Dodge Dakota 260K mile 3.9 V6 and loosing the battle with #5 misfire code.

[Tuesdak]

Friends 2000 3.9 V6 Dodge Dakota pickup. It has over 1/4 million miles, 260K, towing a single axle trailer loaded scrap metal to yard in it's past for The Boy Scouts. Still makes a trip 2-3 times a week, when it runs. (Wrong engine for the job IMO, but, it's what he owns and takes it easy on it as much as one can towing.) Regardless it's loosing the battle with a check engine light and #5 misfire code that has come and gone over the past year and 30K miles. It sounds like it's missing. Been to a couple shops that were not much help.

New injectors were installed. (No change.) Fuel pressure was said to be ok at the time. ECM was replaced long ago.

Last shop removed and resealed intake manifold. No change to how it was running, badly, with no power. (May have helped overall as they missed a TSB below.)

Found then and has now: IR temp gun shows the manifold for 3 and 5 is colder on the side closest to #5.

Due to high summer temps only the #5 was compression tested and it has 120 PSI.

Ran across this TSB:

various single cylinder misfire (1, 3, 7,) and especially 5
http://dodgeram.info/tsb/1998/18-48-98/18-48-98-v6.htm

Along with following the TSB: Replaced the entire secondary ignition with aftermarket: ACCEL coil, ACCEL Ceramic boot plug wires, rotor, plugs, coil harness adapter, and lots of 8mm Mopar wire standoffs and spacers. Ran great afterwards for the rest of the summer, but, intermittent SES light for the #5 misfire. (When the plugs came out for the TSB #3 and #5 were fuel wet. But there was a clear crossfire problem.)

Now it's back to not starting well and #5 misfire. Engine has a dull thud like running rich. Test light shows #5 injector firing.

As it's cooler a compression test for all 6 holes can happen. Valve covers will be coming off to check all valves move enough.

With the miles on the engine is there a way to test for timing chain slop with minimal disassembly?

Do the distributors and/or drive gear wear out enough to cause this?

Anything else to look for?

 

[BigPapa]

I would check all electrical connectors associated with the ignition. I bought a Chevy with a similar misfire condition that ended up being one pin in a 5-pin connector that was corroded to the point it had eaten both terminals away in both connectors. The PO had replaced all the parts you have and the ECM with no results.

 

[JR]

If the timing chain has never been done it's definitely due either way. Generally they're not much good past 125k miles give or take. Problem being mileage and power drop off subtly enough it's often not noticed by the owner. Here is the procedure from ALLPAR.

3.9/5.2/5.9
CHECKING THE TIMING CHAIN SLACK
NOTE: This procedure applies to all models that use a timing chain. [ol][*]Position a scale (ruler of straightedge) next to the timing chain to detect any movement in the chain.[*]Place a torque wrench and socket on the camshaft sprocket attaching bolt. If the cylinder heads are installed on the engine, apply 30 ft. lbs. (41 Nm). If the heads are removed, apply 15 ft. lbs. (20 Nm) of force to the bolt and rotate the bolt in the direction of crankshaft rotation in order to remove all slack from the chain.[*]While applying torque to the camshaft sprocket bolt, the crankshaft should not be allowed to rotate. It may be necessary to block the crankshaft to prevent its rotation.[*]Position the scale over the edge of a timing chain link and apply an equal amount of torque in the opposite direction. If the movement of the chain exceeds 1â„8 in.(3mm), replace the chain. [/ol]
There is also a TSB out there for adding a tensioner if he has to get into it.

Has the lower plenum gasket ever been replaced? They are notorious on the 3.9/5.9, symptoms include rough idle, lack of power, oil consumtion, random/multiple misfires.

 

[Wayne M.]

Find someone who still has a DRB or something like Autoenginuity that can do what a DRB can do. It can check crank/cam sync. There could be a problem with the flex plate and crank pos sensor, or some other issue like that. You can also do function tests like singling out injectors.
Of course I only reccomend this after a thorough basic principle check. With modern electronics, it's easy to miss the basics but sometimes diagnostic equipment can help square route that.

 

[Tuesdak]

Original timing chain looks like it's way past it's "best if by" miles.

Lower plenum gasket: I will double check if it was replaced when the shop 'resealed the intake'. Not seeing any oil consumption or oil on the plugs.

Engine runs and has run with a rapid speed change you can hear like a solid miss when at idle. Smells like it's running very rich.

I can rotate the rotor in the distributor IMO an excessive amount, but, there may or may not be a spec for this.

Autoenginuity like the following?
https://www.autoenginuity.com/wordpress/

 

[Wayne M.]

I can rotate the rotor in the distributor IMO an excessive amount, but, there may or may not be a spec for this.

Autoenginuity like the following?
https://www.autoenginuity.com/wordpress/

With OBDII vehicles, there is no mechanical spark advance. In other words, the distributor shaft is one piece. There should be no play there.

Yes that is Autoenginuity. Excellent IMHO.

 

[DonFitzwater]

That lower plenum gasket can be a hidden nightmare for the inexperienced tech. On the little magnum engines I work on, they all get the Hughes plenum plate kit and never go bad again.

Basics first, spark, compression and fuel pressure need to be verified good.

 

[Tuesdak]

The Cloyes timing chain is a work of art and will be part of a complete rebuild... Redoing the compression test, some 6000 miles later since the summer, found 50PSI in #5. Oil added brought it up. Valves look ok, regardless, heads are being sent out for rebuild as well as the entire engine. New cat going on as part of the rebuild as it's suspected the raw fuel from low compression ruined it. Ran really good when it ran, but, Check Engine light wouldn't turn off and hard starting while running bad till it warmed up.

 

[DonFitzwater]

Well at least you'll know its right.

 

[Tuesdak]

Update after the repair...

Pretty sure the camshaft's done. eXtremely Well Done. Sadly the owner is running a off the shelf Synthetic oil. Synthetic marketing term anyway... You could hang a fingernail on the camshaft where the lifters contact.

Block had a crack in a head bolt hole - scrapped.
Both heads had cracks.

Had to find a used block to build and they used new heads.

No more #5 misfire after literally replacing (not rebuilding or overhauling) the engine.

 

[Wayne M.]

Wow! I'd like to see the lifters. Did they survive? The rollers have come a long way in terms of durability.

 

[BigPapa]

Well, I guess all our electrical projections are out the window...........

 

[Wayne M.]

Well, I guess all our electrical projections are out the window...........

Certainly. These things are quite rare nowadays- right? This engine must have had a rough life early on.

 

[Tuesdak]

Long story, but, replacement engine was getting UOA with coolant in the oil. Shop closed it's doors so warranty = Poof!

Ran it a couple years till the reason for coolant showed up clearly. One day pressure blew a radiator hose off.

Got away with just replacing a head. Then sold the truck shortly after. He was the original owner.

Finally he is able to order a new RAM 2500 with a 6.4L V8 in it.