usoff89

iTrader: (2)

CEL light came on on the way home tonight. Checked it when I got home, and got codes 27 and 29. Both left and right O2 sensors?

Ok so my question is.... Could both of them have gone bad on the way home tonight? I replaced both of these about 2-3months ago because I had been running with the AFM/MAF unplugged for awhile. The car seems to go in and out of running perfect and bogging down.

Are the sensors bad or could there be something else causing these two O2's to throw a code?

Yes, the ECU has new caps (the right ones) in it too. FYI

Oh and I should add. When the car is cold, it runs great! As soon as it hits running temp (open/closed loop?) it starts bogging down and has no lower end power at all.

usoff89

iTrader: (2)

Ok, so rookie move here. I just relized that codes 27 and 29 are not the ones I replaced. These are the downstream ones after the cats.... Which i don't have. lmao. This is the first time the light had come on though because of them gone.

But that still leaves me trying to figure out why its bogging down? I'm going to pick up a OEM temp sensor and try that. I replaced the current one with a autozone one, and I need to rule that out. This problem I'm having has something to do with temp.

LScowboyLS

did you use the real Nippon Denso O2 sensors? (and not their universal fit ones, either)

usoff89

iTrader: (2)

I used bosch ones.

deanshark

When you had the AFM unplugged it ran good, right? Did you put a new one on? Your problem might be the (IAT) Intake Air Temperature sensor which is inside the AFM. Sometimes it wont throw a code, mine didn't. I had the same "no low end power" until I unplugged the AFM.

usoff89

iTrader: (2)

Correct.... MAF unplugged it runs like a beast. lol. I tried replacing it with a used one, but I guess the one I put in there might have the same issue? So far, I have tried three different AFM/MAF's. They were all used, but I would think that the chances of me getting three bad ones would be slim.

LScowboyLS

I think the IAT's commonly go out on these when the cars get this old, see if you can buy the IAT separately as new

deanshark

I remember reading something a few years ago that the IAT can't be changed by itself, the whole AFM needs to be changed. But hey, I could be wrong. It happens to the best of us.

usoff89

iTrader: (2)

Deanshark, you are correct. The IAT is built into the AFM. I still have one of the other AFM's in the garage. I might try and put it back on there. When I tried the other AFM before, it was before I did the ECU caps and I was having a lot of other issues.

LScowboyLS

anything can be changed if you have soldering skills and an evil scientist/MacGyver mind!..........muhahaha!

usoff89

iTrader: (2)

Ok so some new symptoms.

I decided to unplug the afm/maf because I was really getting tired of the bogging down issue.

Now with the afm unplugged it is wanting to buck under a constant throttle. If you are accelerating or WOT it runs great. Also idles perfect. I guess you can call it a "burp". It shut off on my at the gas station when I was just giving it lite throttle. You can feel it pretty hard, as if the fuel cuts for just a quick second or something?

So, I think I can rule out the afm/maf because I had it unplugged and it was still acting up. I think its doing the same thing with the afm plugged in, but the ECU helps make up for the "burp" and it bogs down.

Any ideas. I was wondering if you guys think I might have a fuel pump issue?

PureDrifter

iTrader: (10)

no, if it's running fine at full throttle it's not a pump issue (though could be a pump resistor issue, possibly).

the reason it runs fine at WOT is because at that point you're under open loop, and the ECU is ignoring most sensor inputs.

swap AFM for known working then start tracing wires to make sure all connections are good.

usoff89

iTrader: (2)

I'll look into getting a known working AFM. BUT I want to add.... A while back when I drove with the AFM unplugged, it ran great. No stumbles, burps, or shutting off. With the AFM unplugged, doesn't it ignore most of the sensors all the time anyway? Since its still doing it with the AFM unplugged, which sensors can I start to rule out?

Are there any sensors that would cause these issues with the afm unplugged. Maybe a loose connector or bad ground? This weekend I'm going to start checking all connections and what not.

On a side note.... I got my Apexi NEO in today. When installed would this override an issue like this? Im going to figure it out before installing, I'm just curious.

timmy0tool

iTrader: (7)

could it be that all your problems are due to the cats not being there? could be that the downstream O2s are not reading properly thus compensating fuel irregularly? try and run an anti-foul riser on the O2 bung and see if it clears it up some.

usoff89

iTrader: (2)

I'm pretty sure the downstream o2's will not affect the way the car runs. They are only there to let you know if the cats are working or not. The ECU gets its readings for adjustment from the upstream o2's.

PD, do the 93's have a resistor? I recall reading somewhere the 92 and olders had the resistors, but not the 93+? I'm going to go jump it right now and see if 12v to the pump helps or not.