Kurb Master RV project misfiring issue

[KrubMaster]

Hello everyone!

I've spent many hours reading on this forum and others and still have not figured out the issue I'm having...I have a P30 van with GM TBI and adapter plate on a Chevy a 350 HEI 7 Pin. I'm using MS1 V3 running 029y4a. It idles great and runs smoothly putting around residential streets. Free revs with no problems. The issue is when under light loads or trying to maintain any speeds over 60kph around 2k rpm. It breaks up and makes fluttering and popping noises and if pushed further sometimes backfires through intake. It seems to me like a ignition issue but I've tested/replaced plugs,wires,coil and distributor. Maybe someone with more experience will be able to look at the logs and have a better idea of whats going on than I do?

Van



I've attached 2 short logs of the issue. Bluetooth logging in MSDroid. Older one is with unshielded wiring and working wideband. My wideband sensor has died since then....New log is with shielded wire and all the fixes I thought might be the problem Also logs may have different values for IAT and CLT as Ive changed it with easy therm.

I bought V3 board used which proably wasnt a good idea. All Ive done is add jumpers and bluetooth




Please halp

Thanks

[DaveEFI]

Your VE table, which controls the fuelling, looks to be rather strange. Use tools on Tuner Studio to generate one based on your actual engine specs. If only to compare to your existing one, and to give a better starting point.

Basically, the cell values round about cruise seem to be random.

Also, go though your req_fuel calculation again.

Once the basics are near right, VEAL should sort it out.

[KrubMaster]

That table is bumped at cruise to ensure I'm not lean. The ve table is mostly unchanged from default. Wideband shows it's mostly okay as default is settings for a 350 as well. I've play with the table a bunch and still same issue.

If wideband shows enough fuel it should be close enough not to cause this much of an issue no?

[Matt Cramer]

I'm seeing a lot of RPM noise. Consider re-jumpering it to use TachSelect to VRIN and TSEL to VROUTINV. This will let you use the VR trim pots to filter out noise.

[KrubMaster]

Sweet thanks. I noticed that too and redid the harness with shielded wire but it didn't make any difference. I used 4 conductor shielded wire with ground on 1 end and other floating. Everywhere I've read says to use hall/optical input for a hei 7 pin module. I'll try switch to vr input and spend some time with the tooth logger. I'm using low impedance injectors with pwm, do you think that might be where noise is coming from?

[Matt Cramer]

Yeah, low impedance injectors are very noisy. Where's it getting power and ground?

[jsmcortina]

Everywhere I've read says to use hall/optical input for a hei 7 pin module.

Please read the current manuals instead of "everywhere".

James

[KrubMaster]

Power is coming from fuse box and run with injector wires and everything else in main megasquirt harness.

The Tbi injectors are grounded through the throttle body. EDIT lolol oops wasn't thinking when I said that. Ground goes to ecu in main harness.


Thanks for your help, will try switch to vr input today.


These are the current manuals?
http://www.msextra.com/doc/ms1extra/MS_ ... htm#gm7hei

[jsmcortina]

Ah... MS1, I didn't notice that when I replied earlier. Yes, those manuals are old and won't be updated.

James

[KrubMaster]

Changed jumpers as described above for VR input. Now I'm not getting any tach signal. I've set R56 and R52 fully counterclockwise to start. Do I need to change the ignition input options from HEI 7pin to something else?

I setup the board exactly as described in the msexta manual for HEI 7pin and everything works well except for the original issue I'm having.

Thanks.

[Matt Cramer]

Ignition settings shouldn't change. Can you get RPM on a Stim?

[KrubMaster]

I fixed the no tach signal by plugging in my distributer

Thanks soooo much Matt. Putting the input through the vr conditioner solved the problem. Now I just need to get another lsu4.9 and finish tuning the thing...

Do you think the pwm for injectors would be a factor in deciding to use vr or hall input? Is there any reason to use hall input if you could just put through vr conditioner and be done with it?

Thanks,
Colin

[Matt Cramer]

The VR input is generally better. However, using the optoisolated method was scienced out pretty well in the days of the V2.2 board (which didn't have the VR input) and has stayed in the MS1/Extra documentation by its own inertia.

[KrubMaster]

I should have driven it more before I decided it was all fixed I bought a cheap hantek scope and it shows noise on the tach input right where the pwm of the injector pulse is. I got excited thinking that was the problem but I turned off pwm and engine does same thing. I've triple checked timing and even verified the timing mark is in the right place. I've changed timing table to match base table in ms2 firmware and now I can rev to 3500.

I will be checking fuel pressure next but I figured it must be okay as wideband shows lots of fuel. Maybe not? Any other tests I can do with scope to pinpoint me in right direction?

Thanks