All my fuel trims are at 139.8%

[turbo2086]

Whether its at idle, to mid, to high loads. Always stays the same. I no longer recieve an O2 cycle at idle either. I already replaced the O2 sensor. No luck. I'm using MMCD. I posted a reply under the other fuel trim in thred in the tuning section. Didnt get a reply so trying here. Sorry.

 

[xcz504d]

Check your ECU CAPS to see if they're leaking...

Go to your parts store and pick up a volt meter for $20
Check the voltage at the 02 sensor off the plug, the output comes off terminal 2, should be 0- 0 - 0.4 volts at idle

Then work your way back to see where the voltage drops out at, check the wires going into the ECU, the 02 sensor wire is the 4th wire fromt he left on the largest plug (white wire I believe)...

Check out www.vfaq.com in the electrical section for the ECU pin outs...

Haynes manual will tell you how to test the 02 sensor also...

 

[xcz504d]

Also check for battery voltage to the O2 sensor (harness side not the plug side) on terminal 3 of the plug

On the O2 plug side, check the resistance between terminals 3 and 4, it should be appx 12 at 68 degrees...

Check terminal 2 with terminal 4 on the O2 sensor plug, there should be continuity... Check that with a continuity test funciton of a volt meter, or a "diode test" if there is continuity there with be a steady tone...

 

[turbo2086]

Thanks on the reply, I dont think its my o2 sensor though. The o2 sensor works fine while im cruising, it cycles back and forth. I will test the o2, when I get access to the garage, since its 15 out

 

[xcz504d]

Trace the voltage back until you loose the signal

If you just replaced the O2, I doubt it's that either, but never hurts to check... I just posted in the problems section, about ECU caps and where to get them if you find that they are leaking...

 

[steve]

I dont think its my o2 sensor though. The o2 sensor works fine while im cruising, it cycles back and forth.

It will help if you note the parameters where it works and doesn't work, like what it outputs when it not working.

If the heater isn't working it could have a low output and starts working again once your cruising and the exhaust gas temp comes up.

Steve

 

[turbo2086]

Thats what I first thought as well. But then when I replaced the o2 sensor again, I got the same results.

 

[xcz504d]

Maybe it's not getting enough voltage from the battery See previous posts

 

[steve]

when I replaced the o2 sensor again, I got the same results.

There is more to the O2 heater working than just the sensor, but this is all speculation since we have no data to work with.

Steve

 

[turbo2086]

Okay guys got a warm day today 40degrees . Went out and did some testing. I also have the service manual on CD, that was really helpful.

My o2 shows continuity for the above pins.

I tested the voltage at the HARNESS, on pin #3. I got 12.1v, so thats good to go.

On the manual I hooked pin #3 and #4 to the o2 sensor. Hooked up my voltmeter to #1 and #2. I got 0, then reved it and started getting readings up to .85ish. On the manual seemed that was normal.

Boost leak tested to 15lbs. Came out good, small cut in pcv hose, fixed that.

Did a log at 2800-3100 rpm in third gear for about 15sec. O2 shows cycling from .05ish up to .75ish. Guess thats normal. Timing around 38 degrees. During that log my FTO2 varied between 126% to 140%.

At WOT o2 reads .87, and FTO2 100%.

During Deaccel o2 is at .00 and FTO2 still at 100%.

During driving seems like everything is working fine, fuel trims remain the same.

I didnt get a chance to test at the ECU, however have pulled the ECU out once and it was a REMAN so Im sure it got replaced before because of the capacitors. And it has NO EPROM

I will keep testing things and keeping you guys posted. Let me know if ya have any thoughts or suggestions.

 

[titogs95]

In your mod list say you have a Hacked MAF (how many honeycombs are out?). If so, you might be running a little lean at idle because of that.....
have you tried swapping to another MAS in case that is the problem?

I think your O2 is fine, it is something else, fuel wise...

 

[turbo2086]

Yeah, I took out the BOTTOM honeycomb. I did back the screw out all the way for a day, when I first bought the car. I didnt know what it was doing, so i put it back in a good way, where I think it was when I first saw it.

Yeah I have bid right now on ebay for an unhacked 1g MAS for 15bucks I will see what happens when I put that in.

 

[dsmsucks]

Man talk about having the same problem But my fuel trims are stuck at 100%. The car is runing rich as hell. I replaced the o2 sensor with a denso change what so ever!
The trims wont change no matter what. I took as much as -18 on the safc, backed out the screw on the 2g mas, and even took some honey combs out. This made no difference
I would say its your ecu being that you have a 1g. I sent my ecu to steve. He does ecu work