Any of you guys with widebands. What is your AFR when you are decelling with the throttle at 0 percent in closed loop with a MAF tune? Mine hovers around 13 and I'm wondering if that is normal. I cant find a table to adjust this and the long term fuel trims stay at zero in that cell. Its almost like it goes open loop when decelling.

 

decel my wideband shows infinite or 21AFR no fueld and injectors are at 0.

 

If you decel enough then DFCU kicks in and shuts for injectors off and you get up to 20.9% oxygen

If your deceling but injectors are still on then ideally you should still have 14.7afr, with my 83lb injectors and stock min injector pulsewidth I got about 10.5 on decel (before DFCU kicked in) plus a nasty surge when the DCFU kicked off (returning to run mode).

I lowered the mid pulsewidth from 1.4 to ~1.0 and it's perfect now. YOu have to have your VE's or MAF values right as well for everything to work. I would look at your injector pulsewidth on decel see if it's below 1.4ms, if it is then you need to lower your min injector pulsewidth accordingly.

 

MAX lean when deceling....AEM only reads to 18AFR

Jay

 

Dookie454 I think you are on to something here. I will give it a shot to see if it works. I think I will reduce the whole min pulse width table by 30% and see if it helps.

I put my DFCO values high enough that it rarely comes on. So I'm mainly concerned with why the computer is not adjusting the cell for decelling. I think maybe when it hits the min injector limit that it will not allow the long term fuel trims to do their job. Thanks guys for your input.

 

Not only will it not allow it to do it's job, but the PCM senses rich conditions and keeps pulling fuel, but if the min pulsewidth is too high the computer keeps trying to pull fuel... then what happens is when you get above your min pulsewidth but in the same cell that is now all leaned out you get a lean condition for a moment until the 02's start richening again.

I think the mid injector pulsewidth is a hidden/silent setting because no matter what Datamaster says for pulsewidth the PCM only allows down to the min pulsewidth limit.

I went too low at first (lower than 0.9-1.0ms) and I got some nasty idle surge,, I think because the PCM cant control injectors below 1.0ms.

 

The PCM is not pulling fuel. It has no long terms and short terms in the decell cell. Its like it kicks into open loop when decelling.

 

I have two versions that show "open loop" and "closed loop" decel based on Sterm and Lterm activity. The open loop decel shows very rich decel and the closed loop decel shows good decel AFR ratio.

My "closed loop" decel shows only "open loop" when DFCU is actually on (all Lterm and Sterm defaults to 128 because injectors are off).
My fuel trim cell is 17 while injectors are off and when they kick back in on both setups. Looks to me like PCM tries to acheive 14:7 during decel (while injectors are on - not when they're off). When I had this file with the wrong pulsewidth It was trying to lean everyting out during a long decel and would mess things up.
Fixed my min pulsewidth and everythings good.

 

Guys, I reduced the stock injector min pulse width table by 30% and now my fuel trims are working and the computer is holding the car at 14.7 on decel. Apparently the stock PCM goes into open loop when it is bouncing off the min pulse width. Thanks guys this should really help out with gas mileage.

 

Mine still reads "full lean" (18+) when deceling even in open loop

 

that means either your in fuel cutoff mode which you will see by your pulsewidth and duty cycle reading 0's, or your VE's are setup wrong. If your still getting full lean and there's something in the duty cycle and pulsewidth other than 0 then your min pulsewidth is set too LOW... bump it up 0.1 at a time.. I had to set mine higher than 0.99 to get it to work cause was getting idle surge and extra lean on decel when set under 1.0-0.99.