boost leak or ignition problem?

I'm not sure if i have a boost leak or if it's an iginition problem or what but I can be just driving lightly, (maybe 1/4 throttle?) and my stock and autometer boost guage will start to creep up until i hit maximum boost (10 pounds - for winter anyway) and it'll run really shitty like it has no power at all, and as soon as i let off the gas all i hear is PSSHH! from the blow off valve, kinda like i should be moving somewhere. Then i'll get pissed off, slam on the gas, say five minutes later, and there it is, full boost and full power. My car then begins to lunge with no problems. This happens all the time, moreso when it's cold, but really at any moment. When it does, my car jerks and loses power. But like i said, it only happens sometimes, other times it'll boost up perfectly. I have a mitsu 16g turbo, if that helps for any reason. Can anyone help me diagnose the problem? I kinda feel like if it were a leak, it would do it all the time. HELP!

Sounds like maybe your having a really bad misfire? or fuel? check your plus make sure there like isnt oil in all of them or something not sure.

I replaced the coil pack last year so i don't think it's that, and just replaced the plugs a few weeks ago. The only thing it could be is the plug wires... that is to say that it's even an ignition issue? But would it boost sometimes, and then not?

You either got a boost leak or your car is severly out of timing. Get a timing light and play with your CAS, make sure its 5* BTDC!

i doubt it's timing... cause my car was be severely fucked up upon everyday driving. It only does this sometimes. Just the times it happens are always the worst. Just when you think you're about to lunge on 5.0 ...

BUT on another note, what are altima quarter mile times? I raced one on the highway last night, i couldn't pull on him, and this was quite upsetting. But he couldn't pull on me either, so at least we can't call it defeat. I know right now, given my mods and boost i'm running that i'm probably only running mid 14's. Given i'm only running 9-10 pounds for winter i'm not that upset. But i still should have smoked his triflin' ass! Shut down at 115 w/ no pull on either side.

i doubt it's timing... cause my car was be severely fucked up upon everyday driving. It only does this sometimes. Just the times it happens are always the worst. Just when you think you're about to lunge on 5.0 ...

Check timing! It's always a good thing to check, I'm sure the timing belt is on good but your ignition timing seems to be off.


BUT on another note, what are altima quarter mile times? I raced one on the highway last night, i couldn't pull on him, and this was quite upsetting. But he couldn't pull on me either, so at least we can't call it defeat. I know right now, given my mods and boost i'm running that i'm probably only running mid 14's. Given i'm only running 9-10 pounds for winter i'm not that upset. But i still should have smoked his triflin' ass! Shut down at 115 w/ no pull on either side.

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I have a hard time believing an altima runs lower than a 15!

When you replaced the plugs, what did you gap them to?

When i replaced the plugs, i didn't gap them. I know you're supposed to gap them at .30, but i was in a rush and just threw them in. Now that you mention it, would it make that big of a difference? Besides, i never gapped my plugs and i've never had these problems. It didn't start happening 'til lately, and i figured if that wasn't the problem... ?

There is most likely your problem! The boost is blowing out the spark. Take them back out and gap them, you should always check the gap before puting them in. The gap should be around .28-.30

Also the wires could make you missfire just a thought you said wires might not be it they could be. Inspect your wires and check to see if they have any white cracks or bubles forming in them or something like that it could be the cause.

My car is a little different because of the boost and airflow levels, but the point is still valid. The car works great at 026, but wont run at 028. I'd say it make a difference ;) For normal cars, jakes suggestion is balls on. These plugs are mostly used in NT cars and come gapped closer to 040-045 in most cases. And they vary too, you want them all to at least be the same! Gap those bastards, and tell us if it worked.

Edit> Even BRAND NEW wires can misfire on a turbo car. I've seen almost every major brand of parts store/redneck wire fail on install. NGKs are even more amzing when you look at them in this light, they always work. Magnacores are popular, but I can't get a set that doesnt misfire... One of the biggest mistakes people make is to say "I put in a new xxxxx, it can't be that."

Also this could happen be careful. You gap your plugs then dont just drop them in, because dropping them in could dent it and change the gap. Take your finger and kind of slide it in along the edge with the plug, so you dont dent it in and mess up the gap.

Thats a good tip. And anytime you drop a plug on the floor/ground it has to be checked over carefully and regapped. They will always fall heavy end first ;)

well looks like i need to check my plugs now too because i have a problem very simlilar to this....thought it was a boost leak, but when i checked for leaks, i couldn't find any...the problem i'll have is, when i try hitting boost in 3rd-4th gear, it will start to boost, then my car gets real jerky and it seems like i should be hauling ass when i'm not, then when i let off the throttle, it's louder than all hell...could having an extremely small amount of shaft play cause this in a T25? Also, i do have aftermarket wires...Thundervolt 10.4mm, but i have had this problem before the wire upgrade...

a 2005 Alitma se-r runs a 1/4 mile in 14.2 and a 0-60 in 5.5. http://modernracer.com/nissanaltimaser.html

ive got .046 gaps on my 92 talon. does that give you a better spark?

a 2005 Alitma se-r runs a 1/4 mile in 14.2 and a 0-60 in 5.5. http://modernracer.com/nissanaltimaser.html

:) FYI...

That's the SE-R though... There's also just the 4-cylinder 2.5 liter with 175 hp and the V6 3.5 with 250. The SE-R has V6 with 260 hp.

HEY GUYS! Thanks a bunch for the tip on gapping the plugs. That was the problem all the way. Mine were gapped at anywhere between .35-.45 ... so i gapped them all to .28 and it runs fine, no more problems boosting up. I love AF, but i owe to you fine gentlemen who have gone before me :)

Nice, glad that worked. :)