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Another O2 issue?

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iamtall77

20+ Year Contributor
185
1
Oct 9, 2002
Las Vegas, Nevada
I've been trying to get my Colt GT (4G63t) running, and it does. However, it sounds like it's got really huge cams and won't idle at all. It has a difficult time just trying to stay running and I have to keep tapping the gas pedal to keep it running. I have good compression and I definitely have spark and fuel. I have a 255lph pump, AFPR set at stock fuel pressure, 2G MAS and my SAFC-II set at +20% with stock 450cc injectors. I'm running MMCD and everything reads good except the O2 readings which read nothing at all.

I thought maybe the O2 was bad and swapped out 2 other ones. Bought a new one. Jumped the wires from the sensor to an A/F gauge. Tried reading directly from the ECU wire. Nothing seems to work. I can't imagine that this would cause so many issues. I can't seem to figure out where the "real" issue is. How can the sensor just not put out a reading? I know it's getting power and the 2 grounds are good. The wire from the connector to the ECU is good. The sensor shouldn't be bad, it's a brand new OE style Bosch unit. What else can I try? Changing the fuel trims on the SAFC doesn't seem to do anything either. This sucks. :cry:
 
No voltage at all on the O2, or just not what you want to see?

I ask because I'm having a problem where mine will cycle normally sometimes, and other times go -.2v and stick for little bit, resulting in problems just like what you have...
 
Not a new motor, but timing marks are right on. Haven't set the timing cause it won't idle well enough to do so. The car runs like it has a bad MAS signal, but all that checks out. The only thing my Palm w/ MMCD won't read is the O2 signal. I'm going to bump the fuel way up to see if it changes anything at all.
 
Not a new motor, but timing marks are right on. Haven't set the timing cause it won't idle well enough to do so. The car runs like it has a bad MAS signal, but all that checks out. The only thing my Palm w/ MMCD won't read is the O2 signal. I'm going to bump the fuel way up to see if it changes anything at all.

You are certain the o2 sensor itself is wired up correctly?
 
On the O2 sensor thing, I can attest to that having the fuel as little as 10% too lean on the bottom end will not let it cycle at all. If it doesn't even attempt to cycle, the ECU doesn't compensate (guessing that it thinks the sensor is bad if there's NO indication whatsoever from it, fuel trims never move and the idle is horrible)... BTDT :)
 
Still don't have O2 volts after bumping the fuel to +40%. It will idle and drive, but with reduced power. I drove it about 2 miles around my neighborhood and got the FTLO to 118%. It seems like I'm not getting fuel from #2 or #4 cylinders. I turned them off from the Palm and nothing changed. However, when I turn #1 or #3 off, it tries to die. Right now it idles anywhere between 800rpm to 1500rpm. I'm not complaining, this is a step forward. Now I just need to find out why #2 and #4 are not firing, or at least firing correctly and fix my oil leak from the turbo drain at the oil pan.

And I am positive the O2 sensor is wired correctly, it's an OE type Bosch unit. Can't mess that up.
 
Are you sure it's fuel, and not ignition? I believe that 2 & 4 are on the same coil. Sounds suspiciously like a failed coil when you put it that way...
 
Definitely not ignition. I have spark on all 4 cylinder and 1 and 4 are on the same coil. 2 and 3 are on the other. I can check to see if the injectors are getting a signal with a timing light, or I can check it with the little injector plate I made that holds the 4 injectors and the rail together. I'll see what's up with it tomorrow.
 
If the wiring is good then try to get a new o2 sensor. Even with that unplugged the car should still run so it may be something else. Could be a bad ecu you never know.

If you cant figure it out and you can get someone to give you a tow down to the springs there is a good shop that can figure it out. It would have to be on a flat bed and it is pretty far but if you come to last results.
 
You're probably speaking about Jack's shop in Springs, but I don't think I'll need his help yet. I've narrowed it down to the injectors just not firing. #2 and #4 seem to be having issues and that's causing the bad O2 signal. I got all 4 firing for a short drive and everything worked great. I did need to keep the fuel on my SAFC at +40% to get decent fuel trims. That's probably because of my 2G MAS and 1.6L Turbo ECU. I'll fix what I can and see if I can figure out what the deal is.
 
Finally got it running ok. I went ahead and wired in some newer injector plugs and that seemed to do the trick. My fuel trims are still way off. It's been a while since I tuned a car so I could be wrong.

My SAFC is set at +40% for my low trim and I'm still getting readings from the O2 trim in the area of 140%. My short trim is setting at about 118%. I need to keep richening it up right? I can adjust my fuel pressure to get a little more fuel in there, but I'm not sure that's a good fix.

I have a 2G MAS and 450cc injectors with a Walboro 255. Last time I ran a 2G MAS I had 550cc injectors and had to lean it out a little. The 2G MAS is good for roughly 20% more air at the same reading as a 1G on the ECU right? If so, I should only need +20% on my SAFC right? I guess I'll get most of this figured out, but thought I'd ask for some input. Also, base timing on the car seems really high and that could be some of the issue. But now it runs and I can move on to other things. :)
 
Running that ecu and a 2g maf I would get a wbo2. Tune to 14.7 afr at idle and cruising. It will take all that guess work out. Most people have to add a little fuel running a 2g maf and 550's in a 1g. I add 4-5% to reach a good 11.1 afr. I was thinking maybe you dont an afpr but that would make your run rich and you would be pulling fuel.
 
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