Idling Problem / Dying - 95 5.0

RustangJeeTee · Jan 2, 2015

My car has been hunting for idle and dying at stop signs. It's not doing it all the time, but it seems to be happening more often. I smoke tested it to look for a vac leak and smoke came pouring out of the back of the motor underneath the plenum. I'm pretty sure its the PCV assembly and from the looks of it I'm going to have to R&I the intake to get to it. Before I spend anymore effort on it, does anyone have any thoughts? This motor isn't as easy to work on as my 4.6 was.

mcglsr2 · Jan 2, 2015

Does it still have the smog stuff on it? And if not, I assume the holes in the back of the cylinder heads have been adequately plugged?

Could very well be your PCV, it's back under the plenum towards the driver side IIRC.

RustangJeeTee · Jan 2, 2015

mcglsr2 said:
Does it still have the smog stuff on it? And if not, I assume the holes in the back of the cylinder heads have been adequately plugged?

Could very well be your PCV, it's back under the plenum towards the driver side IIRC.

Smog Pump is still there, but bypassed. I saw that there's some stuff with the IAC that becomes a problem with these, and that could be it. Even if it is, I'd still need to get the vacuum leak fixed.

mcglsr2 · Jan 2, 2015

Could be IAC, but I think you are on the right path - get all vac leaks shored up first. See if that corrects the issue.

toyman · Jan 3, 2015

The PCV is located at the rear of the lower intake manifold. The vacuum line runs to a nipple on the underside of the upper intake from the PCV. This rubber hose is likely broken or cracked due to age and heat.

CC'S95GT · Jan 3, 2015

the surging idle is usually caused from a vacuum leak.
When replacing the PCV, don't forget the screen under it. It's hard to see and likely coked up with baked on oil. It help to remove with a pair of needle nosed pliers.

Michael Plummer · Jan 4, 2015

toyman said:
The PCV is located at the rear of the lower intake manifold. The vacuum line runs to a nipple on the underside of the upper intake from the PCV. This rubber hose is likely broken or cracked due to age and heat.

:laughing4: Good advice, and the best place to start.

5literstang95 · Jan 4, 2015

I had the same problem and eventually it got to where I couldnt make it out of my driveway. I tried IAC, TPS, new dizzy, plugs, wires, and cleaning TB and MAF. It ended up being a bad MAF. Bought a new one and problem solved. Good luck.

toyman · Jan 5, 2015

5literstang95 said:
I had the same problem and eventually it got to where I couldnt make it out of my driveway. I tried IAC, TPS, new dizzy, plugs, wires, and cleaning TB and MAF. It ended up being a bad MAF. Bought a new one and problem solved. Good luck.

Speaks volumes to pulling codes. A $25 reader will pay for itself quickly.

5literstang95 · Jan 5, 2015

toyman said:
Speaks volumes to pulling codes. A $25 reader will pay for itself quickly.

I pulled the codes and all it was saying was misfire and left bank lean. I had a shop do it and it came up MAF. But yeah, you are absolutely correct

RustangJeeTee · Jan 6, 2015

I don't have any codes popping up, and I thought that it was harder to read because obd1. Anyway, if I have to replace the pcv assembly, do I need to pull the intake? I don't really want to, but a guy I work with says I should.

NXcoupe · Jan 6, 2015

No, don't pull the intake. Pulling the upper helps to access it on these cars, but not necessary. Just unplug the pcv valve from the hose and plug the hose and smoke check it again. If no smoke then you are chasing your tail, move onto other checks.

These OBD1 cars will rarely tell you a sensor like the maf is bad. It's stupid but a lot of times parts changing with a known good unit will net results that couldn't be gained with a scan tool. I always pull codes first and go from there.

5-oh-MUSTANG · Jan 6, 2015

do a koeo test for free, no need for obd1 scanner.

RustangJeeTee · Jan 12, 2015

Well, I replaced the PCV valve, grommet, and screen. It fixed the vacuum leak, but I'm still having an idling problem. Next step is the koeo test I guess.