Truck is running rough. Smokes really bad after sitting for a day then clears up. It’s intermittent. Runs great for a bit then rough. Had it with 3 different shops and no one can tell me the problem.
what has been done?
1 throttle body cleaned
2 airflow sensor replaced
hooe to get some answers

 

The first question I need to ask is have you had the OBDII system read to see what Diagnostic Trouble Codes (DTCs) are present?

The second question depends on how you answer question 1. If you answer yes, what are the codes? Not the code definitions but the actual alphanumeric 4 -6 digit codes.

If you answer no, then you need to get the OBDII system read. If you go to an auto parts store to have the OBDII system read, DO NOT purchase any auto parts they tr and sell you because the computer says that 91.2% of the time the problem is this or that part. OBDII DTCs never ever tell anyone that a given part is defective. All OBDII DTCs do is tell one that there is a problem with a specific circuit or a system.

 

yes but the codes come and go. P0300 is one. It gives a misfire code as well but again it’s intermittent

 

Knowing what the other codes are would be extremely helpful.

Is your OBDII code reader/live data scanner able to display misfire counts for each cylinder individually?

Is your OBDII code reader/live data scanner able to display Short Term and Long Term Fuel Trims?

 

The reader can detect misfires. Not sure about fuel trims. I don’t have those codes handy. We drove it yesterday and it ran like normal but day prior it was smoking very badly then after about 30 minutes it stoppped smoking and began running well again.

 

I hate to say this, but drive it until it runs poorly again and then use your OBDII code scanner to see what all of the DTCs are, and write them all down. It will be extremely helpful in trying to diagnose the problem.

With respect to the misfires count, try and figure out how to get your code reader/live data scanner to read the misfires for each cylinder and then when the engine is running poorly and there is a P0300 DTC, write down the misfires for each cylinder. Looking to see if the misfire count is significant for one or more cylinders.

If you can determine if your code reader/live data scanner can read fuel trims, that would be helpful too.