Possible Solution To FS "Surging" Problem!!!

[Maxx Mazda]

Well, some of you may have had the dreaded "surging" problem after you fill up with gas or drive the car hard. Both me and my girlfriend (she has NO mods on her car) have experienced it. Surging is when the engine will climb rapidly to about 2000 rpm, then drop to almost stalling, and back up again in a loop for about 10 minutes. I've been able to reproduce this happening on my car indefinitly everytime I fill up with gas.

Now, for the longest time when it did that the MIL would come on. My Mazda dealer said it was indicating an O2 sensor failure. I've come up with a new theory as to why my car (and fro mwhat I've heard it's a popular problem) have been surging everytime I fill up with gas. I don't overfill the car ever, just until the handle clicks once.

The problem may lie with the EVAP system. The EVAP system is responsible for filtering and returning fuel vapors from the gas tank to the throttle body / manifold so they can be burned. What may be happening, is raw liquid gas is getting through the EVAP system and into the engine, in addition to the fuel already being delivered by the injectors. The O2 sensor sees that the car is now running WAY too rich, and cust fuel back far to much, causing the engine to almost stall. It adds more fuel, but once again discovers it's too righ and cuts it back again. (In a loop.) This may be indicative of the MIL on the O2 sensor.

So, please provide your input as to whether my case holds water of if I'm full of **** here. It's just something that hit me one day, so I thought I'd share. I dunno if there's even a way to test for EVAP system malfunction, but it's an idea.

[midnightblue97]

Funny you should mention that. It happens from time to time on my BP powered second gen. When it would set off the MIL the code was a p0170 Fuel trim malfunction bank 1. There were several possible causes for it happening including a problem with the EVAP system. Unfortunately for me it doesn't happen on a regular basis to its hard to replicate the problem and check out evrything on the list. The only consistent thing when it happens to mine is that its only happened in the morning hen its cold, and maybe a little damp, and the engine hasn't really been running that long like maybe less than 15 minutes or so.
I was talking to Kdawg and he said it happens to him as well on his second gen and apparently Mazda haas no Idea what it is. But that seems like it might be worth looking into.

[DooMer_MP3]

My gf's 1990 MX-6 did this all the time before we sold it. Mainly when it was cold out. It sounded like I wanted to race everybody at a god damn stop light constantly revving up and down to 2500RPMs. Never figured it out.

Chris

[Audiodub]

I've been having this problem too. But my prot acts up when it's too cold and when it's too hot. or maybe it's just coincidence. My check engine light used to turn on and off every other week, but it's been on for two weeks now. I'm gonna have a friend check it out soon.

BTW, anyone else getting hesitation in second gear?

[plymouthprotege]

i just had my car in the dealership cause it was hesitiating in 3rd, but that problem only arose after the day where it wouldnt shift into third until near redline