How to Check for a Vacuum Leak???

[BuffaloXplorer]

I've read so many posts regarding vacuum leaks but i haven't seen one regarding how to check for them...so i'll ask now.
I just erased a p0420 error code. I'm sucking 10-11 mpg and with gas at $2.05/g i've gotta do what i can to fix my problems. The error is related to the O2 sensor in bank 1.
I've just realized that most of the problems i've had since purchasing this BEAST have had "vacuum leak" as a probable cause. How do i check for a vacuum leak, as well as the checking the fuel pressure regulator? Can i do either without buying an expensive gauge? The gauge for the FPR is 1/2 the cost of a new regulator. Also, anyone with the link to the "How to" diagnose/replace either feel free to pass it on. Thanks a LOT

Chris in Buffalo

 

[adale]

Checking for vacuum leaks

Ok, I am confused as to why to are thinking a vacuum leak but yet you say the problem is related to the O2 sensor. Any way the easiest way I have found the leaks is to first make sure the problem is a vacuum related issue. Vacuum leaks can be something like poor mileage, hesitation from a stop, hard brakes, etc. I have checked with a propane torch (DO NOT LIGHT THE TORCH!!!!!!) by putting a good tygon hose on the end then cracking open the valve and moving the other end of the hose around each vacuum hose and manifold, but be VERY VERY careful. Since the propane is combustible, the leak will suck in the propane and you can hear the engine increase in RPM. I also look around any rubber hose attachment coming from the air box, these do break down after a few years.

I would check you fuel pressure regulator, as this is a very common problem that causes your mileage to drop like a rock. Hope this helps

 

[BuffaloXplorer]

If there's a vacuum leak then the engine combustion isn't quite right, therefore resulting in poor exhaust biproducts being sucked into the O2 sensor, causing it to go bad. (guessing here - but it seems practical)
Regardless to whether or not the two are related, vaacuum leaks are a major fuel efficiency problem and that's y i'd need to get that checked out. The O2 sensors going bad could be a direct result of that and/or many other issues with my engine.
Right?????
And finally, if i "reset" the computer by disconnecting the battery without fixing the problem causing the error code, whay hasn't it come back on months later? If these computers are supposed to detect the slightest variance in engine performance, how can one be so easily "fooled." Not to say that resetting the code helps with the poor gas mileage, b/c it doesn't, but shouldn't it detect the original problem within the next couple hundred miles given the same diving conditions?

 

[BuffaloXplorer]

Ok, I am confused as to why to are thinking a vacuum leak but yet you say the problem is related to the O2 sensor....

for what it's worth, the autozone quickbook that they look into for possible causes of error codes specifically mentions vacuum leak as a cause for bad O2 sensors

 

[aldive]

Have you used a scanner to check and monitor the O2 sensor(s) function?

 

[BuffaloXplorer]

You seem to be the resident gas sipper, so i'll throw it your way...

can't afford to buy special tools i may never need again - by the way, is there a way to test the FPR w/o buying the $38 gauge?

Since i bought my X Conversion (raised fiberglass roof, tv, vcr, bodykit, etc) in Nov '01 @ 105k, (presently 142k) i've installed a K&N Filtercharger, new plugs & wires, custom bent/welded SI/DO Ravin High-flow exhaust, pcv, thermostat, all (3) 02 sensors, recently cleaned the K&N, IAC & MAF, & had the tranny rebuilt 2 weeks ago (torque converter blew up). Since the rebuild, it seems to run more smoothly (i'm getting 11mpg, used to get 9).

I'm pretty sure my problems start with a vacuum leak, b/c it seems to idle high & surge once in a while. I'm skeptical about the FPR, but don't have the $70 to invest in a new one, nor do i know how to go about changing it if i do.

Ideas, pointers???

 

[Robb]

The cheap tools:

FPR: fuel pressure is measured off a shrader valve on the fuel rail. If you can get your hands on a simple tire pressure gauge with a round dial that will read up to about 50-60psi, you can use it. It isn't the optimal tool, but it will get you in the ballpark. Some of these gauges will only show "peak" pressure without dropping, so you may end up plugging in, removing, plugging in, etc. Or, if you have any type of air compressor around the house, you can usually remove the pressure gauge and thread it into a simple shrader valve nipple.

Vaccum Leak: you can use either compressed air (from tank or can) or a propane torch (unlit of course) to check for leaks. Just direct the nozzle slowly around any surface that may create a vacuum leak, and if you hear the engine change tone at any point, that is the sign of a leak.

 

[BuffaloXplorer]

thanks Robb, i'll be checking into that this weekend...i see you've got a 95 & 96 - any problems with the locks/latches on the doors/hatch? Check out the following thread when you've got a chance...i'm having problems with the hatch latches/mechanism as a whole AND my autolock system...ever have troubles with yours? Let me know what you think. Thanks much.

http://www.explorerforum.com/forums/showthread.php?p=967584#post967584

 

[adale]

Vacuum and O2 sensors

I have never looked at the Autozone book. As for vacuum leaks, if they are after the MAF the engine will be running lean and before the MAF should not effect the system. I agree with using the tire pressure gauge to look at fuel pressure, but remember you are going to have raw gas spraying out of the valve. I thought you could also check the regulator by pinching the vacuum hose going to it and the engine will change speeds. I think it will speed up infact, i.e., less vacuum more pressure.