stalling at red lights

[cobradude360]

i have a 92 grand marquis and when ever i pull up to a stop light it stalls so i tryed runing a higher octain what should i do i think its in the fuel system because if u appply the break and put it in gear it will start to bog down but if u lightly apply the gas the lights get brighter and the rought idel stops so what should i do im leaveing for a trip tp kentucky to day so i need help fast

[Samurai0]

Well, as with any engine problem, you need three things to have it run: Fuel, Air, Spark.

How many miles does the car have?

I have an '87 with 123200 miles, and it does idle better in gear.

I fixed some power loss, by tightening the valve cover bolts, oil pan bolts, and transmission bolts. Replacing PCV. Replacing factory valve cover gasket on right side.

My idle, acceleration and overall powerband is much better.

Generally, any vacuum loss can affect engine performace.

But this sounds like it could, believe it or not, be related to your electrical system. Say:
* A corroded battery cable that can't handle the
current.
* A spent distributor rotor and cap.
* A weak battery.

Since the lights get brighter, it may be a bad Regulator in the Alternator.

Please post more info.

[fredjacksonsan]

Hey, I just fixed a similar problem on my '86. It was a combination of a vacuum leak under the dash (in the auto brake release, a white plastic crescent near/above the brake pedal) and the idle air sensor/motor(which if yours is 5.0 is on the rear of the intake, driver's side and you can get to the two bolts holding it on pretty easy)

The combination of the two was stalling the car @ lights, or sometimes when I let off the gas while moving, and definitely when changin gears from forward to reverse and vice versa; it was perfectly fine when moving and not idling......

Hope this helps, and thanks to all the AF people that helped me out!

[Samurai0]

Fred,

The closest thing I find to an "idle air sensor" on the 5.0 intake manifold, is located opposite to the EGR valve. It looks like a cylindrical object bolted on at a 45* angle (on it's side).

If you goto this website www.rockauto.com, and check under "Emissions", it's called and "idle air control valve".
See part here:
http://www.rockauto.com/ref/Motorcra...ml?cx-1824.gif


Maybe it could be a (TPS) Throttle Position Sensor issue.
Here:
http://www.rockauto.com/ref/Motorcra...ml?cx-1133.gif

All I know is that even though I just replaced the right valve cover gasket, and tightened the valve cover, oilpan, tranny pan bolts, my performace and power band are stable. But the damn idle is almost too low, and even hesitates a little when just touching the pedal. But that's it.

Hmmm.....could it be the Coil?

Later

[fredjacksonsan]

Yep, that's the one alright. Sorry I had the name wrong, it seems to vary between "motor" and "valve" depending on year, and my parts guy said some vehs have both. The "Idle Air" is common to both the motor and the valve.

Anyway, I had the same problems you're having, and once I replaced that sucker, idle steadied up, hesitation went away, and it quit dying at lights. I thought my throttle position sensor might have gone too, but from checking here and there (including here @ AF) thought I'd throw the $72 for the Idle Air Control Valve at the car first. Dealership wanted $140, so I called around.

It's about a 10 minute replacement, bolts holding mine on were 8mm.

[cobradude360]

it has 128000 miles on it but the thing is is the battery and alternater are just bout 2 months old i got them to gether

[fredjacksonsan]

I'm at 136K.... as my brother and I like to say:

"You make payments or make repairs"

[Samurai0]

Hmmm.

Well, I guess either I'm gonna try going to the local Lincoln/Mercury parts counter, a NAPA I used to work for, or the RockAuto.com site, to see who can give me the best deal on the IAC sensor.

We'll see. I'll report.

[fredjacksonsan]

Mine's an 86, and sure enough it does have the Idle Air Valve. With the shaking and the smoke (sorry didn't look at your post as well as I should have) you may have a burned valve or bad compression on one cylinder, but hope not. I'd start with a good tune up-- plugs, cap and rotor, and replace the spark plug wires if they're old/cracked, and see if that helps. Also, Samurai had a similar problem and plugged some vacuum leaks.

Does the car run smoothly when moving on the highway? How many miles?

[fredjacksonsan]

Good luck I'll be interested to see what gives.

(whups, replied to wrong thread. Ah well.)

[Samurai0]

My car has 123,200 miles. '87 Merc. 2 Door.
I wouldn't doubt the compression thing, I do have a compression gauge though. I'll test it soon.

My cars runs superbly on the highway, purring without any problems, even at 75mph.