Hey All,

So I have read all 102 pages of the plenum thread and still have a few questions.

I have replaced the cap, rotor, plugs gapped at .045, wires replaced twice w/TSB done as well as the PCV valve and the IAC valve TPS & MAP sensor as well as done the Hughs plenum fix and also took the head off the passenger side of the motor to make sure the head gasket was not burnt leaking gasses in between cylinders 6 & 8 and no cracks in the head or blown rings as there was no heavy wear on either cylinder walls. I checked injectors 6 & 8 to make sure they have power and used a injector tester to make sure they pulsate and ran a couple cans of seafoam through the entire fuel system.

When at idle the truck shakes/wobbles lightly on occasion like it is only running on 7 cylinders or less and when the wife ever follows me in her car she has said it reaks like unburnt gas from the exhaust. I have unpluged 1 plug wire at a time from cylinder 8, 6 and 4 cylinder and can hear that it is making a spark to the plugs. The one thing I have not checked is the fuel pressure and or pump. Now the one thing I did notice that happens on occasion and I can barely hear it is what sounds like a pressure release is I get on the gas for a few seconds and then let off

Now if I keep the hose connected from the PCV valve to the intake the truck always stalls out and will not stay running with out keeping my foot on the gas. If I unplug the hose from the intake it will stay running but at a higher idle and the niple on the intake has a LOT of suction from it. I do have the engine light on with a code of 25 which is the IAC which has been replaced already and the cat is hollowed out too. If I unplug the vaccum hose from the booster pump the truck will stay running and I do have a code for the IAC valve or vaccum leak but I imagine I have that due to having the PCV hose disconnected from the intake

I have a 95 dakota with 275k on it.

Thanks for all your help and insights.


vizi

 

You may have excessive blow by witch could cause it to stall. Try capping the vac port when you take off the hose. The rpm will go up because of the vac leak. Wouldn't hurt to do a compression test and check fuel pressure. Was the throttle body ever cleaned(physically taken off and cleaned)? It can build up carbon and cause issues. Also have heard of the throttle shaft wearing into the body causing a vac leak, You might want to look at that and see how worn it is.

 

Yup gonna rent the FP gauge from autozone or the like as well a a compression tester. At this point I hope its the fuel pump as I am tired of it running like this.. I could be wrong but I don't think it is the blow by scenerio as this all started one day on my way to work when the truck was making a popping/backfiring sound kinda bucking losing power almost like it was coming up through the TB and I was getting annoyed and floored it and ran it through and it stopped but started running as it is today.

I cleaned the TB when I did the plenum gasket .


vizi

 

could be a timing chain issue, I have done the timing chains on both of my Dakotas within the past 3 weekends.... both 318s, a 92 and a 96. The 92 had 203K miles on it when I pulled it apart (timing chain was a "might-as-well" kind of replacement, my water pump blew and I was only 5 fasteners away from it.... and I had previously noticed the timing chain cover seeping coolant anyways) now at 205K miles....and counting.

My 96 was also a "might as well" type of timing chain swap, as was the water pump while I was doing other repairs..... (I replaced the intake gaskets and had the accessories off and the antifreeze drained already, was over halfway there anyway, plus the fact that my other truck blew its pump recently, I had not previously put one onto this truck yet either) It had a lot of annoying little leaks all over... mostly oil, from the intake end seals, valve covers and front crank (timing cover) seal..... but the T stat and timing chain cover were found to be seeping coolant too, once apart) Though this truck has 20k less miles on it than the 92, it turns out that the timing chain on it had more slop in it than the one did on my 92.... I know that before I got it, the 96 has not had as good of care done to it as my 92 has had. It also has 3.91 gears meaning that the engine turns more RPM for a given road speed, as compared to the 3.55s in the 92... though not terrible it did have more sludge within than the 92 did....
with yours being at 275K miles, I can imagine how much slop that chain must have in it as compared to my 2.... being the problems came on "all of a sudden" I wonder if your chain didn't skip a tooth or 3.... the symptoms you mention, sound like they could be a timing related issue, as the chain wears, the cam timing becomes retarded as compared to the crank position.... meaning the valves open later in the combustion cycle than they should.... I did notice a difference in how my 92 ran after vs before and its chain wasn't even all that "bad" I thought it ran good with the old one but I can tell a difference in how it runs when I get on it..... my 96 has always been a bit sluggish in comparison to the 92 even with the different gearing (I would expect it to have more "get up and go/ not less with the gearing it has but that has never been the case..... ignition timing is a separate but related issue since the distributor is driven from the cam.... which is driven off the crank by the chain.....

 

So I changed out the timing chain and gears with the Cloyes c2830x set using the circle mark for the stock timing.. I did see a little slop on the old timing chain and it was still in time of course when putting it all back together I wanted to make sure the dizzy was pointing to cylinder 1 but forgot to do so.. if this does not work the only thing left is the fuel system or more so fuel pressure... After that I am completely stumped unless the motor / rings are just too worn out in which case ill just rebuild it as all the sensors are already new so.

Tomorrow I will finish up putting the belt on and hook the battery up and refill the coolant and maybe take a gander the the dizzy cap.



vizi

 

Timing critical on these magnums. If I were you I'd go ahead and do the usual tune up stuff. Plugs wires cap rotor, put a new pickup/ cam POS sensor on, ignition coil, and definitely a fuel filter. You wouldn't believe how easily a clogged up fuel filter can cause problems.
a.z.boy

 

So today I installed a new ignition coil and checked the fuel pressure and am getting 45psi while running which is correct. The plugs, wires, rotor and cap only have around 5k miles on them. It goes to the shop now on Thursday if I am unable to fix/figure it out by then. Gonna do a compression test in a bit to rule out serious blowby on the rings. Driving it I can hear a popping noise which sounds like it is backfiring up into the intake if I keep the PCV hose connected to the intake. If I disconnect the PCV hose from the intake there is serious sucking pressure comming from that nipple. Not sure if it is suppose to be like that though?



vizi

 

Ok so there's a chance your off a tooth on the timing set. If your cam is off it can allow fuel to go back up into the intake and ignite. Even being off by one tooth can do it. There's also a chance that one of your injectors is sticking open a bit when the truck is running, usually caused by small particles of debris that get I to the injector. What happens is after the cylinder goes through combustion the cylinder is hot and if the injector hangs open too long the heat in the combustion chamber can self ignite the fuel. There's some videos online of people removing injectors and cleaning them out. I've never tried it so idk if it'll work

 

Honestly though, if it has 275k on it and is having issues.... I'd go grab a spare motor from a scrap yard for a few hundred bucks n swap them out so you can drive the truck while you have the other motor rebuilt the right way

 

I just did a compression test on it and the PSI per cylinder is as follows.Remember its only cylinder 6 & 8 that are not firing.

Cyl 1 -181
Cyl 2 -170
Cyl 3 -180
Cyl 4 -175
Cyl 5 -155
Cyl 6 -160 plug is wet with fuel
Cyl 7 -135
Cyl 8 -170 plug is wet with fuel


vizi