I was out Christmas shopping the other day when my 02 4 door began to act up. While driving slowly through the lot looking for a space, the truck began to idle really rough and stalling out if i did not keep my foot on the gas. I limped to to the nearest auto parts store and had them check the codes to find a random misfire (of course) and a misfire in cylinder 2. replaced the wires there in the parking lot, no change. limped home and parked it, began researching issues. It has thrown the cyl 2 code twice, clearing itself both times but has thrown seeming endless random misfire codes. Also, after I parked it, I find it is blowing raw fuel out the tail pipe. tested and replaced ignition control module and coil, no change, inspected cap and button, looked fine, checked fuel pressure at the schrader valve, running a constant 50, which is low, obviously. i'm not quite sure, however, if low fuel pressure would cause the motor to miss that badly, and push raw gas out its ***...i had initially though it was the regulator, but the pressure does not bleed down very slowly for that to be the case, it lost 25 lbs. pressure over 12 hours.also, the fuel filter was replaced on halloween, although i have not ruled that out entirely. there just seems to be something i'm missing, something just out of my reach...Can't afford a mechanic but i am rather capable if given the right information...any ideas?

also have my freeze frame data for the random misfires, as follows:
Fuel System 1 OL
Fuel System 2 OL
Calc. Load % 16.86
ECT (F) 104
STFT B1 -2.34
LTFT B1 0.00
STFT B2 1.56
LTFT B2 0.00
MAP (inHg) 21.85
Eng RPM 1072
speed MPH 3
MAF (lb/min) 3.76
TPS % 21.18
in case any of that means anything to anyone out there.

 

If you have raw fuel coming out the tail pipe and do not have short term or long term fuel trim (STFT & LTFT) problems, then there is something very wrong...

Here is the P030x thread:
P030x - Random/Multiple Cylinder Misfire Detected

I'm not sure how helpful that will be though since your problem is coupled with raw fuel out the tail pipe... You need to get this fixed sooner rather than later or you could end up with a plugged catalytic converter as well.

Do you have any exhaust leaks between the engine and the upstream O2 sensors (those sensors which are located closest to the engine on either side)?

 

well that is not terribly encouraging...
There is no evidence of any exhaust leaks that i can see.
I was confused by the negative reading in the first bank of the STFT, i was not aware that could...uh...be.
as for the cat, i'm not terribly worried about that, as i'm in my brothers loaner at the moment...geo metro...it's like driving a motorized aquarium...
Also, as i understand it, the CKP is responsible for telling the fuel metering body which cylinder to supply with fuel, so if that is faulty, could it cause the spider to shoot fuel at incorrect intervals thus allowing the piston to push unburnt fuel out the exhaust port before or after the plug sparks?

 

so last night after pressure testing the fuel line again it gave me readings that checked out within the parameters. I removed and cleaned the filthy crank position sensor, no change. i turned it on and let it idle till it reached operating temperature and rechecked the OBD and got the same random misfire code, although this time without the freeze frame data the only thing i learned was the sulfur smell was enough to drive us out of the garage when the door was wide open. incidentally, i seem to have been mistaken about the fuel out the tail pipe, turned out it was more likely mass condensation mixed with fumes that was coming out...my next course of action is to test the cat by pulling the O2 sensors to see if that reduces the backpressure and lets the truck breathe easier...if thats not it then i dont know where to look next, I'm running out of ideas...

 

That would be my next suggestion. Since you have revised your symptoms to not include raw fuel out the tail pipe and now have noted the sulphur smell, it definitely sounds like a catalytic converter issue. Pulling one of your upstream sensors completely will set a code for that sensor, but should relieve the exhaust pressure and allow the engine to run easier.

 

i was hoping that it would throw an o2 code last night while it ran but never did, not sure what their good for if they don't read what is obviously too much fuel in the exhaust...dunno, should i pull both upstream or would one be enough?

 

One should be enough.

O2 sensors do not sense fuel, but rather, they sense free oxygen. A clogged cat can do some weird things in the combustion chamber that really doesn't affect free oxygen in the exhaust as much as you would think.

 

well i pulled them and it idles a bit smoother, and the sulfur smell is gone, but the misfire continues, as well as backfiring, though i would assume that has something to to with open o2 holes. i am concerned however, because generally a plugged cat is the symptom of something rather than the disease itself...anyone know anyone is Indy thats got a full diagnostic scanner that i can talk to the PCM with? Also, would a cat clog suddenly like that? truck was fine one minute and not the next...

 

Thinking about taking the truck into the dealer to have them hook it up to the diagnostics machine...pertinent thoughts?

 

**UPDATE** I had my mechanic friend come over and hook it up to his bi-directional scanner, he found that the PCM had logged over 1100 misfires in the No. 1 Cylinder in the two hours of run time since it began acting up, so yeah...spider is/was bad. I also decided to go ahead and change the lower intake gasket, as it's leak had begun to increase, dramatically. anywho, got the upper intake off and found that i also had a leaky FPR, though it passed the fuel pressure test. Picked up the new Delphi spider with the mini injectors and ye olde lifetime warranty from Linder Fuel Injection (plug) in Speedway, IN for the same price as knockoff reman at the parts stores , so yeah, win there. Had the Intake cleaned and started putting things back together when one of the new intake bolts i had bought failed and broke off in the head while setting it to torque...so off comes the head, and also goes into the shop where they remove the bolt so we can re install...only to find out we need a angle torque meter...well we get that, put it all back together and it runs like a champ, except it doesnt want to start...so i get it going and take it to the dealer to have them do a CASE relearn and find that the dist was advanced one tooth due to the oil pump shaft being in the way ...even improved the fuel economy by about a 1/2 mpg, not great, but compared to my brothers Ram with the 4.7, my blazer looks like a smart car...we did have a bit of an issue where i thought that it was still leaking coolant, but a close inspection revealed a hose clamp out of place...anyway, i though i'd bring some closure to the thread and thank everyone who helped. now its back to mods rather than repairs...