Lean under boost!!!!

[Mx6GT91]

My friends MSP's having boost problems. When driving normal the car is fine, but once he gets to around 3500-4500rpms and and its pushing full boost the car pops and the Air/Fuel gauge goes lean. He has a filter, 3in turbo-back and a MBC @ 10psi. The car usually is pretty rich under full boost.

We checked the plugs and they seem to be fine. Could wires cause this also. I remember when one of my wires was barely touching the spark plug it did this. We tightend all his down but it still does it. Is it time for him to put in new wires?? How much are they from the factory and are there aftermarket wires.

Also when the studdering happens the CEL comes on. After driving normal for a while it goes away.

Thanks

 

[jus10 msp]

check the plugs! are they copper plugs? and what is the gap? gap them to .032


thanks justin h

 

[Mx6GT91]

The plugs are the NGK BKR7E's. The car has never done this before.

I think I gapped them to around .035. Again its been holding boost with no problems till about a week ago. I really think its the plug wires, when checking the plugs one of the wires kinda got messed up. It still connect to the plug though, or at least we think??

 

[thunder]

I don't think the plugs have anything to do with this situation. Maybe the injectors are maxed out...

 

[Mx6GT91]

Ok, I was thinking about that also.

Why is it happening now and not before?? Hes been running 10psi for a while now. Usually the Air/Fuel gauge is pretty rich when boosting. I know its not wise to tune by a gauge. His plugs arent white either??

 

[turbo speedy]

do u guys think it could be a broken ic line i was thinking that but not sure
, it only does this in first gear and sum times in 2

 

[BinaryRotary]

By 'pop' to you mean backfire? If so, that means the car is running rich. I don't know how you're telling the car is running lean, unless you have a wideband.

 

[orangezoom]

What are you using to know it is lean?

 

[BlkZoomZoom]

If its backfiring or bucking and it has just suddenly happened I would say that you have a leak in the intake system after the maf sensor. It may only be leaking after you have built boost pressure. Also a good idea would be to re-set the pcm, the computer may be able to learn around whatever has changed.

 

[kingpin7666]

mine at full throtle goes lean at 4000 rpm for a seccond and back to rich. so needless to say this thread intrests me. but on the dyno when it went lean it made 9more ftlbs of tq

 

[1338]

mine was doing the same thing check the gam mine were gaped to .35 take it down to around .30-.32 and it should be fine. mine is anyways.

 

[mp5jeff]

if you are looking at a narrow band a/f gauge, that's the 1st mistake =)

 

[acidbug]

I don't think the plugs have anything to do with this situation. Maybe the injectors are maxed out...

There's no way in hell he maxed them out at only 10psi.

when i am runnin a bigger turbo...and runnin 10-12psi daily!

(blah)

 

[II-Savy]

if you are looking at a narrow band a/f gauge, that's the 1st mistake =)

You can get a GENERAL idea of what the car is doing.

 

[acidbug]

My friends MSP's having boost problems. When driving normal the car is fine, but once he gets to around 3500-4500rpms and and its pushing full boost the car pops and the Air/Fuel gauge goes lean. He has a filter, 3in turbo-back and a MBC @ 10psi. The car usually is pretty rich under full boost.

We checked the plugs and they seem to be fine. Could wires cause this also. I remember when one of my wires was barely touching the spark plug it did this. We tightend all his down but it still does it. Is it time for him to put in new wires?? How much are they from the factory and are there aftermarket wires.

Also when the studdering happens the CEL comes on. After driving normal for a while it goes away.

Thanks

Well around that range..is where the hesitation was before mazda released the Flash.

The increased the timing..which is why it goes lean..and than rich.

My suggestion is to lower boost setting..before he blows it up!
Or to invest into a piggy back like the mpi tuner...

Chas

 

[acidbug]

You can get a GENERAL idea of what the car is doing.

This is true to a point. When i was at the dyno..we used a stock narrowband vs. Dyno Wideband..and the stock narrowband read 1 full point leaner than the dyno wideband.

chas(RTM)

 

[BinaryRotary]

Those damn A/F gauges are wack. Get a wideband and THEN see if its running lean. A backfire is nothing to worry about, I get them all the time with my BOV installed.

 

[orangezoom]

if you are looking at a narrow band a/f gauge, that's the 1st mistake =)

I agree with this, Worthless

 

[Yay-Boost]

Has it been colder out than it was when 10 psi was fine? He might be hitting fuel cut. I hit fuel cut around 9psi when it was around 60 deg. out. The injectors get turned off so the engine would go lean.

 

[changedman]

wow, a ton of different opinions- a lot of people don't know what they're talking about.