I have a 06 XA with about 5000 miles on it. It sat for about 48hrs and yesterday when I started it up the engine shook pretty good like a cyl was firing rough or something. After 40 seconds or so it cleared up and ran normal. Today I started it up and it did the same thing, a real rough idle the first time it was started and then cleared up again.

I'm going to take it to the local dealer and have it looked at. Any ideas what is causing this?

Thanks in advance!

Hodakaguy

 

A cylinder was not firing. One cylinder with a miss makes a 4-cyl engine shake badly and barely run. A cold miss that clears up can be caused by moisture in the ignition, often in the plug connectors or plug recesses. Was it rainy, did you drive through puddles fast, or did you recently wash the engine? If moisture-related, you would expect the ignition to dry out completely after it starts and drives around for awhile.
Since your problem re-occurs, maybe it's not moisture.
If it's a problem in the ignition system itself, I would think the CEL would come on and there would be a trouble code to work with.

 

Your problem when starting is not pinging. The noises you heard mean it is not even likely to be ignition-related, and more likely to be mechanical-related. So don't mess with your plugs or ECU.
The brief "rocks in the engine" sound, combined with the roughness, occuring momentarily only on a cold start, probably indicate a valve problem, sticking or whatever. It has happened in two of our vehicles (not xB), where it was transitory; it happened once and then not again. Unless it happens several times, I would not worry.
Unless the dealer can repeat it, and/or see a trouble code, I don't see what he can do about it.

 

I cant answer your question as to "why" your engine does that at startup, but I can give you a tip that will both clear up the rough idle and give you better gas mileage (I cant take credit for this advice, its old news, tried and tested). Go to most any autoparts store and go to the paint section, look for Klean-Strip pure acetone, next time you fill up put 2 ounces of the acetone in the tank first (use a long skinny funnel so the acetone bypasses the charcoal cannister thingy), then fill up.

Are you using 87 octane gas? Sometimes bad gas can cause your engine to idle rough, im no expert...If you want to know more about acetone in gas go to brightgreen.us or to lubedev.com and read about, or let us know if you find out what is causing it and what it took to fix it, thanks.

 

Acetone has been "debunked" in one of the SL threads on it.
https://www.scionlife.com/forums/viewtopic.php?t=99679
At least, it is controversial. If 2 ounces of acetone to 10 gallons of gas really, by itself, increased the mileage by 10% or more as some claim, acetone would not remain such a secret or myth.
What does "bad gas" have to do with 87 octane ? 87 octane is the only gas recommended in the manual, and Scion Customer Experience emailed that the engine was designed for 87 and there was no point in using any higher octane.

 

Sounds like something is up with the cold idle circuit. Being that new I would just leave it at the dealer overnight and then let them witness it the next morning and go from there. Good luck and keep us posted with the results please.

 

Same thing happend to me. My Scan Gauge showed that my idle dropped down to -12 then it repaired itself. I have a manual 06 xb with 5k miles and this was the first time it happend. The only thing different that I did compared to other nights was that it was parked at an angle the the left rear (gas cap side) suspension was almost fully extended, I parked on a hill