Intermitten Missing Problem

[smoore0449]

I have a 4.0 sohc that has had an intermitten missing problem now for months. I have done everything I can think of to solve it. It has 61k on it. I have changed the spark plugs and wires, cleaned the MAF, replaced the IAC and TPS, had the 00M12 done on it and still the engine missfires when I am at a stop light or idleing in park. it has only thrown a code once and that was for a misfire on cyl 2 and 3. I checked the coil and it was ok. After the code was thrown that is when I replaced the plugs and wires and cleared the code. It is still misfireing but it hasnt thrown a code. The oonly other thing I notice is that iit wont do it on a full tank of gas. It starts doing it when the fuel is below a half a tank. But it doesnt do it on every tank of fuel. I am at a loss and dont know what toi do next. Please help.

 

[bipolarbob]

Couple of things

Change fuel filter
air filter

And check that the little breather hose from your oil filler neck to your air intake hose is on. Then put in some gas line antifreeze. It will burn through any impurities in your gas tank, then run some injector cleaner.

 

[smoore0449]

I changed the fuel filter already and ran water remover and fuel injector cleaner along with using seafoams deep creep in my intake.

 

[smoore0449]

Still no new fresh ideas? I am at 1/4 of a tank of fuel and my misfire is rearing its ugly head. Not to mention that since I have changed plugs and wires and put a tank of 93 octane in my fuel milage is down, way down. I am thinking that its due to using super and the fact that I have been in 4wd for the better part of the week due to all the snow we have up here.

 

[aldive]

Maybe a can of Sea Foam through the intake would help.

 

[smoore0449]

Been there done that as well. I used the deep creeep and sprayed it through the crank case vent hose opening on the air intake tube. I noticed no smoke nor any correction to my misfire. I am starting to wonder if there is any kind of debris on the bottom of my fuel tank that is getting stuck on the pickup tube when the tank is below 1/2 a tank.

 

[smoore0449]

One other thing that I noticed was I tested the output of my TPS and I get two different results. I put the test leads in the correct place on the TPS and I get a value of .96. When I move the ground lead to the negative terminal on the battery I get a value of 1.01. I have checked the connector to the TPS and its a new TPS everything seems fine. Which value should I be using?

 

[smoore0449]

Well I went out and readjusted my TPS to a value of .95 and it reads .98 when grounded to the battery. I also noticed that the seafoam was still in the intake tube and near the MAF. So I cleaned out the tube and used electronics cleaner to clean the MAF. Took it for a test run and the idle and shift points seem to be better. It didnt misfire but I will wait till I go through a few tanks of fuel untill I call the problem fixed.

 

[bipolarbob]

Did you put gasline antifreeze in? it will burn through any impurities as long as they are liquid.

 

[smoore0449]

Yea I put some in with the super unleaded I filled up with. I am thinking that maybe I will run another bottle of it through another tank full.

 

[sabatosh]

If you have over 60k on the truck and haven't changed the O2 sensors you might wanna start there. I noticed big improvement in acceleration and agility after just swapping one out. It was stumbling and missing a lot you could feel it, lagged acceleration jumpy torque revs with the sensor wires cut.

 

[Brandons]

Listen to the fuel pump too, if it sounds real bad and ugly then it could be the culprit, im on my 3rd now.

 

[smoore0449]

I was debating amongst myself about the O2 sensor but I would figure that if it was the sensor then the misfire would be constant. Other then the misfire the truck runs great. I have listened forr fuel pump noise and cant hear anything out of the ordinary.

 

[Brandons]

tis good the pumps alright, there quite fun to replace though. Is there any wiring problems you can see?? Or how bout powersteering fluid, crap like that.

 

[sabatosh]

Well it could be losing resistance, O2 sensors are the most wear ready part on your car at that age. I wouldn't expect to find problems elsewhere...because those are not wear parts.

 

[smoore0449]

Ithink I will test the resistace on the O2 sesors and go from there.