Breaking up issue

[bentley429]

Quick rundown of the car:

MS v3.57
89 mustang
83lb injectors High imp
h/c/i
347
blower
digital 6, blaster, firecore wires, good tested dist.
SD

The firing order is the NON HO order which is, 15426378.

Plugs are looking pretty bad now but I am guessing it is just from all the missing. New plug recommendation would be great. Currently running NGK 9's.

Currently I am running off of the base tune that can be found on the megasquirt site that has been edited some for my setup. At idle the car runs great. Up to 2k rpm it runs good, after that it starts to miss then starts breaking up bad at 2500 and over. Boost gauge is fluttering pretty bad during all of this. Now I was thinking, could this have something to do with my firing order and the fact that the megasquirt is assuming it is the HO order? If so how can I change the injector squence around, as the injectors are still wired for the HO order? I am really at a loss on this.

[Matt Cramer]

The distributor is handling the firing order for the spark plugs, and fuel is bank to bank so the firing order doesn't really matter. What is your O2 sensor reading doing when it's breaking up? Could you post a data log and MSQ?

[Arrowhead]

Boost gauge is fluttering pretty bad during all of this.

Matt,

I've been struggling with a similar problem. I'm running MS-II v3 with the latest software/firmware/megatune and am seeing boost pressures that shouldn't even be possible with my setup. I've run the map cell all the way up to 180 and can max it out with just a blip of the throttle while it normally will max at 150 at WOT and 5000k full load. I've had the same engine running with an older version of MS and no problems. I've done a lot of reading through the forums and there has been a quite a few users struggling with accel / boost issues and this seems to be a common thread. Call it a hunch, but something weird is going on here and I can't put my finger on it. I've even tried resetting every accel parameter but can't keep it from dumping fuel under accel / boost - super rich breaks up and black smoke.

[bentley429]

Here is a datalog and the tune file. On the datalog where the af goes flat I was just using the playback on the wideband monitor. A few other people have told me this could be a noise issue? The wideband does go rich but nothing to crazy. Any help would be great. Thanks.

[bentley429]

This is my thread over on the corral if it helps. http://forums.corral.net/forums/megasqu ... issue.html

[Matt Cramer]

The only place I'm seeing noise is on the CLT signal. However, that's noisy enough to be adding up to 50% more fueling at times, which could account for the stumble. I would check your coolant sensor wiring.

[bentley429]

The only place I'm seeing noise is on the CLT signal. However, that's noisy enough to be adding up to 50% more fueling at times, which could account for the stumble. I would check your coolant sensor wiring.

Got the coolant sensor squared away. Still have the exact same problem though. I noticed the IAC has a lot of noise also? It actually makes noise too, as in noise I can hear. Makes a humming sound that it didnt with the stock computer? Here is a new datalog with the CLT fixed up. Thanks

[Matt Cramer]

I'm also seeing noise on the battery voltage that is affecting fueling. Where's it grounded?

[bentley429]

I'm also seeing noise on the battery voltage that is affecting fueling. Where's it grounded?

Where is what grounded? The battery goes straight up front to engine block. From there it goes to the sway bar mount. Everything in the engine harness is just factory I did not ground anything different, including the sensors. Thanks

[bentley429]

UPDATE: I found a loose ground fixed that up, same issue. I tried putting the ignition advance to fixed timing from use table, revs to the sky no missfires or anything. What would this indicate? Could my trigger offset be incorrect? if so can someone guide me through the steps incase I did it incorrect? Thanks

[Matt Cramer]

If the timing you see with a timing light matches the timing in the tuning software, your trigger offset is correct. However, you may need to adjust the spark latency. To do this, set fixed timing and check with a timing light at both high and low RPM. Make sure the timing is not changing as the RPM comes up. If it retards, add more latency; if the timing advances with high RPM, use less latency.