weird hesitation

[mustang6tee8]

every once in while, under heavy acceleration, the car acts as if it has less power. after holding down the gas pedal, it goes back to full power all of a sudden (same feeling that a vtech has). everything under the hood is now back to stock. what could be causing this to happen?

 

[Tom95gt]

I had something like that... check to see if your distributor is tight and check o2 sensors

 

[Adam95GT]

yea my 02's caused this... i guess at wot it was by passing them... so it would bog till i hit full wot then be fine...

 

[mustang6tee8]

alright, i'll check the distributor and replace the O2's. thanks fellas

 

[KamiKaziDK]

Clutch slipping?

 

[mustang6tee8]

Hell, it better not be! I replaced it 500 miles ago

 

[KamiKaziDK]

has it done this ever since you replaced it?? Did you get the flywheel turned when you did replace it?

 

[mustang6tee8]

it's been doing it most of the time. and i did get the flywheel ground. im still thinking it could be O2's- im going to install them today. will let ya know if it helps.

 

[HISSIN50]

If it was the clutch, it should slip under WOT at high RPM. It sounds like your car clears up during this time however.

If not the O2's, check the TPS for a break in the reading as you run it through its range (KOE-Off)

 

[mustang6tee8]

Clutch problems aren't a cause of it- it'll do it at any RPM now.

New O2 sensors did not solve the hesitation problem. Now it's acting as if it's starved for fuel- I'll put in a new fuel filter tomorrow since it's been around a year since the last one. If that doesn't fix it I will check fuel pressure.

What is the ideal range for fuel pressure? 39-44?


JT! How you been man?

 

[KamiKaziDK]

If it's totally stock, anywhere from 36-40 usually

 

[HISSIN50]

Hey Wade!

Look for 38-39 with the vac line off, and 32+ with the vac line attached. Under 30 is out of spec.

Do you have a means of viewing PIDs (AutoXray 5000, etc)? It'd be neat to stream data while it craps itself.

No chance of a MAF issue? Inlet tubing still all nice and tight, MAF wires clean, etc?

Run your TPS through its range too. Maybe the wiper started to degrade (the carbon flakes off) and it's getting worse...... This leads to flat spots in the output signal.

Good luck buddy!

 

[mustang6tee8]

new fuel filter helped a little bit. but it still feels like it's out of gas (even though it isnt). i just posted on the local car club forum to borrow a fuel pressure gauge. i'll check out the MAF in the meantime.

how do i test the TPS?

i also dont have a way to view PID... heck i dont even know what that is!

 

[HISSIN50]

On the TPS, the middle (grey/whi) wire should be the signal wire, IIRC. It should sweep from about 1 volt to about 4.5. Open the TPS really slowly and make sure there are no breaks in the reading (an analog VOM is nice for this test since the needle sweep makes it easy to see a dead spot).

If you had a code scanner, you can see sensors in real time. Sometimes it helps to stream and capture the data while a car runs normally and while it acts up, and compare the two to see which sensor craps its pants. No biggie if you can't do that.

 

[mustang6tee8]

alright, here are the codes i pulled today.

172- o2 sensor fault/lean
173- o2 sensor fault/rich
176- o2 sensor fault/always lean
177- o2 sensor fault/always rich
542- fuel pump secondary circuit fault

im resetting the ecu right now to see if it helps. anyone have suggestions?

 

[mustang6tee8]

SWEET!!!!! resetting the ECU brought it back to normal!

ohhh what a happy day.. lol