Having trouble figuring this one out...

1993 pickup with 22re

Engine idles and runs well, maybe a little down on power, but from idle when you first give it throttle it hesitates/bogs if you open the throttle quickly. No problem if you open throttle gently but a quick push and it bogs. Seems as if it can't keep up with the sudden increase in airflow. If it had carbs I would think it was going lean as the throttle cracked open, but not as familiar with what would cause that with EFI.

Injectors are brand new. (had one go bad so all 4 were replaced today)

Brand new cat converter today

Is showing a check engine light and code 21 (bad O2 sensor) since the new cat went in, will chase that down but don't think it would be the cause since I am pretty sure the O2 sensors are not in control of instantaneous fuel mixture near idle, but I could be wrong about this.

Have checked TPS adjustment, makes no difference when adjusted or unplugged.

AFM seems to be working fine. (the top has been cut open for acces and when I manually mess with it the engine responds.)

If you jumper the timing the engine idles down. Have not checked timing yet since my light broke, buying a new one soon.

Throttle body is grungy but not sticking, throttle and cables move smoothly.

Not sure if it was a problem before injector replacement since the the truck was only running on three cylinders, but things were fine before the injector failed.

Unhooking the vacuum line to the fuel regulator doesn't change anything.

I am thinking it might be a fuel pressure issue and have a gauge on order, but would love to hear any other ideas.

Thanks

 

wait for the pressure results. that will take away the guessing.


wow, joined in 2009, first post in 2016!

 

Agree. Check your fuel pressure. Possibly a weak fuel pump. I had a similar condition, although mine would only rev to @2000rpm before it would cut out and die. A new pump fixed it.

If you have to change the pump, watch out. Often the connector at the pump bracket and/or at the frame as completely frozen. I cracked the hard line at both ends trying to get my original pump out (my 4rnr is an '88). It was maddening trying to find the right stuff to connect the replacement line.

 

I did the pump about 6 years ago, so I know the drill if it needs another. Going to do the fuel filter tomorrow since I have one and it's been on my list of preventative work to do anyways.

Pressure gauge should be here in a few days.

 

Just checked timing, was off a bit but didn't change much.

Don't think it is related but...
When I have the hood open and open the throttle quickly I can here a strong sucking noise at the intake for a second while the motor bogs, air filter is new, intake seems unobstructed.

 

Check the pipe from your air cleaner to the TB for any cracks or breaks.

 

wait for the fuel pressure gauge to be installed. otherwise, you are chasing your tail.

 

Fuel gauge will be here tomorrow. In the meantime...

I found a crack in the plastic air intake hose after the AFM, taped it up and it made no difference. Checked the airbox etc over real well and didn't find any other leaks.

O2 sensor is fixed, truck is no longer showing any codes.

When I hold it at steady medium throttle (about 2500 rpm or higher) in neutral the truck is surging. Sounds like it runs well and then cuts out for a second every 3-4 seconds. It stops doing this when I unplug the TPS or put it into diagnostic mode, but the stutter off idle does not go away.

Timing is dead on and seems to behave properly, advances as the engine revs and then drops back when it stutters.

 

Checked the TPS with a better multimeter and found it wasn't matching the resistance numbers from LC engineering. New TPS got rid of the surging. Combined with the O2 sensor fixed it is driving quite a bit better and power feels good. Still a little lag off idle when the throttle is opened, but much improved.

Will get the fuel meter on in the next couple days to double check that as well.