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Discussion Starter · #1 ·
I decided to test the a/f via the VF signal today, maybe some of you techies could help me out with the results..

At idle, cruising, and light throttle im getting 5v - Maximum rich.. So the engine is running lean and the TCCS is dumping extra fuel in.. OK

Mid throttle, up to 2psi it reads 3.5V - Minimum rich, so its gettin better..

As soon as I hit ~60-70% throttle, or anything higher than 2psi it goes right to 0v, Maximum lean..

Running completly stock fuel system and stock AFM.. mods are 57trim ct-26, 3" BIC exhaust to stock muffler, and custom air intake with hardpipes..

is this normal? is there any way to straighten it out a little w/o risking engine damage? or w/o spending a pile of $$$ BTW, i do not have dyno access.. Since its already lean at idle, I didnt want to back the screw out of the AFM
 

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I don't want an MK4!
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The 5V at idle light throttle and crusing seems a bit high.

The 3.5V is okay.

Going to 0V at WOT is what mine does as well.

You can do some limited closed loop tuning with the SAFC. You might also be able to tighten it up with an aftermarket, adjustable FPR.

As I am sure you're aware, the goal is to have the least correction from the ECU as possible as it does have an affect on your open loop feul maps that the ECU learns based based on the amount of correction in closed loop.

If it is in your budget, for about 500.00 you can get the SAFC and a wideband. If you have access to a laptop, I recomend the ZT2. If you don't, add another 100.00 in to buy a used laptop to datalog with.

Dan
 

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The Vf will read 0 whenever your ECU goes into open loop.

It'll also be whacked out during deceleration.

How long has it been since you added the mods? Have you given the ECU time to relearn yet?
 

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when this baby hits 88mph
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yikes thats kinda scary. mid thottle and wot is normal, as dan said. but you need to get that idle/cruise sorted. under those conditions the ecu should maintain somewhere around 2.5v if you are getting 5v that means its dumping fuel. my first look would be the 02 sensor. that has a drastic effect under idle/cruise and when they fail they usually fail on the rich end and dump a bunch of fuel since its safer. if there is someone in your area w/ a good 02 id swap and see if it makes a change.

good luck

dave
 

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Discussion Starter · #5 ·
I was driving the car around for about 2 days after the exhaust/dp when I did the test.. All other mods were inplace since last summer..

the car was also stumbling at idle when i did the test, thats probably why my idle/cruise reading was so off.. I guess its time to search for vacuum leaks again..
 

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I don't want an MK4!
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In my experience, once warmed up at idle, the vaccuum should be about -20.5 inches of whatever its called.

Thats what mine is anyway.

Dan
 

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how do you go about monitoring VF's during cruise and idle and whatnot? is there a special piece of equipment needed?
 
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