Intake Manifold Vacuum Leak? Is it?
Just when I thought I’m done with vacuum issues (just replaced vacuum element for RECIRC/FRESH AIR flap), and got my SRS light taken care of, the car started misfiring at idle and low RPM.
I replaced the spark plugs right away, but wasn't any better. Left it overnight and when started in the morning it was fine, I drove to work, stayed parked under the sun all day. Starting the car after work it started doing the same thing, it feels that the hotter the car gets it effects the idle.
I opened the hood and gave it some gas, I could hear hissing sound somewhere at the back. I tried to spray brake cleaner, but didn't notice any effect. I've put my hand in every corner of the intake manifold and the only slight difference in the hissing sound I could get is when i touched the connector hose between the top plastic intake manifold and the bottom aluminum part, and this is the one in the back of the engine. I've tightened both clamps but no visual effect.
I think I wanted to believe that this is where the problem is that I've pulled the intake manifold out, worked till 2 am until I was done. Now I regret it, should have done more investigation.
Anyway...I think I have to pressure test the intake manifold to make sure it's not a crack in the plastic, based on the symptoms it very well might be it, when it's cold it's fine and when it warms up the crack expands, and here you go... vacuum leak. On other hand It felt like a big leak, based on the sound seemed like a lot of air, and the plastic could have just an hairpin crack.
I'm open to any wise words from people that had to deal with this problem.
1995 C280 charcoal metallic
well I inspected the two aluminum intakes on the bottom manifold and the one in the front is pretty clean inside, but the one in the back has some very fine sand inside, so I hope that's my problem with the leak on the hose connecting the top manifold to the bottom manifold. Also the rear connecting hose has some sand build up where it connects to the aluminum intake and it's very rough. the front one is pretty clean.
I got some penetrating dye and I'm going to test my intake manifold.
Get your hands on a smoke machine. Fog up the intake until smoke starts coming out of the area where a leak is present
Maybe ill get the machine when i put it back together. Need to buy all new seals, probably will take a week.
Im wondering about 2 hose connectors. 40$ each. Maybe i can use the blue silicone intake hose, ill check tomorrow if they have the right size, its 2-5/8 diam.
I still hope its the leak in that hose connection.
Did the dye test on the manifold, couldn't find anything.
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