ok here goes.... About 2weeks ago my car decided to start acting up. When ever I get on it, build 13psi, and go anywhere above 4000-5000- rpm my motor just quits....I put new plugs....older but better wires than i had in. and now i have a S-afcII but i still dont get it...i want to say its fuel cut but i dont see why it would be other than its cold outside...i have a mbc, 3inch d/p, k&n, rewired fuel pump(stock), blah blah blah any ideas? this is making me go insaine! thanks guys!

Kevin

What do you mean it quits? It kills completely?

it feels like fuel cut...its got a nice violent jerk to it....and if i keep it floored it goes no were and keeps cutting in and out.... so i cant accelerate at all

find some race gas so you can safely lean it out on the AFC. toss that in, lean it out, and try again. If it goes away then it was fuel cut and you need bigger injectors.

I've been thinking that it might be a head gasket also....colant was full about a week ago... now the upper hose it barrely full.....except the fact that you cant smell or see it through the exhaust system.... so idk its weird...

Nah....

I mean, im sure you have a blown head gasket, but that wouldnt cause your problem ;)


A lot of times with DSMs (like mine) when the HG goes it doesnt burn coolant, but it pushes it out. The system pressurizes under boost (or whenever, depending on how bad it is) and it gets pushed out the overflow. Empty the overflow and let the car warm up, then do a few pulls. If the overflow is full, then its a HG.

yeah thats whats been doing on..... i just don't wanna do a hg....im to lazy but i guess i will.. the overflow is overflowing about...lol

since you have stock head bolts you can do the lazy method. just take out the bolts, and lift the head up just enough with a cherry picker so that you can slide out the HG, so you don't have to detach anything. then slide a new one in and retorque! do it the dsm way, the lazy way!

i'd recommend doing it right..
or redoing it 3 times.
sounds like fuel cut/mas overrun. I'd try cvd's suggestion or maybe log your hertz value on your afc, if it looks like a 'city skyline' thats mas overrun.
Mas overrun doesn't hit as hard as 'fuel cut' but you can feel the car 'die off'.

i think i had same issues a few times... what does the mass overun mean?

and yeah, if you are going to do it, do it right.. so that you can boost without having to worry, is it going to hold?? do it right or don't do it at all!!!

MAS overrun is when it's sucking in more air than the MAS can accurately keep count of. It isn't a problem with a 2G MAS until your making 450whp or so. It is a problem much much earlier on a stock 1G MAS. You might have overrun issue at even less than 300whp on a 100% stock 1G MAS, I am not exactly sure when it starts happening. Most people have already at least removed the bottom honeycomb by that time. With just the bottom honeycomb removed I have had it happen in the low 300s. Overrun problems usually seem to start happening around the 2000hz area on the AFC with the 1G MAS.

With a very hacked 1G MAS though you can make well into the 400s or more and keep the hz down low enough to keep overrun from happening. You just don't want to go overboard with the hacking though. Hacking the MAS more than it needs to be can cause some knock/timing tuning problems. You usually only want to hack it to the max if your running a big turbo and injectors that are just big enough for the setup. I had one 14B car with too big of injectors that just removing the bottom honeycomb was enough to cause problems. With a medium amount of airflow signal being removed by the AFC to get the fueling inline and the missing lower honeycomb causing it to measure even less of the actual airflow, the ECU wanted to run the car in an incorrect timing map with way to much timing which ended up making the car knock.

Figured out that my ecu has a bubbled capasitor... i replaced it but it still runs like it does as described above. But I put a different ecu in and it ran like a champ so i need a new ecu...

That makes sense. I was having intermittant coil cutout and I traced it down to my TMO ECU. Now it's somebody else's problem since someone decided to remove it from my garage without my knowledge. Hope they figure out it has the security feature.