It has 97,000 miles on it and when I accelerate on an incline around 55-65 miles per hour it knocks horriable and I have to back off and it goes away. Any ideas on what this could be??
2007-12-08 09:43:47 · 5 answers · asked by dkcasad 2 in Cars & Transportation ➔ Car Makes ➔ Jeep
your motor is on its way out! try some Lucas oil that might put a temporary fix for a little while
2007-12-08 09:52:27 · answer #1 · answered by momo2765 3 · 0⤊ 3⤋
There is a Chrysler engine builtin on this issue, I bet you have the 4.0L as well. I had the same problem with mine and unfortunatly mine was worse than I wanted and nothing worked except taking the head off and having it cleaned at the machine shop ($60 and about 3 hours on my part) but here are a few things you can try.... might get long.
When present, carbon continues to glow after the combustion stroke so the glowing carbon ignites the air fuel mixture prematurely during the next combustion stroke, causing knocking.
The service bulliten says to do a engine hot soak. Drive above 3,200 rpm to rotate the valves....
Several ways to get rid of carbon. Take the Jeep onto the highway and blow the carbon out by repeatedly accelerating at full throttle to near redline in 1st and 2nd gears which will eventually blow the carbon out. You can do this over several days if you like. Or, trickle 12-16 ounces of water VERY SLOWLY into the throttle body while the engine is running, keeping the RPMs up a tad to keep from letting the engine stall. The water will break up the carbon very effectively and leave the engine sparkling clean. Trickle the water slowly enough that it will take 1-2 minutes to empty the entire container into the engine. This is the easiest method, especially if driving like I suggested in the alternative method isn't acceptable to you. (Another way is to take a spray bottle and just spray water into the throttle body...again take your time with this one.)
Another thing I tried was Marvel Mystery Oil, I put some in the gas and then started pouring it down my throttle body until it would almost stall (yeah so I stalled it a few times) I think I used 2 bottles of the stuff...it didn't seem like it worked until I took the head off and saw how much it had "cleaned" the valves and intake ports. Unfortunatly it wasn't enough to clean the valve seats.
So after all that I pulled the head and took it to the machine shop fix the problem and drove 1600 miles from VA to MO 3 days later.
Thats my .02 worth, hope it helps and good luck.
2007-12-09 09:56:15 · answer #2 · answered by Ashlee 5 · 0⤊ 0⤋
Mustanger is almost right..but you do not have adjustable timing, so not adjustable.
The later 4 liters do not have a knock sensor. He is right in that excess carbon will raise the compression ratio and cause this, but there is really no sure way to get it out without tear down. Yes, there are additives that could help, but will not clean it.
Let me ask this, do you live in higher altitude or marginal high.
The octane rating of most fuel is lower in higher altitudes, which ususally does not hurt anything, but you could be on the edge.
If you go to the next higher grade of fuel it should stop it or look for at least 87 octane at the pump.
You could have a vacuum leak with will cause a lean condition..rare, but possible. A lazy oxygen sensor will not supply correct fuel ratio. One last one..Now, I do not have a 1999, so you will have to look, but you should have a MAP sensor that changes the fuel settings and timing in the computer. Early one's, it was on the firewall connected via a vacuum hose. I am not saying it has failed, but if there is a leak or it is not working correctly, it will affect the engine.
Sorry, but cannot actually hear this, but this is how I would proceed.
Good Luck
Good Luck
More...Which engine?? http://www.jeepzj.com/faq/pingtsb.html
2007-12-08 20:18:21 · answer #3 · answered by Anonymous · 2⤊ 0⤋
Sounds like spark knock. Could be the timing is off a bit or could just be that the engine is carboned up causing higher compression than the regular gas can handle. Have the timing checked, if that's good try a tank of high test.
2007-12-08 18:04:53 · answer #4 · answered by mustanger 7 · 1⤊ 1⤋
Does it vibrate when it knocks? Mine had the dampener come loose... something to do with the shocks. It got shakey if I hit a bump. Could also be a cylinder thing.
You can take it to an AutoZone and they can connect it to that digital thing that will tell you what is wrong with it. I think it's free. At least, it used to be.
2007-12-08 17:53:02 · answer #5 · answered by Columbia 3 · 0⤊ 2⤋