Part throttle lean miss

Decipha's custom GUFX strategy covers all 89-93 foxbody ecu's including the 88 mass-air california ecus.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Part throttle lean miss

Unread post by bad86capri »

20210612_152646.jpg
So I've been fighting a part throttle lean miss for awhile now. It happens at light throttle below 2k rpm. I've been going on datalogs today and noticed that the LTFT1 is actually lean at those spots. LTFT2 is not. Any ideas why this is and if it could cause my lean issue? I know most on here is tunerpro so I'll post up pic of the log.
Brewster
Posts: 92
Joined: 2021 May 15, 15:59
Location: Edmonton, Alberta, Canada
Vehicle Information: 1992 Mustang LX
347 Cui
AFR 185

Re: Part throttle lean miss

Unread post by Brewster »

Just curious but have you pulled the plugs to check them all for the heck of it?

Are you running CL ?
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: Part throttle lean miss

Unread post by bad86capri »

I am running closed loop. and i did not have time to pull the plugs. At the moment im waiting on the parts to put the lightning maf on. when i get those im going to start over with a fresh tune using tunerpro. im not a huge fan of binary editor but have the dongle so figured id use it. i think im going to sell it.
Brewster
Posts: 92
Joined: 2021 May 15, 15:59
Location: Edmonton, Alberta, Canada
Vehicle Information: 1992 Mustang LX
347 Cui
AFR 185

Re: Part throttle lean miss

Unread post by Brewster »

I have BE as well but haven't used it in years.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: Part throttle lean miss

Unread post by bad86capri »

Update* so I finally switched back to tunerpro and loaded in the 90mm lightning simplified maf curve. I started the car and let it warm up for a few min then took it on a long drive. The low rpm miss is still there but not as bad, that leads me to think my fuel pump is on the fritz. Anyway, logging the fuel error table showed that the simplified curve is about 26ish% off. Not to bad I don't think. But the problem I had is after driving for a good 20 min or so. I get back home and as I'm getting ready to me with the decay rate on the iac the car starts to slightly surge then shuts off and won't start back. I have fuel pressure while cranking and spark. I tried adding fuel in the cranking pw at 160 degrees and up but it didn't help. Now I'm kinda stumped.
One other thing to note is when you crank the car the fuel pressure rises to about 40psi but it sounds like air in the fuel rails as its priming. I'll post up a log shortly when I get to my laptop charger.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: Part throttle lean miss

Unread post by bad86capri »

Here's the tune and log
Attachments
Updated Capri Tune 90mm Lightning MAF (copy from B.E).bin
(56 KiB) Downloaded 184 times
90mm lightning first drive.xdl
(1.73 MiB) Downloaded 171 times
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: Part throttle lean miss

Unread post by bad86capri »

Another update* I came out today and the car started up but I had to crank it over several times before it would try to hit. Then it finally started. Idling kind of rough but it started. I know my fuel is not dialed in with this new maf. I couldn't get it to start back yesterday so I didn't fool with the tune anymore. Could the fuel being off by as much as 26-28% cause my issue on not starting when hot?
dleach1407
Posts: 468
Joined: 2021 Mar 21, 15:17
Location: Colorado Springs, CO
Vehicle Information: 95 Mustang GT, CBAZA Quarterhorse
331, 190 11R heads, Edelbrock Victor 50 manifold, F303, T5, 76mm Turbo, 91 octane, Returnless dual pump 03 cobra tank, Behind bars rails, 80# siemens injectors
wbo2_030MtxL

57 F100, RZASA, 04 Crown Vic ecu and harness, 302, GT40 heads, 4r70w, 80# deka5 shorties, Holley carb style throttle body, Speedmaster high rise intake manifold

Re: Part throttle lean miss

Unread post by dleach1407 »

If you know the curve is off by 25+% why not just change the whole MAF curve? 25% is a lot
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: Part throttle lean miss

Unread post by bad86capri »

I'm going to. I ran out of time and have to go out of town for work tomorrow. Hopefully when I get back I'll have time to get it straightened out.
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