Unmeasured air through intake leak causing cylinder 1 missfire

Compare the MAF left and right readings. Perhaps replace the plug and coil first?

 

Finding the exact location of a vacuum leak is extremely easy. Auto repair 101.

 

My tb tubing was cracking due to worn out engine/transmission mounts. Replaced everything w new.

 

Intake leaks are very common with the 360. And no the top does not need to be removed to change them either.

Easy to check. Buy a can of air intake cleaner. Start the car, and spray the cleaner around the base of the manifold where is attaches to the cylinder head. Listen for a change in engine sound. It will be noticeable if it is leaking.

 

Since it is specifically the no 1 cyl I’d look at the intake manifold gasket at that cyl and do the smoke test again. How does it run when driving? The miss is probably intermittent and difficult to track. The smoke Test should have made the diagnosis. Replace the plug coil and intake manifold gaskets and your problem should be sorted.

 

Far easier and more definitive to read the o2. Even small leaks really show up. . You may not hear a change unless huge leak. Also an unlit propane torch is better than an aerosol.

 

True..was trying trying to give the simplest way to test.

 

So you wouldn't use a smoke test to find the leak?

I'm always amazed at how a perplexing condition can be so easy diagnosed by an experienced professional. I'm often torn between wanting a professional to fix it for me and wanting to learn how to do it myself. Then, my wallet convinces me to do it myself.

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A good smoke machine is rather pricey for the average home guy who like to tinker. A good scan tool that can give you reliable data is also a bit on the pricey side. A can of air intake cleaner is about 5 bucks. If the leak is large enough to cause a misfire then a 5 buck can of air intake cleaner is more then sufficient to confirm the leak.

 

I've been down that road with BMWs and haven't had satisfactory experiences using cans of starter fluid. You can get smoke machines for less than $150. That's what I'll use the next time I have to run down a vacuum leak.

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Where do you inject the smoke on a 360.... and are there any evap valves which have to be in a certain position when doing the tests?

 

Most would rather try the 5 buck option then 150 before going further I would think.

Engines are very simple devices. No matter who makes them. Basics apply across the board. Don't over think because of the name on the hood.

 

Complete misapplication of smoke tester. Waste of time and money.

 

I'd be grateful if you could expand on your answer. When are smoke testers most useful? When are they a waste of time?

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Checking integrity of evap systems.

For a high pressure differential system like an induction system.

With all due respect with your level of knowledge you are better off hiring someone good to fix the car.

 

Like the Oracle at Delphi, your words can be difficult for the everyman to understand.

I believe that you are saying that a smoke test can be helpful in a system that is always open between two points, but a waste of time for systems that are only open when certain conditions exist. As Qavion pointed out, an induction system has valves and sensors that prevent air movement when not energized.

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Complete misread.

An evap system may see 4 lbs of pressure. it takes very little to have a leak and a leak will exist under nearly all circumstances. With so little resistance smoke can waft out easily. An induction system with no supercharger runs at 15 lbs of pressure and can easily make leaks where none exist statically. A smoke system will not waft out of those leaks.

Not the right tool for the job nor was it ever intended to be.

 

OK, that makes sense. Thank you for the explanation.

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Could also be an aged MAF giving bad info to the car. Did you swap swapping between the banks?

 

360 Evap Air Leak

If an evap leak is suspected on one bank, can the problem be verified by removing the evap hose, plugging the intake (and the hose), and seeing if the 02 or trim changes?