Check engine light

3.4 1996 runs fine with check engine light on no codes. Check engine lights goes off then comes back on with truck misfiring at intake power loss over 2000 rpm. Changed camshaft position sensor, crankshaft position sensor, new spark plugs, new coil packs, new fuel pump with pressure regulator. I’ve seen that everyone is saying MAF sensor but everyone changes it with no change. Not sure where to go from here.

 

If you let it cool down it usually goes back to normal operating conditions with the check engine light on.

 

Cool down as from it over heating?
I’d at least clean the mass air flow sensor they have specific cleaners for it. Could also be injectors. Throttle position sensor. Low compression. A dirty fuel filter. Bad head gasket. Vacuum loss. Spark wires. What codes did you pull?

 

Wait? the check engine light comes on but does not have any codes?

 

Cooling down as from normal operating temp. No codes show up with light on.

 

Ahh wow that’s odd. I’m sure someone with more knowledge will chime in soon good luck. Can you make a code pop up by unplugging something?

 

Odd, took the Tacoma to get lunch just now and on the way it stumbled, check engine light came on and now I have about 50% power.

Looks like I’ll be pulling out the code reader when I get home.

Mines a 99’ 3RZ though.

 

Update: So after lunch I drove to the dealer to pick up a new gas cap, just had a feeling.

$42 dollars later I install the new gas cap in the parking lot, start it up, check engine light still on, still can tell power is limited. Pull out on the road, check engine light goes off and engine power restored.

I’m having a hard time believing the gas cap was causing the stumble, loss of power and the check engine light to come on. But the whole way home all was good

I still need to check for soft codes.

 

I've seen one car that the fuel cap was not letting fresh air into the tank so the fuel pump was having a hard time pulling fuel.
This was a while ago, no codes although it was stumbling, but no check engine light.

 

I'm going with Injectors. Pull the codes anyway.

 

I’m gonna put my money on a p0171 or p0172 code coming outta this one… unless ur fuel pumps on the fritz..