Backfiring is killing me!!!

[PlasticBoob]

Rang, can you post up screenshots of both your 401 fuel table and the 454 fuel table for us to look at?

How exactly is your ignition set up? Is the Hall Effect sensor output feeding directly into your ECU, or is the sensor output going to some sort of ignition module first, which is then feeding your ECU a tach signal? If it's the former, does your tuning software allow you to see an actual tooth count rather than just RPM ticks? You should be getting one tooth count each time a tooth passes by the sensor. That's what I would double-check while it's backfiring, though it seems ok.

Also, is your Hall Effect setting in the ECU/tuning software set to "normally high/on" or "normally low/off"? I think GM sensors are "Normally On," but you're running a Motorcraft distributor right? Ford sensors are "Normally Off". I don't even know if the engine would run if this setting was wrong, but it's something that can be easily checked.

I'm definitely no expert, and I'm not familiar with the details of your system because I run MegasSquirt, but everything looks ok to me in your graphs, including the tach signal. Just by eyeballing it, it SEEMS that the MAP drops first (from the backfire), before the throttle is closed, which then cascades to some of the other variables. Is that correct? Let's see what the injector pulsewidths are, and what the timestamps are for everything.

Are all of these logs in open loop (O2 correction disabled)?

I am starting to think I may have a distributor phasing issue. I "think" it seems to backfire when timing is max. If my hall sensor is locked down in the wrong spot, I wonder if my spark is jumping to the wrong post. I have a cheapie cap in route so I can cut a hole in it and will verify my phasing (hopefully) this weekend with my timing light. Then I will start looking into tuning more.

Great thinking. Triple check all the basics, always. We just want to rule out the EFI system as a cause, so don't get so focused on it being an EFI problem that it stops you from doing the other simple tests that were suggested in this thread. If it were my rig, I'd be tempted to go back to fuel-only EFI with mechanical/module ignition and see if that stops it, like Levelhead said.

[rang-a-stang]

Rang, can you post up screenshots of both your 401 fuel table and the 454 fuel table for us to look at?

How exactly is your ignition set up? Is the Hall Effect sensor output feeding directly into your ECU, or is the sensor output going to some sort of ignition module first, which is then feeding your ECU a tach signal? If it's the former, does your tuning software allow you to see an actual tooth count rather than just RPM ticks? You should be getting one tooth count each time a tooth passes by the sensor. That's what I would double-check while it's backfiring, though it seems ok.

Also, is your Hall Effect setting in the ECU/tuning software set to "normally high/on" or "normally low/off"? I think GM sensors are "Normally On," but you're running a Motorcraft distributor right? Ford sensors are "Normally Off". I don't even know if the engine would run if this setting was wrong, but it's something that can be easily checked.

I'm definitely no expert, and I'm not familiar with the details of your system because I run MegasSquirt, but everything looks ok to me in your graphs, including the tach signal. Just by eyeballing it, it SEEMS that the MAP drops first (from the backfire), before the throttle is closed, which then cascades to some of the other variables. Is that correct? Let's see what the injector pulsewidths are, and what the timestamps are for everything.

Are all of these logs in open loop (O2 correction disabled)?



Great thinking. Triple check all the basics, always. We just want to rule out the EFI system as a cause, so don't get so focused on it being an EFI problem that it stops you from doing the other simple tests that were suggested in this thread. If it were my rig, I'd be tempted to go back to fuel-only EFI with mechanical/module ignition and see if that stops it, like Levelhead said.

Yep! Here is the 401 table (keep in mind, it's rough draft).


And here is stock 454. When you look at the graph, notice the scale is different. So on initial look, it looks like I increased the values but really, they are less.


Ignition set up: Factory pickup is screwed down to the plate, wires come out the side of the dizzy, through a weatherpack connector, and are hooked to the 7 pin ignition module pins P and N. Ignition module pins + and C go to my coil and pins E, R, B, and G all go to my computer.

I don't see tooth counts, just engine RPM.

I searched all my parameters for "Hall", "Pickup", and "normally" and cannot find anywhere to adjust it or verify it.

Only run 1 of the 401 bin is open loop. My engine went closed loop toward the end of run 1.

here is Run 2 with 401. New color codes because I removed some items and added pulse width:
Light/Sky blue=throttle position
Red=Engine temp
Light blue=timing
Dark blue=Speed
Green=Pulse width
First backfire is around 3:31

Here is the 454 bin with pulse width added.


Will do. I have found another duraspark distributor so if I cannot get thsi to work, I may go to fuel only EFI. These buisiness trips are killing me! I just want to go home and fix this thing!!!

[PlasticBoob]

Couple of quick points...

1) The 454 tune is, of course, dumping in WAY more fuel in a lot of areas, so it makes sense that the backfire is worse with that tune.

2) Looks like the commanded timing is fine and steady? Of course we have no idea what is actually happening at the output of the module.

3) What would you say your redline is? 4,800rpm? 5,200rpm max? I would get rid of every row after 5,000rpm and then smooth out the RPM axis for better resolution.

4) This is where a wideband O2 is essential.

Try changing the following on the 401 map just for fun:

40x1600 from 53.9 to 58
40x2000 from 56.6 to 60
40x2400 from 60.9 to 63
40x2800 from 65.6 to 67

50x2000 from 59.4 to 65 ****Important
50x2400 from 61.1 to 68
50x2800 from 67.6 to 70

60x1600 from 61.7 to 65
60x2000 from 68.0 to 66

Then go hang out in that same area of the map with as steady a throttle as possible. If that makes things worse, then restore the map and then try going the other way:

50x1600 from 63.3 to 55 ****Important

40x1200 from 60.2 to 50
40x1600 from 53.9 to 51
40x2000 from 56.6 to 53

Be careful when going lean, you are flying blind with no wideband O2 readout so you want to do so in small steps. And don't change any bins you know for a fact work better than the numbers I'm giving you.


You can always restore to your current map if it doesn't work out.

I'm not saying the fuel map is the issue, even though it's very rough indeed, but I did have some misfires/cuts and near backfires that drove me crazy - all due to an improperly aligned VE/fuel map. There was just too much distance between bins, in certain areas of the map, for the ECU to interpolate correctly.

Where did you get your base 401 map? Is there anyone else around running the same system/cam/compression who can give you their map that might be more dialed in? Does your tuning software have a base VE table generator?

How high have the RPMs got on this EFI system? I'd be very leery of pushing them too far with a questionable map and no AFR data to watch as you're leaning on that throttle in real time.

Will do. I have found another duraspark distributor so if I cannot get thsi to work, I may go to fuel only EFI. These buisiness trips are killing me! I just want to go home and fix this thing!!!

Yeah, it's quite a process but you'll get it figured out eventually! Going fuel only for the time being will definitely tell you a lot of things either way.

What about EGR? How do you guys deal with it on this EFI system? Is it opening up or somehow leaking on cruise and messing up the mixture? You said it's disconnected for the time being?

[rang-a-stang]

Couple of quick points...
1) The 454 tune is, of course, dumping in WAY more fuel in a lot of areas, so it makes sense that the backfire is worse with that tune.
2) Looks like the commanded timing is fine and steady? Of course we have no idea what is actually happening at the output of the module.
3) What would you say your redline is? 4,800rpm? 5,200rpm max? I would get rid of every row after 5,000rpm and then smooth out the RPM axis for better resolution.
4) This is where a wideband O2 is essential.
Try changing the following on the 401 map just for fun:
40x1600 from 53.9 to 58
40x2000 from 56.6 to 60
40x2400 from 60.9 to 63
40x2800 from 65.6 to 67

50x2000 from 59.4 to 65 ****Important
50x2400 from 61.1 to 68
50x2800 from 67.6 to 70

60x1600 from 61.7 to 65
60x2000 from 68.0 to 66

Then go hang out in that same area of the map with as steady a throttle as possible. If that makes things worse, then restore the map and then try going the other way:

50x1600 from 63.3 to 55 ****Important

40x1200 from 60.2 to 50
40x1600 from 53.9 to 51
40x2000 from 56.6 to 53

Be careful when going lean, you are flying blind with no wideband O2 readout so you want to do so in small steps. And don't change any bins you know for a fact work better than the numbers I'm giving you.

You can always restore to your current map if it doesn't work out.

I'm not saying the fuel map is the issue, even though it's very rough indeed, but I did have some misfires/cuts and near backfires that drove me crazy - all due to an improperly aligned VE/fuel map. There was just too much distance between bins, in certain areas of the map, for the ECU to interpolate correctly.

Where did you get your base 401 map? Is there anyone else around running the same system/cam/compression who can give you their map that might be more dialed in? Does your tuning software have a base VE table generator?

How high have the RPMs got on this EFI system? I'd be very leery of pushing them too far with a questionable map and no AFR data to watch as you're leaning on that throttle in real time.

Yeah, it's quite a process but you'll get it figured out eventually! Going fuel only for the time being will definitely tell you a lot of things either way.

What about EGR? How do you guys deal with it on this EFI system? Is it opening up or somehow leaking on cruise and messing up the mixture? You said it's disconnected for the time being?

1) copy. It runs smoother (espeacially at idle) with the 454 tune, but its pretty gutless. Throttle is much crisper on my 401 tune, too.
2)The only way I can think to verify actual timing is I stick my laptop on my inner fender, while it's running, with my commanded timing showing on TunerPro, and my timing gun pointed at my timing marks. I have verified it at idle with my timing light and it seems to be spot on.
3) I built the motor for 5500RPM. I had it balanced, ported the heads, and the cam is supposed to be good to 6k. I have not gone north of 4k yet though, some because I cannot tune there without a wide band but, mostly because I backfire before I get there. I will try your recommendation, though.
4) concur! (wideband). Will do (update 401 map to those values). Copy (careful when going lean)

Base 401 map started with the 454 map. I smoothed it, drove on it, data logged on it, plugged my numbers into an excel spreadsheet I got from gearhead-efi, re-did the map with the excel numbers, and repeated. I don't know anyone running the same system/cam/compression. I know several with 2 of those 3 (babywag has same system, Full Size Jeeper has similiar cam and compression). Honestly, I feel like if I can get this thing to stop backfiring, I am pretty confident I can get the maps close enough to run really good. Nope, no base VE table generator in TunerPro. I have many options on the the interwebz to download though.

Highest I have gone is about 4k becuase backfiring. Concur (leery of pushing too far).

I have an EGR mounted, I have an EGR solenoid mounted and wired, but it is disabled in the bin. I forgot to disconnect the vacuum line (a guy on theamcforum noticed that in a picture) during troubleshooting so there is a possibility that it is leaking but I am not too worried about that.

I really appreciate you guys all helping me out! This is all new to me and I would be lost if it weren't for folks like all you guys on here! I have been fighting with this and other things for so long, it's easy to get distracted and miss things.

[babywag]

What is your FP set @
Did you change the injector flow rate in .bin to match your injectors @ that FP?
If the value isn't correct the pcm calculations for fuel will be wrong.

It appears to be rich, but without seeing the logs or the fuel trims just a guess.
You might want to look @ INT & BLM in monitor to see what's occurring ~backfiring?

Before significant changes to fuel map as I suggested a couple times already force it OL and see how it runs.

[rang-a-stang]

What is your FP set @
Did you change the injector flow rate in .bin to match your injectors @ that FP?
If the value isn't correct the pcm calculations for fuel will be wrong.

It appears to be rich, but without seeing the logs or the fuel trims just a guess.
You might want to look @ INT & BLM in monitor to see what's occurring ~backfiring?

Before significant changes to fuel map as I suggested a couple times already force it OL and see how it runs.

Fuel pressure is at 12psi.

Yep, bin is set to same flow as injectors.

I look at BLM and INT while I am driving and did look at them in the history graphs. They are better for the 401 bin than the 454 bin but I don

[rang-a-stang]

What is your FP set @
Did you change the injector flow rate in .bin to match your injectors @ that FP?
If the value isn't correct the pcm calculations for fuel will be wrong.

It appears to be rich, but without seeing the logs or the fuel trims just a guess.
You might want to look @ INT & BLM in monitor to see what's occurring ~backfiring?

Before significant changes to fuel map as I suggested a couple times already force it OL and see how it runs.

Fuel pressure is at 12psi.

Yep, bin is set to same flow as injectors.

I look at BLM and INT while I am driving and did look at them in the history graphs. They are better for the 401 bin than the 454 bin but I do not really understand it or what is “good” or “off” so I don’t pay a lot of attention to it yet.

Yep, gonna drive with O2 sensor unhooked and log. First I am going to check my dizzy phasing, then take for a drive with O2 unhook

[babywag]

Fuel pressure is at 12psi.

Yep, bin is set to same flow as injectors.

I look at BLM and INT while I am driving and did look at them in the history graphs. They are better for the 401 bin than the 454 bin but I do not really understand it or what is “good” or “off” so I don’t pay a lot of attention to it yet.

Yep, gonna drive with O2 sensor unhooked and log. First I am going to check my dizzy phasing, then take for a drive with O2 unhook

In CL BLM & INT should be ~128
Anything under 128 the pcm is pulling fuel over 128 adding fuel.
Cannot tune VE tables without them.
Need good data to get in ballpark.

[rang-a-stang]

In CL BLM & INT should be ~128
Anything under 128 the pcm is pulling fuel over 128 adding fuel.
Cannot tune VE tables without them.
Need good data to get in ballpark.

Ok, that's what I assumed but wasn't sure. I did use them for the VE tables but plugged them into the excel spread sheet and it did the computations.
*********************************
IT'S "FIXED"!!!! It was distributor phasing!
Sorry the pictures are so bad. It's pretty hard to get these pictures. I basically video'ed them and screen captured it.

Here it is with the timing plug pulled (timing at 0 degrees):


Here it is at idle with the timing plug in (so timing is at 20 degrees advanced). With the spark that far over, I don't know how it even ran at max timing!! I should have had LOTS of mis fires and back backfires.


I pulled my dizzy, brought it into the garage and unscrewed the pickup lockdown screw. I marked the location of the #1 stud on my cap adapter and rotated it so when the star wheel and magnetic pickup were centered for #1, the rotor tip was just passed the stud. This would mean that at 0 degrees, the spark should be on the trailing edge of the rotor. This moved the pickup about 10 degrees so I screwed it back down.

Here it is after moving the pickup. This is idle at 0 degrees timing:


And the best picture! At 20 degrees of timing, it's pretty much centered.


I took it for a spin. Did my normal route, with 401 tune. I did not data log because I didn't feel like grabbing my laptop and booting it. Got up to 70, eased of the throttle.... NO BACKFIRE!!!!! WOOOOoo HOOOO!!! I got off the freeway, headed down run 3 and cruised at 50, NO BACKFIRE!!!! I was feeling pretty triumphant as I turned at the gas station heading toward home.... then it stalled. I cranked it over, no start. Are you 'ing kidding me?!?!?!?! Fuel pump died. At least it doesn't backfire anymore.

[posulli88]

Thats Awesome! Congrats on figuring it out, nothing better!

[Mikel]

[Full Size Jeeper]

Glad you have it figured out

[chubbinius]

Those are two of the greatest words to hear...bet you're smiling from ear to ear...hopefully the fuel pump will be a quick swap.

[johnsonic]

YASSSSS - victory! Congrats!

[PlasticBoob]

Great job! Now go crank trigger with LS coils.