1998 S70 10 valve M56 tuneup, stutter at mid rev

Post by **Ocelot** » 22 Dec 2018, 06:10

Hey guys,

It's not something I did tot my S70, but something I noticed driving today. The engine idles just fine, without anything noticeable. But when I accelerate from 1st to 2nd gear or from 2nd to 3rd, it hiccups a bit, you can feel the engine stall a bit. I know it's a lot to ask giving so little information, but I'm curious, maybe you guys can help me start to troubleshoot this hiccup.

It's a 2.5 engine with 10 valves, the B5252s from 1998. I have changed all filters, but have not looked at the spark plugs or wires.

Hope to hear from you guys!

Post by **bmdubya1198** » 22 Dec 2018, 07:37

Ocelot wrote: ↑22 Dec 2018, 06:10 Hey guys,

It's not something I did tot my S70, but something I noticed driving today. The engine idles just fine, without anything noticeable. But when I accelerate from 1st to 2nd gear or from 2nd to 3rd, it hiccups a bit, you can feel the engine stall a bit. I know it's a lot to ask giving so little information, but I'm curious, maybe you guys can help me start to troubleshoot this hiccup.

It's a 2.5 engine with 10 valves, the B5252s from 1998. I have changed all filters, but have not looked at the spark plugs or wires.

Hope to hear from you guys!

Hmm... is it automatic or manual?

Post by **Ocelot** » 22 Dec 2018, 08:33

It's a manual transmission. Funny thing is, this started today. Yesterday and the days before, there were no hiccups at all.

Sidenote: a cold engine doesn't hiccup, so my theory is it only hiccups with a warm engine.

Post by **bmdubya1198** » 22 Dec 2018, 18:44

I was going to suggest the clutch switch, but that would likely affect the car at all times. Also, I don't think the clutch switch in these cars affects the engine, it's just there for cancelling cruise control.

WhatAmIDoing · Post by **WhatAmIDoing** » 22 Dec 2018, 21:22

When I had hiccups as you described, new plugs, cap, rotor, wires, fuel filter, and finally a new fuel pump relay fixed it. Would start with testing the relay, especially if it's aftermarket.

Post by **Ocelot** » 23 Dec 2018, 02:10

Thanks for the advice! I will look into buying new plugs, wires, a rotor and cap since I can't find in the maintenance history when they were last replaced. Should I buy OEM parts in this particular question or is aftermarket also okay? (except the fuel pump repay, I heard ya about that one)

Post by **abscate** » 23 Dec 2018, 04:28

OEM parts for everything if you want to run the car long term. Spark plugs are important too, especially in turbo models. We have had a couple of stutter threads resolved by switching to Volvo plugs

Post by **abscate** » 23 Dec 2018, 04:35

Moved from chat, created new thread, retooled

Post by **Ocelot** » 23 Dec 2018, 06:13

WhatAmIDoing wrote: ↑22 Dec 2018, 21:22 When I had hiccups as you described, new plugs, cap, rotor, wires, fuel filter, and finally a new fuel pump relay fixed it. Would start with testing the relay, especially if it's aftermarket.

Is there an easy way to check the fuel pump relay before buying a new one?

Post by **Ozark Lee** » 23 Dec 2018, 09:23

Ocelot wrote: ↑23 Dec 2018, 06:13Is there an easy way to check the fuel pump relay before buying a new one?

You can use a piece of wire to bypass it altogether. The wire goes between the socket positions associated with pins 15 and 87 that are marked on the relay.

...Lee