Gang,

I'm gettin gthe P0174 message and am going to start by searching for either an intake leak or vacuum leak, so I Googled 'leak detection', and came up with all kinds of methods.

I called the auto parts places around town, and nobody rents smoke machines.

I am tempted to use carb cleaner or WD40, but there's just a huge safety debate on the internet.

Who's right here, and what's the best method from all you experts here on the forum?

Thanks

 

What is the safety concern? I have heard of using wd40 and I would assume you would use it with caution and a little common sense when spraying around the hot eng and exhaust manifold.

 

I couldn't agree more Gus.

One guy on the internet said that he caught 3 engines on fire, but later admitted he used starting fluid.

I just finished my inspection using carb cleaner, and found a very small hole (about .5mm) on the main vacuum reducer, and nowhere else.

Would a hole that small cause this much headache (check engine light with P0174 code)?

I erased the code and did a hard battery boot (recommended in another post), so we'll see how it goes.

More than anything, I wanted to know from the members what method of leak detection works the best for them. I would still like to know this.

Over all my years as my own shade-tree mechanic, I've never had to resort to this much detection...the leaks have always been obvious brittle or broken hoses.

 

Well the way I see it yes a small leak in the hose between the MAFS and the Throttle Body could cause the p0174 along with the MAFS problem, Fuel blockage and injector blockage and a few other things. You did the right thing with checking for leaks, fix it and then clearing the fault. If it comes up again you will need to check in the other areas. I recently found where my son took his s-type in for an oil change and in the process of trying to sell him a new filter they failed to put the cover back on correctly and created a code.
Now for this hard start! I have never done this to my car and I would think with the computer systems on this car it is not the best thing to do. The reapplying of the battery terminal improperly could cause a problem.

 

I think the reason you see the warnings about testing with carb cleaner and WD40 is more for protection than reality. As you said, you are a long time shade tree guy. That's good. Many of the people on forums like this are delving in for the first time. No one wants to give the advice that sparks up a "car-b-que." So the warnings are there for the less informed. We all started somewhere on repairing cars. When you first started working on your cars do you remember how many things you broke in the process of fixing something else? It's all a learning curve. We may play down to the more informed, but I'm sure the guy that hasn't been there appreciates it.

Lord knows I don't know it all. Hell, I'm proud to say I know a little!

 

There are 2 things to check on an xk8 for this code.
The air intake tube from the air box to throttle body. Check the bellows(acordian part of the tube) theyre notorius for becoming brittle alond the bottom and leaking. Is so you can shade tree it and clean with brake clean then wrap with electrical or black duct tape, both work well. The other area is the part load breather tube that goes from the drivers cam cover under the intake to the base of the throttle body "t" then to the purge valve.
If both of these are fine, replace the mass air flow sensor, or you can try to clean it with mafs cleaner, of which i have personally only had luck with once. But its still cheaper than a mafs of which i have a new 1 for a $100 shipped if your not super charged

 

Thanks for all the replies so far...greatly appreciated.

And Ken...I love the "car-b-que".

My air intake tube looked just fine upon visual inspection, but when I removed it last week, I was in shock to find that the bottom (the accordian area that's out of sight when installed) looked like someone dragged it against concrete, and there was leaks-galore!

I was tempted to use tape, but here in Arizona, I feared it may not hold up too well, so I cleaned very well and repaired it with black gasket silicone. I was hoping this did the trick, but the fix only delayed the check engine light from coming on after resetting.

Yesterday I found the small hole in the vacuum hose reducer, and that helped delay it even more, but it still eventually comes on.

I cleaned the MAF sensor last week also.

I'll look into the load breather tube yet today.

I really didn't want to install a new MAF sensor until I'm absolutely sure I've got my leaks investigated.

A big hearty THANKS to everyone!

You guys (and gals) ROCK!

 

I have used a propane torch (unlit) to search for a vacuum leak. It doesn't put out enough gas to blow up, has a long tube to get into unreachable places and increases the RPMs when a leak is found.

Spraying a flammable liquid around a running engine is not a good idea even for an experienced mechanic.

 

That is the way I've looked for leaks too. I don't like to use liquid sprays, not because of fire or "blowing up" but because of the mess they make. MAP gas works well too.