I’ve been driving my project Dakota now for maybe a couple hundred miles, trying to work out the bugs. One of the things I’ve found is an oil leak at the rear of the manifold, not at the plenum, but rather the manifold to block mating surface. I’m planning to fix it at the same time I install a plenum kit. The engine was taken apart and reconditioned as part of a vo-tech class, overseen by an SAE-certified mechanic. I wish they (the class and instructor/mechanic) had re-assembled the engine with a plenum kit, but they instead put the factory parts back with new gaskets. Oh well.

So, drive-ability wise, I have this little issue. The engine is running rich, backfiring through the exhaust when you let up on the accelerator, sometimes taking longer to start when its warm (when it catches, it chugs to life like its flooded), and it also seems to lack power under extreme load. The observation about lacking power is a little hard to judge, as the truck had a V6 previously and so I don’t have a “before” comparison with the 5.2L V8. It’s much more powerful than before, but I had a full size Ram 1500 with this same motor and it felt as fast, maybe faster, than this lighter Dakota.

I say “little” issue because despite how this sounds, the engine actually runs well otherwise. When started cold it starts right up, and when its warm it usually does so as well, though not always. Sometimes it will stall at the first stop sign I come to (could be a sticky IAC), but it only does that when its cold. I never detect a “miss”, whether idling or accelerating, in fact it sounds very smooth. When I put my foot in it cold, it feels fairly strong, but by the time I make it to the highway it doesn’t seem to have quite as much pull. If I run through the gears it sounds great, but seat-of-the-pants tells me it’s not moving like it should. Does that make sense?

OK, so I pulled the plugs yesterday to see if I could tell anything. On the passenger side, the two rear-most plugs (cylinders 6 and 8) look like they’re varnished with shellac, but otherwise clean. They’re too clean looking, like they’ve barely been used. I’m not losing any coolant, and my oil isn’t showing any foam at all, so I don’t think there’s an issue with water in the cylinders. Is this an indicator that injectors are plugged and combustion isn’t taking place? Is this related to the manifold leak (not my bet)?. Or do I have a stuck valve? None of these makes sense, given that the engine starts so easily and runs so smooth. I will say that when I assembled everything I flushed the fuel lines, but not the fuel rails, and I’m wondering if some scale didn’t clog those rear injectors because the motor sat a couple years before being installed.

I’ve looked at plugs many times over the years, but I’ve never seen plugs look quite like this. They’re telling me something, I just don’t know what it is. I’m hoping one of you smart folks has seen this or can figure something that can point me in the right direction. There’s always something new to learn.


Here's the plugs:








This picture shows what comes out the tail pipe after its run for a short

time. Its water, but very sooty and black:








This is the tailpipe:

 

Did you put the v8 computer in? Or are you sure they put the v8 computer in? Looks like those two cylinders aren't doing squat which would explain the lack of power and unburned fuel coming out the pipe.

 

I did the installation, and it's the correct computer for a '92. This is one of two computers I've run in it since putting it on the road. The first is a plain '92 V8 ECU, the one that's in now is a Mopar HP for a '92 5.2L. Both computers had the same symptoms, although it runs a little stronger with this one.

 

I agree ragged that 8 and 6 plug do not look used. Have you tried pulling them one at a time and cranking it to see if they are getting spark? You have given me an idea for why my 4 banger Ram50 has so much soot coming out the exhaust and MPG's worse than the V6.

 

I haven't tried checking for spark at those two cylinders yet, but I think you're right, I need to have a look. I'm just struggling with the idea that it sounds fine when its running.

 

If you've got spark then I guess I would try to see if the injectors are firing in those cylinders? Maybe switch an injector from one of the cylinders that look good? I have no idea how one might check an injector.. Maybe with a 9v battery and some wire?

 

I can try the metal-rod-held-against-the-injector method to see if those 2 injectors are clicking, but if the injector's screen is clogged with sediment, it can click away and still maybe not deliver fuel, or a decent spray pattern.

I think I'm going to replace the ICT sensor. The one that's in it is new, but that doesn't mean its good. Seems like a good place to start, at least it might account for the rich running, if not the clean plugs.

 

Im probably not much help here, but if it was mine, I would check compression to verify its ok. The other thing I would like to check would be to verify the timing chain is not 1 tooth off. I know on a chevy, it will run 1 tooth off. (with a new chain) It will be down on power, but otherwise not run that bad.
Also, I would switch the plugs to different cylinders and see if the problem follows the plugs or not. After that, swap wires to diferent cylinders.

One last thought, any chance the injector wiring is mixed up?. ie: cylinders swapped?

 

Been away for a while, but I'm finally getting back to this rich running/power loss thing. I think I failed to mention it before but the engine feels strongest, and runs best when it is first started and isn't warm.

Ragtop, I'm taking your suggestion, I'm gonna do a compression check. I just picked up a budget-priced compression leak down tester from Harbor Freight, I think it'll tell me something about what may or may not be going on in the passenger side cylinder bank. I'm starting to wonder if I might have a blown gasket or a cracked head. Hope its not the latter.

 

My V6 runs better cold. I put the 180 thermostat in, down from the factory 195, and it has helped. It also occurs you may have blow by and a air flow problem causing that carbon. The choke on my 85 4 banger was not open enough (Weber carb). That seems to be where the carbon came from because it was being flooded then when it eventually starts it doesn't burn it all cleanly.