Crazy_Jake

My car slightly surges when the O2 sensor voltage (as seen on my PFC commander) does the normal (I think) fluctuaion from like .30 V to .80 V. So it surges about every 1 second or so. However, when the voltage is steady (not fluctuating) the surging stops. What's going on?

Jake in San Antonio

Crazy_Jake

bump

Crazy_Jake

any ideas?

j9fd3s

iTrader: (3)

my t2 did the same thing, i never figured it out, i tried almost everything though. i changed the following parts with NO effect
o2 sensor
coolant temp sensor
tps
ecu
inlet duct
exhausts
turbos
air temp sensor

mike

mr_jonboy

Well I believe the higher the voltage the richer you are running. That's telling me that you are getting bursts of fuel or losses of air (doubtful). Maybe there is a problem with injectors or something in the fuel path. What mods do you have besides the PFC?

KZ1

first off, with airpump connected and 02 correction you are goign to see voltage go crazy at idle. that is normal. if your probelm is normal you may have pronblem other than my solution wich will follow. if o2 correction is off adn prorblem i snot at idle, then it is that you are running lean. this happened to me at about 2k when I removed airpump, just dialed in a bit mroe fuel, 02 readings back to normal, and car running like a well lubed bitch.

Crazy_Jake

So the surging means i'm running lean? I do notice at higher rpm's the car stutters like it's getting a fuel cut but then again maybe i'm running rich. I had ray at shaneracing program the PFC for cat-back exhaust, 3" downpipe, mild street port (10% to 15% according to Hayes), and an intake. Although right now i'm still running stock airbox w/ a K&N stock replacement filter. In first gear if I'm putting around a parking lot or something and I let off the throttle it slightly backfires (pop..pop...pop...pop) so I'm running rich on the low side.

KZ1

can you be more specific as to when your surging happens, you said only happens when 02 voltage fluctuating. is it at full throttel at higher rpms, or just light throttle and cruising around? do you still have airpump? is your 02 voltaeg steady at WOT, if so what readings are you getting. letting of the gas and gettingthe little pops is normal, means you are runnign rich, do not worry about that. just try adding more fuel through test menu at time when surging is happening, see if it goes away, if it is at partial throttle I bet it will. if it is at full throttle you may have differnt problems. especially ince you pFC hads been tuned already.

ciao

Crazy_Jake

The surging happens with a steady throttle, I notice it most on the highway just cruising in 5th gear. If I get on the throttle the surging stops and the O2 voltage goes to somewhere around .85 volts or so, although I've only looked at that a couple times. The car doesn't surge under deceleration either. Let me point out the surging is very slight, doubtful the passenger would notice, although it is very annoying for me. I am currently running the air pump, although planning to remove it when the pulleys and midpipe comes in. Also running a heated O2 sensor I think may be the problem.

rotorhead333

Crazy Jake, I have the same problem w/ mine, I turned the O2 setting to the off position in the PFC (no midpipe). You may notice, with it off the problem is non existant. I believe it to be a conflict between the PFC and the O2. The PFC is running rich and the O2 is switching to lean. I am about to get the car tuned, and this should bring the readings closer to the same plain of things, and the surge should be gone. hipothetically speaking..We'll see.. I know I am running it rich, this may be your problem too.

Crazy_Jake

I think you may be on to something, makes sense.

Thanks guys, Jake

KZ1

how old is yoru 02 sensor? it shoudl be reading much richer with your mods and base maps. Mine read about .95 before adjustments. This could be your problem. I woudl just replace it with ford escort one or bosch universal and then test. the 02 voltage will jump around when airpump is on, that is supposed to happen, so just cruising below 3800 rpm, you are goign to see it and may be unrealted to your surging. AGain, surging is usually caused by lack of fuel if your 02 sensor is good. THe PFC maps during cruising arethe most lean parts of the maps, they do this to save fuel and emissions at a point where you don;t nned much. so you want just enough fuel at this point to make it run smooth and not surge. It is so close that when I made a few changes I had to add fuel to cruising areas to stop the surging.

ITry teh o2 sensor correction off, this will diagnose your 02, then try this. if you look at your map between around p3-p5 and n4 to maybe n9. there are a lot of 100s in fuel surrounded by 106 and 108s, those are yoru cruising cells, increase the fuel there adn shoulf stop it.

search in PFC forum for Spoautos post about it, Chuck posted a revision to help his surging.

Crazy_Jake

Thanks for the information, I think I may be getting somewhere.