Post Manual Swap: 1994 Volvo 850 Turbo

Conn9er · Post by **Conn9er** » 22 Feb 2025, 10:40

Hello I am posting asking for some advice following my recently completed 850 Turbo Manual Swap.

The car runs and drives and is responding well enough for regular highway driving, however I have experienced some issues with what I assume is the engine tune and how the ecu is reacting with the throttle. When throttling quickly it seems like there's almost a lurch or stutter from the power before really engaging. This stutter seems to only really happen either when throttling quickly or past 3k rpm and also seems to be correlated with the amount of boost being generated. The mechanic who did the swap for me did not completely remove the tcu from the ecu like most people recommend (he was trying to be a least invasive as possible which i totally get) but he found a way to essentially circumvent that process and gain the same result by removing everything from the transmission rather than the ecu. The fact that it runs and drives is clearly indicative that this worked but i know the car and drive and generate power much more smoothly.

Im wondering if its as easy of a fix as just getting the ecu tuned for the manual transmission? I know ipd sells flash tunes for the 850 turbo for around $500 and this would add a little bit of power as well but im wondering if there are any other options? I live in Austin, Texas and i don't think there are any tuners in my area that have the software to work on Volvos. Should I go down the ipd flash tune route or is there a better solution? Could this also be something unrelated to the tune that i haven’t thought about?

Thanks y'all.

V50M66 · Post by **V50M66** » 22 Feb 2025, 13:08

VAST Tuning is your place.

Post by **Sveedy** » 22 Feb 2025, 13:10

^ Yep.

Post by **foggydogg** » 22 Feb 2025, 22:30

Conn9er wrote: ↑22 Feb 2025, 10:40 Hello I am posting asking for some advice following my recently completed 850 Turbo Manual Swap.

The mechanic who did the swap for me did not completely remove the tcu from the ecu

Thanks y'all.

I have a couple P80 manuals, there is only one computer in the box. That's how they were born. Pull the AW TCU and drive it as a test.

Post by **Chuck W** » 23 Feb 2025, 07:24

Without knowing exactly HOW the swap was done, it's hard to say. It's possible the mechanic just bypassed the NSS/PNP switch so the starter will actually engage and start the car, but left all of the other wiring, etc in place.

Are you getting a CEL at all? (Does it even work?) I'd imagine that you'd be seeing codes, if he left all of that in the car.

You're also going to want a manual throttle cable, as there is a difference. Not going to cause the issues you're seeing, but will affect drivability.

VAST will be able to set you up with an M4.4 conversion (which uses the 98MY ECU) and you can get a "basic" R tune for under $300, it looks like. VAST . The early non-M4.3 cars require a little more work, due to the lack of OBD2 port.

At that point, you should have what you need for drivability's sake. If you want to play with things a bit and add some power, you're at a good start point with a tunable ECU.