16 replies to this topic

[gotmeaT-5]

I've recently had to buy a new TCV for my 1997 850 T5 and replaced it with a V70 one all was fine at first now I'm suffering with bad overboost: the stock needle swings all the way across off the scale and I seem to be getting fuel out/sparkout whatever you call it.

I did a full stage 0 before fitting the TCV went from NGK plugs to Bosch Irridium ones with the fine point electrode

I know several other 850 owners who have the same TCV with no overboost problems seems really odd I should get serious overboost

Suggestions please

Edit the boost was fine for two weeks with the new TCV I have replaced all the pipes going to the Turbocharger

Yellow to Wastegate
Blue to air hose
Red to Compressor

I've lifted off the wastegate arm to see if its jammed the wastegate mechanism will check tomorrow when the engine is fully cold

[--Aaron--]

Your vacuum lines are correct. Your plugs are an issue, Coppers or OEM only. Start off with the gap at .028. Why did you use a V70 TCV? IIRC the ports inside are different diameters so that is probably throwing something off.

Edit: OEM's GREATLY outlast coppers, it's your call. Some people don't mind changing spark plugs every other oil change. Personally I prefer to only change mine once every ~40K miles. That being said I likes the Genuine plugs.

Edited by --Aaron--, 16 March 2011 - 06:16 PM.

[gotmeaT-5]

I'm interested in why you believe the irridium plugs are a problem considering Bosch are the recommended ones over NGK? Or at least they are in the UK for late 850 T5's. I swapped to the V70 TCV as it was the only thing I could get one the I needed a replacement as my 850 round one had fallen appart and wasn't working also several other UK owners have the same unit without any issues

I have changed all the vacuum hoses on the T/C and added new pipe clips throughout. One thing I have found was the waste gate vacuum unit was jammed solid so I've disconnected that to see if it can free itself off over night and tomorrow morning I'll see if I can move the vacuum arm

[laird]

The plugs have nothing to do with your overboost and the cutout is the ECU trying to keep your engine in one piece. You need to verify that the vacuum lines are in fact, connected at both ends. What custom map are you using and where is the MBC in all of this plumbing. Having said that, OEM plugs are the best and Iridium plugs are near the top of "what plug not to use" list.

[--Aaron--]

I'm interested in why you believe the irridium plugs are a problem considering Bosch are the recommended ones over NGK? Or at least they are in the UK for late 850 T5's. I swapped to the V70 TCV as it was the only thing I could get one the I needed a replacement as my 850 round one had fallen appart and wasn't working also several other UK owners have the same unit without any issues

If you search the term spark plugs you'll find out why I'm saying Coppers/OEM only. Did you put up a wanted ad here? I'm not saying the V70 TCV is going to cause these issues but if it were meant for the car it would be listed in the computers for 850's and x70's.

You have a problem, you have a variable that doesn't belong. I would start by putting in the correct BCS.

The plugs will probably serve you alright for a little while but then you'll start having idle hiccups, random unexplainable misfires, etc.

[gotmeaT-5]

The MBC is no longer being used as it fell to bits. I'm using a Rica based map. Theres a list which shows the TCV's? or BCS's never knew that see how far out of the modification game we are here in the UK the part number was checked for a 97-98 V70


Yes I did put a wanted ad up for some oversized pistons +0.50mm as I can only obtain +0.40mm and my engine rebuilder has suggested that the block needs a 0.36mm rebore [it's a for an engine upgrade I'm planning later in the year as my current engine has 270.000miles on it and rising

[gotmeaT-5]

I cannot find any information regarding not using Bosch Iridium plugs in favour of Platinum/Silver or Copper can you point me to where this list is

[gotmeaT-5]

0.028inch would be around 0.70mm ish ? here in the UK it's getting harder to locate imperial feeler gauges everything is metric

[troyhyde]

If you've messed with your wastegate opening threshold, you ought to put it back to stock. The 4.3 Motronic doesn't react very quickly to unexpected events.

You'll get timing pull and reduced performance if you try and trick the turbo into working harder...

[--Aaron--]

The MBC is no longer being used as it fell to bits. I'm using a Rica based map. Theres a list which shows the TCV's? or BCS's never knew that see how far out of the modification game we are here in the UK the part number was checked for a 97-98 V70


Yes I did put a wanted ad up for some oversized pistons +0.50mm as I can only obtain +0.40mm and my engine rebuilder has suggested that the block needs a 0.36mm rebore [it's a for an engine upgrade I'm planning later in the year as my current engine has 270.000miles on it and rising

What MBC? I'm confoosed. Your BCS is round. Is the part you bought round or more rectangular?

What do pistons have to do with your issue?

I cannot find any information regarding not using Bosch Iridium plugs in favour of Platinum/Silver or Copper can you point me to where this list is

Go through a few pages of these threads in regards to the plugs: http://www.google.co...=volvospeed.com

0.028inch would be around 0.70mm ish ? here in the UK it's getting harder to locate imperial feeler gauges everything is metric

http://www.google.com/search?q=.028+inch+to+mm&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

[gotmeaT-5]

Pistons are something totally different I answered the question regarding putting a wanted post which was for pistons.

[Q-Ship]

I can't point to a list, but I will say that I was having weird bog problems in a perfectly set stage 0 engine at ~4k rpm. I changed to some copper plugs gapped at ~.26 and it all the problems disappeared instantly and have yet to return. At $8 (us) there is not much to lose by trying them out. .

Here is my experience.

And make sure the wastegate arm is set correctly.
Here is IPD's how-to video.

[gotmeaT-5]

Pistons are something totally different I answered the question regarding putting a wanted post which was for pistons.

The MBC reference was from what appears to be a glitch in one of the replies, that has gone as has the reference to gapping the plugs to 0.028inch odd but not essential, It's also listed in my signature which I haven't amended yet.

The wastegate has been adjusted to the 3 turn adjustment it will be put back to stock in the morning.

[gotmeaT-5]

I'm scanning through your posted reference on the Iridium spark plugs and yet to find anything to suggest they're bad, ok theres one showing a snapped plug another showing a rusty plug both of these can be attributed to either badly fitted.

One very interesting article claiming that the Haynes is showing an incorrect way to fit the HT leads but again nothing to claim iridium plugs aren't good, very expensive yes [£39 a set of 5 against £16 for NGK's]

Will keep scanning through to see where the justification is got from though.

[laird]

Spark plugs are an ongoing debate here. Most of us have tried all of the fancy plugs only to return to Bosch Coppers or OEM. I have used both with fine success. 0.70mm or LESS would be a good starting point. If you are up near 18psi, 0.635mm would be in order.

[ozzimark]

Your vacuum lines are correct. Your plugs are an issue, Coppers or OEM only. Start off with the gap at .028. Why did you use a V70 TCV? IIRC the ports inside are different diameters so that is probably throwing something off.

Edit: OEM's GREATLY outlast coppers, it's your call. Some people don't mind changing spark plugs every other oil change. Personally I prefer to only change mine once every ~40K miles. That being said I likes the Genuine plugs.

I've had my coppers in for 25k so far, no misfires yet with a starting gap of 0.032" and the stock coil system on an engine that hits 6k a couple times a day.

[gotmeaT-5]

Problem has been resolved. The problem of the overboost came from a stuck wastegate vacuum actuator once replaced works fine now and no where near as harsh with the V70 TCV as it was with the old 14 year old 850 TCV/BCS