1985 Mercury Grand Marquis - HELP!

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I bought this car from its original owner for $500 with only 65,000 miles on it. Seems like it runs and drives pretty good, but it's getting horrible gas mileage. Seems like it's getting about 9-10 MPG.
It also idles very high all the time. And sometimes when you start it up in the morning it sputters and doesn't want to run unless you give it some gas. When it finally comes out of this, it starts idling high again. Anybody have any ideas what might cause this? Stuck EGR maybe?
I have no experience with EFI systems of this vintage. I didn't even realize Ford started using fuel injection this early on it's full-size cars untill I bought this one.
Also, there seems to be some kind of vaccum switch connected to the gearshift linkage. It's down on the floorboard near the gas pedal. What does this thing control? It obviously has a vaccum leak in it because it constantly hisses, and the hissing seems to change when I shift between the gears.
Any help with this old boat would be appreciated.... Thanks!
-Tony
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snipped-for-privacy@frontiernet.net wrote:

The vacuum thing may be for the automatic parking brake release when you shift out of Park to Drive. The erratic idle & hard start could be from a dirty IAC valve. You say the engine on the '85 is EFI, with fuel rails and not just a fancy carburetor (CFI)?
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The engine has TBI (Throtle Body Injection). From what others have told me, it was standard equiptment on these cars.
-Tony
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On 18 Feb 2006 08:36:27 -0800, snipped-for-privacy@frontiernet.net wrote:

The 4.6 was never TBI. It has always been SEFI port injection with distributorless ignition.
Lugnut
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An 85 GM should have the 5.0L (302) engine, not the 4.6 modular. TBI makes sense for that vintage. The hissing is from the automatic parking brake release. It's either disconnected or (most likely) defective. There is a vauum switch on the steering colum, and a rubber tube which runs from there to a diaphragm-operated actuator in the parking brake control mechanism. If you are not going to fix it, simply cap the vacuum supply to the switch. Hopefully it will solve some of your irregular idling problem. Next order of business: invest $1.50 in a test light + paper clip and read the trouble codes out of the computer. Also run KOEO/KOER (engine on/engine off) diagnostics. Very simple to do and no tools needed. Google for EECIV and you will find how. If you want to splurge, buy one of those $35 EECIV 'code-readers' (a tiny box with a switch, a battery, and an LED). They don't do anything more than the paper clip + test light, but come with an instruction booklet and a list of trouble codes. Post here what you found, and someone will offer (hopefully) useful hints.
Good Luck

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Happy Traveler, Thanks for the good advice. I'm actually very mechanically inclined and have worked on several cars and engines over the years. Although, most of my experience has been with GM makes and models, so when it comes to these older Fords, I'm in the dark on a few things.
I plugged up the vaccum line that supplied the E-brake release switch. Didn't really help with the idle problem. I also took the EGR valve off and cleaned alot of the carbon out of it. That seemed to help, as the car has MUCH more power and pep than before. I think it is still sticking though, because sometimes when I go to start it, it acts like it doesn't want to run unless you give it gas, and runs erratically. The problem with the idle turned out to be the high idle solenoid, which is apparently stuck in the high idle position. I can manually flip the little cam down and the car will idle down, but as soon as I give it any gas, the cam flips right back into high idle position. I will have to test the power lead and make sure it's live. If so, I'm guessing I'll just have to replace the whole high idle unit?
I will run a diagnostic test on it today as soon as I do a google and find out what I need to do. So far It hasn't set any check engine lights, but possibly there's some underlying codes stored.
These old cars sure are great, but man there's alot of old 80's technology do-dads and gadgets to go wrong under the hood! :-)
-Tony
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snipped-for-privacy@frontiernet.net wrote: I think it is still

I think you hit the nail on the head, but don't quite understand what you hit. TBI used a mechanical fast idle mechanism ans had little control over warm curb idle.
The fast idle setup is nearly identical to the choke/fast idle setup on a carburated engine. It uses an electrically heated spring (black cap on the left side of the TB). The power to heat the spring comes from the "S" terminal on the alternator so it only heats when the engine is running. Check for power on the conector at the spring housing, should be 12 volts with the engine running. If you have power, check the continuity (resistance) of the heater. You will probably find it is open. Replacements are about $40.
Once you replace the spring check the curb idle. It is very common for a previous owner to back off the curb idle adjustment in an attempt to lower the high speed caused by the failed spring heater. If this is the case, it will cause the curb idle to be too low. Until you replace the spring you can loosen the 3 screws holding it's retainer and rotate it about 1/2 (clockwise I think) turn to allow the cam to fall to the curb idle position. You can then address your idle concerns.
On the EGR, these engines were prone to carbon buildup in the passages under the throttle body spacer. Bits of carbon would then randomly block the EGR valve. Remove the TB and clean out the passages. If there is an EGR cooler between the valve and spacer, clean it out thoroughly as well.
Here's a link to the "choke thermostat" at Auto Zone: http://makeashorterlink.com/?C15231BAC
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Tom, Yes it sounds like I have a bad fast idle spring heater. It has power to the input lead, but never comes off fast idle. I rotated the whole unit like you decribed and it idles fine for now.
As far as the EGR goes... I will go buy some gaskets tomorrow and take the whole unit apart and clean it. I hope I can re-use this EGR valve, as the replacement cost for this unit looks to be well over $100. Hopefully I can pinpoint the cause of this car's quirks. It's a decent old car and I'd love to drive it for a while, but not at 7-8 MPG!!!
Anyone know what the average NORMAL MPG of these cars was?
-Tony
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snipped-for-privacy@frontiernet.net wrote:

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snipped-for-privacy@frontiernet.net wrote:

Oops, wrong button. I've heard of folks getting 20-22 on the highway. I've never owned one. My 84 Mark VII with the same CFI motor and trans gets about 20.5 with my heavy foot, about 17 city.
Draw a vacuum on the EGR valve. If it holds vacuum and the pintle moves freely it should be ok. The EVP sensor on top of the EGR valve is a common failure item. I would replace it while servicing the EGR, it is 22 years old. Same with the Throttle position sensor. An O2 sensor couldn't hurt. This is just my personal preference on a car that old. If you do this, avoid Wells brand parts, they're no bargain even at half the price. Failing EVP and TPS will kill your fuel mileage. Be careful of the plastic vacuum lines, when they get old they get brittle and break if you look hard at them. They can be repaired with small (1/8"?)rubber vacuum line. While you're working around the CFI, look at the bushing in the transmission Throttle Valve rod (kickdown rod)as they tend to disentegrate after 20+ years. $2 part that can cost you $2000. At that age and mileage you may see numerous age related failures like the water pump, radiator, etc. Like other folks have said, start with a complete tune up including all of the filters. Use your judgement after that.
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On Sat, 18 Feb 2006 21:39:32 -0800, "Happy Traveler"

You are absolutely correct. I must have still been on some of the stuff I got at the cardiac ward last week when I posted that!
Thanks for the correction
Lugnut

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lugnut wrote:

Your point is?
Rob
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On Sun, 19 Feb 2006 00:44:24 -0500, trainfan1

Sorry! See above. Thanks
Lugnut
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One of the first signs of getting old is that you can't keep your decades straight.... lol. The 4.6 was offered in 1995 but not 1985. Bob

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I don't think getting old really affects such things. There is, however, an associated oxygen-starved syndrome that comes from blowing out birthday candles. s
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wrote:

Yeah! I blew that one wide open. I spent last week in the cardiac ward and should not have gone close to a keyboard.
Lugnut

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We're glad you're back and seem, ahh, ...normal, Lugnut!
PoD

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An 85 Grand Marquis was not a 4.6 nor was is SEFI, most of them have 3.8 V6s, an older version of what ford put in Taurus'
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Nevermind I am referencing to the little Marquis they made in 85, that car came with the 3.8 TBI. What you have is more than likely a 5.0 TBI.
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wrote:

Exactly! Sorry. see above posts
Lugnut
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