KC95SC400

iTrader: (3)

Ok, some of you may be familiar with my car, some not, so here's a couple of links.

Lextreme http://www.lextreme.com/forums/showthread.php?t=8757

Club Lexus https://www.clublexus.com/forums/sho...sting+projects

I've had quite a few problems along the way and up until now, I've always managed to figure them out. I am very stumped on this one, I don't know what else to do.

Car: 95 Lexus SC400 with V-9 vortech supercharger. Non intercooled with the piping ran outside of the engine bay. About 135k on the odometer.

Problem: With a COLD start, my AFR stays at about 14.5 to 1 while at idle and while cruising. Goes lean with boost. Doesn't matter if I drive the car 2 miles or 20 miles, the idle and cruise AFR stay at about 14.5 to 1. With a HOT start, the AFR starts out at about 14.5 to 1, but then starts to go rich after about a minute of running, down to 12.5 to 1. Still goes lean with boost. Also, fuel cut operation seems kind of funny, ok at higher RPM's but pulses rich at lower RPM's.

Testing, parts changing:

I've tested and changed a million and one things, which I'll go over, but this first thing is kind of interesting.

With the car HOT, I shut it off, then start back up, AFR is normal. As stated above, slowly goes to 12.5 to 1 after a minute or so. If I disconnect the MAF while the car is running, the AFR stays at 12.5 to 1. When I plug the MAF back in, the AFR goes to 14.5 to 1, then does the same thing, goes down to 12.5 to 1 after a minute.

I figured out that my FPR was leaking vac / boost, replaced it, no difference.

I did some testing on my fuel pump, seemed a bit shady, so I replaced it with a high flow Walbro. No difference.

I checked my fuel pressure, about 40psi at idle. 50psi with the FPR vac line removed and plugged. And..I saw as much as 65psi while blowing air into the FPR with an air gun. This all seems normal.

I have removed or bypassed the charchol canister, the VSV for the FPR, and the power steering idle up swith. No difference. My EGR is and has been blocked for a while now, since before this problem. The only thing, that I am aware of, that is still connected to a vac source is my boost gauge, the heater control valve and the FPR (without the VSV). I've checked everything for leaks, can't find anything.

I took out my plugs, cleaned them. No difference.

I changed some of the piping before the MAF sensor to 3inch. I did have 2.5 inch all the way up to the MAF with a 2.5 to 3 inch coupler on the MAF sensor itself. Didn't make any difference.

Unplugged all of the O2 sensors, no difference. Normally, I have all the sensors installed except the drivers side front sensor, this is where my wideband is installed and is where I'm getting all my readings. I've thought that maybe my wideband is reading funny, but the AFR readout reacts as it should during testing. Shows leaner if I pull a vac line for example.

Within the last year (before supercharging), I have changed the coils, wires, caps, rotors, t-belt, all the fluids and a few other things I'm not remembering at the moment.

I checked every single wire between the ECU and the MAF and TPS sensors. Also checked for shorts to ground, no problems found. Checked the IAT sensor, good.

I plugged the throttle body side of the PCV hoses, no difference.

I've unplugged the coolant temp sensor on the radiator, no difference.

I'm sure there is a few other things I've tried, but I can't think of them all.

I'm really at a loss here. I'm assuming that the lean with boost and HOT AFR decline to 12.5 to 1 are related, but I'm not sure. The only other thing I can think of is an IAC problem. The car runs smooth otherwise, so I wouldn't think it could be a mechanical problem. I also don't suspect injectors, I think I'd also have other issues. Like I said, I'm really at a loss.

Please help!

Thanks for reading my novel.

c0wboy

What are you using for engine management? You're introducing much more air into the system, and it's quite possible your stock system can't compensate effectively.

Eric

KC95SC400

iTrader: (3)

cOwboy,

I'm using the MAFTPRO. http://www.maftpro.com/tproinfo.shtml

Most of my testing has been done without it hooked up. I have, in the past, had it disconnected running the stock ECU alone without any problems. Keeping a 12.5 to 1 AFR till about 6-7 psi. Now, I can't even go into boost without going lean.

The thing that bugs me the most is the way the AFR changes when the engine is hot.

KC

c0wboy

It really sounds like a tuning issue. When was it last dynoed?

Eric

KC95SC400

iTrader: (3)

I would agree, except I didn't have the problem before. I just recently did some cleaning up of my piping, and removed the intercooler. I also shortened my MAF harness, I had extended the harness in an attempt to put the MAF before the supercharger at one point.

I've checked the wiring 3 or 4 times and haven't found any problems. I have the same pipe routing more or less, just without the intercooler. But I didn't have this problem before I made those two changes.

It was alot worse than it is now. I bypassed the FPR VSV and routed the vac line from the manifold straight to the FPR. Also, I did have my boost gauge tied into the same manifold port. After changing that around, I'm not going as lean.

I'm actually in the process of putting the intercooler back in, just to see if it makes any difference. I don't think I'm seeing much benefit without it anyway.

Last note, it's not so bad now, I could likey tune it out, I just can't help but think there's another problem somewhere.

KC

ihiryu

iTrader: (7)

KC, when it's cold the car runs in open loop from readings from the o2 sensor. As it warms up the car goes into closed loop which doesn't require the o2 sensor. It could be due to the fact that you only have one o2 sensor.

To my understanding our cars have an ability to relearn what we do to it. I know that from my SAFC, I just reset the ecu, and my car runs like poop and I had to retune it again.

I don't know if this is your issue exactly, but I just wanted to put it out there.

KC95SC400

iTrader: (3)

Well, I'd have to say that with the luck I've had with this project, anything is possible.

I need to stress something here though. Try restating to make sure it's clear.

For example. Car is cold, been sitting overnight lets say. I start it up, I almost always wait until the car idles down before I move. So the car is now warm and happily idling at 700 +- RPM. The AFR is sitting at 14.5 to 1 or so. I pull out and drive. The AFR is staying around 14.5 to 1 while cruising and idling. I drive say 20 miles, stop at a gas station, turn the car off of course. Go in, buy some stuff, come back out and re start the car. Idles at about, 14.5 to 1 for about 30-40 seconds and then dips down to 12.5 to 1 for no apparent reason. Only after starting warm. If I shut the car off, and then restart, it will do the same thing. Ok for about 30 seconds and then go rich. It will stay this way until it sits long enough to be somewhat cold again, then I start at the beginning.

The going lean with boost very well may be a tuning issue and nothing more, but idling and cruising at 12.5 to 1 only after a warm start is not normal. There has to be something weird going on. I don't see how your suposed to tune for something like that, we're talking like a 10-15% increase in fuel for no apparent reason.

Also, I've had that O2 sensor out since I put the wideband in quite a while ago, and I've only been having this problem for a week or so.

ihiryu, sorry if I'm sounding sarcastic, I'm just frustrated.

KC

Lextreme

Perhaps you should go back to MAF. That might solve your problem.

KC95SC400

iTrader: (3)

I am running MAF, never really got the MAP thing to work right, yet.

I did put it in speed density to see if it changed anything. It's hard to say really because it's always been a bit unstable when running SD, but it seems to be doing the same thing.

Would you happen to have a spare MAF laying around Lex?

KC

Lextreme

I have a housing but not the sensor. You can test out the MAF and make sure it up to ohm. Do u need the diagram or ohm spec?

KC95SC400

iTrader: (3)

I don't think it's possible to ohm the actual MAF. The IAT resistance can be tested.

If I'm wrong, then yes, link me to an ohm spec.

Thanks,

KC

SC400TT

iTrader: (4)

KC, I have an extra MAF, hit me up if you need it. I agree that the lean at higher load, boost, or throttle is probably a tning issue...If you read in my thread earlier, when I had the stock engine and fuel system running, I ran very lean every time I boosted beyond a few lbs...No tuning at the time, I also ran rich at idle...The stock fuel system does not handle much boost without a better tune, and I never hooked up my Split Second because it was built as as extra injector controller, and I waited for a very blong time to get that modification to the intake, so long that I canned the whole set up...

Let me know if you need the MAF...

Ryan

twizted

iTrader: (2)

I would say MAF as well, I have found if you cut the wires and splice them back there is added resistance at that point. Try unpluging your AIC and bumping your idle and see what happens for the hell of it...

ihiryu

iTrader: (7)

No it's cool I understand what it's like to be frustrated, I just wanna see you at v8 in 08.

Are you sure it's not the actual WB02???

KC95SC400

iTrader: (3)

Expect a PM in the near future.

KC