hard stumble in boost

[Jamesl]

Is there anything that could go wrong with an aging MS1 unit that might cause a hard stumble only in boost? An '87 MR2 I put together back in 2004/5 has run flawlessly for the past many years, but recently started experiencing a hard stumble in boost. The car runs great at idle and cruising up to about 5 psi and then the engine cuts out rather dramatically. We've regapped the sparkplugs to a smaller gap and have gone through the fuel system. Nothing has helped. No changes have been made to the MS settings in the past several years, so it's not a software issue. I wonder about the MAP sensor, but it seems odd the car would run fine and only experience this problem while in boost.

My laptop battery died so I haven't been able to conduct a datalog while driving, but at idle in the garage everything looks perfectly normal.

Any thoughts? A wild guess would be fine.

Mr2 with a 4age engine, t25 turbo, running up to 14 psi max for the past 9 years or so....

JamesL

[Matt Cramer]

Wild guess - some sort of fuel restriction preventing it from getting enough fuel pressure at high flow rates.

A data log and MSQ will help if you can post them.

[Jamesl]

Thanks, Matt. I'm now about 95% certain it's not an MeqaSquirt problem. In the meantime, the car's current owner is ordering one of your USB adapters so he can hook up his new computer for a datalog run.

Jamesl