Update:
Driving this morning...hesitating again at lower rpms. Then after while the check engine light flashed a bit and then shortly after that went out, and from that point on it's been driving like a champ(a thirsty champ, but one nonetheless). Still surged at idle a little bit.

SO...did a scan of the pcm. P0300 misfire is the code. TONS i mean thousands of misfires on cyl 4. O2 sensor 3 pegged (dead) causing the trims to be really fat(makes sense with the thirsty fuel mileage).

SO...ran seafoam through intake, throttle body cleaner, plugs and wires changed. Voltage test...no issues there.

Went for a run and rescanned. No more misfires, truck still running strong, no hesitation..surging gone.

So...is sensor 3 the one in front/behind the cat? Would that one cause the rich compensation and be killing my fuel mileage? It would also be responisble for misfires no if it was running rich?

If that is the cat o2 sensor, is it just 7/8ths inch wrench, un plug and swap or are there any tricks to it?

THanks!

 

B1S3 has nothing to do with engine operation. It is a catalyst monitoring sensor only. If you were watching the actual mV output, the post cat sensor will be flat lined under normal conditions as it shows that the converter is working properly.

 

Crap! I thought we figured it out finally.

Any thoughts as to why the trims are fat? It must be sensing a lean condition on one of the other 02s? There still is a faint ticking from under the truck...perhaps an exhaust leak?

 

By fat, how off are they...? What are your LTFT1 & LTFT2 values?

 

If I recall correctly, the LT's are showing ~ + 10%. Short terms
are also + 7-10%.

That's interesting as the scan shows a dead straight and steady
output. I was expecting to see some deflection +/- from the
nominal value.

Mind you, the motors I'm used to monitoring are performance
engines with tweaked out fuel curves, and high flow inefficient
cats.

These types ofengines say a prayer, and roll dice before their
emissions tests

So...if you're saying that a dead flat line is fine, then we'll
move onto other areas.

When we pulled the plugs last night, I had a look. There were
certainly a couple that looked richer than normal, however this
was after the Seafoam test so it's tough to say whether the
plug read was indicitave of the positive trim readings.

Besides that, a plug read should be done with a fresh plug of
course.

We're getting closer to a solution. Everything that has been
done has certainly improved the performance. During the cruise
last night, there were zero misfires.

The previous numbers showed tens of thousands on some cylinders.

#4 was over 40,000!

Next step is to look for an exhaust leak between the flange
and catalytic, as well as check the coolant. There is an odd
'gurgling' sound just behind the dash area which I suspect are
the heater core lines.

 

Well we solved the coolant issue... while the overflow tank was at the correct level the rad was nearly empty I fought overheating all yesterday and finally could let it cool down enough to check and sure enough the rad was really low. I guess teh previous owner didn't take as good care of the truck as it appeard. Now with a full rad the temps are perfect, the gurgling sound gone and with about 350kms on the truck since our tuneup night not a single performance issue.

Still would like to better understand the fuel trims and we'll be scanning for exhaust leaks probably thursday but i'm a lot happier with the truck now than i was a week ago.

 

Okay... just when i was getting excited about having no problems... today on the drive to work i had the misfiring/hesitation at low rpm/low speed again. I think it has to be electrical..only difference today from the past couple is it's raining and the roads are wet. Doen't seem to happen on dry roads but on wet yes.

I know the rubber 'shields' in the wheel wells are pretty much gone so i'm wondering if too much water is getting at something around there? The plugs are all tight.. i dunno.

Any ideas?

 

Wow...coming home today i didn't think i would make it The car shuddered so much i could barely get it going..i limped it home as carefully as i could. Ih ave a check engine light again and it was misfiring like a bitch! It's really damp and raining right now... what could cause such extreme misfiring if it got wet or moisture in it??

 

I'm sorry, but I just can't seem to focus enough right now to read through this entire thread to see if you have replaced the cap, rotor, and wires... Have you done this? Sounds like an ignition problem as it is affected by moisture.

 

Sorry...i guess the thread has become somewhat cumbersome I appreciate you taking the time to begin with! We have changed the plugs and wires previously.

Update: Decided to spray the coil and distrib cap with wd40 and seemed to improve the idle. Talked with purss-yn and he was thinking coil as well. Looked for arching, scanned pcm(p0300 again). I took it for a drive and it was much better after spraying the coil again with wd40. Went out to local store and got the Haynes manual and an ignition coil...swapped the coil and it was perfect! The real test will be in the morning after it's sat out all night in the rain.

I'll post up then, but i think this might be the end of my issues(for now..it's a car afterall )