1998 S80 T6 driving me nuts..... Help?

My first post and it happens to be begging for help (shame on me)!

The car in question is a 1998 S80 T6 2.8 twin turbo. Its GREAT. When it decides to work properly...

I haven't owned this car long (about 2 weeks) and the entire time has been spent chasing oil leaks and generally being under the lid ... Hmmph.

When I got the car it was boosting fine, completely mental and insane fun.
Now, not so much....

I will start with the things replaced and jobs done because its easier to outline:

New battery as the previously fitted one was hilariously under sized.

New TCV and ALL of the vacuum hoses associated with the turbo circuit. (3 TCV units fitted to date and none made a difference to this fault).

Replacement cam seal, exhaust cam transmission side.

New camshaft solenoid reset valve gasket along with unit cleaned and checked for operation.

New turbo return line gasket and o'ring on one turbo because some moron thought silicone would repair the leak before I got it.

2 replacement coil packs (all the rest are tested good order.

Full set of iridium NGK plugs.

Most recently a new Volvo genuine inlet temperature sensor ( part number 9445153 )

3 of the coil pack connectors on the coil loom as they were all smashed up.

Brand new fuel filter!


Now down to the issue!

The car starts readily and idles well when cold. Once warmed up it gets very slightly lumpy but I have had worse idles on some of my cars.

The car drives great around town and so long as you don't want all of the power its great and returns good mileage.
The second you use most, or all of the throttle, the engine goes up to 3500 rpm and then shuts off (like a fuel cut off). If you keep your foot on the throttle it surges power .... Full... Nothing....full....nothing and so on.

I have no idea what to check next or replace as the ecu isn't throwing fault codes.

I have previously seen ECM 6806 Indicating low boost pressure. Since the repairs listed above, it hasn't thrown that code again. ECM 980A something about intermittent ecu internal fault (only does this if you have the battery off) and one I can't recall to do with can reset valve .... That hasn't come back since the valve was cleaned and new gasket fitted!


What the heck is going on with this thing??? I have thrown around ?200 at things that should have fixed this fault in a week (I do all my own work). I seem to have made no ground towards solving the issue ..... Time to ask the experts of this parish I think before I end up in a nut house haha


Thanks in advance for any responses either leading to a repair or not

Just as a precaution, swap your "fuel system relay" with another one and test again. I had a 960 that would give me similar problems (no fault codes though) that ended up being the fuel relay. I guess it was getting tired, but I didn't figure it out until it totally quit. Swapped relay and all is good.

I wonder if the ac relay is the same? I'm going to test because anything is worth trying at this point.

Major fast response, thanks

There will be another couple of relays that fit. Thats how I figured it out.

I also left the key on “run” which should kick the relay on and plugged it in and out of the socket. The bad one would not click. A good one had a healthy click you could hear and feel.

There's not gonna be a lot of diagnostic crossover between a 960 and an S80...

OP, do you have VIDA or are you using a generic scanner? What color is the label on the throttle body and how old is it? Were the turbo control valves you installed brand new or new to you? Are you sure you have the TCV hoses hooked up correctly?

FWIW I would never pop iridium plugs in a boosted (read: older Volvo turbo) engine. NGK copper core or OEM plats (= bosch plugs.. meh) at most.

Not saying that's the root cause, just throwing $.02 out there on plugs for turbo cars.

kampman said:

There's not gonna be a lot of diagnostic crossover between a 960 and an S80...

OP, do you have VIDA or are you using a generic scanner? What color is the label on the throttle body and how old is it? Were the turbo control valves you installed brand new or new to you? Are you sure you have the TCV hoses hooked up correctly?

Click to expand...

Yes. Having a factory level scan tool would be ideal.

Don't trust codes on generic readers unless it's something like a P0171 lean code. I had my $50 generic scan tool report a factory code as a speed sensor code incorrectly once.

OP still here?

Sorry about the silence ... I have been frantically busy and trying to get this car just to behave!

I have replaced all but 1 of the coils (there is no more local stock left) so have to wait until Monday to get the last one.

I have found some grim issues that I wish that I hadn't found ....
I replaced three of the coil connectors already as 3 were bust. While replacing the coils I noticed several bad wires, by bad, I mean melted and or cracked casings.
I cannot get a loom for it as Volvo discontinued the part so I will have to get smart here.

It hasn't had a Vida on it as nobody local has one and the car drives like hell so a 30 mile trip is a big no no.

The iridium plugs are a like for like replacement for what was fitted to start with, also listed for the car (NGK as previous and they were fine tbh).

I'm not sure what is meant by the label colour on the throttle, all I can see is a big yellow sticker but also have no clue as to age!

Every single one of the coils removed had noticeable cracks in the bodies of them and down the stems internally. The remaining one is the best of 6 refitted until I can get new monday.

Changing 5 coils so far has improved the hard cut.... However it still has a stutter at around 3.5k stationary and also still cuts at above 4k (slight improvement there) under any load.

Have a new intercooler to throttle pipe arriving soon as previous owner has siliconed it for some reason. They had done the same with the turbo intake pipe too so that has also been replaced. The reason I went down this route was being unhappy with all the bodge in there. All other hoses and pipes check out good.

Also I now have a really slightly lumpy idle but no warnings or lights on the dash.

Staring to mull over whether this engine would fit in anything else so I can run it on an omex 710.... That can of worms is to stay firmly closed for now though

It would be nice to get to the bottom of this, as a side note all of the relays have been replaced with no difference in running but was worth a shot

I actually am not sure regarding the TCV hose connections being correct or not as I have just plumbed up as was

Pull codes.

No code reader? Start spraying around with brake cleaner and see if you can get the idle to change.

Small update with the situation ....
Last coil pack swapped out today! The idle is now super smooth with no apparent misfire or lumpy running.

I'm yet to take it out for a drive, however it needs petrol (story of my life with this car haha), I guess I will find out at that point if it is fixed or not.

OK.... Took the old tank for a drive.
The response is .... Hhhhhhhhh.... Still doing it!

It's not as pronounced as before, however, WOT is still not allowed.

The only thing that I am conscious of. And this happened right before this hard cut issue (best way I can think to describe it). The old previously bodged up air intake sensor flew out of the pipe as it was missing a leg. I replaced this with a genuine Volvo one ASAP and really didn't drive far with it secured with a tie wrap.

The Map sensor (turbo boost sensor?) Lives next to it.... Could a sudden decompression in that pipe have caused it to totally fail??
I have run with it unplugged and it runs more lean and a bit hotter so plugged it back in. Also if you unplug the maf it dies and you have to restart with the car being near unusable.

I have looked all over the internet and always find lots of dead threads without a fix. I know that I am not alone with this issue. I am determined to fix it and post the fix for the issues. However I do feel like I'm chasing myself around in circles with this fault!
I'm happy to rule out the coils as they are all shiny and new. This now ensures a silky smooth idle as it should be..... If you put on revs while in park, it stutters like its at the limiter from 3k to the limiter at 4k..... If you put on the gas gently this doesn't happen and it's smooth all the way to the 4k limiter (being an auto I'm used to this feature having owned Mercedes for a long time).

Anyone got any other suggestions? Apologies for my rambling too!

High end scan tool to monitor fuel trims, codes, and misfire data. It would tell you which cylinder is missing.

Again, lacking that, hit it with brake cleaner. I monitor fuel trims on scan tool data and if there is a leak the trim will go negative as it sucks in the cleaner.

Or hit home depot and get a PVC cap, hose clamp it to the intake hose disconnected from the MAF, add a pressure fitting (first) then apply 10 psi and spray with soapy water

Or use a smoke machine.

Or listen around with a vac line in you ear for leaks.

Or it could be a vvt issue, fuel pressure issue, or a myriad of other things. With no good scan tool you are really going in blind.

New parts don't mean good. Keep your old coils in case the aftermarket junk fails quickly. I really would have done a leak test before tossing 6 coils at it.

What about one of those Bluetooth scan tools and a smartphone app. You should at least be able to pull codes and hopefully see fuel trim data. It would be cheaper than a couple ignition coils.

It could be a crank position sensor? An intermittent crank sensor often will not set a code.

Does the tach go to zero when it shuts off?

I will check the tach operation when I go out a little later. Something that I'd taken for granted and kind of gets ignored really.

As for throwing 6 coils at it, every one of them had huge cracks the length of the packs. The isolation tube things on them were all cracked and split too.... They really were ready for doing. I have kept every single one of them (just in case).

I had a look around for some end caps but most of the diy stores around here don't have them on the shelf.

The high end scan gear is expensive, nobody local to me has the Vida software and mostly use snap-on junk that seems to think my 98 2.8 t6 doesn't even exist. I hadn't actually considered a Bluetooth unit so I will look into that. This car has thrown a few random codes while I have had it, including multiple cylinder misfire which threw it into limp mode. Had the code cleared and there was in fact absolutely nothing wrong

I am now giving up with this hateful lump of ****.

The car is off to the breakers yard in the morning, I am done spending money chasing unfixable faults and have had enough of it!

Thanks for the advice and help guys .... Obviously the glory days of the 740 and 240 alike are long gone

Sorry dude. The early S80s are widely regarded as some of the worst cars Volvo made. Hopefully you weren't in it for too much money.

Yeah the guy in heavy line got really good at dropping those transmissions. $

In 1999 I bought a new Volvo S80 T6. I sold it within two years as it was spending as much time at the dealer as it was in my garage. I swore that I would never own another Volvo. Yet here I am all these years later happily driving an '88 244 NA. Go figure.