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  Soarer Central * Mechanical - V8 * Running rich at 2200 RPM *long read* Previous Previous    Next Next  

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Steven Nguyen
Newbie
TX
V8

Posts: 1
Reg: 08-2012

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Friday, August 24, 2012 - 01:04 am, by:  Steven Nguyen (Ihiryu) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

I have a 92 Lexus SC400, I've been having a problem that has gotten worse over time.

First the girl has about 300K miles on her. The car has been running exceptional for as long as I've owned her.

After doing a compression and leak down test (the motor tested awesome), I went ahead and put a supercharger on her. Using a Vortech unit along with Lextreme's "Fish" bracket.

Currently I'm am using stock injectors and ecu matched with an Apex'i SAFC II (I installed the SAFCII about five years ago).

Originally I had the KMV sensor in the stock location, but I began to force the KMV to come apart under boost. The car would jerk, and ran poorly unless she was at WOT. Sometimes she'd idle, sometimes she wouldn't with this setup.

So I relocated the KMV sensor to the intake side of the blower. Once I did that, most of jerking was gone, she idles so much better this way.

Now the jerking was bad prior, and would jerk at virtually any RPM band if I was at cruise. Now the jerking is gone EXCEPT for 2200-2400.

According to my wideband when I reach 2200 the car will start to go rich. If I keep my foot there (as best as I can) it jump back and forth rich and lean. It's unbearable because 2200 is about my cruising speed on the highway.

My first thought was ECU, so I replaced it with a spare, and the exact same issue. I took a look at the KMV and realized that this was starting to come apart, so I put a spare one that I tested as good. Same thing.

I unplugged the o2 sensors, same thing.

The only thing I can do is unplugged the KMV sensor, and the car runs good, but is stuck at 12:1 AFR's

I've double and triple checked my wiring with my multimeter at the ECU to be sure that my wiring is right.

I look at the live data that the SAFC shows (KMV, TPS) and that shows normal. There's not a dead spot in the TPS, since I've tried the TPS from open to close while monitoring the SAFC.

At this point I have no earthly idea what it could be, I've even added grounds to it.

The car runs exceptional, minus when I'm in this RPM.

I've posted on both Lextreme, and club lexus, but to no avail. Its seems like you guys modify the V8 more than anyone else in the world.
Dan McColl
Goo Roo
Victoria (The Nazi State)
Pretty Red Thing and The Black Rattler

Posts: 3666
Reg: 07-2005

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Saturday, August 25, 2012 - 05:39 pm, by:  Dan McColl (Hoon) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

If unplugging the Karmann Vortex?? makes it run right then the problem is most likely a bad ecu or a bad KMV, or some wiring broken/damaged.
Steven Nguyen
Newbie
TX
V8

Posts: 3
Reg: 08-2012

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Tuesday, August 28, 2012 - 02:53 pm, by:  Steven Nguyen (Ihiryu) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Yeah I'm starting to think I've got a stuffed ECU.

I disconnected the TPS to see if there'd be any change, drove it on the high way for a few miles, and it never threw a CEL.
Dan McColl
Goo Roo
Victoria (The Nazi State)
Pretty Red Thing and The Black Rattler

Posts: 3672
Reg: 07-2005

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Tuesday, August 28, 2012 - 08:35 pm, by:  Dan McColl (Hoon) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Find an electronics guy (maybe someone at your local radio shack would be keen to make a little cash on the side) and get them to change all the electrolytic capacitors in the ecu, and clean up the mess the current ones have made and you should be good to go.
Steven Nguyen
Newbie
TX
V8

Posts: 4
Reg: 08-2012

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Saturday, December 01, 2012 - 05:56 am, by:  Steven Nguyen (Ihiryu) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

It's been awhile, the car went down, and have been working on my S30.

Anyway, so the car still runs like crap. I've put a new ECU in it.

Replaced the Cam sensors, o2 sensors (primary), checked for vacuum leaks, tried another KMV sensor. Still nothing, the car still runs terrible. I don't know what to do, I'm at wit's end with this car. I'm worried that even if I install a standalone ECU that it won't fix my problems. The car only runs good with the KMV sensor disconnected, I've tried to shorten and extend the KMV to the supercharger inlet with no luck either.
Steven Nguyen
Newbie
TX
V8

Posts: 5
Reg: 08-2012

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Sunday, December 02, 2012 - 02:31 pm, by:  Steven Nguyen (Ihiryu) Quote hilighted text Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Changed all timing sensors and no dice. So I did make some progress, I was running without an air filter because it sat in the front bumper with nowhere else to go, I moved the KMV sensor as best as I could where it sat outside of the engine for temporary testing.

I noticed that my air filter adapter had a hole on the tube. So I placed my hand over the opening of the MAF adapter, and the car began to run better. I added a filter, and plugged the hole on the bottom and bam!

Super good idle. She idles at 13:1, and drives much better, but still not good. It's still bucking and studder, but so much better.

So the KMV sensor sits in the original location (under the driver's side headlight), and the filter portion sits behind the intercooler. I wonder if need to move the KMV sensor further away from the blower. The only problem is that space is VERY limited. I have no idea what else I can do though.

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