Hesitation after 50% throttle

[dkdontforget]

Hey guys, new to the forum but have been looking around for a while.

i have a weird issue i havent really seen before

so i have a 94 with 150k miles on it 5 speed

if i press the gas further than 50~% it will hesitate stumble and misfire, it is more noticeable in the 1k-3k RPM range, it will also do it while parked and flooring it, it will go to redline but it stumbles

so for example, ill be going 40MPH and want to pick up speed i can push the peddle right before 50% and itll pull strong, any further it stumbles and loses power, and i can back down and it will gain power pretty consistantly

I was thinking maybe the TPS or MAF

i checked the MAF the other day and there was some bent wires down at the bottom but they werent bad

the wires look good
distributor / rotor looks good
the ignition coil looks a little rusty on the inside of the contact but not bad
no vacuum leaks.
fuel filter has very little resistance

i dont have the money to just start throwing parts at it so im trying to narrow it down

thanks in advance

[dkdontforget]

heres some pics




the bend is on the far left

[dkdontforget]

Update, Pulled the codes

23 Idle switch
45 injector leak
12 MAF sensor
34Knock sensor

Alrlight lol, where should i start first?

Update: cleaned the MAF still have the same issue

[smj999smj]

Write down the codes and erase them, then take it for a drive and re-check for stored codes. Some or all of the codes could be old codes that were set and never erased, so you want to make sure you don't start diagnosing problems that don't exist. I would also do a component check of the TPS.

[dkdontforget]

Alright, cleared the codes, now im getting just the knock sensor code, would that cause the hesitation?

[smj999smj]

Knock sensors won't cause driveability issues. It generates a voltage when the engine "knocks" that is read by the ECM. When the ECM sees that signal from the knock sensor, it will retard the ignition timing to help prevent engine damage. The fact that it reset means either your engine is "knocking" or there is a problem with the sensor or circuit. The bad thing about the VG engines is that the knock sensor is located on top of the block, in the valley, and the intake manifold has to be removed to access it. Some relocate the knock sensor to the top of the intake manifold where it is more accessible, using a knock sensor and subharness from a 95 Maxima and splicing the new subharness into the wires in the vehicle's EGI harness that go to the original knock sensor. There are write ups on the web of the procedure and probably some You Tube vids, as well. It's a more common procedure on the R50 Pathfinders, I believe, than the WD21, but the procedure should be similar.

The diagnostic system in the WD21 is pretty basic and while "state of the art" when it first came out, is pretty crude by today's standards. It takes a good, hard failure to set a code and it may take a while to get one of the other codes to reset if there is a problem. You can still go through the diagnostic procedures per the service manual for the previous codes; I would pay attention more to the 12 and 45 codes than the other two. Keep in mind that just because there is a MAF code, it doesn't necessarily mean it is the sensor, itself, that caused the problem or that cleaning the MAF sensor will fix a MAF sensor that is not working properly. I would also still test the TPS based on the symptoms, making sure there is not a break in the signal around the 50% throttle range.

[dkdontforget]

thanks for the info, ill test the tps after work but theres also an error in my part, i misred the instructions and the codes were actually the ecu cycling thru the modes hence 1 2 3 4, and i thought 5 meant a loop. i did it the correct way

red led blinks 3 times
green 4
so 34 which is still the knock sensor

ive reset the codes, checked to makes sure it cleared, got 55 for no fault ran the truck in idle for a few min and got code 34 once again

also something interesting, this morning when it was cold out it ran perfect, no hsitation at all

but as soon as it warmed up it started again and after about 4k rpm the hesitation stops

this hesitation happened over night before it only did it randomly under load, then one day its doing it all the time under load

[dkdontforget]

Alright, doesnt seem to be related to throttle, i had the A/C going and i was barely able to get the truck to move it was hesitating so much, i also picked up a ignition coil for really cheap and made no difference.

seems to be related to load

checked the air/fuel ratio on the comp and its good also checked the o2 sensor and thats fine

[smj999smj]

You might want to remove the distributor cap and check for play in the rotor shaft as this is a fairly common problem on high mileage VG engines. The distributor bearings tend to get worn and a little sloppy and great driveability issues. You can sometimes hear the rattle coming from under the distributor cap when the engine is running.

[dkdontforget]

Well i found out the problem, i had a hunch the previous owner didnt take much care of it, so i bought all new fuel filter distribuitor cap and rotor air filter and NGK platinums

I took out the old spark plugs and they were some cheap walmart brand that were very worn they also had alot of white on them (clogged fuel filter?)

after the tune up it runs like a champ! not one miss!

I appreciate your help very much, and i should have probably started there first

guess you just cant go on good faith that the person before you takes care of the truck