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post #1 of 8 Old 05-07-2013, 06:44 PM Thread Starter
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Air Fuel Ratio

Hi, I recently hooked up a autometer air fuel ratio gauge on my one vehicle.

never ran correct. Constantly spit soot out the tail pipe. Always seemed to be like getting over fueled or flood conditions.

I had intentions to hook gauge up sooner but never got around too doing it. upon installing and having it working correctly, the vehicle is now indicating a RICH condition ( in the amber region of the LED gauges ) . Eventually it will jump to like 16-17 and choke it self out it seems like and stall.

I have a 3 inch dump for exhaust and it dumps right before the passanger wheel, the ground where it dumps is like all black, and carbon soot.

The A/F gauge is reading 10.4 and Im wondering whats going on with the system. I dont know anything about tuning.

I am trying to diagnose further... thanks in advance.

Last edited by SYCLONE; 05-07-2013 at 06:48 PM.
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post #2 of 8 Old 05-08-2013, 08:58 AM
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So many things to check. First off, what model vehicle is it? There are "known" issues that pertain to all vehicles... Do you have a MIL lit? Can you pull codes? Some auto parts stores will do it for you free... This is where I would start, then:

Is it modified and re-tuned accordingly? If so I would start by verifying that tune. Check for vacuum leaks upstream from the O2's, Check MAF or MAP and its source vacuum line however equipped. Check ECT sensor (could be telling the ECM the engine is still cold when fully warmed)... You could have faulty injectors or fuel pressure regulator (a fuel pressure test/leak down would tell)...

Just a few things that come to mind....

Chuck
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post #3 of 8 Old 05-08-2013, 05:54 PM Thread Starter
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Thanks-

Truck is a 91 GMC syclone. 4.3 engine platform.

I already did suspect the ECT and replaced it with a OE gm part. One thing I notice was that the truck stays cool. The temp sensor does not rise Like I believe it should. I just replaced the ECT sensor not too long ago and my truck has not really seen the road at all.

Just wondering why Its leaning back to the Coolant sensor? I had thought this was the issue befoere. But I want to add that I did notice the actual temp gauge not rise.

I have run through alot of the other issues like ALL new vac hoses, New o2 sensor, has a 3 bar map sensor which is also relatively new.

I cant remember correctly but I did buy noid lights and everything worked, I just dont know if it told me my injector is stuck or not.

I pretty much cover alot of the bases, Just hesitant to take to a get dyno/tune I would like to try and rectify the issue at home here first.

Thanks again
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post #4 of 8 Old 05-09-2013, 06:55 AM
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Quote:
Originally Posted by SYCLONE View Post
Thanks-

Truck is a 91 GMC syclone. 4.3 engine platform.

I already did suspect the ECT and replaced it with a OE gm part. One thing I notice was that the truck stays cool. The temp sensor does not rise Like I believe it should. I just replaced the ECT sensor not too long ago and my truck has not really seen the road at all.

Just wondering why Its leaning back to the Coolant sensor? I had thought this was the issue befoere. But I want to add that I did notice the actual temp gauge not rise.

I have run through alot of the other issues like ALL new vac hoses, New o2 sensor, has a 3 bar map sensor which is also relatively new.

I cant remember correctly but I did buy noid lights and everything worked, I just dont know if it told me my injector is stuck or not.

I pretty much cover alot of the bases, Just hesitant to take to a get dyno/tune I would like to try and rectify the issue at home here first.

Thanks again
There is one sender for the ECT data to the ECM and another one for the gauge. You may also have a failed t-stat that is stuck open. This would cause the gauge not to rise as the engine is not warming AND cause it to run richer. Tho I doubt it could be the sole cause for a 10.4 AFR but possible.

Is the truck tuned? For the 3 bar? Been out of the business for 13 years now so I can't remember if the truck will run on a 3 bar with the stock tune or not... Lastly, if there are no codes present and all components check out, it just may be the ECM itself....

Chuck
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post #5 of 8 Old 05-09-2013, 05:07 PM Thread Starter
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Hey, Thanks for the imput again. I am on SYTY but I am not getting the help I need. Especially from the bone head who burned or re-flashed my chip for me-

I told him all my mods and what I have going on and he custom tailored a chip to get me started- Since than Truck really never ran correct.

I recently did replace the T-stat with a 160* stat. On the same token I note that the gauge did not rise at all.

I replaced the ECT sensor on the manifold, I am pretty sure that is the one which controls signal to the ecm. The other is on the cylinder head, Driver side and is a reference for the temp on the dash gauge.

I replace the ECT sensor with a OEM AC delco part. I know I may have repeated my self on that But I did check my paper work out and it is a Delco part I purchase less than 8 mons ago. I dont really even drive the truck due to it not running correct.

Truck is stock a 2 bar, I upgraded my CAM and it required a 3 bar. The cam was the big issue with 3 bar and chip re-burn.

Thanks again-
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post #6 of 8 Old 05-09-2013, 05:31 PM
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NP, I hate to say it but the more we chat about it the more it sounds like a tuning problem. Except for the gauge, its sending unit is most likely bad.

Chuck
2010 SIM 2SS/RS A6 SC - Born on 10/05/09
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post #7 of 8 Old 05-09-2013, 06:13 PM Thread Starter
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Just took the vehicle for a quick scat, and it was well heated up and the gauge never really rose, I guess it is a bunk part.
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post #8 of 8 Old 05-10-2013, 07:12 AM
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Quote:
Originally Posted by SYCLONE View Post
Just took the vehicle for a quick scat, and it was well heated up and the gauge never really rose, I guess it is a bunk part.
See my response to your PM for further testing....

Chuck
2010 SIM 2SS/RS A6 SC - Born on 10/05/09
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