Rough Running!!

**Dan H** · Wednesday 9th July 2014, 21:26

So, I've now found out that the head gasket has gone on my car, (2.5t v70 AWD) after having a bit of advice from you guys!

I was out in the car on saturday coming back from valeting somebody's van, Anyway I had an audi a8 trying to have a little play wit me, had little go, came off at my junction on the duel carriage way, and it started running really bad as if it was misfiring, I changed the plugs the day after for some bosch plugs, started it up, still ran the same.

My boost gauge used to go to 25/27 In HG. But now it is at about 10-15 and flutters around that area. When i put my foot down past 3k rpm it will still boost and pull like it should, Just anything below it runs like crap and is really annoying me. I asked on one of the facebook groups and someone mentioned it could be the fuel pump, Bought one, Went to fit it, Turns out I need to drop the tank down because its the AWD model

so just trying to see if anybody else has any idea's what it could before I drop the tank down.

And my EML light came on the other day as my lambda sensor, so its got me wondering if that could be anything to do with it?

Here are a few screen shots I have got from my OBD reader/Phone

**Jamest5r** · Wednesday 9th July 2014, 21:38

Are you saying your boost used to hit 25-27psi?? that's 1.9 bar!!!!!!

**Dangerous Dave** · Wednesday 9th July 2014, 21:41

I'm guessing 25-27 inHg at idle

**Dan H** · Wednesday 9th July 2014, 21:46

What Dave said

I apologize for confusing you lol

**Jamest5r** · Wednesday 9th July 2014, 21:48

Originally Posted by Dan H

What Dave said

I apologize for confusing you lol

I was about to say that's going some no wonder your headgasket has gone lol

**Dan H** · Wednesday 9th July 2014, 21:51

Yeah something would of gone bang by now with that amount of pressure lol! I've got a T5 Lump coming this week or next so I just need this to run a little better until I can get the new engine in and hopefully be gone with all these issues

**Dan H** · Wednesday 9th July 2014, 22:23

I've just realised that its MAP Pressure too! where is the map sensor? should it run ok if i unplug the MAP sensor? Just so i know its that, thats causing issues?

**Dangerous Dave** · Thursday 10th July 2014, 15:41

Is it an ME7 engine or earlier?

**Dan H** · Thursday 10th July 2014, 22:33

Pre ME7

**Dangerous Dave** · Thursday 10th July 2014, 22:38

Ah, it won't have a MAP sensor. The only pressure sensor on the M4.4 is the barometric sensor behind the headlight which lets the ecu know what altitude the car is at so it can adjust boost accordingly. Sometimes these sensors break down which can throw a pressure sensor code. If it has lost vacuum at idle there could be a leak somewhere in the intake system, have you checked them all?

**960kg** · Friday 11th July 2014, 10:09

Originally Posted by Dan H

So, I've now found out that the head gasket has gone on my car, (2.5t v70 AWD) after having a bit of advice from you guys!

I was out in the car on saturday coming back from valeting somebody's van, Anyway I had an audi a8 trying to have a little play wit me, had little go, came off at my junction on the duel carriage way, and it started running really bad as if it was misfiring, I changed the plugs the day after for some bosch plugs, started it up, still ran the same.

My boost gauge used to go to 25/27 In HG. But now it is at about 10-15 and flutters around that area. When i put my foot down past 3k rpm it will still boost and pull like it should, Just anything below it runs like crap and is really annoying me. I asked on one of the facebook groups and someone mentioned it could be the fuel pump, Bought one, Went to fit it, Turns out I need to drop the tank down because its the AWD model

so just trying to see if anybody else has any idea's what it could before I drop the tank down.

And my EML light came on the other day as my lambda sensor, so its got me wondering if that could be anything to do with it?

Here are a few screen shots I have got from my OBD reader/Phone

The fluctuation of your boost guage between 10/15 inHG is correct for a blown head gasket....they usually fluctuate between 14 and 19 with this problem also could be worn valve guides but you do say you know it`s the HG and it will be between two cylinders.

Just to help!.....i wanted to change my boost guage and i had the same as yours and i had readings of 30 inHG which is absurd at idle, a petrol engine in good nick will only return about 16/22 ...

The company sent me another without me even returning the faulty one and yes, the second one was faulty and i then had a third one exactly the same.....in the end i paid more for a digital one which even gives battery voltage on start up and it idles as it should on 22 inHG

Your PO133 error code is the first oxygen sensor got kaput or the connector has oxydised, this will cause bad running including 15 to the gallon...although because the HG has gone it may be giving bad emissions which will give you that code as it has effected the sensor.

Also on a standard motor keep new Volvo plugs for best performance......!

As above ...squirt some WD40 into that altitude sensor behind the headlamp as dirt can get into the hole, don`t poke it though!........they are reliable sensors.

**Dangerous Dave** · Friday 11th July 2014, 11:14

Ironically I recently read on Volvospeed that the solder joints inside the baro sensor can crack after so many years so I took mine apart the other day to re-solder them.

Snapped off the outer surround

Prised the cap off all the way round

Can just see the ring in the joints. One I saw on VS was a lot worse.

Soldered it up, glued the cap back on, problem solved.

**960kg** · Friday 11th July 2014, 13:14

Very interesting that one Dave, as i repair old reel to reel tape recorders and am always repairing boards......

Although i never had a problem, i do preventative maintenance and cleaned the hole out after reading about it.....my motor is 17yrs old 161,000 and still the original sensor

**Dan H** · Friday 11th July 2014, 20:50

Cheers for the help guys! I will whip that sensor off and spray some WD in it tomorrow to see if it makes any difference.
The car has just ticked over to 203k so I can expect a few things to go wrong every now and then at this millage. The car only started running like this after I had a little play with an Audi A8, But was running fine before that.
Well i cleared the code for the Lambda the other day and it hasn't came back on yet so will leave it be for now.

I think if the WD40 in the sensor doesn't change it i'll just buy a new Sensor just incase it is that, wont hurt to replace it anyway.

The car hasn't got an Vac leaks from what I can hear/See, It still boosts to 10psi at times like it should, I've got a 15g Turbo instead of the 13g, So will Just have to see what happens, It's still being driven untill it goes pop! New t5 lump was collected today so should be here ready soon.