Hello this is my first post. I just bought a 92 last week and am having some problems I am not sure how to remedy without dumping a bunch of money into it and not sure if it's going to help or not. I was wondering if someone might have some ideas where to start.

Anyways the issues I am getting major carbon in the exhaust. It's black soot and I am getting code 44. I don't know if the soot clogged up the o2 sensor or what is going on. It seems to lack power and the only time it smokes thick is when I rev it.

I just did a tune up new plugs, wires, cap, and rotor hoping it would fix the problem but it hasn't seemed to. Oil change was done the next day after buying it and I have put about 300 miles since and the oil is already black tinged not black like burnt oil but like the soot is in the oil too.

Yesterday it wouldn't start in the morning and I played around with it a bit till I ran the battery low and then I jumped it at first it wouldn't start so I pulled #1 wire off and put an old plug in it. When I did this it acted like it was going to fire so I put the wire back on and it fired right up. Massive carbon coming out with rev at idle there is no smoke. Checked the soot on the ground and it really has no smell no fuel smell or anything. Today I did the tune up and it still wouldn't start up so I pulled the negative wire off the battery to see if clearing the code would help and it started right up. It runs the same as it did before the tune up like it might be lacking a bit of power but I haven't romped on it. When I stepped on it a bit I did notice a puff of black smoke, I did it again and the same thing. When I got home I parked it and I revved it and didn't notice a spot on the ground, but I don't think I was looking when I revved it to see if I could see smoke as I was talking to my girlfriend at the time.

One thing I am not sure of is I gapped the plugs to 0.045 since it was on the rad support sticker and the Haynes manual said if there is a sticker indicating a different gap to go with that.

Could this be just carbon build up from it sitting for the a month or two before I bought it? I would think going over a mountain pass with it on the way home from buying would have blown it out but it seems excessive. Another thing is I dumped some Marvel Mystery Oil into the tank with this fill up so could it just be cleaning things out? The gas mileage has been horrible as well somewhere around 11 mpg. I don't really city drive either since to get into town from where I live the road is 50mph. I have noticed the SES light comes on when it's idling for about 1-2 mins or when I hold the throttle steady for a couple miles while driving.

Sorry for the long post just trying to be through with the problem. Thanks in advance for any help.

Forgot to add when I pulled the old plugs all of them were coated with carbon deposits.

 

Test your fuel pressure. It sounds as though you are getting way too much fuel which can be caused by a leaking FPR (fuel pressure regulator). It is a fairly easy fix. Watching the fuel pressure, specifically after the pump shuts off, will tell you whether you have a leak or not.

 

Ok thank you. I will have to figure out where the valve is and pick up a gauge. It did start this morning first try took a couple seconds but the fact that it did start is good.

The plug gaps, is going with the sticker on the radiator support the way to go?

 

Yep. Use the correct AC/Delco plugs for your engine gapped at what the sticker says.

 

The schrader valve to test your fuel pressure is at the back of the driver's side head, on one of the 2 lines disappearing into the upper plenum.

 

Thank you both of you. I did make sure to get the AC Delco plugs I read enough on here to know. I will have to find a dealer that has the cap, rotor and wires though but I just wanted to make sure it had a tune up and didn't want to wait for shipping. I think Carquest should stock them but didn't take it into consideration at the time so I will just have to upgrade soon again. I did make sure I bought the better of the available wire set.

 

when you pick up the cap/rotor, make sure you get the brass one. it's far superior to the crappy aluminum one that most people get.
regarding your plugs though, i've found that the Champion Copper Truck plug is better than the Delco's in these 1st gen trucks (i've owned quite a few of them over the years).

 

Yeah I ended up getting an aluminum one as I didn't know at the time so I will have to change that out too. I just want to get the current issue figured out then I will start to make sure I have everything correct as far as tune up parts. Seeing as it didn't make it worse yet they were affordable enough that I can eat my mistake on the parts this time around.

I have been a VW Audi guy for years so these parts are pennies compared to what I am use to paying for a tune up, not that I have the extra money to waste but one time around with truck is better than one with a European car. The whole tune up for this was cheaper than just the wireset for one of my past cars.

Any advise on where to get a fuel pressure gauge? Are they affordable enough to buy at a parts store or should I order one online?

Trying not to clutter the forum so I will ask here. What size of 17" tires will be close to stock I think the wheels are 17"x8" or 17"x9"? They have 225/50/17 on there right now but my speedo is running 7 mph off and it's annoying and I would like to have something I don't have to worry about if I want to take it off road.

 

i hear on that one. you can do a 4.3 for the price of a 1.9, and still have money left over for lunch.

regarding your tire issue. it's not cluttering if you post another question, just do it in the right section (ie; Tires and Wheels).
you need to remember that to maintain brakes, ABS, cruise, and speedo fuctions accurately, you need to stay within 3% of your factory size, and your tires are currently out by 10.47%
your closest tire size needs to be 245/60R17 (this gives you a 1/2MPH difference or 1.04%) but is 9.64" wide (compared to 9.25"). you can also try a 235/60R17 but this is out by 1.6MPH (or 2.67%)