454 Starts-Idles-Stumbles

[Buick462.efi]

Could you assist me with your expertise? I'm running an MSII on a V3.0 board to control fuel on a mildly warmed over 454 in a 1988 C1500.

Current tune is attached. Engine specs are below:
-1988 454
-Peanut port heads
-Edelbrock TBI manifold
-454 TBI
-Erson cam - 280/290 (204/214 @.050; .476/.501 lift; 112 LSA) going for low end torque, it''ll be my daily driver
-Old School HEI, vacuum advance, initial timing 16 degrees
-1.75" long tube headers
-2.5" true dual exhaust with H tube

It starts great and idles at ~750 RPM when warm. The problem is when I try to blip the throttle - it goes lean and dies. I have driven it once around the block by very very gently accelerating. I would not want to drive this in rush hour traffic.

I've been through the MegaManual multiple times, made many adjustments, tests and trials. All I end with is harder starting and a degraded idle. HELP...I want to drive this thing!

P.S. This is my first MegaSquirt experience

[kjones6039]

I would start by lowering the TPSdot Threshold to about 100 and adjust as needed from there.

Set Decel Fuel Amount to 100, for the time being at least.

I would also increase both Accel Time and Accel Taper Time.

Just my way of doing things of course........

Ken

EDIT: A log showing your "stumble" would also be helpful......

[Buick462.efi]

Ken,

Thank you for the direction. I'll try it tonight and will post a log (if I can get out to the shop).

[355vette]

I have a very similar motor except you have a non stock intake and a little more cam. I compared your msq to what I think is my current.( I let it sit for months, start and drive it an don't pay much attention to it as I am fooling with a mpi project now) and yours is quite different from mine. I am using 85lb injectors at stock tbi fuel pressure. If you are interested I could try and help you out. The truck is in the barn with a dead battery right now so a little harder to check the installed msq but I think what I have is pretty close.

[355vette]

here is an msq to try taking into account the motors might be very different.

[kholman]

Differences, even minor ones, in configuration can make a huge difference in the way your engine runs. To guard against possible damage to your vehicle, we caution against using someone else's map for your install.

[355vette]

Admin--Looks like only one look at msq which was probably yours so if you delete it, problem solved. I am unable to delete.

[Buick462.efi]

355vette - thanks for the .msq, I may not run it but I'll look at it. It could be a great learning experience. Thanks for sharing.

[Buick462.efi]

I made it out to the shop today and attached is my current tune and a data log. It starts and runs and I can rev it a little thanks to the advice from kjones6039. The data log is from when I backed it out of the driveway and drove it around the cul de sac. Still seems a little lean. Going to beef up the duty cycle and make another run at it tomorrow. However, I am interested in any and all advice - I'm learning and need all the help I can get.

[kjones6039]

Took a very brief look at your msq and noticed that you have ego control set to Narrow Band. Is that correct? If so, I suspect that you will have a very difficult time tuning with a narrow band sensor. A wide band would help immensely!

Ken

EDIT: just curious.... Are you tuning with TS's VEAL?

[Buick462.efi]

Ken, thanks for the quick response. Yes, narrow band is correct. Seems like you are recommending the wide band. Could you help me understand why? What are the benefits?

Mike

[kjones6039]

Yes, narrow band is correct. Seems like you are recommending the wide band. Could you help me understand why? What are the benefits?

Yes, I certainly do recommend using a wide band if, you intend to take advantage of such things as the VE Analyze Live function in TunerStudio. Narrow band merely tells the ecu whether the mixture is rich or lean. The wide band ,on the other hand, outputs a linear voltage to indicate the extent to which the mixture is rich or lean.

I have experience with both, and found early on that meaningful tuning was near impossible with nb.

Just my opinion of course! Others will vary, no doubt.

Ken

EDIT: you might take a look at the one listed in my signature.....

[355vette]

I too would only use a wide band. Big block chevs really don't like lean idle. Even the GM code has a bias to richen. The ones I have worked with wanted at least 13.5. I use a much leaner mixture as soon as the table gets to about 1000 rpm.

[Buick462.efi]

Thank you for the advice on the WB - I have one on the way from 14point7. In the interim, I've been refining the tune and have it starting nicely, idling smoothly and I have been able to drive it a bit and zeroing in on the VE table. I'm still having trouble with the ignition signal though. Attached is my current tune and data log from a short drive through the neighborhood. You'll notice the ignition signal dropping out a lot at part throttle and then a couple of spikes - one up to 8473 RPM then back to normal. My board circuits are set up to fire of the negative side of the coil, the tach wire is shielded and grounded and goes direct to the DB37 connector. Anyone seen this before and if so, what did you do?

[kjones6039]

I'm still having trouble with the ignition signal though. Attached is my current tune and data log from a short drive through the neighborhood. You'll notice the igni

Huh??

[Buick462.efi]

I'm still having trouble with the ignition signal though. Attached is my current tune and data log from a short drive through the neighborhood. You'll notice the igni

Huh??

Why does my ignition signal drop to 0 rpm?

[Buick462.efi]

What MSII settings should I use in base ignition settings using the negative side of the coil for the tach signal? I'm running an old school 4 pin HEI. Found info on the 7/8 pin module HEI. unable to find setting info for the 4 pin HEI. Thanks!

[kjones6039]

Why does my ignition signal drop to 0 rpm?

I would be equally concerned about why RPM also jumps to ~8400!

IIRC you are using HEI........ Where are you getting your trigger from?

Ken

[Matt Cramer]

For fuel only, most of the settings have no effect; just be sure you don't have the wheel decoder turned on.

[trakkies]

What MSII settings should I use in base ignition settings using the negative side of the coil for the tach signal? I'm running an old school 4 pin HEI. Found info on the 7/8 pin module HEI. unable to find setting info for the 4 pin HEI. Thanks!

Think you can ignore what type of ignition you have if triggering off the coil negative. Just follow the instructions for fuel only and points etc ignition.