Hopefully i wont get to the point in which i have to deal with EPA after tossing the truck...

I dont have like a full blown scanner. What i have (and i was playing with it today btw) is an obd Bluetooth adapter and the torque and dashcommand apps on my phone. I can do some basic loging with them. What PIDs do you recommend me to add and log to see if i catch them while the issue is happening?

 

Go to a good shop that can scope it out is your best bet.

Watch part 1 and 2 this is what Im talking about.

 

If you can, please log:

TPS percent/voltage
MAP pressure
Ignition Timing
STFT Bank 1
STFT Bank 2
CKP Counts (if supported)
CMP Counts (if supported)

Those core values should give a good enough basis to interpolate various unaccessible sensor inputs.

 

Well, i have never done data loging before so im trying to learn as i go.

I have not been able to reproduce the problem while loging but meanwhile something i noticed is that my o2 sensor readings are mostly leaning towards rich:





At the same time my long term fuel trim is always negative




Does this looks odd?? Seems that the sensor is always thinking that the mixtures is rich and the fuel trim trying to compensate by leaning it out but when i took my spark plugs out they didnt look like the truck is running rich.... Perhaps a bad 02 sensor?

 

If it's the original O2, it sure wouldn't hurt to change it. NTK or Denso sensors only please. Skip Bosch, these trucks don't like 'em.

 

OK so im back with this again.

Over the last few days i did the following
- Replaced upstream O2 sensor (actually couldnt take the original out at all, had to take it to a shop and they welded a new pre-cat bung to install the new one, the old one is still stuck there forever)
- Since i was at the shop there they also repaired a post cat crack on the exhaust
- Took off the fuel rail and injectors and cleaned them all
- For the guy that said to check my u-joints, turns out that i did had a bad u-joint on the rear shaft, i didnt think this was related at all but just for shts and giggles i changed the u-joints

My god! the truck drives so beautiful now, it was not bad before but now its so smooth and also i definitely feel more power but... the issue is still there

I drove it on short 15 min trips over the week and it never did it but today over a longer period it started, seems that it really needs to be at operating temp for a while to start acting up.

I tried doing some data logs with my limited tools and knowledge and this is what i got

This graph has the MAP Pressure, TPS position and Spark Advance. Red circle is when the issue happened. Weird thing i see is that the TPS is reading as if i was accelerating, MAP pressure goes up confirming it but i really dont recall accelerating at all i was crusing at constant highway speed, like 70. Spark Advance goes down during the problem.




Below the O2 graphs and Fuel trims. O2 seems to read rich during the problem (maybe because timing was retarded and un-burnt fuel made it to the sensor??) and Long term fuel trim seems to want to place more gas into the mix





Any thoughts?

Im running out of options, should i go for replacing the TPS and MAP? that would complete my replacement of all available sensors that have anything to do with fuel/air/spark/crank

 

What brand crank sensor is on there? Cam sensor? Take a look at pending codes, and, if you can, misfire counts. Counts should be listed on a by-cylinder basis. I suspect your hard jerk is a misfire.

 

So,

MAP from 20 to 25 inHg
Spark from 25 to 20 Degrees
TPS from 20 to 28%
Upstream seems normal but downstream seems off to the rich side
Short term wants to add fuel but longer term wants to subtract

That's an odd set of circumstances.

But HeyYou might be onto something. But as sporadic as it is, it's hard to pinpoint.

 

When this started i had the original crank and cam sensors then i replaced them from some aftermarket brand, i think Standard Motor Products but behavior is exactly the same as with the old OEM that used to be there.

There are no pending codes and unfortunatelly i cannot see cylinder misfire counts with the tool i have.

Maybe its time for me to get a proper OBD scanner, have been meaning to get one for a while and i have the perfect excuse now to pull the trigger . Any recommendations of a budget friendly tool? Do i need bi-directional or uni-directional?

 

Snap On MT 2500, or MTG 2500 would work great. (the "g" version also does graphing....) Prices for those aren't too outrageous.