92 Dodge Dakota 3.9 L automatic.

I recently developed some kind of noise (sounds somewhat similar to detonation....i.e. marbles in a tin can). Gets worse when you raise the RPM. I tried listening with my stethoscope, I can't tell if it's coming from the rear (distributor end) or front (timing chain end). There are TSBs from Chrysler about the distributor bushing and the timing chain (already ran the engine without the serp belt, no change whatsoever to noise). TSB for timing chain also mentions that the loosy-goosy chain can sound more like it's coming from the valve train, even though it's not. Oil pressure is good. If anything, it's too good. Mechanical gauge says 25-30 PSI at idle, 70-75 at 3000 RPM. I have not had the valve covers off, but looking in the oil fill cap holes, I'm more than a little suspicious that the oil pressure is that high from frequent oil changes. Ignition timing bounces slowly from 14-24 degrees at idle. Off-idle, it's a steady 40 degrees. These numbers are through the scan tool, someone is borrowing my timing light. One thing I noticed is that I'm getting a lot of fluctuation when I try to adjust fuel sync. +1 to +8 and everywhere in between and it changes pretty rapidly (My other Dakota bounces around by 2 degrees at most (and it also makes no abnormal noises either). The truck goes down the road pretty well, noise aside, all things considered.

Anyone got any suggestions? Anything else to check? Distributor bushing (I really don't think it has more than 3/16 inch play, but I did not put a ruler on it)? Timing chain? Or do you think I have a problem unrelated to either? I've put so much damn work into this truck already, I'd like to have a better idea before I do any more, because it's really pissing me the eff off at this point. The car gods are not smiling on me. I have a 'spare' engine I just bought a few weeks ago dirt cheap, but I have no idea if it actually runs like the guy claims it did (he bought the donor Dakota for the frame to use for a 50s Ford truck cab).

 

Take off the distributor cap, turn the engine by hand until the rotor is pointing to number one firing position, and the crank shows the balancer at TDC. Once there, try turning the crank backwards, and see how far it goes before the rotor starts moving. That will tell you how much slop you have in your timing chain.

 

Please post if you figure out the bouncing fuel sync. Mine does the same thing. Closest I could get to zero is +1 and I do not think it sits there even though the dist anchor nut is tight.

 

HeyYou, I got 16 degrees (by the marks on the damper) before the rotor started to move backwards (roughly an inch of the damper's circumference). Seems like more than a bit, but I've never used that trick before. What do you think? I was trying to google that trick, but I did not come up with any definitive answers.

OneMore, I was actually aiming for +4 to +6. I've read a couple places that they run better there, and my 94 Dakota (not THIS dakota ) runs better there as well. I will definitely let everyone know for posterity, assuming I don't end up 'just' swapping out the engine.

 

That's WWWAAAYYY too much slack; I'd be tearing into that timing chain before your pistons made intimate love to the valves (or vice versa!)

IDEALLY there would be none; but there will be some.

(That's why you can't get fuel sync set; the sucker's bouncing around in that 16 degree window!)

For a comparision, the timing spec for my 1988 is 10*BTDC, +- 2* ...

(Yes it's settable on the LA 3.9s and 5.2s; and on several of the 4 bangers. NOT settable via the distributor on any of the Magnums.)

RwP

 

Thanks Ralph. Just kinda surprised it runs as well as it does for a timing chain issue. My Shi, I mean Saturn, had a timing chain issue, and besides being audibly obvious where it was coming from, also ran even poopier than it usually does. Only reason I was even remotely suspecting timing chain on Dakota was because of TSB about noise being hard to pinpoint / sounding like it was coming from valve train.

 

+1 is the only spot it would stay stable in. If I tried to get +3 which I wanted to try out because I read the same thing you did, it would bounce from +10 or so to -6. The only setting it would just sit on is +1 I had a pretty new timing chain and tensioner and cam sensor in the dist too. I might try out that hey You suggestion once I get some time and this smoke clears.

 

Thanks HeyYou and Ralph, timing chain seems to have fixed the mystery psuedo-lifter noise. Old chain was definitely loose, Not as loose as some of the videos I saw on youtube, but loose enough that when applying finger pressure, it came within 1/8 inch of touching the oil dripper.

OneMoreDak, after I did the chain, fuel sync was still jumping, but not as badly. I was aiming for +6, it was jumping between +7 and +4 (before the new chain, it was jumping between +1 through +8). I swapped in a new distributor that I had laying around, and now it's holding pretty steady at +6. So a little bit of column A (timing chain) and a little bit of column B (new distributor). Maybe...

 

Cool. It should definitely run better for ya.

 

What is a good reliable Distributor brand? The pricing and names on RA don't impress. One is $40 and one is $115 and several in between.

I grabbed the one on wholesale closeout and a cap rotor combo. Maybe that'll fixer