Topic: Any Dodge mechanics here?

[Bailgang]

AH HA!! We may be on to something now. After 2 years of begging for info on a Dodge site my BIL has been asking questions on someone on the site has FINALLY come up with a possible cause and it makes all the sense in the world and would explain the insane amount of blowby and poor compression #'s as well. Funny thing is that not only will my BIL be eating crow for his wild goose chasing but I'll be eating crow with him because it may not be the trucks ECU either and to add insult to injury it was something both of us had considered 2 years ago but figured "nah that can't be it" and didn't pursue it any further. I'm not going to say what we think the problem is just now because we may be wrong but I'll be going over there today to lend a hand and I'll report the news later. In the meantime anyone want to take a guess?

[05c50]

I'll take a stab, You have a plugged catalytic convertor causing the exhaust pressure to back up.

.......Paul

[Bailgang]

I'll take a stab, You have a plugged catalytic convertor causing the exhaust pressure to back up.

.......Paul

Oh you're a clever one Paul. Yep that's what we're thinking but if it is the cat converter it will be the most plugged up solid cat converter I've ever seen but with a previous problem a few years ago the truck had with a leaky intake plenum gasket which allowed it to suck in oil it explains how the cat could've plugged up so bad. With hindsight being 20/20 it all falls into place, something that was staring at us right in the face the whole time but we never put the pieces together. In the meantime I have to figure how to load my mig welder in the back of my truck so we can repair the exhaust system, the plan is to remove the cat, gut it out then reinstall it. If that turns out to be the problem which we think it is then we'll get a new cat.

[05c50]

A quick test to check for back pressure: remove the upstream oxygen sensors. That will relieve the backup enough to see if that makes a difference.

........Paul

[Bailgang]

A quick test to check for back pressure: remove the upstream oxygen sensors. That will relieve the backup enough to see if that makes a difference.

........Paul

My BIL did that last night and that's when the engine actually responded as in it not only would it stay running but would respond to throttle as well so right there said something was definitely wrong with the cat. Afterwards he immediately called me to tell the news and that's when everything fell into place and made sense.

[05c50]

I've followed this thread since the beginning and now I feel bad for not suggesting this earlier. It's relatively easy to check for plugged exhaust when the engine is completely together, but can be tricky to diagnose when it's torn apart. On the older vehicles with EGR valves, the trick was to unbolt the EGR to test. Hope it all works out.

.......Paul

 

[ekpent]

Back when unleaded fuel first hit the seen back in the day a lot of people were punching out the smaller filler hole and still using the cheaper regular leaded fuel which used a wider nozzle.  I was one of those dummies also and my cat converter on my Ford 351 truck became so plugged it would barely run. As soon as I cut the upstream pipe the roar was restored.
  My simple test back then was to simply put my hand at the end of the exhaust pipe and feel practically nothing coming out 

[Bailgang]

A bad cat was considered at first but this is the first time I've ever seen a cat plugged this bad which is why I disregarded it at first. I had a cat go bad once before but the car would still start and drive at least for a bit, this truck on the other hand acted as if it had just curled up and died. A local Dodge mechanic who initially looked at it said the ECU was bad and that's when the idea of a bad cat was shelved and all attention was focused on the ECU and the goose chase followed. I'm feeling just as stupid as my BIL feels about it because it's something we should've followed through on regardless of how far fetched it may have seemed to us long before the goose chasing was allowed to happen. Having a bunch of mechanics on the site my BIL was going to that kept saying "I had the same problem and this is what it was ..." did nothing but feed the chase more. You wouldn't believe how many claimed to have had the same problem and each one had a different solution. So much has been replaced that the only thing old on the engine is the dust.

[DH]

I haven't seen this condition in many years, and feel foolish missing it. It is indeed
a good possibility that you guys are right. It used to be fairly common. Shame so much was thrown at it to make it run. But, we're all human, and mistakes are made.
Unfortunately, we bark up the wrong tree sometimes, especially if the problem isn't readily visible. Glad you have it (probably) sorted. Also unfortunate that there were no map sensor related codes, as that might have lead you in a different direction.

[Bailgang]

Well we dropped the cat converter out, gutted it out and yes it was definitely plugged. A few years ago the truck was loosing oil somewhere but there was no leaks anywhere to be seen yet wasn't smoking either but it had gotten so bad that it went through 8qts of oil on a trip my inlaws had to Florida with it and that's when we found out about the leaking plenum gasket which turns out was/is a common problem with that engine. That was taken care of with a kit that not only supplied a new gasket but came with a 1/4" thick aluminum plate to replace the factory stamped steel plenum plate. The reason for this leak to be common is because the intake manifold is cast aluminum while that plate on the bottom is steel and being steel and aluminum have different expansion rates when heated, that's where the gasket fails and replacing that steel plate with the aluminum plate takes care of that. However it's all that time it was burning it's own oil due to the plenum leak is what spelled doom for the cat converter even though we fixed the oil leak before the cat actually plugged up.

Well anyhow we got it all back together, it started right up and ran and responded to throttle but still idled rough and sounded like one cyl wasn't firing, it was definitely and improvement but it still wasn't quite right so I changed the sparks plugs and pcv valve and that's when it idled smooth so we took it for a spin down the road for a few miles and just the fact that it was able to move on it's own power was enough to make my BIL and myself smile. The insane amount of blowby it was showing before is now minimal as well. The only error code the comp was showing was a bad O2 sensor which we were expecting because when my BIL removed the upstream O2 sensor to test the theory yesterday he damn near destroyed it trying to remove it. So to wrap it all up we have to replace that O2 sensor plus make sure the the fuel injection is synced with the crank position sensor, right now it's synced close enough to run but in order to get it running as good as it can we need to make sure it's as spot on as possible. Only problem with that is that it takes a different meter to do it which we don't have so we may have to take it to a shop that does in order to have it set correctly. Both of us were feeling pretty stupid that it took us so long to figure this out but the smiles on mine and my BIL's face when we finally realized we figured it out far out weighed any thoughts of being stupid. You wouldn't believe how much stress this has put on the family as a whole so before my BIL and I called it a day we decided to call my father inlaw to let him know by getting him on the phone, starting the truck up and revving it up so he could hear it over the phone and hearing it run was such a relief to my father inlaw that he started crying "happy tears". As far as I'm concerned I normally don't drink alcohol but my son left a couple of beers behind the other day for me to use for cooking bratwurst, well I tell ya what, to hell with the bratwurst because I'm going to drink that beer tonight. 

[05c50]

Great news! I'm glad you got it. Most people would have given up a long time ago. You must feel like you're walking on clouds.

..........Paul

[ThomasD883]

Don't kick your self over it. Remember how complex of a system an engine is. Great catch though, i think the O2 sensor being out will cause it to run cruddy because the ecm cannot get a read on the A/F ratio.