I'm out of ideas on what the problem on my truck can be so I'm going to put up here and see if anyone has some input on my problem.

-1999 dodge ram 1500 4x4, 318, auto trans.

Now a little history before the problems...Awhile back i spun a rod bearing in the motor, so i pulled the pan to start to replace the entire set of bearings. I found in the pan what looked like a piece of oil ring off of the piston so I pulled the heads off and pulled the pistons. All of the rings looked fine, with the proper stagger, so I put them back in the truck. new rod bearings installed, and then put everything back together.

PROBLEM--- When i fired the truck up after reseting the fuel sync to 0, i had a miss..but only under load. The truck idles a bit rough when it is in park, but as soon as you put the trans. into gear, the motor starts missing really bad. the motor pops through the exhaust when your accelerating, and the diagnostic computer says there's cyl. misfires in cyl. 6 and 8.

So far ive replaced plugs, wires, cap, rotor button, ignition coil, entire distributor. Pulled the valve covers off before replacing the distributor to check the torque on the valves/springs and everything was tight. did a fuel injector test through the diagnostic computer and they all checked out fine. once I replaced the distributor and reset the fuel sync again........i drove the truck down the road and it still missing, popping through the exhaust, and now theres a rattle while accelerating like a spring retainer is loose or something. checked the cat. convertor and thats not clogged either.

I'm completely out of ideas on whats making the motor misfire..can someone help? I've been fighting this for a long time now and I want my truck back. PLEASE HELP!!

 

Checked all your sensors?

Shawn.

 

no, i havent checked every sensor on the truck.......just the ones that pertain to the ignition system. Ive never had a case where the truck didnt throw a code when a sensor was bad though.....and the only codes i have are for cyl. 6 misfire and cyl 8 misfire.

 

Crossed wires between 6th and 8th cylinders? if not ignition wires maybe the injector wires so that it's feeding the cylinders at the wrong time.

 

Check the plug wires/injectors first...... if those don't solve it, do a compression test. Two cylinders right next to each other misfiring isn't really a good sign.

 

wires aren't crossed at all, injectors are plugged in correctly. compression test shows that the number 6 and 8cyl.s are 15psi lower than the other 6cyl. i dont think the valve seats are cracked because the compression would be a lot lower than it is, and the valves are fine because once again i wouldnt be getting compression.

 

did a leak down test on the block and it looks fine.

 

Hhhmmm..... some of your data is indicating a leak between 6 and 8. Seems mighty suspicious that those are your two misfiring cylinders, and they just happen to be lower on compression than the rest...... Coincidence? Wouldn't bet on it.

What did the leakdown test show, and could you hear where the air was going on 6 or 8?

 

i used a block tester from napa. once the motor is hot you pull the radiator cap off and stick this tube in the radiator hole, fill it with the liquid that comes in the kit to a fill line, and put an air pump over top of it and while the motor is running, you pump the pump for 1 minute. if the liquid in the tube changes color to yellow, then theres a leak in the block(for example like the head leaking). the liquid didnt change color at all. what kind of test are you refering to?

 

Cylinder Leak down. Two gauges, and compressed air. Screws into the plug hole, just like a compression tester, but, pressurizes the cylinder (needless to say, piston needs to be at top dead center, with both valves closed....) and gives a reading of air pressure the cylinder holds. If supply side is 100 PSI, and the second gauge reads 80, that means 20% leakdown. (anything up to 25% is acceptable, supposedly, seems excessive to me, but hey, that's just me.) If you have a reasonably quiet environment, you can hear where the air is leaking... (rings/valves) if you test number 8, and have air blowing out 6, you have a problem. (one of the reasons I like to use 100 PSI, you can REALLY hear that leaking.....)

Sounds to me like that test is to check for combustion byproducts in the coolant..... If you have a leak between cylinders, you won't necessarily get that.