davekuhar

LEXUS SC400 misfires on 2,4,6 & 8,(sometimes misses on just one cylinder) Seems like I checked everything. Well here are the facts. 1997 Sc400 v8 4.0 1uz-fe engine, automatic trans. Timing belt failure, bent two valves on left hand bank. Went ahead and pulled the heads and had a valve job done.The bottom end was really clean (no ridge at top of cyl). Cleaned everything up. put it all back together (by the
book).After it was totally reassembled, the engine started right up first try(cool, all appears good), no smoke, no funny noises. Feeling pretty good at this time. Well the engine is idling poorly. I plugged in the hand held scanner, all values are within range of charts in the lexus book, but the scanner shows misfires on just the right hand bank. OK the engine runs poorly at lower rpms. if you take it for a drive, when you get to 2800 rpms the engine clears right up and will put you back in your seat. Runs great at higher rpms. Seems to run better before it get to 154 degrees. Here's some things I've check to
be sure (or did because other people said it would take care of the problem). Check vsv's and vacuum hose routing, vacuum tested appropriate devices and hoses. Good fuel pressure and fuel flow. Replaced fuel filter. Pulled fuel pump out and tested/visually inspected. Triple checked timing belt alignment. Then had a diesel mechanic tell me to switch injectors over-left bank to right bank..visa versa--. Also checked plugs and ignition wires.STILL MISSES ON 2,4,6,8..It starts missing on one of the even cyls, usually #8 and then the other slowly start missing in no particular order. It doesn't matter if I clear
the memory or not. Engine normally stays at 189 degrees. One other thing to mention the temp gauge goes straight up (hot plus) after a few minutes of running. The scanner show 189 degrees. Like I say if you the car hard, it runs great. Normal driving the engine misses often. Maybe someone else has encountered a similar problem. Thanks. Car has 200k on it. I did play around with the fuel system to try and somehow luck out on fixing it. But check this out, I restricted the fuel return line in different increments (10%,20% & so forth) and the car was a lot more responsive at about 80% return line restriction. I checked fuel pressure and it was in range during normal operation. Thanks again.

VVT-i

You may need to check the VVT oil control valve and/or wire harness on the right hand bank. You said that you did the work on the left hand bank,but now it's misfire on the right hand. Did you do anything on the right hand bank?

davekuhar

Yes, pulled both heads off. Had the heads done but not shaved. Put new ignition wires, distributor caps, rotor buttons and plugs. Tested for spark at all plugs. I didn't do a compression test. I believe that the valve adjusting shims may have got mixed up. Also a (real) mechanic friend said that the exhaust smell like it was running lean. I don't know what the term VVT stands for and I can't find it in my Lexus book. I'll run a scan on the car later and post the results, which may help. Thanks.

davekuhar

Here's the scanner information. The scanner is made by Autoxray model ez-scan 6000.

Readiness monitors
Complete No 01

Fuel system 1
Closed loop 02

Fuel system 2
Closed loop 03

Load value
23.9% 04

Coolant temp
176 “F 05

Short term fuel trim
1 -1.6% 06

Long term fuel trim
1 1.5% 07

Short term fuel trim
2 -20.4% 08

Long term fuel
Trim2 -25.8% 09

Engine RPM
524 RPM 10

Vehicle Speed
0 MPH 11

Ignition Timing Adv
11.5 “ 12

Intake Air Temp
77 “F 13

Air Flow Rate
0.67 lb/min 14

Throttle Position
11% 15

Oxygen Sensor 1
Bank 1 0.245 V 16

Short Term Fuel Trim
-2% 17

Oxygen Sensor 2
Bank 1 1.245 V 18

Short Term Trim2 Not
Supported 19

Oxygen Sensor 1
Bank 2 1.245 V 20

Short Term Fuel Trim
1 -21% 21

Oxygen Sensor 2
Bank 2 1.245 V 22

Short Term Trim2 Not
Supported 23

OBD II Require
OBD II (CARB) 24

Misfire RPM
2025 RPM 25

Misfire Load
1.21 g/rev 26

Idle Air Motor Posn
53 steps 27

EGR Step Position
0 steps 28

Misfire Rate Cyl1
0 % 29

Misfire Rate Cyl2
2% 30

Misfire Rate Cyl3
0 % 31

Misfire Rate Cyl4
69% 32

Misfire Rate Cyl5
0% 33

Misfire Rate Cyl6
0 % 34

Misfire Rate Cyl7
0 % 35

Misfire Rate Cyl8
11% 36

EGRT Gas
133.1 “F 37

Vapor Pressure
28 lb/sq-ft 38

Trouble Code Count
6 39

Injector Pulse Width
3.3 ms 40

PowerSteer Oil Press
Switch Off 41

Stop Light Switch
Off 42

Electric Load Signal
Off 43

Park/Neutral Switch
On 44

A/C Signal
Off 45

CIP Switch
On 46

Starter Signal
Off 47

A/C Cut Signal
Off 48

Variable Intake
Valve Off 49

Fuel ressure Up
Valve Off 50

EGR System
Off 51

Intake Control
Valve Off 52

Fuel Pump Relay
Off 53

Second Air Valve
Off 54

SCU Valve
Off 55

A/C Idle Up Valve
Off 56

Fuel Pump Speed
On/H 57

Purge Cut Valve
Off 58

A/C Magnetic Clutch
Off 59

Evap Valve
Off 60

Vapor Pressure
Valve On/Tank 61

VVT Ctrl B2
Off 62

Intake Ctrl Valve
Off 63



I hope this can aid in figuring out the engine miss. Like I said before after 2700 rpm or the engine clears right up and runs like a rocket. The low rpm miss does not occur right away, the engine has to run for awhile and then it is intermittent. Thanks.

RTIS250

iTrader: (9)

Uhm... am i reading that right? 1.25V on bank 2 o2 sensor? According to your fuel trims, you are running extremely rich. I would check out that o2 sensor... they are supposed to work on a range from 0 to 1 volt.. and you're well above that. I would suspect a bad O2 sensor.

davekuhar

Thanks for pointing that out. I went to the Lexus manual and it showed the value for the mention O2 sensor should be (at Idle) 0.8-1.2, I'll give that a try and run a new scan and post the results. Thanks.

mitsuguy

iTrader: (2)

All of your O2 sensors are showing whack readings except for B1S1...

Because of this, I would imagine, your fuel trims are way off base as well, as high as 25% off it seems...

davekuhar

I'd like to get am opinion on using a non OEM o2 sensor. OEM is made by Denso, the cost is about $50 apiece. Well I found some on Ebay made by Standard (Standard Smp 4 Wire Universal Oxygen Sensor Sg450) for $19.95 with free S & H. Has anyone had any problems with Non OEM sensors? Thanks.