

Had the Jeep die a few days ago while stopping at a red light in the morning. Read online the TPS or IAC is usually the culprit.. so I go to Advance Auto and purchase and replace both... now the thing if anything is worse. It will run, but the RPMs idle at 500 RPM average, and when stopping while in drive or reverse, it dips down to 200-300. Had a alternator/battery test done, and it all checked out (take that test for what it's worth), went back home, un-installed, and re-installed things.. cleaned the throttle body best I knew how, looked for vacuum issues on any hoses, removed battery power to reset.. started it up and it was horrible and kept dying. After a few times started running and was ok... until I turn the AC on high.. then it's like it has barely enough power...

Had to be at work so drove it about 10 miles with AC on low.. didn't die, but I could tell the problem of RPM droopage was still there...

When I got on a backroad with no one else around close to work, I cranked the AC up on high, and as I was coming to a stop sign, I turn signal on, braked, and turned wheel a little bit to prepare my turn, and as I stopped the RPM kept going down to 0 and died... started right back up.

I have tried new IAC, TPS, cleaned throttle body, checked hoses, batt/alt test (good)

What am I missing?

Have an appt on monday at the dealer for the ignition recall, and a computer flash recall for 4Lo I believe that were never done by PO.

PLEASE HELP!
 

·
Registered
Joined
·
309 Posts
I had something similar once with my engine. I went through all the plugs, opening and re-connecting all of them. I checked for corrosion in each plug and cleaned if necessary.
It took an entire weekend, but what ever I may have touched seems to have fixed it. It has never dipped RPM since.
 

·
Registered
Joined
·
359 Posts
I have a similar issue. Except my mander shakes... terribly. I initially thought it was spark plugs, they were due anyway, so I replaced them, and it was a no-go. after a few hundred bucks later, discovered it was misfires due to vacuum issue in a cylinder or two caused by bad valve springs.
 

·
Registered
Joined
·
21 Posts
Discussion Starter #4
**UPDATE**

So about a week or so has went by and what seems to have solved my problem was simple as spark plugs... the previous owner apparently never did this as these things were SHOT.. on a few the electrode was so worn down they were flush.. the gap on them all was ridiculous.

As far as the replacements, I followed the specs and went with Champion Copper Plus 439 plugs... They're cheap, and if you know the tricks to Advance's site.. you can get 20% off on in store pickup which makes this an UNDER $15 job (assuming you don't have the Hemi). Champion Copper Plus Spark Plug 439: Advance Auto Parts

So far I've seen no negative effects.. mileage went up a bit from 11.5 to 13-14mpg, acceleration is WAY better, call me crazy but I notice it actually goes when I push the skinny pedal, and most importantly, it doesn't randomly die in the mornings.. why only after I just start it up and get a mile or two in and dies at a light, I don't know.. but the problem has went away.

Only other things that were done were 2 recalls, ignition recall and a final drive flash that fixes the "Service 4wd" notification, and I had a smoke test ran to find my "check gas cap" problem, which upon testing turned out to be my leak detection pump (dealership did this and replaced it, $109 for test, and maybe $30 for parts).

So far things are still going good, anything changes I will update again.
 

·
Registered
Joined
·
3,037 Posts
All of those benefits are typical if you replace worn out plugs with new. Engine power, mileage and smoothness slowly deteriorate as the spark plugs deteriorate. Like the frog in a slowly warmed pot of water, the owner doesn't notice the slow deterioration. Then when you replace them with fresh plugs, suddenly the engine is back to its original power/mileage/smoothness.


Many an aftermarket ignition product company has taken advantage of this to make misleading claims that their "special" spark plugs will get you 6% more power or mileage, etc..... No, an engine with worn out spark plugs gets 6% less power/mileage, as soon as you replace the plugs with fresh ones, you get back that 6% that was lost. These companies get people to believe the 6% is from their "special" spark plug.


BTW, its rare aftermarket ignition products alone provide any additional benefits, usually the OEM ignition is more than enough, even if you've modified the motor and are making more power. A particular engine will need a spark X big and Y hot, any bigger or hotter gets you absolutely nothing.


Ask yourself, if a simple spark plug that costs no more than the others could really increase engine power and mileage, why didn't the company that builds the car use that spark plug? Because they can't, Chrysler tested your engine with several different types of plugs, they picked the one that worked best, note they didn't pick one of the ones making the claims that they make more power over other plugs.
 

·
Registered
Joined
·
16 Posts
Mongo, a few weeks ago I put a code reader on my '06 4.7 V8 Commander. ( new toy - had to see how it worked ) When the code reader was taken off the engine light was glowing steady amber. I've seen that happen before, Jeep says not to worry unless it flashes and it will go off after a few driving cycles. The time before it did. This time, it did not. It also started to idle roughly and suck gas, and had no acceleration at all. Code said a misfire on #7. If it weren't for you I'd have probably sunk a ridiculous amount of coin into a set of those "extra special expensive and better' spark plugs. But what you said makes perfect sense. Thanks for informing newbies like myself.

Back to the rough idling and engine light. The light has stayed on, I have not changed the spark plugs yet but I have bought a set and I have a date with a mechanic. Get this tho' - I put the code reader back on, same code for misfire on #7 came up, nothing new was added. Then I I cleared the codes. Wouldn't you know that Jeep got up and moved like she used to? No roughness to the idle, no sluggish performance. Why does this happen? Could it be that it doesn't need plugs after all, but it has a vacuum issue in the #7 cylinder? And why would performance be superior on one day and then ill on the next?

Thanks. I'm new. Trying to learn a thing or two here. :|
 

·
Registered
Joined
·
309 Posts
Some conditions will put the car into different safety modes to reduce further damage to the vehicle, other times the software just cannot handle having an issue.

I am a big fan of OEM plugs, with computers you want exactly what was designed for the motor to sense and run efficiently. I have never had a 'premium' plug register on a machine with the exact same feedback as an OEM plug (for expected range of cycle/frequency).

Best maintenance on the Hemi, or most motors, is to replace with OEM to bring it back to the expected parameters. Anything further will always require forethought and most likely a trip to the dyne tuner to correct fuel maps/sensor data. Which after all that you end up reprogramming for a specific profile just like the OEM was anyways.

Unless someone adds more air (pumped by something)+a higher capacity for exhaust volume (headers/bigger stuff)+more fuel, you really do not see any need beyond the already good OEM equipment.

Changing out the hard line vacuum tubes is also a great under $70 fix for any Hemi. The dealership sells two kits, you need both for a full replace.

My 115K motor ran like a champ once I brought it back to OEM... Then I messed with it :)

Although it may be time to get the heads refreshed and a look at the valve seats.

Dave
 

·
Super Moderator
Joined
·
5,693 Posts
I agree with you about the OEM spark plugs Dave.

I had all 16 of mine changed about 2 1/2 months ago at around 83,000 miles.

Just figured I'd do it and get it out of the way. I have aFe's Mach I cold air intake system and their 3 1/2" stainless steel cat-back exhaust, so I do have more airflow than stock going through my 4.7L - but it's nothing that the OEM plugs can't handle.
 
1 - 8 of 8 Posts
Top