Engine Stall when Hot, like there's no fuel reaching the engine.

Guestwhat,

For accurate and vehicle specific repair information you gotta post the year, make, model, engine size, and mileage of your vehicle. The way you checked the fuel pressure is wrong. You gotta check it with a fuel pressure gauge. static, residual, and running. Running means you gotta drive with the gauge attached and post the PSI values. Yes it could be the catalytic converter or any other excessive exhaust back pressure problem. Use an engine vacuum pressure gauge to check for a back- pressure problem and post the results. Ignore the MIL, and do a scan for error codes even if the MIL is off. A scan is free at Auto Zone, so you got nothing to lose. Post any codes that are set so we can see them. After it stalls, does it start right up, or do you have difficulty starting it? Also is there a specific wait time you have to wait before it starts again AFTER it stalls?

Guestwhat,

I'm guessing that you edited your post after Big Blocks response. With a 1990 there is a good chance that Autozone will not check the codes for you. In many cases they only do 1996 and newer. You can use the links below to perform a KOEO (key on engine off) and a KOER (key on engine running) test.

KOEO

http://www.troublecodes.net/Ford/

KOER

http://fordfuelinjection.com/?p=94

You can use a test light if you don't have a meter.

You mentioned that the coil has good spark and that the cap looked good but you didn't mention mention that it was reaching the plugs.

Big Block said you should use a fuel pressure gauge and he is right. You can probably borrow one at Autozone for free (with collateral). Let us know if you need help performing the test.

You said the tach was reading 2 rpm and is now reading 4 rpm. Common sense would lead one to believe you meant 4000 rpms. You should check the computer codes first but also double check for vacuum leaks. A visual is not sufficient in most cases.

I would recommend that your tests be performed in this order:

1 KOEO
2 KOER
3 Ignition (spark)
4 Fuel pressure volume and delivery
5 Vacuum leaks
6 Exhaust back pressure
7 Compression

If you don't perform the computer tests 1st you can set false codes with your other tests.

Let us know what you find and if you have any questions. Also, when you post back you can use the "post new answer" feature. I don't recommend the reply feature and if you edit your initial post it makes us look like we're crazier than we already are. Thanks.

Last but not least, I recommend inspecting and cleaning the thottle body and IAC (idle air control) but again, not before you test the computer.

Guestwhat,

Take your time.
No rush.

Answer the questions that have yet to answered so we can help you. This is obvious and I shouldn't have to mention it but I just wanna remind you that this is an online auto repair forum. Obviously that means that we don't have your Mustang in front of us to check and run any tests on. That means you gotta be our hands and eyes here. You gotta answer the questions we ask, because that serves as feedback, and without feedback from you your Mustang is never gonna get fixed. Just so you know leaking intake manifold gaskets were a common problem on ALL 90's Mustangs. Confirming a leak is easy and quick. Less than 5 minutes actually, but you gotta be skilled with an Engine Vacuum Pressure Tester. Let us know if you need help in that area?

Hi guys (Big Block 409 & Drivability)
Thanks for the inputs. Yes I'll need time to do each & every recommendations. It may take a while.

Mr. Big Block 409, here's additional informations:
A) After it stall, it will not start up again. Have to wait for an hour to cool off then it'll start again without difficulty.
B) Ford Mustang 1990 (bought it brand new in 1989)
5.0 LX HO engine, 8 cyl., 300,000 miles
C) Yes, please help! on how to check the intake manifold gasket leak and do back pressure test.
Mr. Drivability,
a) I did the KOEO its ok. I try the KOER but it
won't show any code. You're right auto zone scan
only 1996 and up.
b) Did checked one spark plugs and it fires good.
Do I have to check the rest (7 spark plugs). Think I should...
Thank you guys, so very much again!
Guesswhat

Guestwhat,

You said the KOEO showed to be ok. Does that mean you received a code 11?

You said the KOER showed nothing. That's concerning. Please try running it again. The test is really picky. You have to jump through every hoop in a timely fashion or it might kick it out or give false codes. Also, when you check for codes I recommend that you look at the test light or meter instead of the check engine light.

You asked about checking all eight plug wires. The text book answer is yes but the fact that the engine will run until it is hot, tells me that your problem is likely common to all cylinders. I just wanted to confirm the operation of the cap and rotor.

You said it won't start for an hour. You will want to confirm spark and fuel during that time.

Guestwhat,

You said you have to wait an hour before the car starts again. Well that hour is helpful in narrowing down the problem. Use that hour to determine what the is NOT reachin the plugs.

Spark
Fuel
Or both

Let us know if you need help with spark and fuel delivery tests to the plugs. Check for excessive exhaust back-pressure as per below.

Check for a back-pressure problem by checking intake vacuum at the engine. It's a lot easier to hook up a vacuum gauge to a vacuum hose or port than it is to remove an O2 sensor. Vacuum gauges display readings in inches of “Hg Mercury”. One inch Hg equals a pressure reading of (0.49 psi or 3.38 kpa). Normal atmospheric pressure is around 14.7 lbs per square inch at seal level. Temperature and humidity will cause this reading to vary a bit, and the reading goes down in higher elevations. Vacuum is created inside the intake manifold by the intake stoke of the pistons, when trying to overcome the restriction created by the throttle butterfly. Most engines develop 16 to 22 inches Hg of vacuum at idle, except for most diesels which have no intake vacuum because they don’t have a throttle plate. The vacuum reading at idle will depend on engine wear, throttle opening, camshaft overlap, exhaust back-pressure, air temperature, and density. To check vacuum at the intake manifold make sure the engine is off. Now disable EGR valve by disconnecting its vacuum hose or solenoid control for the EGR. Connect a vacuum gauge to a ported vacuum source on the intake manifold or throttle body. Start the engine and note the vacuum reading at idle with the transmission in neutral. If the idle vacuum reading is lower than normal, or if it continues to drop while the engine idles, an exhaust restriction is causing exhaust pressure to build up and backup into the engine. If you increase the engine speed, the vacuum reading should drop slightly and then stabilize. After that it should rise back up to within 2 to 3 inches of the original vacuum reading you had (and should have noted) at idle. Any sudden drop of over 10 inches Hg of vacuum may indicate an exhaust blockage problem. Erratic swings of the vacuum indicator needle could mean there is a periodic blockage that being caused by loose exhaust components that are temporarily blocking the exhaust system. Other things like weak or broken valve springs over advanced or retarded valve timing and/or ignition timing can affect vacuum readings. If you see the needle on the gauge bouncing around, it could mean there is a mechanical problem in the engine.