HELP! weird bog/boost problem! help asap at track now! naked chicks inside!

[wawazat8402]

I believe Im maxing the MAF out as well, mine just feels like it is pulling timing up top at WOT throttle. Its pretty much at the VTC threshold at WOT. SAFC shows 83% MAF voltage and Im running +17% correction so I just planned on picking up a Z32 MAF to see if that fixes it. Oh, and up top after it pulls timing, I can back off the throttle a little and it pulls hard again. There are no misfires and I have checked my base timing several times and it is dead on 15*.

[Darius]

I guess the only thing I noticed (and don't think for a second that I know what I'm talking about), why is your timing jumping from ~4 to ~35 when your throttle is staying relatively steady as are your RPM's? Also, why is the timing decreasing irregularly as you climb above 2200 rpm (boosting I'm assuming)? I would think that it would be gradual as your motor gradually builds boost, the ECU pulls timing accordingly.

And where are the naked chicks inside?! I've been HAD!

[ISUJinX]

Yeah, seems like your timing is jumping ALL over the place. Seems like it is trying to compensate for running rich/lean even when you aren't on boost. Perhaps the O2 sensor is bad (instead of dirty), Bad grounds on your engine harness? What injectors are you running? Are they maxed out, or sticking? Obviously this is just if you've never had it working at this boost level before. If something jsut broke, you can ignore me :-p.

Do you have a graph of EGT, RPM, O2 and timing? The EGT comparison will help determine if the O2 sensor is getting a good reading based on RPM. That should tell us why its correcting the timing so drastically.

[300Plus]

as requested, here is a comparison of O2 sensor and timing. The egt is simulated by the reading from the O2 so its not a true egt.

Would it be possible that a bad O2 could cause the computer to pull so much timing??? I hope its that easy.

[ISUJinX]

That O2 is way goofy. O2 sensors should give a smooth basic line with only very minor bumps, and those bumps should be correlating with the timing increases. Its too bad its simulating the EGT - that is a very useful tool. I'd say check the wires running to the O2 sensor and then check/replace the sensor.

[rcrdps]

Narrowband O2 is supposed to bounce when in closed loop. He was keeping the RPM steady, so it was in closed loop. Then he floored it, and it went rich. Then he let off the throttle, so it went lean because it was coasting. All you get with narrowband is bascially on and off. Rich or lean.

The ignition is kinda interesting unless you slowly came on the throttle. Your first graphs up top look more like it. The timing should drop off the face of the earth when you floor it. I'm guessing on this lower graph, you kinda got on it, then floored it. After the MAF problem, you started letting off. That's when it spiked back up. Your timing map reduces timing the more you floor it, so as you let back off, timing is added back. Hence the spike back up.

You said your wideband pegs rich, and your MAF pegs. You are definitely maxing your MAF, and it's reacting properly to that. Now the reason you're maxing your MAF,...????? It's too small,.... boost leak,....turbulence as you stated,.....?????

Gene

[300Plus]

well you got me interested in the 02 so i went and the first thing I did was unplug the o2 and take it for a ride... same exact problem no difference. But the interesting thing is I hooked up the laptop to check codes and found no codes... all good. Shouldn't I be throwing a code with no 02 sensor hooked up? So I think I'm going to check the O2 wiring. But like you said (rcrdps) I doubt it would cause such a problem (but it will still be checked and fixed)

I have checked everywhere possible for vacuum/boost leaks, which is everywhere except underneath the intake mani... if i can't find the problem soon enough I guess I'll be forced to remove it def NOT looking forward to that.

And I figured yea could be turbulence being close to the throttle body and the huge intake. but the question that keeps baffling me is what happened that caused the problem all the sudden at the track, after 3 months of no problem... again this makes me lean back towards a boost leak again.

You guys are doing great in helping me, thanks to everyone for their input! and please keep it up! I'll give all data needed and answer ANY detailed questions with pic if needed lol Thanks again guys!

[300Plus]

any more thoughts? I'll have some time this weekend to do more test and data logging. and f I can't find or fix the issue. I'm going to take a day off some time and yank the intake mani and go over everything I can think of!

[northstar ninja]

this may seem like a seemingly retarded idea, but my friend has a 90 eslipse gsx and hes using map system instead of a maf. because its just a line off the intake piping theres no restricive sensor setup. hes using the stock ecu, with a safc2 and a hks vpc. granted the car isnt completely tuned properly, yet. i was thinking of doing the same, using a map system and vpc instead of a maf system.

[300Plus]

well if i could "just go with MAP" I would lol not that simple and don't have the money to go stand alone yet.

But I'm def tired of having all this money in a car that sits there. I really hope you guys can help! Because I'm in dire need of it.

[rcrdps]

How long have you had your boost controller? Boost controllers[most] are boost leaks. Not huge, but possibly enough to put you over your MAF's limit.

Just get a better MAF. It's a piece of cake install, and will help you ignore slight boost leaks.

In the mean time, put your boost back down and enjoy having a working car.

Gene

[300Plus]

How long have you had your boost controller? Boost controllers[most] are boost leaks. Not huge, but possibly enough to put you over your MAF's limit.

Just get a better MAF. It's a piece of cake install, and will help you ignore slight boost leaks.

In the mean time, put your boost back down and enjoy having a working car.

Gene

I replaced the MAF with a stock replacment after the problem came up but it didnt help.

Its not simple to swap to a bigger MAF when I dont have a piggy back or standalone...

I removed the manual boost controller and connected the vac line directly to the waste gate acuator, nothing changed...

anything else ? anybody ?

[300Plus]

Full report guys: NEED HELP!!!

OK so we tried and ruled out a bunch of stuff this weekend. so please help with more questions or thoughts!

1. I was thinking maybe there was a boost leak somewhere so... we yanked the intake filter off slapped on the boost leak checker with pressure gauge. at first got no pressure build up. so closed the Throttle body, which was being held open slightly by the idle screw. this gave us a little pressure but still below 1 PSI. I reach over to the hose that goes from the intercooler piping to the IACV under my intake manifold. This gave us full pressure. we were able to reach 10 PSI and at that point we stopped and listened for leaks... found none. So no boost leak. But a related question would be, is the IACV suppose to be in the open position when the car is off ?

2. I figured if it wasn't a boost leak maybe it was turbulent air kicking back off the throttle body or out of the intake, since I'm using a Blow through MAF on the cold side. So we replace the MAF with a section of pipe (on the cold side) and moved the MAF over behind the filter, as it would be from the factory. no change same problem.

3. Just as a "why the F*** not test" we remove a coupler on the hot side and basically make the car run naturally aspirated where it would see no boost at all. take it for a very very short run and this was the only time I had been able to drive the car over 3500 or 4000rpm since this problem popped up.

4. Check continuity between ecu plug and MAF plug on all wires found no resistance to corresponding wires, so the wires are intact.

5. Hell I even opened the ECU to look for obvious burnt or fried sections, found none. and still showing no ECU codes.

Im out of ideas guys, and still very desperate to get her running perfectly again. Please help me diagnose

To review the problem: Car bogs and almost cuts completely off when boost hits about 3-4 psi at 3200 to 4000 rpms wideband reads 10.0 when bog occurs..

[redtop91]

Ok I lied about the naked chicks but I've got a serious problem.

Bastard! No help for you!

[northstar ninja]

can i make a seemingly stupid suggestion? borrow an ecu from someone, perhaps its not the maf itself having a problem reading boost, its the ecu... it might not be something as obvious as something burnt or fried...

[300Plus]

WELL I FOUND THE PROBLEM!

FINALLY!!!!!

after spending my 3 day weekend under the hood, check continuity, opening the ecu checking for burnt/fried spots, moving the MAF location in case it was turbulence, even checked compression... etc.etc... we found the problem!

And I know everyone (including myself) thought it was a boost leak. but after checking and checking for one i just couldn't find one between the MAF and the Head. But with 2 buddies,a boost leak tester, some ramps, a bunch of flashlights, and a cardboard box, we found the leak! turns out there was a bad leak at the intake mani gasket, on the bottom side only on the # 6 and 5 runner. the leak was so big it didn't whistle and it was so far under the intake i couldn't reach it or feel it without a lot of work. I think the last time we took the intake manifold off we must have neglected the rear bolts when we check torque specs. but anyways.... I can finally die a happy man having found the problem. Now its time to fix it and turn the boost up

Thank everyone for their input no matter how small or big!!! thanks to Kamin for all the "quick questions".and def thanks to integra7 for the late night phone call that got me back on the right track!!

While the intake is off we are going to make some modifications to it, and I was thinking more into deleting the IACV. what are every ones thoughts on this. Will just using the idle screw work well enough to keep the car from stalling coming off load? and will the motor be able to compensate for power steering at idle? just a thought not a definite route.

[Sky80]

Well, im anxious to see if fixing the intake manifold was the solution to all of your problems? I am still having the same problem as you, and have gone through all the same steps you had, i even got an emanage ultimate to hook up a rb25 maf and still stuttering(i have also since installed a AEM wideband that is pegged at 10.0 just like you are stating...) Let me know bro, im going out tomorrow to check under my IM as well

[300Plus]

Well, im anxious to see if fixing the intake manifold was the solution to all of your problems? I am still having the same problem as you, and have gone through all the same steps you had, i even got an emanage ultimate to hook up a rb25 maf and still stuttering(i have also since installed a AEM wideband that is pegged at 10.0 just like you are stating...) Let me know bro, im going out tomorrow to check under my IM as well

are you running blow threw or stock setup MAF? if it sounds exactly like mine it probably is a bad boost leak. mine is blow through so it was hard to find the boost leak. but yea what I did to find the leak with the boost leak checker was, close the TB and pinch iacv hose if needed and then open the tb letting the built up air pass into the plenum, that is what revealed the problem to me. good look let us know what you find.

I'm yanking the intake this weekend and hope to have it back on asap, I'll update the thread when that happens

[Sky80]

No i am not running a blow-thru setup, i am running the stock setup right now... I was going to go out tonight and check everything out for a leak around the IM but now its snowing here and i dont have a heater out in my deatched garage, so its gonna have to wait a few days... Do update though when you finish, i know your pain of this stupid problem :/

[Sky80]

So quick update! I took off the intake manifold and while cleaning off the gasket i picked up the manifold and moved it onto my workbench and noticed a puddle where i sat it and what do you know! There is a crack in the weld on the IM plenum part, super tiny hairline crack about 5 inches long!!! Will update soon when i fix it and put it back on...