Last Friday, as I was heading to work, I noticed a miss in the engine... I've got a 1997 5.2L w/ over 330,000 miles... It was just a single miss, and I thought it was just a fluke...

Later that afternoon, I noticed the idle becoming very rough...

Then the miss reappeared... The idle dropped to right at 500 rpm and I noticed smoke coming from the tail pipes, along with the smell of unburnt fuel...

A miss and a rich mixture? Sounded like an electrical problem to me. A quick check of the service records and I found that I was just overdue for a coil, plugs, cap, and rotor, so I purchased them over the weekend and put them on... The plugs were first, as I was trying to issolate the cause for future reference... That helped, but didn't fix everything... I repeated this step for the other parts as well, and eventhough everything helped a little, the engine still isn't running 100%...

What gets me is that everytime you start it, it runs perfectly - smooth idle, no misses, nothing - but after a few minutes, the engine slowly slows it's idle and the missing and smoking start up again...

Now, since it's doing that, I'm beginning to think the computer is going out... Is that what it is? I even went as far as to check the and toy with the timing mechanically, as I thought that could have been causing it, but nothing changed regardless, so I reset it where it was...

Also, while driving, at certain throttle positions, the engine seems to be starving for fuel...

Now, the fuel filter and pump on this thing are fairly new, as we replaced them both this winter, so something fuel related would surprise me...

Just to be sure, I ran some injector cleaner through the system, but it didn't seem to change anything...

I'm just utterly confused... At the moment, this is my only vehicle, so major repairsw/ lots ofdown-time are hard to do... The engine needs to be rebuilt, but right now I cannot do that... Is it the computer, or am I overlooking something else? Or is it finally just time to pull the engine out and rebulid the whole thing?

 

do you have an exhaust leak? had similar problems which were caused by a (significant) exhaust leak right behind the (empty) cat

 

Have you looked at your pre catO2 sensor?

 

I have a custom exhaust system - true duals, x-pipe... no cat... I plumbed the O2 sensors into the pipe thought... I replaced the after-cat sensor a while back, but left the front one...

I do keep getting a Catalyst Eff. BelowThreshold fault code though... Since I didn't have a cat, I figured that I'd just have to put up with that... Is all this being caused by the damn O2 sensors? I hate those frickin' things...

 

try to replace the frist O2 sensor as that helps tune the a/f mixture. the one after the cat is to monitor how the car is working for the most part. they make a sim O2 sensor for Post cat O2s so u dont get the check engine light.

 

yeah definetly check out those O2 sensors. that would be the next step after engine components. look for some cracks in the exaust manifolds. it might also be a crack in the head by the misfiring cylinder. hard to find but a possibility. that high milage of an engine i'd be leaning towards a head problem or head gasket blow up.

also is it white smoke? black smoke? or blue smoke?

white smoke- coolant
blue smoke - oil
black smoke-- you've got a MAJOR problem

 

See, that's the thing... It burns a little oil if it idles for too long, and the timing cover leaks a little bit, but the heads seem to be fine... I didn't check it this last time, as I was rushed, but only a few months ago I checked compression and they all passed and were within tolerances... I do not think that it is the heads...

The coolant is no problem, it stays full, although it runs around 205, which is about 5 degrees higher than it should be from whatI hear...

There is NO BLACK SMOKE - so I'm glad about that...

If I had to pick a color, I'd say it's blueish, but only slightly... The "smoke" isn't so much colored that you can see it, but when a light is behind it, it is visible... And it smells extremely rich...

I must say thought, these damn 02 sensors **** me off... Also, I thought it was the post-cat sensor that dealt w/ the a/f ratio... That's why I replaced that one last time...

Oh, and where can you get that dummy sensor so I don't get the code... The I hate people looking over and saying "Hey, your 'check engine' light is on" when I know the truck is running just fine...



I purchased a pre-cat O2 sensor today - it was only $55 (!) - and I'm going to put it on tomorrow... Hopefully that will fix the problem...


On another, somewhat related issue, why do people say that these trucks (at least the 5.2l's) can't run w/ two cats? Is it b/c of the sensors? If so, could you not run two cats but only read one? As much trouble as these things are, and as much as they can effect, I'm considering adding a high-flow cat to each pipe... But I want to keep the true duals for the added power and the incredible sound.

 

I had to make a midnight run with the truck, so for the hell of it, I thought I'd pull the connector on the pre-catO2 sensor... I had the truck running at the time, rough idle and all, so I could see if it made a difference... as soon as it was disconnected the idle cleared up... It ran almost perfectly after that... I'm going to put the new one in tomorrow...

 

I hope it fixes your problems, those pesky O2's sure can make an engine run like garbage sometimes they won't even throw a code. But when they are working they do a their job at keep the truck runningproperly...330,000 miles!.......good luck!

 

black smoke is usually a extremely rich mixture. oil tends to be blue/gray. and coolant is white and smells sweet.

i dont kno about dodges. i kno with the GM F-bodies u could order it from a parts site(hawksthirdgenparts.com and such)