Bucking under throttle

[encasemyheart]

Okay.

I've spent the last week setting timing, fixing boost leaks, fixing exhaust leaks etc. etc. etc.

Then, the car ran great. Perfectly, just how it should.

It was running great and all, but whenever the car would be driven more than 5 minutes or so, it would act like it had a hose leak somewhere, no power etc. Now, when driving, the car will buck and buck with any throttle and if I try to boost, I get backfire.

Any ideas? I haven't messed with any wiring between when it was running fine and now, the MAF is exactly like it was, and I retested for leaks, and it holds strong up to 10-11 psi, which is as far as I test it. That's as high as the turbo boosts.

Could it be something leaking only when hot? Everything is tightened dow like I said, but maybe this is it? I tested it for leaks right after a drive and it held fine. But the problem isn't even under boost exclusively, it is under all throttle. It won't even idle correctly without dying now.

[robbbby]

Sounds like maybe a maf problem? While the car is idling unplug the maf and see if the idle smooths out

[encasemyheart]

Just tried that.

The car wouldn't idle at all without a little throttle. I got it to idle at 1400rpm for about 30 seconds on it's own, after that, nothing.

It does this with or without the MAFS plugged in. It dies regardless.

[180fan]

check the injectors, timing, and rocker arms.

Mine's been doing similar crap and after testing them, #3 went out I'm guessing yesterday. My injector problem has these symptoms - no power, stalls when up hill from 0mph, and rough idle. Spark plugs are all way clean.

You might wanna check your timing first, then move onto the injectors by pulling the plug on them one by one to see if it effects your idle at all. If you pull one plug and it doesn't drop your idle, then you've got a shot injector or a rocker arm that's flown off (kinda unlikely that both valves are closed regardless if the rocker arm's jumped onto a spring since that'd still open at least slightly) but yeah might wanna give those a test. If those don't answer your question, open up the valve cover and poke around. All this assuming you've no vac leak or air leaks.

[encasemyheart]

I'll check everything out tomorrow.

How would I diagnose a vacuum leak? Is there an easy way to find them like pressurizing the system to check for boost leaks?

[firekirin]

take like a can of carb cleaner or brake cleaner and while the car is running spray it on everyone hose and joint and clamp that you have and if the car idles down when you spray that then that will be your leak

[encasemyheart]

Well, I started it this morning after plugging the z32 MAFS, and it ran just like normal, so I assumed the MAFS was th eproblem, but just lik eusual, after about 5-10 minutes of driving, it lost all power and started bucking under throttle.

This rules out the MAFS and a wiring problem, too, seeing as how it is so consistent. I smell fuel in all cylinders, so the injectors are okay.

My only real idea is a boost leak that only happens when everything gets really hot and the pipes and connectors expand.

I'll try the carb cleaner thing on the pipes and see what happens. The rocker arms look good as do the spark plugs.

[encasemyheart]

Could the car be oulling timing due to higher than normal coolant temps? The temp gauge is just a little above halfway, is it supposed to be that high?

Maybe I'm maxing out injectors and it's pulling timing really badly?

[encasemyheart]

It does only happen when I boost, if I drive with no boost I can go just like normal forever.

[johnyQ]

Did you ever find a resolution to this?

[mynismo]

my guess is that after 5-10 minutes, the connector to the maf is coming loose. happened to me numerous times..