RE - 1998 S70T5

A few weeks ago I wrote in that I feel a slight "Hesitation" when driving the car on the highway at anything over 100KM or higher. (It might be there at lower speeds but I don't feel it.) I got a tune up and changed all wires and plus. It's still there. The cars still has lots of power and still flys. But the hesitation is still there.

Someone replied and said I should go to the dealer and have the ECU reprogrammed. Can anyone tell me what the ECU is and why this might make a difference?

Thanks

RickB

The ECU is the Electronic Control Unit. A computer. It controls
fuel delivery, turbo boost, spark timing, etc. About 25 sensors
send it information from barametric pressure, amount of air entering,
engine speed, etc. The ECU is a Motronic version 4.4 by Bosche.
Volvo Technical Service Bulletin 2220003 may apply to your problem
(this data from alldatadiy.com -- subscription is $25 / year):

Engine Control Module - Motronic 4.4 Software Upgrade

Vehicles involved: B5254S, B5254T, B5234T

M 4.4 Software Upgrade

Background:

An engine control module (ECM) software upgrade is available to enhance overall engine speed performance. This will smoothen the occasional variation in engine speed which may be experienced on some vehicles.

Cars involved:

Model Factory Chassis no.

S70 1 486000-557290

S70 2 486000-559255

V70 2 432000-533259

C70 J 000650-006752

C70 Conv J -000562