Celicasaur

So I had to change the valve cover gaskets and do all that RTV gunky business but in my wisdom (or lack of it) I decided to unbolt the plenums that say 'AMG' on them. Anyway, so the oil leak is fixed now but I took the car for a drive and noticed immense heat from the engine. Like, so hot, you can feel heat from under the car rising up when the front doors are opened and if the hood is popped, it's hotter than usual. In my drive out on the streets, I noticed the car feeling very sluggish, esp at full throttle. It then started to misfire/wobble on decel (I found this odd) and at a complete stop, it would misfire, idle erraticly and hover as low as 550rpm.

I guess it must be an air leak from the intake chambers because when I let the car idle on my driveway, I could hear a hiss sound, which I don't 'think' i've heard before. Can't be the plugs, but I won't rule them out. I'll give the wire connectors a secon push, to make sure' they're in.

What are the views on what this could be? Are we all thinking yep, it's down to a potential airleak. That to me would certainly explain the abnormally hot running of the engine/car.

Toadster

Heat is pretty intense under my car when the fans are pumping heat out.. how are your temps?

Hulk

Did you get a CEL? If you get a misfire, the CEL will light up and when you put a scan device it will tell you which cylinder misfired

stockC43

It's the metal vacume line under the left intake plenum. It bolts to the back of the left valve cover and goes in by the throttle body area. If you remove your left plenum you will see it clear as day. O yea, the heat is normal

Celicasaur

Now that you mention it, that makes more sense. Yeah it was probably the fans blowing the heat under the car.

No, thankfully. I guess it's not the misfire then, if I would get a CEL.

Well, this would be a simpler fix than ordering new intake gaskets I guess.

actually ooooohhhhhhhhhhhhhhhhhhh of courrrseeeeeeee!!!! yep yep, that connects under the throttle body piping, right? Ahhh thanks so much man, I'm gonna check outside right now (lol it's nearly 1am here!)

Celicasaur

Ahhh damnit, I thought you meant maybe the pipe that connects under the throttle body but that is intact as is the black rubber pipe that connects to that metal nipple on the top of the back of the left valve cover.

However, I did notice that the red plastic cap thing which connects to a pipe which is best described as a kind of dipstick tube, was missing. I'm not referring to the one that is in clear view on top of the 'charger near the TB entry - I'm referring to the one under/behind the left throttle body pipe bend. This 'dipstick' bends under the firewall and leads towards the tranny.

Any more suggestions before I give up and take it to the local stealer?

stockC43

That pipe you are looking at is most likely the trans dipstick tube. The easiest way to check for a vacume leak is to spray around the intake with brake cleaner while the car is idling. If it stalls/stumbles your in the right area. Good luck!

blackbenzz

Check the line that stockc43 said. Its a line that comes off the firewall, is bolted to the rear of the left valve cover, and inserts into a rubber port at the back of the SC. You probably didn't put it back in after putting the valve cover back on

Celicasaur

Thanks guys. I'll take a closer look tonight. I might have to invest in some brake cleaner and try that method methinks... I double checked that little rubber hose last night and it's connected to the valve cover for sure. I doubt it would have come loose from the 'charger itself, but I'll give that a check just to be doubly sure.

Firechaser

Please be very careful w/ brake cleaner, it does work however make sure the engine is cold. It certainly sounds like a vacuum leak you are describing w/ the idle...another easy way to find a vac leak is to cut a 2' piece of garden hose...stick one end to your ear and hover around low near the intake...you won't believe the jet-like sound you can hear from a garden hose when you find it!

blackbenzz

Just because its bolted to the valve cover doesn't mean its connected to the port. Let us know what you find

Celicasaur

Ok so I had a good look/listen around. The black hoes at the back of the valvecover were firmly connected and also went nicely into their home into the throttle body. Only thing that was 'off' was the thin clear/white (maybe 2mm I.D.) pipe just by the front left gold circle thing so I had to connect that firmly back into the rubber bung. I think that's for the air injection system though, right, so that doesn't really bring air into the engine....actually...of course it does, it works by leaning out the mixture on cold starts! Could that be what it is? Apart from that, there was nothing else to do really. I looked hard with a flashlight and took it for a test drive n it seemed ok...made sure it got really hot and idled at a few sets of lights...seemed ok. I'll still concede though that the idle is a little rougher than what it should be methinks. If I had a stock exhaust I wouldn't know, but because it's fairly loud at the back, it's easy to distinguish uneven note of the pulses. It's not a hugely rough note, but it's enough for me and anybody with a tuned ear to know what it is. I guess I'll take it to work tomorrow and see how it goes in heavy London traffic. If it survives that journey without any hiccups, then I'll attribute the problem to the thin pipe.

blackbenzz

I don't think you are looking at the line we are talking about. The black rubber hoses are valve cover breathers. The line I am referring to is a metal line that comes off the fire wall and into the back of the SC. I will take a pic for you later. I didn't realize you were in London, I could have fixed it for you.

Celicasaur

Well, I went for a good hour long drive...lots of heat like last night...a varied mix of driving...thankfully the problem appears to have gone away. Feels reasonably strong now when pulling away and there wasn't any jerky deceleration/idle business going on. I did notice though that the idle seems to hang up at around 800rpm for a minute or so after restarting the engine (when engine is warm though, like after you've just bought something from shops) but it could well have always done that and me just notice it now.

Firechaser

If the idle is hanging then settling...you have a vacuum leak.

Celicasaur

If that's the case, then my money is on the intake manifold gaskets...it's the only thing I can think of. I'll have to order a pair over the weekend and try my luck when they arrive.

Firechaser

I spin wrenches like a mad-man...for alot of years, re-using gaskets, unless their rubber....is usually never a good idea as they've been torqued/compressed down and never seal a second time the same way. Hanging idle is common in any car w/ a vac leak...your allowing un-metered air to enter and it throws everything off.

stevebez

Does it matter so much with our cars where we got no MAF? I mean the car sets fuel flow relative to air temp and pressure and calcs the volume on that no?

Clearly a vac leak is not good but wondering how it works here on these cars.

Celicasaur

I think the MAP sensor (somebody correct me if I'm wrong) is between the metal piping where the two plenums connect from the 'charger outlet (the bit of hard pipe held on by the big c-clips). If that's the one, then it would be normal for my car to misbehave, on the basis that my leak is a little further upstream - it's at the metal gaskets where the plenums bolt down to the head. Having said that I gave the bolts on it a slight quarter/half turn last night and the leak symptoms have gone down considerably. The problem was either that, or the thin plastic pipe that I reconnected for the air injection. I dunno, I'm still 'new' to this car.

Firechaser

Actually yes...a manifold leak would affect a MAP sensor more in theory, it reads positive or negative vacuum in Hg from the pressure in the manifold and corrects the fuel accordingly. Manifold Absolute Pressure is what it stands for I believe. I just fought a vac leak on my nephew's VTEC Honda and the car would literally idle at 2200 rpm's

Celicasaur

Update:

So I bought a nice low range torque wrench, loosened the intake bolts then set about having them evenly torqued up. A few of them got torqued up nicely while for a few of them, the torque wrench decided to keep going past 20nm (well, it felt like more than 20nm, compared to the ones that it clicked on) and of course I broke one of my T30 Torx bits and when my friend brought over his one to enable me to complete the job, it ended up rounding 3 of the bolt heads off, but thankfully at least while they were very tight in the bore. I took it for a test run and the car sounded a helluva lot better without that unpredictable Impreza style idle wobbly sound. Power/response feels up too (maybe it was leaning out far too much before...I knew the car felt a bit sluggish!), but when I got home I gave it final test with the brake cleaner. I took the intakes off and sprayed around the gasket mating surface...all was well, but for one area, but of course I can't get the bolts loose again now, to re-tighten, SOooo I decided to use a very light layer of RTV around the mating surface. I hate to do it, but it's the simplest solution for the moment. I'll take it for a drive later on and report back with a further (and hopefully final!) update.

Firechaser

Good to hear! RTV isn't going to hurt anything.

Celicasaur

Yep so it's back.

I decided to treat my car by giving it a tranny service at my local Indy, and tonight I drive around and feel some major wobble and jerky light load acceleration...then up comes the CEL on the dash and I'm like FML that damn vacuum leak won't die will it?!

Can somebody please post a pic of this metal pipe from the firewall that goes into the charger which I may have forgotten to connect? FYI new gaskets and bolts are on order from the Dealer, so hopefully that'll seal the manifold for sure when they arrive.

Celicasaur

I've removed the intakes again now, in prep for the new gaskets and bolts due to arrive during the week. Here are some pics. Can somebody please tell me where this pipe is that I've forgotten to connect?











If there's no pipe that I've missed out, I can only hope that new gaskets and proper torqing is going to solve the problem. It's not nice having a car like this shake and wobble when you're out driving by yourself at night

lowprofile

Look again down here, there will be a black rubber grommet which faces the firewall. You might need a mirror to see it.
Before you changed the valve cover gaskets, there was a ~ 6mm metal pipe which was inserted into this grommet. This pipe also had a small bracket which attached to one the rear valve cover bolts. This pipe should be hanging behind the valve cover near the firewall. Good luck.