Help!!! Explosion and smoke coming from intake grill!
 

Help!!!

Firstly, please bear with me as I'm only getting second hand details from my bro who's with he car.

Bro took the car to a Bosch service center to replace the battery. Shop said it's advisable to change to S5 DIN100 which has a 100Ah rating. After installing, the car was started and an explosion was heard and smoke came out of he passenger side (right side of the car) intake grill!

After a few minutes, the car restarted fine. The shop checked the engine and saw some rubber tubing detached or with loose clamps. (I suspect those are intake parts.)

Shop thinks its probably some gas residue since smoke is white.

I do hope it's just that and not anything worse. Any one have a similar experience? Any ideas of what actually caused the explosion/smoke?

Limp home mode...
 

Okay, the shop has put everything back together but it now appears that the car is in limp home mode and RPM whilst on stop cannot get past 2000.

A bit of background... The battery died a few days back because I haven't used the car in weeks. Bro got it jump started and brought to the shop to replace the battery.

I've done some research on the forum and it appears a few others have had similar experiences about the limp home mode after battery dies. I hope it's just a case of resetting he codes... I've read others had to replace the throttle body!

Still don't know for sure what caused the explosion/smoke.

However, all of these appear to be connected to the intake. MAF issue? Throttle body? Crap!

Sounds like it backfired during startup. What are your DME codes? If the throttle body did indeed take a voltage spike, or some sort of electrical gremlin bit it during the jump start/battery replacement, then it could cause a backfire through the intake. If it failed in a manner to affect the 5v reference circuits then it could cause a backfire through the intake. Incorrect cam timing can cause a backfire through the intake.

The list can continue to grow without DME codes. Start there and see where it goes. Beyond that its lot of speculation.

Skoot

Update: shop cleared the error codes and car running okay. However, when turn of the engine, limp mode comes back at next start cycle. Shop's computer reads fault code 412 but they couldn't tell me what it means as their 'porsche expert' had to leave!

So, bro took the car home and everything appears to be normal for now. Will check again at next atart cycle.

Still worried about that 412. Any help guys?

Did a bit of research and the same symptoms could mean a dirty throttle body, a replacement throttle body, an oxygen sensor replacement or maf!

Your thoughts, please.

This might give you some information about the code

Erratic Idle Code P1502 - 986 Series (Boxster, Boxster S) - RennTech.org Forums

:eek: now, I also have to worry about the DME!!!

I just wonder whether the battery replacement, explosion/smoke had anything to do with all these issues or whether it was simply a coincidence?!

When you "jump started" the car where were the + and - connections connected?

Pcars are finicky about WHERE you place the jumper cables. Improperly connecting those could be an issue. Notwithstanding that, clean the TB and intake system first. Before you touch the MAF - disconnect the battery (using the negative post). Leave 'unbatteried' for at least 30 minutes - it should take a lot longer to clean the intake system.

Otherwise, my money would be on an AOS. You will be able to see how much 'blowby' is there once you remove the intake. Please consult our DIY here to make sure you do it correctly. This is one of the first things I did to my car and it was disgusting! Make sure you have plenty of paper towels standing by.

Good Luck!

The more I read about it, it makes me wonder how all of these are connected.

My theory is that somehow, the intake plenum boots got detached upon start up with the new battery. Maybe there was too much gas vapor inside the engine during the hard cranking when the car was being started using the old weak battery or perhaps during the jump start. The excess vapor when combusted might have produced sufficient pressure to 'blast' out the plenum boots.

Why is there now a fault code 412? My guess is that the 'explosion' could have messed with the throttle jacking sensor and/or the throttle body. Or maybe the throttle body is just really dirty.

I am inclined to think that the problem is mechanical (well, the throttle jacking sensor is of course electronic but it may have been damaged physically) because of the 'explosion', and not the electronic failure of the DME.

I've got an engineering degree...but in a completely different field so I wouldn't be surprised if everything I've just said is pure nonsense to the technically minded!

So I would appreciate any help you guys can offer. I just need to know a starting point on which parts to order. My car is in Manila so I need to source parts online and take to account the longer shipping time.

Thanks y'all!

Thanks, HB. I wouldn't suspect that the jump was an issue as the car managed to reach the shop from the house in one piece and without any issues. The problem only materialized after the new battery was installed.

Anyway, I had a suspicion that the AOS needed replacement as there was the telltale smoke the last time I used he car a few weeks back. Stupidly, I ordered the wrong part from Pelican so the right part has not yet arrived. Maybe the 'explosion' was the extreme result of the defective AOS? Not sure though if replacing the AOS would be sufficient to remove the fault code 412.

This makes sense. Thanks, Skoot. CEL did not light up but there is a fault code 412.

This probably sounds stupid but we only need one throttle body for a Boxster S, right? Just got confused because I was checking Pelican and on a replacement throttle body, it says 'quantity required: 2'.

Just want to be 100% sure that I order the right parts/quantity...if it is indeed the throttle body that I need to replace.

Hey,

One detail which everyone seem to miss is that the right side "intake" is not an intake at all. So the idea of backfire doesn't hold water.

I see. So what's the right side 'non-intake' grill connected to? Or it could have been just the closest outlet for the smoke that came out of the detached intake plenum boots?

This is just a guess. IIRC, the vent on the passenger side is where excess engine compartment heat get ventilated. I assume the explosion blew the boots off the intake plenum. Perhaps the smoke was from the explosion itself which burned off some residual oil in the intake that got there from a failed or failing AOS. If so, then the smoke likely found its way out through the passenger vent.

A couple gentle suggestions:

Open up the engine compartment and look around. When you let the smoke out of a component there are usually obvious signs. Fix those first.

No known 412 error code for a 2001 Boxster. Re-check and get the whole code and it will help greatly in your diagnosis.

Blindly changing parts based on others "smoke" incidents is probably not the most direct repair route. The process of elimination works.

Did a bit of research and found an old thread in renntech relating to the same thing, specifically, 'p1502: Porsche fault code 412 - DVE Fault during spring test exceeds limit value'. I think I saw a similar mention in this forum as well so I guess a 412 fault code does exist.

Of course, your suggestion makes complete sense but I'm still about 5 days away from seeing the car and having a chance to look around the engine comp. I was hoping to get some leads so that I can point my bro and the mechanic to the right direction. One can only do so much when you're 2000 miles away...except to panic and hope for the best!

P1502:
Porsche fault code 412 - DVE fault during spring test exceeds limit value

Panic is overrated. The car is not going anywhere so wait til you get there, put a scanner on it to confirm the codes, open her up and look around. This is probably not a major issue and is quite fixable once you have a good look at the car.

If you are truly 2000 miles way, why not flatbed the car to a trusted local Porsche shop? Those of us on this board have been around for a while and and know the good guys from the shysters. From what you describe I am pretty sure shop labor will be less than airfare. :cheers:

Ah...don't think I need to explain my personal circumstance but I'm pretty sure I won't see the car until Thursday (when i'm scheduled to fly back) and there's a fair bit of distance between Singapore and Manila. Okay, it's not quite 2000 miles - it's 1,486! ;)

Unfortunately, Manila is not quite so fortunate to have so many Porsche shops. There's only ONE and they charge an arm, a leg and your first born!

Hence, it's going to have to be fixed by an indy mechanic and I would have to source the parts online. That's just how it is in the third world. :ah:

Ideally, I'd like to get a lead on what could be the potential issue so that I can have an intelligent discussion with the mechanic when I get to Manila later this week.

So any ideas would be greatly appreciated. Don't worry, i won't buy the parts until i know it's necessary!

Unfortunately we're just as blind as you are in this since you don't have access to the car, and you're the one we're in contact with.

If the smoke came out of the passenger side, as someone mentioned here, you may want to check the air-oil separator. They tend to give up the ghost at random as it is, and I'm sure some form of explosion in the engine compartment could help that happen, and a bad AOS is going to leave the car running poorly, if it runs at all. The only thing throwing me off from looking at the AOS as the culprit is that you're saying the car runs fine at times. Does it run fine like how it always did, or just run a little better than the really bad limp mode?

Kind of obvious, but just so it's said, tell your brother not to start, move, or drive the car until it has been looked at. If there's something seriously wrong, you don't want to keep running the car and make it worse.

Keep us posted on what you find, but unfortunately we really can't do much just based on what's been given so far. Be ready to take and post pictures of what you see when the engine bay is accessed, and folks on here can do a bit less shooting in the dark. There's really almost no point to us throwing a dozen theories out there instead of just waiting to see the situation and what you're really dealing with. Searching online without having that information and the car right in front of you is just going to fill your head with a million possbilities and stress you out.