Lean Misfires at 2700-2800 rpm

[ProwlerGT]

MY CAR's POSSIBLE PROBLEM: Could there be a light at the end of the tunnel? I sent my throttlebody to a guy who rebuilds them and he said that he's pretty confident there was an air leak in it cause one of the seals was all hardened up. I am hoping after all this damn time that this will be the smoking gun. He's USPS'ing it back to me tomorrow. I cannot f'ing WAIT to install it !!!!!! He's sending me a known good FIAV too in case I still have the problem so I can swap it out, but not putting the new FIAV on my rebuilt TB cause he's pretty confident my problem was the hardened leaking shaft seal.

Mind you I have not been able to determine through my own vac leak testing that any leaks were coming from the TB before, but I take this guy's word for it cause he's been a machinist for 25+ years and rebuilding TB's for 10.

Its been 2 years since Hurricane Katrina that I've been able to really enjoy my car at all on the road and nearly a damn year since I installed Ksport's that I have not even had the pleasure of driving on due to this hesitation/sputtering/stalling/idle issue.

Dex - My point is your car is 4 years older than mine. I would bet money the throttle body needs a rebuild and at the least new seals and you might not even be able to leak test this cause I couldn't get it to leak myself. Perhaps the best way to leak test for this would be to move the throttle body butterfly valve as the pressure is applied? Perhaps this "movement" opens up the leak in the shaft seals at a certain spot along the TB shaft.

FYI - I am checking a good source about methanol possibly causing damage to the FIAV. Waiting to hear back.

[badass3000]

I replaced my shaft seals years ago, even made a thread about it.
http://www.ca.dsm.org/faq/tb-shaftseals.html

[DoctorDex]

Same here.

[DoctorDex]

Successfully deleted my FIAV. No change.

[ProwlerGT]

Originally Posted by DoctorDex

Successfully deleted my FIAV. No change.

Damn this is starting to piss me off and its not even my problem! lol - I have to say as I've learned from the past 2 years of my car sitting in the driveway/garage that it might be best to find a mechanic friend or mechanic that works on a lot of imports that doesn't mind troubleshooting it and let them diagnose it. I've already decided now if when I install my newly rebuilt and cleaned tb on Monday if it does not lick the problem then I'm bringing it to the shop. At some point the hours of time in getting no where start to become time wasted. I'd say patience over 2 years or several months is the point of "enough is enough". I would take your list of what you've done with you and hand it to the guy so that he can pickup where you left off. Only other thing left dude is to test your ECU in a friends car and/or start your electrical testing. Got the patience for it? LOL

Just for kicks - tight tape duct or electrical tape over your BISS and see if the problem still occurs.

[brattesani]

one of the clamps that held my y-pipe to the tb was stripped and not tightening all the way. i had similar problems and that seems like it fixed it for me.

[ProwlerGT]

Originally Posted by brattesani

one of the clamps that held my y-pipe to the tb was stripped and not tightening all the way. i had similar problems and that seems like it fixed it for me.

I'd definitely double check all hose clamps and tighten with a ratchet if you can.

[ProwlerGT]

I went and looked at the 1st page of this thread again and did some brainstorming of myself and thru the manual. Here's what I have for today:

-Bad o2 (oxygen) sensors
-Exhaust leak
-Very dirty lower plenum
-Very dirty plugs
-Disassemble everything that has an air seal; reseal all with new gaskets and rtv

Tried putting back the stock MAF?

Are the iron results in your oil analysis suspicious? 20ppm

Suspect a/c compressor is dragging the engine

Spark Plug Gap stock range from the manual:
(0.039-0.043) Limit: (.051)

How modded are you? Enough to justify .028 plug gap?

I looked around at a few threads and found people saying the following different things about plug gap:

Someone said: That depends entirely on your setup, your turbos, and the amount of boost you run. With stock car, I think you will need to keep the plugs gapped near .036 or .038 regardless.

keithmac - I gapped my Bosch Platinums to .030 (0.7mm) due to spark blowout at 15psi.

boyle - Im running .024, any bigger and i blow out spark at 24psi..

hannibalzero - Most people on this board modify their cars; that's why you see smaller gaps. If your car is completely stock and at stock boost levels, then use a .038 - .044 gap. If you raise your boost to 14psi, I would start with .038 and then work your way down by .02 increments until there is no blow out.

Carlo93VR4 - Im going to go with the obvious and say change out your plugs...and gap them alittle more at about .032.. that seems to be the verdict on the forums.

From the manual:
DTC No. Title
PO1 70 Fuel Trim Malfunction (Bank 1 & 2)
Probable causes
Background
-If a malfunction occurs in the fuel system, the fuel compensation value bacomes too large or too small.
-The engine control module checks whether the fuel compensation value is within a specified range.

Range of Check
Set Conditions
The fuel compensation value exceeds the specified range for 10 seconds during closed-loop l Engine coolant temperature control of the air-fuel ratio. sensor failed.

• Volume air flow sensor failed.
• Injector failed.
• Incorrect fuel pressure.
• Air drawn in from gaps in gasket seals, etc.
• Intake air temperature sensor failed
• Barometric pressure sensor failed
• Heated oxygen sensor failed.
• Engine control module failed.
• Faulty injector

[DoctorDex]

Originally Posted by ProwlerGT

-Bad o2 (oxygen) sensors

I have a new (~10000 miles on it) rear O2 sensor. Replaced it because it was a bit lazy. Now both my front and rear o2's cycle pretty much identically. The both cycle quickly and there are nice sharps peaks to their graphs.

Originally Posted by ProwlerGT

-Exhaust leak

Have taken it to an exhaust shop and had them look over everything. They couldn't find a leak. They'd use a long length of hose, a bit like a stethoscope, to listen over a suspect area. No leaks.

Originally Posted by ProwlerGT

-Very dirty lower plenum

Mines clean. The meth kit helps with this.

Originally Posted by ProwlerGT

-Very dirty plugs

I have fresh plugs (< 3000 miles on them). The old ones were clean and had a nice tan colour to them.

Originally Posted by ProwlerGT

-Disassemble everything that has an air seal; reseal all with new gaskets and rtv

I've pressure tested to 22 psi, no leaks.

Originally Posted by ProwlerGT

Tried putting back the stock MAF?

Haven't done this, but it would be a major PITA. Had this problem before switching to a GM MAF, so I'm doubtful this would work.

Originally Posted by ProwlerGT

Are the iron results in your oil analysis suspicious? 20ppm

The iron is a little bit on the high side. I think its probably the result of the low load knock I occasionally see in the 2600 - 3000 rpm range, or it might be related to the ticking I have coming from my rear valve cover. To have a ticking, like I do, there must be metal hitting on metal somewhere. ? Lifter colliding with rocker?

Originally Posted by ProwlerGT

Suspect a/c compressor is dragging the engine

Possible, I plan on looking into this.

Originally Posted by ProwlerGT

How modded are you? Enough to justify .028 plug gap?[/b]

I'm running 22 psi on a daily basis. Since buying a DLI, I could probably increase my gap, just haven't got around to it. Plus, its nice having a bit of blowout "insurance".

Thanks for the suggestions. I think the most logical sequence of events for me would be to try and test my ECU in my friends car (can't ever get a hold of him). I think he's worried my ecu will screw up his car. Then I'd like to get a hold of an oscilloscope to see what the injector/CAS waveforms are looking like throughout the rpm range.

[ProwlerGT]

Tell your friend the only thing it could possibly mess up is the IAC and that you'll give him a new one (revised version) if that happens. Otherwise maybe it would be faster to try someone else; maybe even mail your ECU to them (with an agreement that they'll be quick to test it and send it back) to have them try it and send it back although I'm sure you'd rather someone fairly local as would I to get it back immediately. Pump him up too; tell him he'd be contributing to a cause greater than just your car, but his and a big community. lol

Where do you get oscilloscopes? Are they expensive?

I recall at NG05 that "Import Power" had a leak (boost I think) or similar hesitation issue and he was insanely pissed cause he'd gone over everything and that car was STRIPPED of all everyday passenger vehicle stuff... only rigged for racing. As I recall he wasn't able to resolve it while he was there, but perhaps he did later on. Maybe ask him what he did to fix his issue.

GOOD LUCK man. I'm all out of suggestions. Aside from electrical testing and logging of all results I don't know what else to tell ya. Some have sold their cars and tested just as much and more so than you even without ever fixing the problem. Sad but true.