Rough idle 1998 VOLVO S70 T5

LEEGary · Post by **LEEGary** » 17 Dec 2025, 08:37

Not long ago, I changed the air filter and disconnected the MAF connector. When everything was finished, I plugged the MAF connector back in, and the vehicle started to idle erratically. After unplugging the connector, it ran smoothly.
After driving for a while, plugging in the MAF connector seems to make the vehicle run normally, but it will randomly stall, and sometimes when you step on the accelerator, it will randomly lose power, and rpm will rise again after a few seconds.
I bought a brand new, genuine MAF, but it doesn't work. The vehicle idles smoothly for a few seconds during a cold start, then starts to shake, and my boost gauge needle jumps at this point.
Sorry, Volvos aren't common cars in my country, and I couldn't find better diagnostic tools. If the MAF is plugged in, the OBD scanner can't read any fault codes.

Post by **scot850** » 17 Dec 2025, 08:47

As your car is a 1998 year, they did not have the same OBD2 as 99 on cars so many testers do not work with them reading codes.

Consider a bluetooth OBD2 ELM327 and an APP like 850 OBDII for reading your car codes.

I would look back over the work you did and check you reconnected everything and did not disturb something else while working on it.

Neil.

Post by **misha** » 17 Dec 2025, 10:50

It could be bad maf connector.
They are more prone to failure than actual maf sensor.

I was chasing my tail about this exactly problem for about half a year and nailed it to a bad maf connector.