Engine Car stalls after 10 mins of idling

Maciasmarci · Dec 14, 2021

I have a problem with my 1990 5.0 if anyone can input that’ll be dope. I have a current stalling issue during idle. Around 10 mins my car would start to surge and finally stall. I have a t5, 306 w/ gt40 heads upper and lower gt40 intake manifolds, stock valves from stock 5.0 heads. B303 cam. Cold air intake, Stock exhaust with cats, replaced tfi from autozone, msd distributer, Amazon plug wires, motorcraft spark plugs and Amazon ignition coil . It has no smog pump nor egr , egr is sensor is bypassed. At idle I’m getting 14-15 on my wideband. Made sure to calibrate as well. I’ve done a tps reset base timing @10 degrees btdc. I have New tps iac spark plugs fuel injectors, fuel pump, good oil/fuel pressure @ 39psi, bottom end was fully rebuilt. Couldn’t find any vacuum leaks. Checked fuel and ignition system wires for resistance. I need of help.

Mustang5L5 · Dec 14, 2021

Will it restart immediately without issue?

Start here

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...

www.stangnet.com

Maciasmarci · Dec 14, 2021

It’ll restart but i have to give it gas to keep the engine from dying

General karthief · Dec 14, 2021

When it dies before you try to restart and with the key still on do you hear the fuel pump running?
Do you restart without turning the key to the off position?
that checklist should find the issue, you likely will have to do most of the testing when it dies before you turn the key off.

manicmechanic007 · Dec 14, 2021

I would install a fuel pressure gauge and a spark tester to watch as it dies

Maciasmarci · Dec 14, 2021

after it surges and eventually dies all I hear is all the relays clicking and don’t hear the pump running. I actually tested the voltage at the fuel pump relay when it dies and found that it cuts the power to the relay when the engine dies. I have the key still on the on position and I am able to start the car when I crank it on but I have to give it gas to keep it running after that. I do have a fuel gauge installed and I does show 39 psi until the engine dies. Haven’t checked the spark yet

manicmechanic007 · Dec 15, 2021

Sounds like the processor is cutting the feed to the pump

General karthief · Dec 15, 2021

Will the computer talk to a code reader or test light?
These are all questions covered in the checklist.
Do the checklist when it dies.
Actually, the 'surging idle checklist' is the one to do:

Help me create the "Surging Idle Checklist"

Updated 26-Oct-2019 to clarify creeping idle RPM increase as the car is being driven. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank Checklist. They are very effective in finding and eliminating the problems by use of...

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Mustang5L5 · Dec 15, 2021

The relays clicking make me wonder if it's an intermittent electrical fault. Do you know which relays are clicking? Is it the fuel pump relay under the seat, or some of the relays/solenoids under the hood?

a91what · Dec 15, 2021

Im not sure about the EECV but most ECU stop running the fuel pump when they lose the RPM signal

Maciasmarci · Dec 15, 2021

So the wire that goes to the fuel pump from the fp relay under the seat is getting 12v constantly. only until the engine dies, i hear the relays being de-energized than I no longer receive 12v to the fp. My fuel pressure guage continues to have pressure even when the engine dies so I doubt is a fuel related issue.

Maciasmarci · Dec 15, 2021

Also my afr guage is showing 13-14 upon startup. After 10 mins of idling-Right before it dies and starts surging is when the gauge fluctuates between 15 and 18 but I think it’s because the computer wants to compensate for the crazy surging. Just something I’ve observed for a while now

Mustang5L5 · Dec 15, 2021

So the way the fuel pump relay works is that the ECU controls the negative side of the relay. It completes the ground to activate the relay. The positive side of the relay is fed by the ECU relay which also feeds other relays on the car.

I bet your issue is the EEC power relay mounted next to the ECU.

Zoomed in on the fuel pump circuit.

As you can see, the eec relay feeds the fuel pump relay as well as other solenoids.

What that said, why the eec relay is dropping out is a different story, but first see if you can confirm that the relay is the issue. You should have constant power on the black/orange at all times, and key on power on the orange/black and red wire coming out.

It could be a bad relay, a bad connection or even a bad ignition switch.

Maciasmarci · Dec 16, 2021

I understand that fuel system and I’ve checked the eec and fuel pump relays . I don’t suspect it is a fuel issue only because while observing my fuel pressure from startup to when the car stalls I’m getting 39 psi . And also I have done a continuity check on the fuel system wires and checked out good.

Maciasmarci · Dec 16, 2021

Also correct me if I’m wrong but wouldn’t I get a lean mixture if it was a vacuum issue? My aem afr gauge stays between 13-14 until it starts surging, readings will fluctuate. Should I be looking in another direction?

Mustang5L5 · Dec 16, 2021

Sorry, i misread your earlier post and posted some details that don't really apply.

I'll have to go back and reread before offering another suggestion.

General karthief · Dec 16, 2021

What RPM are you trying to idle at??
The B cam and a low idle may be making the computer mad.

manicmechanic007 · Dec 16, 2021

From what you said your fuel system is ok
Back to the spark testing
Blinking light on the negative side of the coil stays blinking or not when dies?

General karthief · Dec 16, 2021

Try this:
Bump up the timing to 12-14*
It may have to idle around 800-850 rpms
I have found (in my limited) experience our computers don't like a lot of overlap, that 'lope' sounds cool though.

Maciasmarci · Dec 16, 2021

@General karthief i adjusted the screw all the way in when I was doing the base idle reset . It barely idled with that and almost wanted to stall. I’ve set it at 14 degrees before and nothing really changed. @manicmechanic007 I haven’t tried that. I wil though

Engine Car stalls after 10 mins of idling

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wonder how much it would cost to ship you a pair

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That is…until I whipped out my Bissell

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That is…until I whipped out my Bissell

wonder how much it would cost to ship you a pair

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