5.0L Running Rich

[Scott B.]

As the title says, my 5.0L is running rich. You can smell it in the exhaust, and the mileage is not great. It starts and runs fine. Currently has 18K miles on it.

In my '93 Ranger, I have a '91 Mustang A9P ECU and no EGR. The EGR is bypassed with resistors to stop the computer from throwing codes. I am running a Comp Cam with specs similar to the Ford e303, headers, O2 sensors, MagnaFlow hi flow cats and dual exhaust. The timing is set at 10 degrees.

Any thoughts as to why it is rich and how to adjust it?

Thanks.

 

[SoHK_alumni]

First thought is a leaking FPR is dumping fuel fuel through the vacuum line or possibly over pressurizing the fuel system.

Second thought is an ignition issue, iffy coil, dist cap or wires.

A bit more exotic is a firing order problem -- different cams for the sbf use different firing orders, perhaps you've got a mismatch?

 

[Scott B.]

First thought is a leaking FPR is dumping fuel fuel through the vacuum line or possibly over pressurizing the fuel system.

I have checked the FPR - it is OK.

Second thought is an ignition issue, iffy coil, dist cap or wires.

I have battled some ignition problems. I have an MSD distributor, and have replaced the MSD electronics with Motorcraft electronics. I also have an MSD coil which I suspect has a heat issue (several times, when really hot outside - over 100 degrees - the truck would not start. After raising the hood for about 10 minutes, started and ran fine.

I wonder if I should try a different coil?

A bit more exotic is a firing order problem -- different cams for the sbf use different firing orders, perhaps you've got a mismatch?

I am running the HO firing order, and am sure it is wired correctly. I will go check again - just to be sure.

 

[Tbars4]

I'm def not a fan of MSD for the same issues you are discussing..

I'm onboard with everything SOHK has mentioned and since you suspect ignition issues I would resolve that 100% first before altering other items.

I'm suspecting you are not getting the burn you should be and the result is partial raw fuel..

The cam also could be a contributor but I still think its an ignition issue...

 

[Turdle]

Which MAF are you using?

 

[Scott B.]

Which MAF are you using?

A BBK unit, calibrated for cold air and 19 lb. injectors.

Maybe I should verify that with them...

 

[Tbars4]

..What temp thermostat are you running and are you having any overheating or cooling issues?

 

[Scott B.]

..What temp thermostat are you running and are you having any overheating or cooling issues?

195 degree.

No issues since pulling the electric fan and switching to the flex fan and fan shroud.

 

[Turdle]

ECT reporting low temperature to ECM might cause a rich mixture
An elbow or other device upstream of MAF could cause turbulence ( ac noise in signal) which would create a rich mixture. Could there be an air leak causing air to draw in around the filter instead of through it?

I would think the O2 sensors would report a rich mixture though. :scratch:

 

[Scott B.]

So I started tinkering with the coil...

Pulling off the high tension lead, I found a lot of corrosion on the coil terminal and in the connector (in the boot) on the lead. I cleaned the terminal and the connector.

I then added fresh Di-electric grease to the inside of the boot, and slipped the boot over the terminal. There was no "click" or "snap" or ... The high tension lead connector has failed. Oh, this is an MSD wire set.

At least I found one of my ignition problems.

I am going to source a new Motorcraft coil to replace the questionable MSD coil. The difficult part will be getting a new high tension lead. The rest of the wire set is OK. I will call MSD tomorrow, and see if they want to help. If not, I will probably buy a new wire set - made my someone else.

 

[Tbars4]

...That's good news kinda..

 

[Scott B.]

...That's good news kinda..

It is - it's nice to find something that is not right and probably contributing to the problem.