I've been cruising the board for a few days, trying to find someone else who's been dealing with my symptoms but haven't found anyone. The situation:

94 VX 1.6(?)l VTEC, 5 spd; 16X,XXX miles; bone stock

The issue doesn't light the CEL (First question though- do all codes light the CEL?).

Hot or cold, it starts fine.

While still cold, it runs and drives fine.

When it warms up, one of two things happens. The first is the good one- it drives absolutely fine. The other is that it bucks and stumbles and feels like it wants to backfire at partial throttle/cruising loads.

The interesting thing is that sometimes when it gets fully warm, the issue goes away. Sometimes it doesn't.

I can draw no correlation between conditions or actions leading to it running fine vs like crap. If it's running fine and I shut it off (even just briefly, like 6-8 minutes to get gas), it'll run like crap.

What have I done about it? I thought it might be a TPS issue so I checked the connectors. I did the same for the O2 sensor and the MAP sensor as well (electronic contact cleaner for all of them).

I learned a little bit about the FITV and the IACV so I checked the coolant level. While low, the reservoir was had enough in it to prevent air getting drawn back in. I filled it up.

I thought it might be crappy fuel supply, but when I downshift and up the revs, it starts to pull well enough. I replaced the fuel filter anyway.

It still gets 40mpg hwy, mid 30's in mixed driving so it can't be something catastrophically wrong. Still has respectable pep for the size of the motor (when it's not bucking and spitting) so can't be something too major, right?

Any advice as to where to go next?

 

had similar issues, 94 ls b18 in eg. did what you did. and added grounding wires here and there. also... cleaned dizzy contacts. inside and out. removed fuel filter, attached hose/catch can. let flush. seems to have gone. lmk what you come up/w

 

And I forgot- new cap, rotor and wires too.

 

Has anyone ever had an issue with the "air-fuel mixture" sensor? I called it the O2 sensor and went to get a replacement today because they're usually reasonably priced. They couldn't find the correct one listed then had to do some digging and it came up listed as the A-F mix sensor.

And it listed at $623 with a "street price" of $350.

Has anyone had one of these go before? Was there some way to confirm it is/is not correctly functioning? Were your symptoms similar to mine? Did you find a cheaper source for a replacement?

Thanks in advance,
Chris

 

Also, the A/FM sensor was listed only under the VX model (my car). All the other models had an O2 sensor listing and were much cheaper ~$50-$70.