Engine Still Running Problems with 1989 5.0 Engine

[rehoward]

I got my 1989 5.0 running again after a 2-3 year period of inactivity. It turns out that it had lost spark from just sitting. I found voltage at the coil and at the ignition module so I guessed that the module was bad, I replaced that and voila, spark. But it still wouldn't start so I put a fuel pressure gauge on it connected to the fuel rail test port. Zero pressure. So after messing around with it I finally jumped the fuel pump relay directly to B+ and got 40lbs of fuel pressure. Now it starts but runs like crap. It seems to be running excessively rich and has an idle that is very inconsistent running high then low then high again. Eventually it stalls. When throttle is applied it produces clouds of whiteish gray smoke form both banks reinforcing the over rich theory. I pulled a plug and it was black and sooty.

So now I am wondering, did jumping the relay as I did do something to the fuel delivery circuit so the engine control module is out of the loop? How does this engine determine fuel/air ratio and correct it? Is it by switching the fuel pump off and on to maintain a pre-set fuel pressure? I thought it would have a fuel pressure regulator. I am just learning the logic behind this cars engine management system so am still guessing a lot. Obviously I could use some advice.

Thanks,

Randy

 

[rehoward]

Car is a 1989 Mustang 5.0 convertible in stock condition. Car has sat without driving for 2-3 years and recently I got it running again.
Good spark, fuel pressure reads approximately 40psi. Car idles rough and idle RPM hunts and goes up and down repeatedly before eventually stalling.
White/light gray exhaust smoke billows out from both cylinder banks and lots of it. Does not clean out even when warm. Pulled a spark plug and terribly
black and sooty indicating to me it is experiencing an excessively rich fuel condition. Same plug used to run a perfect tan color. I jumped the fuel pump
relay to get the fuel pump to work so it stays on constantly until power is disconnected.

What might be causing this engine to be running so rich? What devices control fuel/air ratio and what should I be checking? Fuel pressure reads around
40 PSI so fuel pressure regulator must be working, right? Does the throttle position sensor affect this condition and if so what ohm readings should I get from it?
Any other ideas? O2 sensor(s)? Car used to run ok before I parked it. Not great, but nothing like this. It seems to be gagging from way too much fuel.

Any ideas? Thanks.

Randy

 

[Noobz347]

Merged into single thread.

There's no point spreading all the issues for one car over several threads only to be missed by somebody trying to help you troubleshoot.

 

[limp]

EEC is 35 years old

 

[General karthief]

You need a total systems check, more than one thing may be messed up and before you get things all goofed up read through this checklist.
Follow directions, step by step.

Help me create the "Surging Idle Checklist"

Updated 05 July 2022 to add rough idle when cold and smooth idle when up to normal operating temperature. See the EGR tech information, section #15 for more help. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank...

www.stangnet.com

Credit Jrichker and other members for compiling this procedure, it works and will help you understand how things work together.

 

[AeroCoupe]

If the vacuum line is connected to the fuel pressure regulator and you are getting 40 psi at idle that is a problem. Should be getting 5-7 psi below what it reads with the vacuum line disconnected and plugged.

Check the vacuum line for gas in it as that indicates the diaphragm in the regulator has failed.

the surging idle check list if followed will solve that problem.

This one is also worth its weight in gold:

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995 A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work...

stangnet.com

As Limp stated the ECU (EEC) is right at 35 years old and the capacitors and other parts are aged out. Not saying this is the issue but if it is most send them here for repair:

Ford Mustang 5.0 A9L A9P C3W A3M X3Z ECU Repair Service

Ford Mustang 5.0 A9L A9P C3W A3M X3Z ECU Engine Computer Repair ServicePlease fill out the R&R form here once you've placed your order.Easy repair process1. Purchase repair service (this way helps us keep track of what's coming in for repair)2. Include order number with your computer and mail to...

www.theecuexchange.com

 

[rehoward]

Not sure I understand. So 40 lbs at idle is too high? What should the pressure be at idle? If I replace the fuel pressure regulator is there any advantage to buying an adjustable one? The engine is stock except for a cold air filter and I do not anticipate any mods. I pulled the vacuum hose on what I think is the regulator and no fuel came out. Does that mean it is still functioning correctly or not? What I located is on the right hand side of the engine at the rear of the fuel log. It is buried under lots of wire and wire connectors and under what might be an EGR valve or something which is located directly behind and bolted to the throttle body and intake manifold. Just identifying all the control items on this engine is a pita. It has a ton of crap that is unfamiliar to me. My 1993 Chevy K1500 truck is simple by comparison. It has TBI injection. Even my 1988 Ford 460 port injected engine is easier to understand than this Mustang is.

 

[KRUISR]

Fuel pressure regulator is at the rear of the passenger side fuel rail. It bolts to the rail and has one vacuum line coming out of it. What he is saying is the pressure should change by a few psi when you unplug the vacuum line.

As said above the Surging Idle Checklist will solve your problem. Don't skip steps and do the whole thing.

 

[AeroCoupe]

Ha ha ha!!! These motors a super simple. Go open the hood on a new Coyote Mustang.

Yes, you found the regulator. Baseline pressure at idle should be 39 psi with the vacuum disconnected and around 5-7 psi less with it connected.

Have you checked for codes? CEL (check engine light) will only illuminate on emissions related codes so others can be present with no code.

Electrical - How To Pull Codes From EEC-IV In 86- 95 5.0 Mustangs

@Noobz347 - The code dump procedure isn't in the sticky - you may want to add it... Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on. Dumping the computer diagnostic codes on 86-95 Mustangs Revised 26-July-2011. Added need to make sure the clutch is...

stangnet.com

Pull the codes post up then go through the check lists.

 

[Potomus Pete]

What happened to this car rehoward. Will the Fox run.