5.0L troubleshooting help; Idle when hot issues.

I am running a 5.0 in a 51 Mercury project im building and need a little advice.

First a little info, 5.0l punched .030 over hyper pistons, factory crank and rods, E303 cam, GT40P heads mild polish with upgraded springs, Explorer intake, throttle body, and 19LB mass, 19LB injectors, GT40P motorsport headers, adjustable fuel regulator at 42 idle, small KN cone air filter, A9P computer, 4R70W trans out of Explorer with Baumann Eng controller.

Now the problem, engine runs great while driving. Great throttle responce and power. At idle when warm it will hunt (sometimes) and die.

Do I need to upgrade to 24Lb injectors and mass? Drop down to an HO cam?
Reset the idle? Converter stall?

The Merc is for long haul cruising and daily driving, check here for the build Project "AREA 51" 51 Mercury update - THE H.A.M.B..

Any help or suggestions would be highly appreciated. Nothing like pulling into a show or gas station and have to work to keep her running!!!

Chad

Originally Posted by tayloredfabrications

I am running a 5.0 in a 51 Mercury project im building and need a little advice.

First a little info, 5.0l punched .030 over hyper pistons, factory crank and rods, E303 cam, GT40P heads mild polish with upgraded springs, Explorer intake, throttle body, and 19LB mass, 19LB injectors, GT40P motorsport headers, adjustable fuel regulator at 42 idle, small KN cone air filter, A9P computer, 4R70W trans out of Explorer with Baumann Eng controller.

Now the problem, engine runs great while driving. Great throttle responce and power. At idle when warm it will hunt (sometimes) and die.

Do I need to upgrade to 24Lb injectors and mass? Drop down to an HO cam?
Reset the idle? Converter stall?

The Merc is for long haul cruising and daily driving, check here for the build Project "AREA 51" 51 Mercury update - THE H.A.M.B..

Any help or suggestions would be highly appreciated. Nothing like pulling into a show or gas station and have to work to keep her running!!!

Chad

Both the E303 cam and the heads and intake are outside the realm of the factory speed density computer, add in the headers and you are past the point where stock fuel pressure 19 lb injectors are comfortable.

I would suggest going to 24 lb injectors (maybe even 36 lb - but that may be a little much).

Factory fuel pressure is set at 35 lb, if I remember right... so you did the right thing going to 42. Still thats a stop gap - the increased pressure helped but it doesn't address the fundamental problem of the injectors being too small.

Get a 70mm throttle body, have the MAS sensor calibrated to match the bigger injectors and maybe have a chip burned to match your setup. You have already invested some time and money, might as we go the rest of the way and have the electronics match the motor.

Before throwing too much effort and money into it, reset your idle pressure. Actually, do it engine off and FPR at atmo. Set it at 40 psig and drive it a bit. Your idle fuel pressure (with vacuum reference) should be closer to 30. Even with undersized injectors for the application, you can determine if the system is otherwise working fine. It should idle and drive perfectly, except at high loads where the injectors would max the duty cycle.

If that's what happens with this minor adjustment, then you know it's all good, your pressure was just too high trying to compensate, and you need to simply upgrade your system for higher flow as necessary. It's good to know where you're starting from. It should idle fine as-is unless something else is wrong, whether the injectors are big enough for full power or not. Being mass-flow, it shouldn't matter at lower rev's.

David

The A9P is a MAS processor guys and he says he has a MAF calibrated for 19 lb injectors. Also 19 lb injectors are good for 300 hp. He's not running out of injectors, he's not even close to those numbers. With the vacuum line removed from the fuel regulator you should see 39 - 41 psi. It will drop down to 35 or so with the vacuum line reattached. Now I don't know if he's using the stock Mustang MAF or one of those aftermarket ones that claim they are calibrated to a size injector.

I do not use the so called calibrated MAFs because that's just the wrong way to calibrate your setup. Out of all the years I've worked with them I have not seen a single one that was truly calibrated and didn't need to have the EEC recalibrated for it. Yes I'm talking about MAFs from Pro M, C & L and so on. The correct way to calibrate for your injector changes is through the EEC with reprogramming. Also a lot of people still think that if you take a MAF from a vehicle that came stock with say 24 lb injectors, that it is calibrated for 24 lb injectors. This is not so, the calibration is in the EEC programming not the MAF.

Now as for his idle problem, he could have a sticking IAC valve. But what I've seen most with these EEC IVs after a cam and larger intake swap is that the IAC function needs to be recalibrated in the EEC, in other words a reprogram. So the second poster was correct in needed a chip with a custom program to make his combination work.

Originally Posted by SnakedMark8

... But what I've seen most with these EEC IVs after a cam and larger intake swap is that the IAC function needs to be recalibrated in the EEC, in other words a reprogram...

I fully agree that programming is always the answer - there are no reliable shortcuts. However, when I still messed with Ford EECs, I didn't see E-cams and improved intakes causing stalling and dying. Unstable idle perhaps, but his symptoms are more severe than I would expect. When in doubt - return to basic settings to see where you are. Even re-tuning, resetting the FP to spec's as we both stated would be the correct direction to go, no? I would have to argue that going straight for a new chip, new MAF, new injectors, etc. is a bandaid without proper baseline settings.

I guess I fail to see what is different between my statements and yours - except that eventually the need for a re-tune is a given. The poster will realize that when he resets and it's close - but probably not right, and not because his MAF or injectors aren't big enough, or he has to buy more junk to crutch it up.

David

If you worked with the Ford EEC stuff before then you know that with the EEC IVs when you increase the FP the processor will learn the change and then adjust the injector pulse rate to back it back down. This is why in the hay day of the 5.0s people would jack up their fuel pressure at the track to get more fuel, blindly I might add. Then they got their results they wanted but by the end of the day or the next day the car wasn't running as good as it did before. The processor pulled back the injectors. So with him running 42 psi I don't see that being a problem but I do agree that he needs to reset everything and start from a base.

It's temp related as he said also. It's time to pull out the multi meter and start taking readings of the sensors. Once the sensor is figure out then he can move on to getting it reprogrammed. Like I said also he doesn't need bigger injectors for the mods he has. If he's concerned about injector duty cycle he can have that checked out at a good performance shop. But I've dynoed 5.0s with more mods than that and the 19s were still holding up fine. 24s would be ok but not something to just jump into now. And we still don't know what the MAF is.

Yeah I would say dial back the FUEL PSI also I know people with very similar setups that are running fine but using stock fuel PSI.

I really apreciate the responce to my problem. Ive replaced or slaved in just about everything I could right down the the IAC, and all the other intake sensors and swapped parts from my 64 Galaxie I have the same set up in, only a stock 5.0lL HO engine. Im almost to the point of putting in a stock configurated 5.0L powerplant but I know that when I get through this it will be alright.

What do I need to do or contact to deal with he computer recal issue?

Here are a few of the two Im working on and driving. Thanks again for all help, Chad

By the way, 42 is not out of stock range. According the Ford manual in front of me 30 - 45 psi is the norm. I personally like to keep it at 40.

I would contact a local performance shop and see what they can do for the trouble shooting and reprogramming if you've exhausted all your resources. I would check out the shop and its reputation first though. I know a few good ones in GA also.

I see you have the Explorer GT40 intake. The vacuum lines under the intake you have plugged with those rubber nipples. I'm all the time finding either the tips missing and or they are cracked and so you end up with unmetered air that throws things off some. I normally put a taper plug in them and then the nipple over that to keep them sealed or I remove them from the manifold and seal them with a plug and sealer. Just a thought since you really can't see under there with it installed.