Ok I havent been on these forums for a long time, I drive a 98 Grand cherokee it has the 5.9 liter V8 in it and for the last 2 years since i have owned it.. It has been pinging when im like at 3/4 of the throttle or going up hills.. Its usually worse in the winter time..

I have had a 1+ quart oil loss every 3k miles on this engine. Inspecting the plate through the manifold however showed it was clean and not oily.. Using a mirror it looked ok too, and the dealership "CLAIMED" they stuck a probe in there and looked and it wasnt oily..
Well yesturday i bit the bullet and bought the pan for $54 on ebay with the 15 botls, and i got new felpro manifold and plenum pan gaskets and coolant, ect stuff i needed to do the job in all i spent $300 because of tools i needed and other stuff that bleeds you dr..y on projects like this

Anyway it took me 10 hours to do yesturday (i was working at a slow pace to make sure i didnt mess anything up) I put the pan gasket on dry liek everyone said to do.. Torqued al the bolts to 48 inch lbs going from bolt 1-2-3-4 in the pattern on the TSB picture.. Then torqued them to 84 inch lbs and then double checked it. and put everything back together... Oh and btw when i took my old pan off the manifold it had a good pool of honey colord oil in the back of it and the manifold itself was oily and the gasket was hard as rock and oily










Let it all dry overnight and ran it today.. It runs good and power seem to have improved and it doesnt ping.. So I drained the cheapo oil put in Max life and i've been driving it around for 3 or so hours today in town.. Giving it heavy throttle often.. It sounded good, but then i went on the freeway and went WOT and i hear the engine crackling again.. then a few mins later i tried it again and its pinging.. So i get off the freeway and driving around town up hills 3/4 throttle and WOT it doesnt ping anymore and its quiet...

I look in the manifold through the throttlebody and the pan is dry as a bone.. The manifold walls tho i noticed are shiny again from my light reflecting off a watery but in this case oily surface... The gasket on the right side is dry as a bone.. The PCV side its dry except its wet on the seem where it touches the walls of the manifold. Im not sure if its leaking through that whole stretch.. I doubt it would be leaking along the whole 5-6 bolts on that side.. So its probly oil coming down from the walls and getting on the gasket.. Thats what i would like to think... So why is my engine still pinging... and why am i seeing oily walls in my manifold... Is this just simply blowby being sucked in from the PCV valve ? I took the hose off the valve and the valve on top is oily so obviously it has to be sucking in oil vapors from the engine... Perhaps i should buy a catch can ??

I dunno this whole thing is just wearing me out big time..

 

Yes on the oil from the pcv valve(mopar only). And a big yes on getting a superchips or an sct tuner to eliminate the death flash you most likely have, that is causing the ping.

 

Try Seafoaming the hell out of it.
That should get rid of the rest of the carbon on your pistons and valve.

 

I did notice my intake valve were horribly blackend.. bumpy oily black.. I asked the jeep people on another forum if i should use some brake cleaner on them when i had the manifold off but they told me not too so i didnt..

I used soem seafoam but i really dont like that stuff... For some reason, whenever i use that crap my engine makes a loud POP/CRACK sound.. like horrible worst thing you can imagine sound for a engine to make.. It does this after you wait 5 min and turn it back on...

But against my better judgement i used half a can turned it off and waited 5 min.. and sure enough when it turned it on it made 2 loud metal smacking metal sound like my engine was destroyed... Then a big plume of white smoke came out for a second and then it turned blue.. so i got in the Jeep and drove out the neighborhood with a blue plume of smoke out my tailpipe but if i went to 1500 rpm the engine started to sound like a diesel... That scared me... so i drove around the neighborhood at 15-25 mph and then it went away after like a minute or so.. So 5 min later i went on the parkway and checked it and it was gone, so i went WOT like 6-7 times up to 80mph and it sounded good..


Question why does my engine make those absolutetly horrible noises when i use seafoam or mopar combustion cleaner ? I have no idea what it is.. Could it be from the oil the stuff melted off my valve and pistons that litterally exploding in the chamber ? Im pretty sure those sounds i was hearing was actual detionation.. So for sure i aint ever using a cleaner again unless it goes in the gas tank...

As for death flash i had checked my pcm codes and to see if i had stickers on it and no its a standard 91 octane PCM for the 98 Grand cherokee 5.9's.. The Grand cherokee had a pcm that ran at 91 octane and a performance one that ran at 92.

However that doesnt mean the previous owner had it flashed at one point but there is no mention of it on the carfax.. if he brought it to the dealership im sure there would be a mention of it.

 

My truck will ping every once in a while if it's carboned up from slow driving. I seafoam and it disappears. You may have so much on there it pisses your engine off. lol

 

My intake valves looked like these. and My piston tops look like this ..

http://bmw.keeler.com/specials/service.htm

http://www.teglerizer.com/triumphstu...hitey/cyl5.jpg

 

congrats on doing the plenum. it sounds like you were very methodical and its unlikely that you fouled anything up.

if your valves had that much crud on them, the pistons may be holding a carbon buildup too. try a seafoam or mopar combustion chamber cleaner.

a tuner like SCT or superchips will cure your deathflash, but it also advances the timing and makes the engine more prone to ping.

a spark plug change to 3923 might (or might not) help. its one heat range cooler.

a 180 t-stat might (or might not) help. dropping the engine temp can reduce ping.

higher octane gas 91/92 will reduce or eliminate ping.

 

carbon deposits turning loose and exploding in the cylinder.

it won't hurt it.

 

^^^ ditto

 

I had the same thing after replacing my plenum, the pcv side was wet with oil and running down side of intake to the bottom seem after replacing the pcv. I installed a oil catch can to catch the oil before it goes into the intake.

Where can I get Mopar combustion chamber cleaner?