Sanity Check Please

My 98 Blazer (4.3L 4WD, Auto, 180k) has some issues suddenly. It runs great, no oil burning, or any of the issues with vehicles approaching 200k. I'm on top of the oil changes, etc. It's got a new fuel pump(a couple of months ago), fuel filter, air filter, and a recent oil change.
It will start fine and randomly will start to run rough, sputtering a bit and power loss, unless you put it to the floor. The engine light will come on at this time and will go away when the sputtering stops. When you stop, it will sound like it's about to stall and smells like sulphur. When driving in this condition, it will puke black smoke (not the too much gas kind). It will also just come out of this suddenly.
I think it's a toasted cat(the original one), but want some input first. We're quite far from anyone that can read that engine code, which, I know, doesn't help, but that's the downside of some privacy, right? Is it worth my cheking o2 sensors? MAF? Fuel filter again? Anything else? or should I just replace the cat?
Thanks again Automotiveforums.com!
-MD

The DTC(s) would be very helpful, but if it's flashing, more than likely it will show a P0300 series DTC. If that's the case, AC Delco spark plugs, distributor cap, rotor, and plug wires would be a good place to start, (due at 100,000 miles). The catalytic converter will not cause an intermittent problem, save your money.

Thanks for the response.
Well I did the whole tune-up. I had done this at 100k, but you're right, it's due again at 180. The cap and rotor showed enough wear to make me happy that this would be the issue. The right side plugs were VERY sooty, but the left were great looking.
I fired it up and the same old issue, not even a little bit of change.
I found someone who could read the code, and it just said engine misfire. No cylinder number or anything... even with a reset and driving until it happened again.

Sooooo...
I replaced the fuel filter again, plus put in the O2 sensor (that I had already bought) on the right side and tossed a bottle of injector cleaner into the tank and it's healed.

Cool, huh? Although, the engine light came back today, but without the sputtering. Oh well, I'll take what I can get.

With one side plugs sooty and other side ok, might want to pull the plenum off and check for any leaks.

If there is a fuel leak in the plenum, only the center plug will foul due to the location of the drain holes. All three plugs on the same bank fouling indicates a problem with the oxygen sensor.

I replaced that one already, and it helped... for a while. After a couple hundred miles of being healed, it's back to the same old act.
Extreme loss of power, in that it will barely climb a hill. Flashing engine light again and sputtering when it comes down to idle.

Here's what I've replaced:
Air Filter
Fuel Filter
Plugs
Wires
Cap
Rotor
Right side o2 sensor

AHHHH!!!!

Check fuel pressure and leakdown. Key on, engine off, fuel pump running: Must be 60 to 66psi. After 2 to 3 seconds the pump will shut off, pressure must remain above 55psi for 3 to 5 minutes. Post your results.

I tested the fuel system as you suggested (GREAT step by step, thanks) and everything was pretty good. It was about 58-60 lbs on the initial pressure, it would slowly drop to about 54, then stay there forever. When started, it ticks around 58-60 the whole time.
I checked the right side plugs again, still VERY sooty. Not sure if they're at all related, but I checked out the IAC, and the TPS, both are fine.
I'm pretty much out of ideas here... Maybe another fuel filter and Injector Cleaner?

I tested the fuel system as you suggested (GREAT step by step, thanks) and everything was pretty good. It was about 58-60 lbs on the initial pressure, it would slowly drop to about 54, then stay there forever. When started, it ticks around 58-60 the whole time.
I checked the right side plugs again, still VERY sooty. Not sure if they're at all related, but I checked out the IAC, and the TPS, both are fine.
I'm pretty much out of ideas here... Maybe another fuel filter and Injector Cleaner?


check the cat on the side that the plugs are getting sooty. the rotten egg smell is a good sign your cat is loaded up.

58psi to 60psi key on, engine off, is borderline low. Technically, anything less than 60psi is unacceptable. It will not cause the engine to run rich, as indicated by the sooty plugs. The pressure drop to 54psi is also borderline but holding steady indicates there are no leaks with the pump, injectors, fuel pressure regulator or lines. Connect an OBDII scan tool capable of monitoring the oxygen sensors and MAF sensor. Post the results with the engine at operating temperature and idling steady at 1500RPM.

Hold off on the injector cleaner for now. That system has 6 injectors and the odds of all three injectors on one bank having an irregular spray pattern are astronomical.

check the cat on the side that the plugs are getting sooty. the rotten egg smell is a good sign your cat is loaded up.

That is exactly correct. The sulphur smell comes from a rich mixture reacting in the converter, and if left alone, can cause the catalyst to overheat and melt down inside. 95% of the time, the catalytic converter is a symptom, not a cause.

58psi to 60psi key on, engine off, is borderline low. Technically, anything less than 60psi is unacceptable. It will not cause the engine to run rich, as indicated by the sooty plugs. The pressure drop to 54psi is also borderline but holding steady indicates there are no leaks with the pump, injectors, fuel pressure regulator or lines. Connect an OBDII scan tool capable of monitoring the oxygen sensors and MAF sensor. Post the results with the engine at operating temperature and idling steady at 1500RPM.

Hold off on the injector cleaner for now. That system has 6 injectors and the odds of all three injectors on one bank having an irregular spray pattern are astronomical.

I agree, if there was too little pressure, why the excess fuel? Plus, the pump is newish(I know, even new parts can fail). And, Gremlin, this only has 1 cat... I wish it was that straighforward!
I'm really thinking that it's the MAF that I already returned to the store... But why only an issue on one side? I already replaced the O2 Sensor on the right side, with no change in the condition. Here's some more info on the issue:
It takes about 5 minutes of driving to really show up... Right about the time that it gets to operating temp.
There's very little power, to climb a hill for example, in the 1500-3000 range. It will run fine and hold a steady speed at 1200-1500ish, but to accelerate, you need to pound the gas, wait for the black smoke and get it up into the 3k + range. Even then, it's not steady power. You can still feel it's lacking, well, it feels like a few cylinders are just along for the ride. Not really an ideal situation.
Once warmed up, it seems close to stalling when shifting, for example, when backing around in the driveway after a 10 mile drive.
When it gets really bad the SES light flashes.

Also, the right front fender area got crunched pretty good recently. Can you think of any potential for issues associated with that? We're talking fender, punctured battery, bumper, grill, hood... (it's a great wife story that I'll tell over a beer sometime) :)

Well, thanks for the continued help. I'll try to get that code read tomorrow.

So, after driving this thing for a couple hours and putting up with what feels like fouled plugs, it seems to come out of the issue. It's done this twice now. After driving 1 1/2 hrs, about 70 miles or so, it seems to recover. The SES light stays on, and sometimes flashes, but it runs normal. I pulled the plugs again to see and they were all perfect tan instead of sooty on the right side.
Any suggestions?
Again, this is our main vehicle and we're a ways from a shop with all the diagnostic goodies so any ideas, no matter how small, would be VERY helpful!
Thanks!

If the SES light flashes, or stays on, there is at least one DTC in memory. Retrieve the DTC(s), and post them here.

If the SES light flashes, or stays on, there is at least one DTC in memory. Retrieve the DTC(s), and post them here.

P0151, P0147 and P0300 Missfire Right Bank

This after a few hours at the dealer, they decided that Injector #1 is toast and #6 is Marginal. They quoted 500 for that job. I found the parts and gaskets for 140, and will jump in tomorrow when they come. Any suggestions, or anything special to keep and eye on?
Thanks,
Mike

When diagnosing DTC's, always start with the first one. Repair the problem, then recheck the OBDII system to make sure the DTC does not reset. If more show up, start with the first one again, and so on. DTC's do not tell you to replace a part, they tell you what circuit to check.

P0151 indicates low oxygen sensor voltage. It refers to the sensor in the passenger side exhaust manifold.

P0147 indicates a problem in the oxygen sensor heater circuit, for the sensor located behind the catalytic converter.

P0300 is random multiple cylinder misfire. Meaning more than one cylinder misfired.

I'd be very skeptical with their diagnosis. Cylinder #1 is on the driver side and none of the DTC's singled out that cylinder, only a random misfire. #6 however is on the passenger side, but again, none of the DTC's singled that cylinder out either. You might want to get a second opinion. It's next to impossible to completely diagnose all malfunctions correctly, without following the proper diagnosis and repair procedure for each DTC.

I completelt agree with you suggestion, if you have a place that can read those codes for you quickly. I got the list, looked them up and went to town.
The Pass side O2 was replaced and it helped a little.
I also looked at other people's issues and their solutions were all over the place, so I was really trying to shoot in the dark.
I cleaned the intake VERY well, and I have to believe that the amount of crap in there had something to do with it. I also replaced the #1 and #6 injectors. I'm still not 100% how they cooked up those two but they were afforable and I didn't want to be in this situation again. When assembling, I cleaned every component, including the MAF sensor.
TA-DA!
The SES light stayed on for about 20 miles, which I assumed was leftover from when I pressuized the fuel system w/o the intake attached(to confitm no fel leaks). But the light went away, and no issues in about 300 miles.
I really appreciate the help and hopefully this thread will be helpful to other too.