Hello,
I have had a rough idle since I bought this used 08 xB 3 months ago. I have had an ongoing code for Evap minor leak. The check engine light, the traction control offline and engine issues. Also I had a P0304 code. The 4 cylinder misfire . I changed all spark plugs, coil #4. Tried changing all 4 injectors and car ran worse than the old injectors. I put the old injectors back in. Hard starts, I checked the fuel pump pressure at the pump 42-50 psi. Then I was driving home on Friday. Stopped at Advance Auto came back out and the xB turned over and chugged but would not start. Towed to repair shop. Next day started for them fine. Did fuel treatment and supposedly cleaned the throttle body. Once I got home it wouldn’t start again. I replaced the cam shaft sensor. It started and I thought that was it, NO. One week later on Friday wouldn’t start chug and sputter. Multi cylinder misfire code. Plugs were slightly wet, could smell gas at the exhaust. I checked the plugs and spark when turned over. One hour later the xB started. It was rough at idle and now still trying to diagnose the problem.
I don’t know if it’s a coil issue, fuel supply issue of pressure or regulator, ECU problem, or something else ? Anyone have a suggestion.

Thanks

Additional Codes P0301, P0304, P0172, P0456, with the new injectors I got P0172. The car is a 2008 Scion xB automatic transmission


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First step is to replace any parts that came from auto-parts store with genuine OEM Denso. That's always main cause of problems. Better to go to junkyard and get used Denso rather than new crap from auto-parts stores.

 

I went to the junk yard today. I brought home a fuel pump, throttle body, 2 coils, ECM, fuel rail with regulator, additional module in the vacuum system. I will be trying some parts tomorrow. Everything same year except fuel pump off a
2009 vs 2008 xB. I want to try the used ECM and see what kind of effect it has? Same codes or run worse or not at all, before I change the fuel pump. I can’t change the fuel rail until I get the Toyota tool to remove the fuel line.

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Change only ONE part at time! Best to measure everything and compare numbers to standards given in manual. As shown in guides above, codes only show you issues with a system, not any particular part. Multiple causes and often linked and overlapping symptoms.

Replacing perfectly working parts with brand-new perfectly working parts changes nothing and symptoms will persist. Best to verify each and every part is functional by measuring and testing. Then work down list and verify wiring in between is good as well. Measure resistance end-to-end. A lot of times, parts are perfectly fine, but it's corroded terminals in connectors that's problem. Nothing some light sanding & OxGard can't fix.

For P0456, most common is cracked plastic connector joining hoses coming from tank.

 

I will take that advice. I tried a used ECM to see if it changed any of the performance and it didn’t. I switched out the Evap valve. Looking for possible vacuum leak.
What is the best manual for trouble shooting the Scion xB ? Something with proper values and resistance of coils to do all this checking ?

When I couldn’t get the car to start and checked the plugs they were slightly wet. Like they were flooded. Code says rich, too much gas.

I was hoping looking at live view numbers would help me, but honestly I don’t know what they should all be?

B1S2 O2 fuel trim 99.06%
O2S B1 S1 3.242 volts
O2S B1 S1. 0.03 ma
O2S B1 S2. 0.780 volts
STFT B1 S2. 99.2%
LAMBDA B1 S1. 0.987 volts
CAT TE 11. 896 degree F
CAT TE 12. 495 degree F
STFT B1. 0.0%
LTFT B1. -6.3 %
Eng rpm 762
MAF. 0.50 lb/min
TPS. 17.6 %
IAT. 115 degree F
Command Evap 48.2%

So I have these readings while idling plus some others. I was hoping to interpret them into a direction, like O2 sensor looks bad or MAF sensor low readings.
I just don’t know enough to make a better educated guess at this point in time.

I need to find a Repair manual with good information.

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instantaneous data is not as useful as datalog. O2 sensors may be off,'but can't tell unless data is graphed. Oscilloscope trace will pinpoint issues with O2 right away. It may be cause of extreme fuel-trim.

Bad sensor like last graph will trick ECU into thinking it's running lean. ECU will try to add more fuel to compensate, but O2 sensor won't register it. ECU will add more and more fuel to bring readings up, nope...



Low MAF reading is sign of intake vacuum leak. Very common problem and it'll throw off all sorts of readings.

Crawl under car and trace all lines going to EVAP system. Most likeky you'll find a crack somewhere.

 

I would also check the gas cap

 

Being that it is an 08, also do a search on the VIN to see if it was part of the very early 08 production run. There was a recall for defective engine harnesses for almost exactly what you are describing. Multiple spark/coil codes sensor issues and such. It may not be the issue but if so the fix is a _____, full harness replacement. Oh, and check your main engine ground under the air box and battery. Another stupid point of failure on snow belt cars.

 

good point! On my 1st xB, the filler opening was slightly deformed. Probably from someone running into pump-nozzle while it was inserted. This prevented good seal with cap and I was getting that code. My wife automatically replaced cap, but that didn't fix it because previous cap was fine too.

I ended up gently sanding filler neck's outer surface so it was flat. Some polishing and it was perfect! Re-installed cap which sealed and no more code!

 

That was my first item I changed. I bought a bran new filler cap. The sealing area is round and no blemishes to allow air to escape or vacuum in.

thanks.
I just ordered new:
Denso Oxygen sensor
Denso air fuel sensor
Denso Mass air flow sensor
engine coolant sensor AC Delco
all should be here by Friday.