Popping noise from engine bay during start up, free rev, light roll on throttle
 

I'm posting this here so the rest of you track guys can know as well rather than the problems/issues section as I think this may become a problem for those of us who do a bit more than hard park/spirited driving/cruise.

I had just recently come back to Las Vegas from an autox in Utah. The next morning I fire the car up to let it warm up while I grab breakfast and right during start up I hear a pop like a back fire of some sort. I quickly disregarded it as it didn't happen again while idling. While driving the 12 miles to work I heard it again on and off while giving a bit more throttle cruising on the freeway, but instead of a single pop it was several pops. No check engine light was on at the time so I wasn't worried as of yet. Driving home from work it was happening more often while accelerating to pass. I didn't feel a loss in power while driving so I thought it was a bushing of some sort binding or a piece of trim coming apart, but I haven't had any offs in my most recent trackdays to even think of something like that. I scanned it with a cheap OBDII scanner and no codes popped up. I also was able to notice that during free rev it would pop but could not locate the engine noise for the life of me as at the time it was still sporadic especially when free revving. The next morning driving to work it was worse than the previous day and since I work across from the Toyota dealership I dropped it off at my local dealer and told the advisor and my friend who's a tech about the symptoms. After a bit of searching, no faults, no tsb's or campaigns, it was diagnosed as an oil contaminated MAF sensor. Part on order and it will take 2 days to come in. My guess is LA Parts Depo didn't have it. They gave me a hot lava iQ to drive for the time being.

Here is a quick video of it recorded from my iPhone last night. The noise is the popping noise when free revving the engine.
[ame="http://www.youtube.com/watch?v=VnFa2IvNs9g&feature=share&list=UUoy1Rjc6ck 9t3zPw-QBuT4g"]Frs popping noise when given throttle free revving or cruising, rolling on throttle to pass. - YouTube[/ame]

Currently the car is stock engine wise. No bolt-ons what so ever. The only mods are Feal Suspension Coilovers 17x8 RPF1s with BFG Comp 2s(will be replaced with RS3s in 245s when they're toast) and Carbotech XP10s fronts and XP8 rears. I have always had 5w30 either Castrol Syntec which is on tap at my dealership and now have switched to MOTUL fluids for everything including trans and diff. I have about 1k miles mixed HPDE, autox, 2 drift events(won't be doing this anymore as the car stock is tough to maintain drift and doesn't have a lot of angle). 11k on the odometer. After every event that I do, I always do an inspection of the vehicle just to make sure there isn't anything I need to address including inspecting the air filter for contamination or some sort of blockage and checking the MAF for obstruction or contamination but after this last event I hadn't had the time to pull it in the shop and inspect.

Being a tech myself I didn't think the MAF would get oil contamination from my guess the PCV vapors since with the stock air intake tube it's pretty far away from the sensor. I was also thinking of blowby from the crankcase but there shouldn't be any at this point. I may check compression when I have some free time on my hands. I'm thinking of either upgrading to some sort of intake like the AFE, Perrin or something similar. Also deleting the sound tube and running an oil separator of some sort. Any others had something similar happen? I didn't search too hard but figured I'd post this experience as it is the first one I've encountered with my car. I'm sure if I had driven a bit longer with the problem that a fault would have triggered or if I was able to record and graph the MAF PIDs I'd see some time of voltage dip when the problem would occur.

Just updating this since the car was down for a bit. The MAF turned out not to be the problem Toyota engineers came and ended up suggesting replacement of all my direct port injector seals. Had to wait almost 3 weeks for parts which was no big deal since I was out of the country. Will be picking it up tomorrow morning on my way to work and finally be enjoying it again.

I just had the same exact issue with my car a couple weeks back. Starting popping and misfiring, and the noise was coming from the intake manifold area. It happened when you would first start it up, and also when you had a lot of load on it at low RPM. Took it to the dealer and they had the car for about a week. They had to get a master toyota tech flown in to really figure it out, since the regular guys at the dealer found nothing wrong. The master tech checked fuel pressure, compression, leak-down, plugs, MAFS, and a bunch of other things and found nothing. Then he ran the car only using the multiport injection and the car ran fine. Then he ran it only using the direct injection, and it was misfiring/popping. They traced it down to a bad isolator on one of the direct injectors. It was actually just straight up MISSING! It was there before, so something happened, perhaps related to heat. I think eventually the injector isolator cracked and broke apart and created a vacuum leak. At any rate, it took them several days to get a new isolator as it was on back order. They replaced it, and the car runs like a champ now. I'm pretty sure it's the same problem you have, and I have heard of a few other people now on here having the same issue.

I've seen this before. Warranty work :)

Yup. I'm an Audi tech and the isolator that they talk about is what we call a compression seal as the DPIs(direct port injector) typically stay pretty tight in the cylinder head with these things brand new. I've never seen one of ours disintegrate though even when a car ran hot. I did have an occasion when I noticed my car pull timing(more than likely due to heat) and lose power but the factory temp gauge didn't show any signs of overheating. I need the PLX gauges, or scangauge to be able to read water/oil temps accurately from now on. It's just odd that it never would store a misfire fault as it was obviously losing a bit of compression from that particular cylinder. I didn't try diagnosing it for long since there is Warranty on the vehicle.

I am having similar issue with you guys. Popping when cold start and high load condition when @ 2500-3500 rpm. Is this dangerous? Is it difficult to replace the seal?

I didn't do the seal replacement and yes there are special tools required. You should be covered under warranty no?

Hasnt happened to me for a month now
But the 4-5 months before I heard a pop every once in a while, twice backfiring (sounded awesome!)

But seeing all of this, I'm slightly concerned. Havent had any of this activity while driving though.

OT but letting your car "warm up" at idle does more harm than good on modern engines.

Good luck with your issue though.

Its been fine since I have had the repair. Going on another 2k since it has been fixed.

I'm just curious when you guys bought your cars?

Heeltoe and myself(roommates) bought our cars the same day mid-july. Both cars have seen around the same track time and I haven't had the injector seal problem yet. I have about 16k on my car at the moment.

If you are trying to locate the problem to a certain batch of cars I'm sure my car and his where made within the same week- 2weeks of each other.

How does it do harm? (honest question)

AFAIK, one of the good things about warming up the engine is getting the oil closer to operating temperature where it has all properties to properly protect and lubricate the engine components.

I was always taught to not idle a cold engine but drive it straight away and gently until the temp is up to normal. Also that it takes up to 30mins to get everything up to normal operating temperature.

Everything I have read about it confirms that to idle a cold engine for any time not only wastes fuel but causes harm and i've just done some more googling to double check.
Basically, a cold running engine is bad news and you need to get up to temp as quickly as possible but on minimal load. To let it idle keeps it cold longer with the rich mixture causing wear to the cylinder walls.