A dip in my timing

[J-440]

 Got a FAST standalone with duel sync distributor and an MSD 6AL ignition. My base timing table is a nice, smooth transition from 20* at startup all the way to 35* at WOT. For some reason my timing "dips" between 1300-1500 rpm and my engine backfires through the exhaust and the car falls on its face. After 1500 she straightens out and is in time with the table. FAST's customer service is non existent so I'm asking the gurus on here. Any ideas on what could cause this?

[metallicareload99]

I have my timing table advance timing down around 1100 to help keep it from dipping. Maybe have your table bump some in around where the dip occurs 

[J-440]

 Well shoot.  I've tried 4 different tunes from the past (all were decent) and I'm getting the same results. This has got to be a distributor issue. Gonna pull her and inspect it soon.

[metallicareload99]

The distributor is just distributing spark, hard to imagine it's causing a problem. Although I've had rotor phasing off a good bit in the past, but that caused breaking up @ higher RPM. Almost sounds like a lean bog, have you recorded any data logs?

[J-440]

 Yeah I've made a lot but am a little inexperienced at reading it. I need to study more. But a lean bog in all 4 tunes?

[metallicareload99]

Good point, but 4 tunes on the same engine How is the "accelerator pump" tuned in F.A.S.T? I'd look at the AFR around the time of the dip

[cdr]

post a picture of your timing table

[J-440]

Here's both tables.

[cdr]

what all is your engine have & car set up

[J-440]

440 36lb injectors, 2000cfm throttle body, roller valve train, duel sync distributor, MSD 6AL box, Holley electric pump with -10 feed line and -8 return line, 6 speed GV tranny, 4:10 gears.

[cdr]

heads, compression, cam specs , intake

[cdr]

does it only do it when going wide open, is it good at part throttle

[J-440]

 Unfortunately it backfires right after idle. Around 2000rpm it smoothes out. It didn't always do this which leads me to believe it's something else.

[cdr]

possible bad plug wires, plug wires not in the correct firing order, coil wire burnt, bad spark plug ect

[J-440]

Preciate it bud. Gonna check those soon.

[metallicareload99]

2000 cfm throttle body? I bet it moves a lot of air even just cracked. Are you running open loop or closed? And I didn't read your first post well enough, so you're actually seeing the timing retard when the dip occurs?

[J-440]

 Running closed loop. Yeah the throttle body is overkill for now. I bought it for a future power adder setup. She breathes really nice. Yeah you can see the timing dip in a small section then jump back up to normal again. Plugs and wires look good. Still searching though.

[J-440]

 Think I found the problem. One of my ECM harness' is right next to my distributor wire harness and I'm getting electrical interference between the 2. I need to wrap these things in foil and get better sleeves. 
Here's something cool I found out. Turn your car on and let it idle. Grab an old AM hand held radio and tune it to a white noise station. Then move the radio around your harnesses and listen for high pitched or odd sounds coming from the radio. You've found your problem. Preciate the help Metal.

[metallicareload99]

  No prob man, glad you are working through it. Interference is one of the few things to make sense

[J-440]

 Well the aluminum foil wrap didn't make a difference. I got another question though. On the A/F ratio table, the football is at the very bottom of the table. Even when I rev the motor it shoots to the right with the rpm's and doesn't jump around like my base fuel table and the base timing tables do. Is that normal? I've even swapped my maf sensor and checked for vacuum leaks but I got the same results. Any ideas?

[cdr]

post a screen shot of that table

[J-440]

Here she is.

[cdr]

Call FAST & see what they say, this is probably related to the running problem you have. if they are no help, call Rich @ FASTMANEFI , not sure he will help without charging you for his time UNLESS you bought the efi from him

[J-440]

 Yeah FAST already told me that this was an electrical interference issue. Been talking to Rich off and on but his message board is not very active. Preciate the help Metal.

[cdr]

Yeah FAST already told me that this was an electrical interference issue. Been talking to Rich off and on but his message board is not very active. Preciate the help Metal.

Does the timing table football move like it should ?

[J-440]

 Yes. There's no knock sensor either so the timing isn't affected.

[cdr]

unless you have something wrong in the initial settings ie, afr learn turned off ect...I would say the ECU is defective

[J-440]

 Man I hope not. Gonna keep trying.