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  Mustangsandmore Forum Archive
  '79 to '93 -- The Fox Mustang
  engine stalls

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Author Topic:   engine stalls
Kirsten
Journeyman

Posts: 2
From: Pukalani, HI USA
Registered: Oct 2004

posted 10-18-2004 12:01 AM     Click Here to See the Profile for Kirsten        Reply w/Quote
I have an 89 5.0 HO that continues to stall. The EGR valve, distributor cap and rotor,spark plugs, ignition module, and Ford ECU have been replaced. It happens only after it has been running for a while and it is good and warmed up. It will 'lug' and then die. Before I bought it in June, the fuel pressure was tested as 'OK' As far as I know it has been doing this since January of this year. If anyone has any ideas please help me out. It is getting to be rather spendy. Thank you for your ideas.

ddenton749
unregistered
posted 10-18-2004 09:13 AM              Reply w/Quote
Are you getting any trouble codes? Is your Check Engine Light working? (My '91 had a burned out bulb) If the light isn't working you won't be able to communicate with the computer.

Try removing the Idle Air Control (IAC) valve located on the throttle body. Make sure it's not clogged or gummed up with oil. If you need to clean it, remove the electrical part first, then use the spray carb cleaner. The IACV controls the engine idle and also acts like a dashpot to keep the engine from stalling when you let off the gas. Also check the ports in the throttle body.

Check for vacuum leaks. If you have one you will probably get an "O2 Sensor Lean Condition" trouble code for both sensors. There are some vacuum leak trouble spots on the bottom of the upper plenum that you can't see unless you have it off. One is a rubber plug. The other is the threaded vacuum tree on the back side of the plenum. Use starting fluid (sparingly) to search for/find vacuum leaks. The idle will change if you spray it on the leak.

------------------
'73 Convertible, 351C 2V
'91 LX Convertible 5.0
Member: Valley Forge Mustang Club
"Tank, I need an exit."

Kirsten
Journeyman

Posts: 2
From: Pukalani, HI USA
Registered: Oct 2004

posted 10-18-2004 11:10 PM     Click Here to See the Profile for Kirsten        Reply w/Quote
Hi was this happening to your car? My boyfriend talked to a mechanic and he thought maybe the fuel pump. But I am failing to believe this. I did forget to mention that as long as I kept it above 2000-2500 rpms it would go okay. So I was wondering if this was an experience that you had. I am going to check into the things that you mentioned. I was just wondering. Thank you Kirsten

ddenton749
unregistered
posted 10-19-2004 08:45 AM              Reply w/Quote
I had a vacuum leak in my '93 Explorer 4.0 L MAF-SFI, EDIS. It had all the symptoms and indications I mentioned above, and it would idle, albeit poorly. It turned out to be the gasket between the upper and lower intakes. I also replaced all the injector O-rings while I had it apart.

I recently had the upper intake off of my 5.0 and I spotted the trouble spots (rubber plug, etc.) Also, check your PCV valve and hoses for cracks.

Your description sounds like a vacuum leak. You may be able to narrow it down by looking at vacuum sources that don't activate until the engine is warm. (i.e. vapor canister purge, etc.)

It takes about 60 seconds to check the fuel pressure, but if it were the fuel pump, it probably wouldn't run at all.

It sounds like a vacuum leak. Try to remember...always start with the simple things first.

Trouble Code readers are inexpensive. Always start by checking for trouble codes...ask the computer what it's seeing. It can tell you a lot. Check to make sure your CEL is working by looking for it with the key on without starting the engine. If the bulb is burned out or a previous owner took it out of operation because they got tired of looking at it, you'll need to get it working first.

------------------
'73 Convertible, 351C 2V
'91 LX Convertible 5.0
Member: Valley Forge Mustang Club
"Tank, I need an exit."

[This message has been edited by ddenton749 (edited 10-19-2004).]

GTRocks
Gearhead

Posts: 4800
From: Lusby, MD
Registered: Jun 99

posted 10-19-2004 08:23 PM     Click Here to See the Profile for GTRocks        Reply w/Quote
Any hesitation under hard acceleration? backfiring? Could be the MAF needing to be cleaned, but I can't remember when they switched from Mass Air to MAF. It was right around there somewhere. I had a similar problem with mine that went away when I cleaned the MAF. My issues were more noticeable under heavy acceleration though, although it wasn't right at idle either and did stall a few times.

Moneymaker
Administrator

Posts: 29200
From: Lyons, IL, USA
Registered: May 99

posted 10-19-2004 08:45 PM     Click Here to See the Profile for Moneymaker        Reply w/Quote
Could be just a dirty throttle body.

------------------
Alex Denysenko
Co-Administrator and Moderator

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ddenton749
unregistered
posted 10-20-2004 05:02 PM              Reply w/Quote
The other thing could be a clogged/stuck Idle Air Control Valve (IACV). Usually though, you'll will get the base idle.

Still sounds like a large vacuum leak to me.

------------------
'73 Convertible, 351C 2V
'91 LX Convertible 5.0
Member: Valley Forge Mustang Club
"Tank, I need an exit."

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