Hey guys, got a 99 XJ, 4.0 L, with about 140k, and i am strongly considering giving it "the seafoam treatment." Engine right now runs great, but want to do this just as routine maintainance. See it as another way to squeeze a little bit better performance out of the already great 4.0! I've read up a lot about it, watched vids on how to do it. I think i've got a pretty good idea how to do it. But want to know if anyone else has done this, how they did it, what they got out of it, precautions, etc. The way i heard is to first get the engine to operating temp, let it idle, slowly pour about 1/3 of the bottle into the throttle body, then shut it off, let it sit for 5-10 minutes, then start it back up, and periodically rev it around 2-3,000 rpm until the smoke stops coming out. Let me know what you think, or if i missed anything in there. Thanks!

 

I just recently did mine, I would recommend using the SeaFoam spray. What I usually do using the liquid form is pour 1/3 in the gas with half a tank, 1/3 in the oil 50 miles before oil change, and the last 1/3 into the intake. On the 97 head and i belive yours is the same there is only one good vacuum hose to pour down and it primarily feeds off cylinders 3-6, there is a bung in place on the forward opening that i have used before as well to get better coverage. The stuff is good I love it. When you pore it in have a buddy hold the idle at ~2000 rpm and SLOWLY pore the stuff in it will drop the idle and be careful not to dump it as it could theoretically hydro-lock the motor. When you get to the last of the can have your buddy kill the motor right after you finish poring it in and let it sit 15-20 min, and then fire her up and drive it like you stole it put a real good load on it, ring her through the gears. She will smoke something fierce so if any of your neighbours are 911 happy let them know.

The spray you can just spray down the TB and it'll be a lot easier.

 

Thanks man! I may look into that spray. And its due for an oil change soon anyway, so that will work perfectly with pouring seafoam in the crankcase

 

There's a while bunch of threads comparing seafoam to mopars combustion chamber cleaner that's available at the dealership. All votes go for mopar and on the spreadsheet of statistics mopar hands down wins. There was a guy that sent it to a chemical lab and posted the results but that was quite some time ago. Worth a thought.

 

BG 44K in the tank will outperform Seafoam hands down.

 

Yup. Also plain water will do a good job de-carbonizing the combustion chambers and won't harm the catalytic converter or oxygen sensors.

 

Yup.

Pretty easy.
Get a cup of water, preferably something like a Dixie cup.
With the air cleaner off, hold the engine RPM at 2000 RPM or higher and dribble the water from the Dixie cup, which you've pinched to look like a spout on top, into the carb or throttle body. Go slowly and the engine will bog a bit. Stop and let it recover. Repeat until the cup is empty.

 

Ive been avoiding the seafoam thing on my 2000 for this very reason. With the 2 extra cats and o2 sensors I dont want to f### things up. Ive done it before with single cat motors but the last thing I need is to have to replace cats and a bunch of sensors. I know these motors are really sensitive in that dept.

 

44K is recommended by many touchy European manufacturers. You swon't be disappointed.

 

i used this method of decarbonization. except I wedged a big flat head screwdriver under the throttle and used my garden hose. unsure of the amount of water, but it was a lot. I made a video and it was about 5 mins long start to finish. it turns out the engine was running at about 4000 rpm most of the time. I kept spraying water until it stopped smoking black. I simply removed the air intake hose from the tb and sprayed it straight in.

this was prompted by a misfire which was caused by a piece if carbon actually getting stuck on a spark plug tip. big chunk. so I did the ethnic cleansing and put new plugs in it. no probs since.

 

That's frickin wild!!!

 

I highly doubt that I'm the only one who would like to see this footage

 

Should'a put some sand down the TB while you were at it. Valve polish and cylinder re-hone at the same time, for free!

 

Not sand. Bon-Ami!!!!

 

Put down the hose. Too easy to misjudge and hydrolock the engine.