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Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3404
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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1998 dodge ram 1500 5.2l plugs and wires and

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1998 dodge ram 1500 5.2l plugs and wires and new valve grind completed 500mi
when accelerating or under medium load the truck has a severe missing but runs smooth when let off the gas....sometimes I can hear what sounds like hitting muffelled coffee can right under the dash where the tranny is.....not sure if it is mis-firing or the the problem is in the feels like transmission
HiCustomer welcome to Just Answer!.

Might this be spark knock (or ping), d?
Is it something that happens only after the engine has warmed to close to operating temperature?

A certain amount of power loss can be attributed to spark knock, but it won't show up as a misfire necessarily. Do you see a CHECK ENGINE lamp illumination as you drive?

What kind of "seat of the pants" impression do you get? Does it feel worse than misfire?
More like a "bucking" type of situation?

It sounds like this is a new situation since the valve grind.
Is that true?

Talk shortly,
Customer: replied 7 years ago.
yes it is like bucking....from severe to just like small bumps in the road...and it starts as you say ..close to operating temp.....also the check engine light did come on and reported misfire from #2....light does not stay on.......feels worse than a misfire maybe the timing is off too...I may be wrong about the transmission bad as it was I thought it was the transmission....thanx
Thanks..... and good morning!
I think your problem is exactly that... distributor position, d. I can't call it "timing" necessarily, but the problem you're feeling sounds a lot like what happens when the distributor isn't indexed properly after a repair like you had (assuming the distributor was removed).

With the actual ignition reference signal coming from a fixed-in-place crank sensor on your Magnum engine, the distributor only has two duties these days. It generates a cam signal for injector synchronization and distributes spark to the distributor cap. If your distributor housing is turned too far one way or the other, you can have an "un-sync" event going on or simply ignition cross-fire... either of which can case a driveability symptom that's beyond that of simple misfire, feeling more like the engine tries to reverse direction momentarily or even that it could be a driveline issue. I had the same impression the first time I chased one of these problems back in '92.

Adjustment of the distributor can be done two ways... with the DRB3 factory scan tool which requires a trip to the dealer or manually, using a digital voltmeter and enough hand tools for rotating and positioning the engine by hand and loosening the distributor base. The electronic method with the "durb" is quick and slightly more accurate in theory because the tech doing the adjustment can read degrees of cam-crank offset directly from the screen, adjusting the distributor until it's as close to zero degrees (perfect) as possible with the engine actually running.

The manual method takes a little time... about an hour... and yields results that are completely acceptable since you realistically have a five degree window of adjustment on either side of zero offset that works just fine. Expect to pay no more than one hour of shop time for your distributor adjustment, which would amount to right around $100 in most cases these days unless you figure to have a warranty claim with the shop that pulled your cylinder heads.

Crossfire can also be produced in theory by inductive electrical transference between plug wires, something that prompted the Factory to separate the coil wire from the rest of the bunch on the passenger side bank wire loom. It's now run through the intake valley, something that's not a bad idea with as much secondary cable length as we use on this engine. Having individual plug wires lying right next to the coil wire for almost 30" just wasn't a good idea. Separating the #5 and #7 plug wires on the driver's side-rear to prevent inductive crossfire there, as well as #8 and #4 on the other side of the engine is a good idea as well, since these cylinders fire consecutively. An early spark transferred from 5 to 7 would light the fire too soon in 7, resulting in a buck or attempted reversal of the crankshaft.

I'll be happy to send you info on setting your distributor up yourself if you're interested! Just say the word.

Talk later,
Customer: replied 7 years ago.
Thanx Ed........the distributor was not moved when the heads were removed......please send proceedure for re-setting the distributor....I'll check the ign wires also......I'm releaved it's not the tranny......Dan
I can't say for sure that it's not the tranny... but it just doesn't seem likely. The way you described it reminds me of what crossfire or unsync feels like and I've never actually seen a problem with the trans that caused something like this in the truck line.

I'll get to work on the reindex procedure now.
Talk shortly,
Customer: replied 7 years ago.
thanx Ed
Huge site problems.... back soon.
Still bad!
No problem!
Start rounding up some tools to begin. You'll need to loosen the distributor hold down bolt, which is 1/2" but 13mm works as well. It's not easy to get to, so you might have to use a u-joint with a socket or even borrow a distributor wrench with all the unique bends made in it for this application. Some of your larger auto parts stores might have these on a lend or rent basis.

Turning the engine to position it for the procedure is the next trick. While you could use a 1- 1/4" socket on the crankshaft bolt, I tend to use the alternator nose bolt for this purpose. The big nut is 7/8" and the shaft will have a 10mm hex cut into it as well, so you could use either size. The nature of your serptentine belt tensioner is that it won't allow clockwise rotation without applying more pressure to the belt... it just slips when turning the alternator in this direction, so I use a 15mm wrench on the tensioner pulley bolt and a motorcycle tie-strap (the friction buckle type) on the wrench to pull the belt tighter which frees up a hand. By working from the top it saves you the up-n-down movements needed to lie on the floor... position the crank... and recheck your work over and over again.

Next, locate the scribe marks on your crankshaft balancer that will be used for engine positioning. You'll find heavy cuts that indicate TDC for all 8 cylinders every 90 degrees, but those aren't the ones we'll be using. We need the V8 marking, which is cut pretty close to one of those heavy marks... about 10 degrees to the left... and might be hard to see thanks to the "scalpel" the factory used to make them... these marks are pretty light and might be hard to find. Another mark that will look similar (V6) is also on the balancer, so be careful to avoid using that one.

Rotate the engine until you align the V8 mark with the stationary TDC mark on the timing cover, which will be at about the 2 o'clock position as you stand in front of the truck. If you happen to go past the TDC mark or just want to try again, back the crankshaft up at least 20 degrees and do it again. This keeps all slack from engine timing mechanisms on the trailing sides of the gears and such, just as if the engine was running.

Now positioned, get the digital voltmeter turned on and be careful to not hit the starter as the key is turned to the ON position. Set your meter to 20 volts DC and connect the black test lead to battery negative or some good ground source. Touch the red lead to battery positive to verify a good ground connection.

You need to backprobe the tan/ yellow wire on the distributor pickup (cam sensor) wire, best done at the harness side connector... the one with the rubber weatherpack sealing at the wire end of the unit. Insert a paper clip into the connector until you see voltage shown on the meter, which could be 5v or something very close to 0v... which is the matrix this sensor operates with. Disconnecting the cam sensor right there momentarily to be sure that you have a good 5v signal and then reconnecting it may be necessary, since you'll either be on one side or the other of the 0-5v square wave it generates and might not be able to tell if you have a good connection at the lower value.

Once you're sure that you have a good connection to the signal wire, reconnect it and we'll move on to the actual adjustment.

Loosen the distributor enough that it can be turned easily by hand and then turn it clockwise as far as it will allow with the hold-down still in place.

Now turn the distributor counter-clockwise until you see a transition in the cam sensor output voltage. It can go from 5v to 0v or the other way around, but what you're looking for is the transition point, which is where you stop and lock the distributor down. Done!

Just like at the crank, I prefer that you back the distributor up a great deal and start over if you're not happy with the adjustment to get everything operating in its normal relationship. With the distributor shaft moving CW during engine run times, you need to turn the housing CCW to maintain that same effect with the engine stationary.

It's not rocket science and you have a full 10 degrees of offset that the PCM will accept in either direction, but you might as well set it as close to center as possible. Although the engine will still run at the limits of 10 degrees, crossfire can still happen with things being at the edges of the acceptable range. If nothing else, getting it as close to zero offset as possible extends the time between adjustments a bit!

So sorry to keep you waiting while JA sorts out its software issues. It was leaving me only about 15 seconds to bring your question up.... type a response... send... SPELL CHECK... and then send again. Not much room for content there! The original post for you was almost done, just getting cleaned up a bit and then this hit and scrambled the whole thing. I disconvered that I could use the EDIT function only within the last 20 minutes... which is what it took to clean the original post back up.

Keep in mind that the site is still messed up for me from this end, so getting back with you might be difficult... but I'll find a way!

Good luck and I'll see you in a bit!

Edited by Dodgerench on 3/13/2010 at 7:38 PM EST
Customer: replied 7 years ago.
Ed....I'm a little confused about the transition the transition point at 0v or at 5v
It could be either way, d. It depends where the engine is positioned when you come up on the V8 mark but it really doesn't matter.

The transition happens every 360 degrees of crank rotation, which computes to 180 degrees of distributor rotation... a half turn. Since what we're looking for is the transition point, it might be 0-5v or 5-0v... depends where you positioned the engine.

It's same-same, no matter. The transition is what we're looking for and will work fine from either direction. You might have more trouble finding the backprobe connection with the engine in the 0v position, so disconnecting the cam sensor momentarily while you backprobe and locate a good 5v signal might help.

Remember that the PCM outputs 5v at all times on the tan/ yellow wire as the signal circuit. The Hall switch in the cam sensor shorts it to ground (or not) to create the 0v-5v matrix. So if you see 0v chronically.... disconnect the connector to remove the shorting influence of the Hall switch (cam sensor) and then reconnect once you're sure it's been made.

Then do your distributor index from there. Just watch for the transition between one voltage to the other. THAT's the point where you stop and lock.

Are you working on it tonight? I'll keep an eye out for you if so!

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