WOT stumble

[ZombieTown94]

What would cause a car to stumble at wide open throttle? Such as flooring it to go around someone on the highway, or even from a stop sometimes. I step on the gas and it either does nothing or sort of bucks for a second, then takes off. No CEL either. I scanned for codes, and only got EGR insufficient I believe it was. This does not happen every time, seems like the car only does it when I need to get out of the way, and it decides nope.

Thanks!

[ZombieTown94]

I should specify not just "a" car, but my car in particular. 1994 TC

[gadget73]

how old is the fuel filter? Dead spots in the TPS or a dirty MAF can do this too. If you can pull the live data, that might tell you something. Also worth looking at what the temperature and O2 sensors are doing just to see if their output makes sense.

[ZombieTown94]

I replaced the fuel filter about a year ago. Tps was replaced probably two years ago, and I have cleaned the maf a few times. How do I go about pulling the live data?

[ZombieTown94]

I will also add that I drive the car a good 200-300 miles a week, and it drives fine under normal conditions. I just can't floor it.

[gadget73]

You'd need a scanner that can read that. I'm guessing you don't have said fancy-ass scanner. That is one of the great things about OBD2, even a cheap bluetooth reader paired with a phone can spit out sensor data while you drive.

Any vacuum leaks? This era was known for cracking an elbow on the PCV valve. Cracks in the air tube between throttle body and MAF are effectively the same. If the air box or MAF aren't the proper ones for the car it will do odd stuff. What do the plugs and wires look like?

[ZombieTown94]

Yeah I only have the little black and yellow code reader. Basically a step above using the paper clip.
I have replaced what I believe to be all of the vacuum lines. Including tees and elbows but I will check them again. Plugs and wires were done maybe a year ago, I used autolite plugs and motorcraft wires. Could it possibly be a fuel pump issue? Or do they basically either work 100% or nothing at all.

[gadget73]

not impossible, but usually if its a fuel pump issue it will lose power as you accelerate, not just bog and then go.

Ever unplug the MAF entirely and see if it runs better?

[ZombieTown94]

not impossible, but usually if its a fuel pump issue it will lose power as you accelerate, not just bog and then go.

Ever unplug the MAF entirely and see if it runs better?

I will try that tomorrow and see if I notice a difference

[ZombieTown94]

So I drove around for a good 20 miles today with the maf unplugged. I tried to get the problem to repeat, and had no luck. Which I suppose is a good thing? I did also notice the car seemed to buck a little bit when letting off the accelerator.

[gadget73]

sounds like its time to replace the MAF then. It won't run entirely right without it plugged in but if it runs better without it, thats usually a pretty good clue that the sensor is bad.

[94Magna_Tom]

https://www.samarins.com/glossary/airflow_sensor.html

Found an article about the MAF sensor. A small piece of debris is enough to foul the MAF sensor. Check for this before replacing it.

[EaOutlaw1969]

You have a 1994 Car with how many miles on it? does it have the orginal engine and or timing chains?
Have you ever pulled a compression check on the entire engine?
I would take the time to pull a compression test just to get a over all sense of the health of the engine.
I doubt this is your problem but since it is a 1994 it is worth doing while you are at it I would inspect each and every spark plug and the entire ignition system.
It does sound like a ignition problem. do you notice if the problem is worse with high humidity or rain?
if you do this make sure to number each spark plug and take pictures of them so we can help read them.

[Rodentkiller]

I say you may have an ignition module going bad or TPS acting up or EGR valve too.

[sly]

94 doesn't have an "ignition module" like the 302. It has a electronic distributor that is basically a second engine computer on the driver inner fender that controls spark only. Since the car runs rinf with the MAF disconnected, the MAF needs attention first. Fix that (clean it or replace it) and get that part working before moving on to other diagnosis.