Engine: 850 T5/R 850 T5 - Hesitating under hard acceleration

[taiwan740]

Hi

***Before you say ANYTHING, please note the lambda light in the video is cos of me unplugging the MAF sensor to test if that was the problem. When driving the car during the video, MAF sensor is plugged in. Problem persists and there is no warning light or code thrown normally.****

Basically I have a Volvo 850 T5 which I bought for scrap money which had no MOT and it went through only needing brake discs. Win(?)

Anyway, it runs great. Day-to-day driving runs lovely, and under medium throttle (halfway into the white bit of the Turbo gauge) it picks up speed fine.

The problem is if I accelerate a micron past this halfway sweetspot, it starts hesitating and loses power. Full throttle is the same. Video below demonstrates this.

I initally thought boost leak, took it into a garage to locate boost leaks and they found one of the silicon hoses was knackered, so I replaced that. Have also replaced spark plugs very recently. HT leads are recent too. Fuel filter needs doing although pressure seems fine, and it needs a new thermostat as its stuck open.

Does anyone have any ideas? I have the kit to replace all of the boost tubing, I just don't want to go to all that effort if you guys have had this before and say its something like the rear wiper is loose.

https://www.youtube.com/watch?v=zOppt8PFF-Y

It's an automatic for general interest (urgh)

[Gaztech]

Had the exact same issue. New distributor cap and rotor fixed it

[taiwan740]

So yours would be perfectly fine, unless you stamped on it, then its a spluttery mess?

Do you know of any decent suppliers of distributor and rotor, or is ECP fine?

[Mkengineering]

Originally Posted by taiwan740

So yours would be perfectly fine, unless you stamped on it, then its a spluttery mess?

Do you know of any decent suppliers of distributor and rotor, or is ECP fine?

Should be fine with ECP chap.

I would change the dizzy cap and rotar arm and get some decent plugs in their if you havet already. Denso or ngk.

Also when your changing the the thermostat change the temp sensor aswell.

Hopefully that will resolve your issues

[taiwan740]

Originally Posted by Mkengineering

Should be fine with ECP chap.

I would change the dizzy cap and rotar arm and get some decent plugs in their if you havet already. Denso or ngk.

Also when your changing the the thermostat change the temp sensor aswell.

Hopefully that will resolve your issues

Is engine temperature sensor an easy swap when the thermostat's out? That's just at the top of the engine, where the hose comes from the radiator isn't it, or is it in some other bastard place?

Feel like I'm loading the parts cannon pretty heavily on this one.

The plugs I put in there were Bosch something or other from Halfords, but it runs better on those that it did on the NGK ones it had before, which it refused to start on.

[volvo again]

I would change the fuel filter as well as the thermostat, if that's stuck open it will be running too cool.

Have you tried pfs for parts...http://www.partsforvolvosonline.com/

[Mkengineering]

Originally Posted by taiwan740

Is engine temperature sensor an easy swap when the thermostat's out? That's just at the top of the engine, where the hose comes from the radiator isn't it, or is it in some other bastard place?

Feel like I'm loading the parts cannon pretty heavily on this one.

The plugs I put in there were Bosch something or other from Halfords, but it runs better on those that it did on the NGK ones it had before, which it refused to start on.

Yea the temp sensor and thermostat is a easy 10 to 30min job. All you will need is an extension with a swivel head and a t40 torx. As well a 19mm and 12mm spanner

The 12mm spanner is where you'll need to remove one bolt from the power steering bracket as it's in the way . If need help mate Dm me I've got pics on how to do it.

[Gaztech]

Yes absolutely identical symptoms. Bosch distributor and rotor off Ebay did the trick. I changed the leads and plugs for Volvo ones whilst I was at it too. Been gone since

[Shinsplintz 101]

Do not buy after market ignition parts for T5s.

OEM or suffer the consequences. Sparks, dizzy, rotor arm, leads & coil should all be replaced & set ypu back about £250ish depending on how good you are at Internet shopping. RUFE (volvo Swansea) are always my first call for OEM parts. Allways price fairly & quick delivery.

Cheers, Morgan

[taiwan740]

The leads that are on there are Bougicord (that's OEM, right?) and look in good (very recent) shape - the distributor cap does look like hammered crap so I've ordered a new bosch cap and rotor. I think we'll go from there.

I only paid £400 for the car so I don't fancy going the whole hog on the ignition system just yet. Gotta ease that baby in, for my own sanity. Plus my "personal parts store" for the 940 is too ****in big as it is. I've got a spare cylinder head sitting there for christs sake

Anyway thanks for the help, I'll report back if its not the dizzy, if it is, then you might see a for sale ad, or I will have left the country, probably in a dinghy