Last few weeks (probably longer) I've noticed my idle drops to 500rpm for a few seconds when at a red light (when the vehicle is fully warmed up) before bouncing back up to the normal range.

Well since I'm right at 120,000 miles and I don't think it's ever been done I decided to get a can of CRC intake cleaner to clean out the intact tract/valves. I loosened the clamp that holds the rubber hose just aft of the MAF sensor, (drivers side inlet) stuck the straw in and started spraying in one second burst as directed. Everything was proceeding as normal, i had the rpm right around 1800 and i could hear the engine bog a bit whenever i sprayed some in.

After about a minute is when things went south. All of a sudden i hear a ticking noise that starts to get louder very quickly, then smoke starts coming from the right side of the engine. At this point i shut it off and seriously considered that I've just destroyed my engine.

Well I waited 10-15 mins and with fingers crossed started it back up. To my surprise it sounded and idled fine. I then decided to take it for a test drive and it runs and accelerated as normal.

So my question is what did I do? What was that loud ticking?

Oh and i could see large droplets of liquid had sprayed out on the right side of the engine, so it appears it expelled or spit out some of the CRC, although I cant say from where.

 

Exactly what product were you using? Throttle body - intake cleaner or INTAKE VALVE cleaner?

 

Hello Cleric, It was the the CRC intake valve cleaner sprayed just downstream of the maf.

A small update, intermittent low 500rpm idle is nearly gone and there is a bit more low-end torque right around 3000rpm (haven't pushed it much further yet). Although I don't think that's worth the loud ticking/ borderline banging sound and smoke coming from the engine. And this is with only 1/4 can used.

 

Yeah that's weird, my 2012 focus is a GDI engine and I run an entire can of that valve cleaner through it every year and never had any issues like that. I spray it slowly though, probably takes me 5 minutes to go through a whole can. Honestly it's not even necessary with a traditional intake injection system like the HR motor has. Fuel washes the intake valves clean, just add a bottle of seafoam a couple times per year for a little extra oompf.

GDI you have to use that cleaner though because the injectors are inside the combustion chamber with the exception of a couple engine, Toyota started adding an extra injector to the intake on their GDI engines just to clean the valves because dirty valves is a colossal problem on GDI motors.

 

Ahh I just re-read your post, did you unclamp the intake pipe BEFORE or AFTER the MAF sensor, you said AFT so I'm guessing you disconnected the pipe between the MAF and throttle body.

This would explain what happened, you essentially created a huge vacuum leak and were running really lean, while also spraying a cleaner through it that screws with A/F even more. You're supposed to remove the air box/filter and stick the long straw of the cleaner up through the MAF so it's spraying the cleaner on the other side of it. This way air/fuel isn't affected as much. What you probably heard was PINGING, sounds almost like someone shaking up a can of paint really fast, that clackety-clackety sound an engine makes right before it kabooms.

 

If that's what happened you're probably ok since the engine wasn't at a high rpm and wasn't under load, pinging is when the combustion chamber pre-detonates BEFORE the piston reaches top dead center, basically it ignites early and tries to push the piston back down even though it's still on the upstroke. Can cause catastrophic engine failure.

Investigate where the liquid came out and where the smoke came out, use an inspection mirror. The smoke probably happened because you were SUPER lean in the combustion chamber and combustion temps spiked through the roof and started to cook something. No clue about the liquid but my gut is telling me it tried to push the HG a little. You'll know soon if that's what happened.

Pull your plugs, I'm betting they're very very very cooked almost to the point of melting.

 

Thanks, the loud banging could definitely be pinging, I was thinking more toward a lifter or some other component that was covered in CRC or had a large amount of carbon come off and was rotating without much lubrication as CRC is not petroleum based like seafoam. Looking online it appears others have experienced this loud noise after doing a cleaning (followed by a loss of power) when trying to accelerate on the highway to clear the system.

I believe the smoke was actually the CRC burning on the exhaust manifold when it was spit out.

As far as my spray method i did not remove the pipe i simply loosened the clamp so i could get the little red straw in the intake stream and spray. The system was still quite sealed. I never even got any CELs the entire time. Since the car is running/idling fine I think the plugs may be fine (still original)

Well all i can say is thank goodness the HR is a stout motor.

edit: it may also be possible the CRC pooled up and hydro-locked one cylinder.

 

Update in case anyone is interested:

My intermittent low idle returned several weeks ago. It would dip to ~500rpm for a second or two before bouncing back up and settling into the normal range, this would happen several times a day.

Yesterday I decided to once again try the intake cleaner treatment, spraying approx another 1/4 can. This time I got very little of the loud banging and less smoke but it appear to belch out the spray once again from one of the spark plug holes where the coil pack is. Only difference this time was I'm using fresher oil (oil change done couple weeks ago) and it was warm out.

So I'd have to say the noise was definitely the lifters. As far as fluid being spit out, only thing I can think of is somehow there's a small gap in the spark plug well allowing pressure to vent in certain circumstances. I also have a slight whistling noise under acceleration, but only after 6000rpm.

Anyway the low idle is again gone, so this spray treatment can clear up these sorts of issues.