SOLVED! Power cut at 4k rpm in 3rd gear 97 850 T5 Topic is solved

smallblackbrick · Post by **smallblackbrick** » 08 Oct 2022, 19:23

Hey guys, just picked up my first Volvo after riding around in my friends' for years. Runs great except for two things. I'm hoping for some help on here because after searching through every Volvo forum I can find I've come up blank. When I'm over about half throttle in 3rd gear, right at 4k RPM there's a power cut. It's very consistent with only happening at 4k RPM, but not about throttle. It drops maybe 100-200 RPM, then usually goes right through 4k, sometimes it stutters twice. Boost does not drop as far as I can tell (Automatic). Sometimes I'll be on it almost floored and it's fine, sometimes it happens at 1/3 throttle. Seems maybe to be dependent on engine load, as it generally happens under less acceleration when going uphill, but I also wonder if it could be fuel delivery.

My main question is, does anyone know what the car could be doing that makes it happen only at 4k RPM? Is it ECU related? Is that when more fuel is dumped in and I'm leaning out, and it cuts fuel because knock? The other thing that may be related is it rough idles and wants to die on a cold start. After warming up it's fine. I cleaned out the IAC really well, full can of cleaner and a compressor. Lot's of nasty stuff came out. Could this be MAF? The car starts up with it unplugged... I should have my hands on a new one in a few days but I'm wondering if there's something else I should order.

Glad to be here and I appreciate any answers or guesses.

Post by **abscate** » 09 Oct 2022, 04:48

Hello Queen City, great place!

First place to look on an 850 is the distributor rotor , cap, plug wires, and plugs. Ignition parts life runs 100k mile on these cars so they get neglected.

Fuel injection and ECU failures are 1;5000 type events in comparison.

smallblackbrick · Post by **smallblackbrick** » 09 Oct 2022, 17:26

abscate wrote: ↑09 Oct 2022, 04:48 Hello Queen City, great place!

First place to look on an 850 is the distributor rotor , cap, plug wires, and plugs. Ignition parts life runs 100k mile on these cars so they get neglected.

Fuel injection and ECU failures are 1;5000 type events in comparison.

Okay, good to hear because those are all parts I have coming. Since I have you here, are the IPD performance plug wires comparable to the OEM Bougiecord? I've seen a lot of mixed answers.

I'll update the thread when I replace all those, I've seen a couple other references to this issue with no resolution on other forums.

Post by **scot850** » 09 Oct 2022, 19:02

I am wary on IPD Performance parts. Some are ok but some are poor with short lifespans. Their stuff used to be good but not so much now. I would stick with Bougicord if you can get them. I have a friend with NGK plug wires, but again there seems to be a lot of negative press on those too. My friend's car after about 35-40k miles is still running well on them.

Good luck finding the misfire. Abscate has hit all the main likely issues that you need to know are good before looking deeper if required. Just make sure the plugs are gapped to 0.028". Don't assume they are correct out the box.

Neil.

Post by **Clemens** » 10 Oct 2022, 14:48

I had the same issues as you, and they were ignition related. Just stick with OEM wherever possible.
Also, take a look at all your vacum hoses, they can cause weird symptoms as well.

smallblackbrick · Post by **smallblackbrick** » 21 Oct 2022, 12:35

It was the plugs! Replaced cap, rotor, wires and plugs. The rest were needed, especially the wires since they fell apart during removal, but the plugs were the source of the issue. Now to deal with the fact that my turbo is underboosting now -_-. Thanks for the advice.

I'm leaving the IPD wires in, I'm willing to be a test dummy.

Post by **matthew1** » 21 Oct 2022, 13:12

smallblackbrick wrote: ↑21 Oct 2022, 12:35Now to deal with the fact that my turbo is underboosting now -_-.

I just made this meme for you.

: its-vacuum-lines.jpg (49.05 KiB) Viewed 813 times

Post by **matthew1** » 21 Oct 2022, 13:14

(And it could also be CBV, negating entirely my cool meme.)

Post by **Clemens** » 21 Oct 2022, 16:07

+1 on the CBV.

Also, a worn beyond repair 15G can easily reduce the max. boost. Ask me how I know. You can usually tell by longitudinal movement of the blade and shaft with the fresh air pipe removed.

smallblackbrick · Post by **smallblackbrick** » 21 Oct 2022, 21:20

matthew1 wrote: ↑21 Oct 2022, 13:12
smallblackbrick wrote: ↑21 Oct 2022, 12:35Now to deal with the fact that my turbo is underboosting now -_-.
I just made this meme for you.

its-vacuum-lines.jpg

riddle me this

I did tcv lines already, the guy before me had them plugged in all wrong or not plugged in, and used 8mm ID rubber

Just ordered IPD TCV, Bosch IAC, and a MAF meter. If I ship of Theseus this car it should run well.