1997 850 NA manual transmission vibration at idle (also sorting out NA EVAP hose routing)

Post by **matthew1** » 28 Dec 2019, 18:18

v-janitor wrote: ↑28 Dec 2019, 17:25 I took some graphs driving (at normal engine temperature, 4th gear about 55 MPH, and 2,500 RPM) of the STFT and LTFT today;

How many minutes were you driving at this steady state before you recorded?

v-janitor · Post by **v-janitor** » 28 Dec 2019, 19:16

About 5 minutes.

Post by **matthew1** » 28 Dec 2019, 20:25

5 should be enough to lose any STFT data from acceleration so that it's not mixing with LTFT.

Did you reset ECU?

Weak battery? See this viewtopic.php?t=61256#p314131

v-janitor · Post by **v-janitor** » 01 Jan 2020, 14:44

Yes, the ECU was reset. The battery voltage is 12.57 volts...

I've ordered a cheapo pressure gauge with a female schrader valve on it, and will then get clarity on the fuel pressure.

Post by **abscate** » 11 Aug 2025, 06:17

Old thread stumble. This was a great thread exposing that the 1997 rear mounted fuel pressure regulation uses an early implementation of the “ return lacking “ FPR system that was used in 1999-

This uses purge line vacuum to regulate fuel pressure and the vacuum hose diagrams under hood might not correspond.

You can search “ return lacking” as it is the official Volvo name for this configuration

1997 850 NA manual transmission vibration at idle (also sorting out NA EVAP hose routing)

Re: 1997 850 NA manual transmission vibration at idle (also sorting out NA EVAP hose routing)