For the auto mechanics out there... (1 Viewer)

[Tim Hoover]

I have a couple questions involving my replacing some minor parts in my '87 Mustang 5.0. I've tried reading through both the Chiltons and Haynes manuals and am about to give up.

#1- I'm trying to replace the PCV valve and simply cannot find the damn thing...

#2- I'm also SOL in locating the oxygen sensors. The computer at AutoZone said my car required 2, but the manual only gives a (poor) location of one of them.

I'm also experiencing a couple of problems with the vehicle, which may or may not be related to the above parts. First of all, the car tends to stall out when idling. I have to keep a small amount of pressure on the gas pedal to keep the RPMs up to prevent this. I'm also replacing the fuel filter, so this may solve that problem. In addition, my temp gauge is all over the place. I can sit at idle and the gauge indicates that the temp has gone up 40 degrees. When the car first warms up, the gauge goes almost 3/4 of the way up before settling back down to around the 1/4 mark, which in my experience is normal operating temperature. Why would the gauge be fluctuating so much? The main thermostat was replaced fairly recently, so I don't think it could be faulty...

 

[Jon_Gregory]

Ok well let's see here. If your 5.0 mustang is about the same as my newer 5.0 Explorer, then the PCV valve is located in the rear of the engine between the firewall and the back of the engine. There should be some vacuum hoses running back there, follow them and it should reveal the PCV on the back part of the throttle body. O2 sensors are on the exhaust parts. One is usually before the CAT and one after. There should be one that you can see from underneath your car and the other should be in the engine compartment soon after the headers. I actually have 3 on mine.

 

[AjayM]

Look for the PCV on the valve covers, probably near the back of the engine.

O2 sensors will be mounted on the headers or the H-pipe with none after the cat (87 emissions regulations didn't have a need for a post-cat O2 sensor), crawl under the car and take a look. And yes, you will need 2, there will be one on each side of the engine.

On the stalling issue, replacing the O2 sensor's may help a bit, the fuel filter might help. Is the car idling at all, or does it stall out all of the time? Have you done anything with the intake system of the car lately? Have you tried resetting the idle speed (check the manual on how to do this), how about the timing on the car?

The temp gauge can be lots of things, perhaps a faulty sending unit, bad gauge cluster (Ford gauges aren't known for being high quality), how about fans for cooling the radiator are they all working (or is the clutch/fan working coming off the crankshaft?).

As much as I hate to recommend this, but check out the Corral, you should be able to get all the answers you need - http://www.corral.net

 

[Bob Graz]

My recommendation for stalling when idling is to take a good look at your vacuum lines. Leaky vacuum line will cause rough idle/stalling.

 

[Tim Hoover]

Thx for the help, fellas. I'll get out tomorrow and see if I can locate the PCV and O2 sensors.

Ajay, the car does idle. It stalls out probably 10% of the time. When I first start it, it immediately stalls and then, when restarted, idles normally. I've never touched the intake system (apart from replacing the air filter) and I've previously reset the idle speed. It idled fine for a couple months and has now redeveloped the problem. The temp gauge itself is working fine. I've tested it via the resistor method, and responds perfectly. I replaced the temp sending unit about a month ago, with no change. The fan clutch is also relatively new, and works fine. I'll give that website a look very soon.

Bob, the vacuum system was my first suspect as well. I've noticed lately that a couple hoses have dry-rotted, but they've been replaced. I haven't noticed any others coming apart in the engine compartment...

 

[Dave Farley]

Tim,

The PCV on a 5.0 is located at the rear of the engine near the firewall, under the upper intake manifold and inserted in the lower manifold. You basically have to feel for it, pull it out still attached to the hose, replace the valve, and feel for the hole and reinsert the PCV valve.

Your stalling problem may very well be the Idle Air Control(IAC) Valve. This is extremely common and most people with a used 5.0 will deal with it. It causes the symptoms you describe. The EGR valve and TPS(Throttle Position) sensor can also cause this, as well as a dirty throttle body. There are even other possibilities, but they are less common. You should do a full tune-up as I'll describe below. I lean toward IAC. The first thing to try is cleaning the IAC valve. Considering the age of your car, I would just replace it. It's about $60-80 last time I checked. It's mounted on the side of the throttle body, near the black intake hose. It's long and odd looking. If you don't want to do that, try cleaning it. In this short thread, the last poster describes the process for doing this:

http://www.corral.net/forums/showthr...ighlight=valve


Here are some pictures, albeit a little poor, that show where the PCV valve and IAC valve are located. The IAC valve is on the throttle body, down in the fourth picture on the right. You can search the message board I'm going to link you to(the links following this upcoming one)for better pictures and advice too.


http://www.allfordmustangs.com/Detailed/2007.shtml


Considering the age of this car, you should give it a full tune-up if you haven't already. Plugs, wires, cap, rotor, PCV valve, air filter, fuel filter, clean throttle body, check timing, replace serpentine belt(if needed), clean IAC valve, and clean EGR valve and spacer. The EGR valve is mounted on the throttle body toward the firewall. Basically, if you lean over the engine, it's the sensor that looks like it sits on top of the throttle body. The EGR spacer is between the throttle body and the upper intake. It's a block that the EGR valve mounts to. Clean the upper intake opening at the spacer as well. Gumout or brake cleaner both work well. If all else above fails, there's always the dealer to have it scanned for codes, unless you already own a code scanner.

This next site is about the best Mustang site on the internet. The tech sections are the best out there, in my opinion. In my opinion, use the search function before asking questions. Most people are cool and will be willing to help you, post pictures, and give instructions. You will get the occasional Search Nazi though. I would use it. If you're still having problems, start a thread, mention that you're new, have tried a search, and ask whatever you want.

The Corral

Here is a link right to the forums page. You'll want the General Tech forum and the 5.0/5.8 Engine forums at the top.



http://www.corral.net/forums


Hope this helps.

I'm on my third Mustang. I've had an 87 GT, 91 GT, and have an '02 GT currently. I'm on the verge of buying an '04 Cobra or maybe waiting for the next one in two years. Still can't decide. The 5.0's are great and easy to work on. Once you get it running right, you'll love it. There are a lot of modifications you can make to the car if you're into that. The above board is the place for that.

 

[Shawn C]

Have you had this car since new? If not, were the emissions components removed by a previous owner?

 

[Tim Hoover]

Dave - Holy crap! Thx for the detailed info

Shawn - I haven't owned it since new, but it was purchased new by my father. To my knowledge, the only mod he ever did was replacing the stock exhaust w/ Flows...

 

[Dave Farley]

No problem. I hope that helps.