Motosport

I am in the process of chasing a rich running condition on my '89 Turbo with M-tune, Vitesse stage 3 turbo, Tial WG and fresh hoses all round. At idle and cruise AFR's will be in the 14,3 - 15 range which is pretty much as its suppose to I believe, but as soon as I get on boost it drops rapidly. At light to medium acceleration it'll go down into the 12's, at 2/3 acceleration it goes into low 11's and at WOT it will go down to 10,2 AFR.

So after doing some searching I concluded that my rich condition is most likely being caused by a boost leak, even though she will make 16psi boost at 3000 rpms. So today I pressure tested the intake system from the turbo outlet hose, and the ISV is leaking pretty badly. It will go from 15psi to zero in 20-25 seconds.

I recently had the intake and ISV off the car and I checked the function of it back then, and also put some epoxy around the plug as I've read they often leak here. But it wasn't around the plug it was leaking this time, but from somewhere around the two hoses or the end of the ISV. it was a bit difficult to pinpoint exactly where, as there's not much space under the intake for my fat fingers. Anyway, while checking the ISV, I just happened to put a large screwdriver on top of the ISV near the intake hose and when I pressed down the air leak stopped..?!? It only moved a couple of millimeters and I had to put some decent pressure on the ISV, but it stopped the leak.. But as soon as I stopped pressing it would leak again. I then played around a bit with different pressure points and also tried moving it back and forth a bit, but it was only when pressing down on the end where the hoses attaches it would stop leaking, but then it would also hold 20 psi for quite some time.

Has anyone had a similar experience.? Can anyone explain why my ISV is behaving like this, where a certain position will cause it to leak and just making minute movements to it will slow the leak and even make it stop completely..? Do I need to replace my ISV, can it be repaired or do I just need to try and put it in a position where it will not leak (which seems like a very short term fix anyway) ? Both hoses seems to be fully seated on the ISV necks and firmly tightened..

Any advice is most welcome.. Thanks..

944Phil

I had/have a very similar issue after m-tune install. I was running too rich under boost and moderate throttle, but at idle it wasn't too bad. I also had a leaky ISV which I covered in RTV, and now I just removed it and blocked the hose. It helped... A bit. I ended up switching the FQS on the DME to a leaner setting and now I'm spot on, except a little bit lean under idle.

I think a few others have mentioned running rich after m-tune. I will eventually buy the tuner/logger and put the FQS back to zero, and tune it properly.

Phil

Motosport

I would like to keep my ISV with our cold weather here in Scandinavia, so for now its either replacing it or fixing it I think..

As for the rich condition, its good to know that I'm not the only M-tune user who experiences this, but I have already gone back to the stock 2.5 bar FPR as well as set the FQS switch to the leaner position 2, but I am still running rich on boost and pig rich on WOT..?!? And besides my leaking ISV everything seems tight so far..

I just can't see anything else that causes a rich condition on boost only and runs fine at idle and cruise..?

fejjj

You may want to verify that FQS 2 position is less fuel.

I don't think that is correct.

You may be adding fuel instead of subtracting.

mahoney944

Those numbers don't seem too bad. Maybe a little rich but I see similar numbers on mine as rich as 10.2 to 10.5 at wot at times and like 12.5 at 5 to 7 psi boost. Idle 14.7 give or take .3

Motosport

But isn't that too rich.? According to Rogue tuning AFR at WOT should be 11.5 - 11.8 and anything less is to rich and leaving power on the table and increase fuel consumption..

fejjj

10.2 at WOT is way too rich!