KC95SC400

iTrader: (3)

Lextreme, paulwd,

I have to disagree on it having anything to do with not having a bypass valve. I have not had one for quite awhile, way before this problem started.

cOwboy. I need some tuning, no doubt, but I really don't think it has to do with my current problem. There was a time where I was running with just the ECU and the MAF, I was seeing 11.5 to 1 with up to 6psi.

I may have found my problem. See next couple of posts.

KC

KC95SC400

iTrader: (3)

Ok, I think I may have found my problem. And in the next couple of posts I goning to show you. Also, I really have no idea how a KV MAF works, but I have some theories, and if I'm correct, I can see why I'm going lean.

Pictured below is the inside of the Lexus KV MAF. If you notice, there is a lot of sealer inside of it. I think that the two parts (no idea what they should be called) in the middle, towards the bottom are the sensing elements, whatever they may consist of. These elements appear to be connected to each other in a V shape and they are directly above the shaft that sticks down into the air stream.

KC95SC400

iTrader: (3)

Pictured below is where my problem is. The sealer is leaking. The area that is filled with sealer appears to be connected to the sensing elements.

KC95SC400

iTrader: (3)

So my theory on how a KV MAF works is like this. Air hits the shaft, which is designed to create vorticies.

KC95SC400

iTrader: (3)

Somehow, the vorticies, or the pressure created by them, makes its way up the two holes, one on each side of the shaft.

Well, if the sealer on the inside of the MAF is leaking, the pressure created in the sensing elements would, of course, be less than it should be. This in turn, would not allow the mirror, or whatever the heck is in there that creates the frequency that the ECU sees, to do its job properly. Lost pressure = less vibration = lower frequency = lean.

In my case, I think the cause of sealer failure was spraying brake cleaner into the MAF in attempt to clean it. This is OK to do on a hot wire MAF, but brake cleaner will eat sealer.

Thankfully, I have a MAF on the way and should know for sure soon.

KC95SC400

iTrader: (3)

If anyone else has ever had one of these apart, please enlighten me. I do think that it could be taken completly apart and resealed, I just can't figure it out.

Maybe I could take it to an electronics repair shop.

In the meantime, I'm going to set the MAFTPro for speed density. I actually unplugged the MAF today with the Pro set to SD and it drove quite a bit better. Still lean with boost, but it always has been, one of the reasons I don't use the Pro in SD. I need to make some logs for TurboBob over at maftpro.com, I'm sure he could fix the MAF / MAP curve for me.

KC

Supra Dr

iTrader: (14)

My .02 & clarification on other operation statements.

Cold engine start up 'open loop' the computer uses preset fuel maps.
Adjusts using airflow/ map, coolant temp, air temp, O2 & predeterminded
amount of run time.
'closed loop' begins when O2's are fully heated up. The computer uses O2
readings as it's #1 source for A/F adjustments when warmed up. (not
as described is previous post)

The AEM wideband I beleave auto calibrates w/ every ignition cycle.
(doesn't mean the sensor can't be bad)

I know you have been running w/o 1 upsteam O2 sensor, but it's still a
bad idea. The computer needs both functioning for comparison. If missing/
faulty the computer substitutes a safe value. This would lead to tuning
issues. (weld in another bung of the wideband)

Overall your describing a hot soak issue. Maybe put the intercooler back on
& see. Possibles: MAF/IAT, CTS - coolant temp sensor or leaking injector
when off - rich start up. Although the injector thing would clear up after
a few minutes of running.

Also, after any 'change' you make I would reset the computer & test drive.
The computer is slow to readjust after a change. You may have 'fixed' it
w/o realizing, then put back & moved on.

And yes spraying any sensor directly is a bad idea. I clean Hot wires w/
spray on a pipe cleaner, not sprayed directly. Altough yours is a carmen
style & should not be cleaned as you can see.

KC95SC400

iTrader: (3)

Couple of things on this. I think (could be wrong) that I would always be in open loop with the one sensor unplugged. Also, after a cold start, I can drive forever without the AFR changing, until I shut it off and then restart hot. At some point after a cold start, the O2's would heat up and open loop would be acheived, so why wouldn't the AFR go rich after the car is fully warm.

All the info I can find says it does auto calibrate. I don't believe the sensor or the unit itself to be bad. I can definately feel when it runs rich or lean. It responds almost instantly to fuel adjustments at idle.

Which do you suppose is better, running with 1 or none in the front? Right now, I do not have the option to weld in a bung. I am intending to add a bung for the wideband at some point, but I'm waiting on my headers. Been waiting forever.

I don't think heat soak is the issue. And remember, on a hot start I start out at 14.5ish then go rich.

You may be right here, I may have touched upon a problem and not even realized it. But..I don't think it is as slow as everyone thinks.

I really think the big hole in the sealer is my lean problem. I don't know that it explains the hot/cold start thing though.

KC

KC95SC400

iTrader: (3)

Not to be a butt here, but EVERYONE seems to be missing the fact that the lean issue STARTED ALL OF A SUDDEN. I have had this blower on the car for months now and have never had the car go lean beyond being able to compensate for it before. I have run before without my fuel computer and was seeing 11.5 to 1 with up to 6psi. Now, I don't even make it to boost, and I'm going lean. Something has failed. I'm hoping its the MAF. I should know in a couple of days.

Like night and day honestly. This actually started happening after I made the most recent videos. Was fine when I was making them, seemed a little lean on the way home, and the next day when I drove it, I couldn't give the engine any throttle without going lean.

KC

ihiryu

iTrader: (7)

KC any update? Have you reset the ECU yet? I know our cars have an annoying self learning ability. I was just wondering if you have reset it yet.

KC95SC400

iTrader: (3)

I have reset the ECU dozens of times.

I had a member send me a spare MAF, helped a little, who knows if the lent MAF is really any better though. It does seem to be a little better runing in SD.

I also figured out that the EGR block off gasket I had made failed on both the intake and exhaust sides. Made a temp block off plate. Bought some stuff at Lowe's to make a permenant one. Considering blocking off / removing the EGR pipe just for temperature reasons.

Replaced the engine coolant temp sensor. This has seemed to help a bit, but it's still not right.

Have a few things I'm going to check this weekend. I might possibly install the 315's I have.

I think that's it for now.

KC

ihiryu

iTrader: (7)

Man it's got to be a vacuum leak somewhere, no check engine lights (well except the o2 of course)? Strange idling? something has got to be amiss.

KC95SC400

iTrader: (3)

I have an O2 code and an EGR code. Both are unplugged.

I don't think I have a vac leak, although who knows. When I was having trouble with leaks in the past, I would run lean at idle / cruise and rich with boost. Makes sense when you think about it. Under conditions of vacuum, unmetered air would be pulled in, causing leaness. With boost, metered air is escaping, causing richness.

I may be on to something on the whole hot / cold AFR thing. Check it out here. http://www.fullthrottletech.com/show...?t=3690&page=7

KC

paulwd

I have been told that you can use a smoke machine to find vac leaks, not sure how it works yet, but will find out more about it if you want me to.

I am sure you will solve the problem soon KC.

KC95SC400

iTrader: (3)

I actually have a decent method I've been using. I secure a plastic zip lock bag to the supercharger inlet using a rubber ring and a hose clamp. Then I blow air into a vac port and spray soapy water. One of these days I'll take some pictures while doing it.

I have found all my leaks this way. The only problem is that it's hard to into some places where there could be a leak. I may try the EVAP smoke machine I have at work, one of these days.

KC