5.0 Idle issues

[friskyfrankie]

Did you shut it off, or did it shut itself off?

Had the same question!

[monotonorobo]

Did you shut it off, or did it shut itself off?

Sorry, shuts itself off. Happens in any gear.

[slack]

When my ignition switch went bad, it would randomly shut off on me.

[monotonorobo]

When my ignition switch went bad, it would randomly shut off on me.

I’m gonna check the connector to it, switch has already been changed out.

[gadget73]

reason i asked is because its a clean turn-off. Weird EFI stalls don't tend to be like that, same with lack of fuel pressure issues. Those are more of a case of it idles down so far that it stalls, or does some other weird gasping sort of crap. That sounds like the ignition shut down, or maybe the ECM turned off injector pulse. Dying ECM relay might do that. Maybe worth giving that a bang to see if it glitches. Behind the washer bottle are some relays under plastic covers. The green one is fuel pump, brown is ECM, black is AC cutout. Those connectors get crusty and things can get strange.

the fact that it doesn't self-test also makes me wonder about electrical problems. Half the stuff on the "doesn't give codes" list are checks for power and ground at various points on the ECM connector.

[monotonorobo]

reason i asked is because its a clean turn-off. Weird EFI stalls don't tend to be like that, same with lack of fuel pressure issues. Those are more of a case of it idles down so far that it stalls, or does some other weird gasping sort of crap. That sounds like the ignition shut down, or maybe the ECM turned off injector pulse. Dying ECM relay might do that. Maybe worth giving that a bang to see if it glitches. Behind the washer bottle are some relays under plastic covers. The green one is fuel pump, brown is ECM, black is AC cutout. Those connectors get crusty and things can get strange.

the fact that it doesn't self-test also makes me wonder about electrical problems. Half the stuff on the "doesn't give codes" list are checks for power and ground at various points on the ECM connector.

Yeah it used to do the gasping you spoke of until I threw on this new tps. This one works correctly and im assuming it’s shutting the injectors off. No stumbled or anything like before. I already changed the EEC relay and fuel pump yesterday, only thing that hasn’t been changed is the AC relay. I checked main grounds for the ECM and those seem to be in working order too. I also put in the ECM I got from wagonman to see if anything would change, same results.

[monotonorobo]

Just referred to this older thread and I think I’m gonna switch back in my old ignition switch and check wiring as well. The only accessory that I notice that doesn’t work is the radio but I just think the radio itself went to shit. Can’t tell cause im not the one who put it in so I don’t know.

http://www.grandmarq.net/vb/forum/technical/box-tech/-5-0-5-8-engine-stock/44920-85-grand-marquis-won-t-stay-running

[monotonorobo]

I thought about it at work today and I don’t believe it’s the ignition switch. Everything works. Unplugged TPS again and now I really am convinced it has to be the issue. With the motorcraft one it’ll sputter and die out, with this one it cuts off the injectors after about a minute, so the pigtail is a possibility. How much resistance is the pig tail supposed to have at each pin? I think either I got two bum TPS or either it’s the pigtail. I’ve done all I could do.

[gadget73]

not sure on the TPS resistance, the ECM reads the voltage, it doesn't care about resistance.

If you mean resistance from the TPS connector back to the ECM, it should be a handful of ohms, just whatever you get from however many feet of wire are between those points.

[monotonorobo]

Alright. I just shoot in the dark for once and buy a new tps and see what happens, then I’ll also get to see which tps sensor was the accurate one, since 2 of them show different readings. If it does nothing I’ll refund it.

[sly]

TPS info: http://grandmarq.net/oldfuelinjection/page30.html

[monotonorobo]

Thanks. Could I drive it over a buddy’s house w the tps unplugged? Wanna get hear his thoughts too. It’s about 8 miles away.

[gadget73]

maybe. If it will stay running without it, yes. Its probably going to act funny though.

[monotonorobo]

Was about to take it this morning but the CEL came on for the first time in forever so I plugged in tps and it didn’t cut off. Drove it no bucking either. I feel like the issue is gonna come back but time will tell.

[sly]

We may be dealing with contact issues all over the place. Those large bulk connectors, if you open them again, pinch the female connectors ever so slightly to give them better engagement. They are known to have connection issues. Might have to do this for all the connectors that use the barrel and pin type connectors that you run across.