Codes P0302 and P0171, Engine misfires when restarted shortly after being run?

BADMRTICKLS

MEMBER
2002 TOYOTA TACOMA
2.7L
4 CYL
4WD
MANUAL
180,000 MILES

Hi,

I go to the store in my Truck and the truck runs great. If I shut the engine off, and then immediately restart it, the engine still runs great.

However, if I shut the engine off and go into the store for 10-15 minutes and come back out, I get P0300 codes and obvious misfire. Primarily cylinder 3, but I have gotten the P0302 code and also lean bank 1 code P0171.

If I let it sit it does not come back unless I let the engine completely cool.

If I just decide to drive it home anyways, about 3-4 minutes into driving the engine will suddenly start running great again.

I changed the coils and spark plugs, I also did a compression test on each of the cylinders and got good pressure with no loss.

Obviously, I have a problem that is temperature dependent. I did clean my MAF. Even with the MAF disconnected I can recreate the issue, so I do not believe the sensor is bad.

I recently had an issue with my EVAP canister which tripped a code, maybe this is related?

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

The idea that you have the P0171 leads me to think either you have an engine vacuum leak, or the fuel pressure is low.

If you haven't already, confirm there are no leaks.

Here is a link that explains how to locate and repair engine vacuum leaks:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If you are unable to find any leaks, I would move to checking fuel pressure to make sure it is within spec.

Here is a link that explains how that is done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

If you look below, I included the manufacturer's fuel pressure specifications.

Let me know what you find.

Joe

See pic below.

Image (Click to make bigger)