danmm7

Hello all!
New member here but not new to working on cars.

This is for 2004 Scion xB with 151k miles on it - M/T.

We got the car few months ago with 140k miles on it. It was well maintained by previous, 1st owner. It has stock intake and aftermarket Borla muffler.

We replaced all filters, belts, put fresh oil (synthetic), it already had newer spark plugs, new fluids - M/T, antifreeze, brake fluid, PS fluid.
It was driving just fine for last 2 months, except having some low idle at times, when sitting at stop lights. It never stalled, but the idle did drop from time to time when idling hot, at a stops. AC being on or off did not make a difference. We cleaned the MAF sensor last week and this helped. Idle got better and more stable. Car ran better.

Well, here is the brand new problem that just happened 2 days ago. The car had a clear noticeable drop in power when taking off from a stop. You now have to really rev the rpm in order to be able to go from 1st to 2nd, to 3rd gear. It's just sluggish and underpowered. If you don't push the gas pedal hard enough, the car will stall.

Once on the highway, it can keep its speed fine for the most part. It does not have a problem reaching 70 mph or so. It is very drivable on the highway but not so much in the city/traffic.
Aside from the power drop, the other new thing is that you can hear an engine ticking/knocking type of noise when you apply the gas pedal. It comes from the engine area. If you accelerate hard, the noise is NOT there. But if you're applying gas just to maintain 60-70mph, you can hear engine ticking noise inside the car.

When parked on the driveway, revving the engine high barely reproduces the ticking. Engine sounds 95% normal. The ticking/knocking seems to be noticeable only when car is in gear and under load.

We replaced the spark plugs this morning with NGKs but unfortunately this did not help much. MAF was cleaned last week.
Checked the engine codes with OBD scanner - no codes stored.
Gas used - always 91 octane Shell

What could be causing this problem? Like i said, this was not a gradual issue that slowly got worse. It happen with no warning signs and it was first noticed while sitting in heavy traffic 2 days ago. No check engine light - no error codes.

Bad valve somewhere? Something getting stuck?
New/sudden vacuum leak?
Bad O2 sensor?


I am very puzzled with the engine ticking/ping noise too. It does sound like a noisy valve ticking but why would it appear out of nowhere?
I am not even sure if the engine ticking is related to the loss of power when accelerating from stop or these are 2 completely unrelated issues.


Thanks in advance for any pointers and advice!
DM

Harvey

Have any bad shifts lately for it to be a valve? I know a number of MT drivers had the same problem I had trying a 3-4 and accidentally did a 3-2, doing a brief over-rev. I'd check the compression, followed by checking under the valve cover to see if something's going on with the chain.

Harvey

Also (I doubt it's the cause, but just in case) are you using the proper Iridium spark plugs with correct gap? I've met Scion owners who thought Iridium plugs were an upgrade, but going by my owners manual, that's standard. I doubt it'd make that big a difference, but again, throwing it out there in case there's something up with ignition.