Question about 1988 Mercury Grand Marquis

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Why does my '88 Mercury Grand Marquis w/5.0 stall when put in gear?

Replaced IAC, fixed a bunch of vacuum leaks, tuned up not long ago. .

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The torque converter could be faulty.

Posted on Apr 27, 2015

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I am thinking that the idle rpms are too low and the tune up is not good enough to compensate for the drop in rpms when the transmission is engaged
normal idle rpms on an automatic should be around 850rpms as they will drop 250rpms on gear selsction
any idle speed around 500 rpms will die when fear is engaged

Posted on Apr 19, 2015

  • John L.Pascetti Apr 23, 2015

    curb idle on fuel injected vehicles is non-adjustable , perameters set by ecm. I got it runnin good now though.Did an EEC-IV diagnostic with scantool and reset the ecm.



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Related Questions:

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This Code is about the RPM not matching the idle settings. A Vacuum leak is tricking the engine into making adjustments based on a lean O2 reading. Correspondingly the O2 sensors are demanding more fuel to eliminate the lean readings. Then the engine realizes the amount of air going by the MAF is not matching the IAC settings(Because the air leak is increasing rpm) and blames the IAC which is a Code P1506.

With the engine running, use an old spray bottle and fill it with water. Spray the seams, vacuum lines and solenoids until you notice a change in RPM. Lastly, spray the EGR pod if the diaphragm is torn it will leak vacuum.

Wherever you find the leak, fix it, then clear the computer and drive it.

Feb 19, 2014 | 2000 Mercury Grand Marquis

1 Answer

Just replaced heater core, now car dies when put in gear

check for pinch wires around core install. also a vacume leak from same job not plugged

Dec 03, 2013 | 1998 Mercury Grand Marquis

1 Answer

Solutions for 1998 grand marquis that will not idle

Have someone check the fuel pressure. Check EGR pod, you may have a Vacuum leak. Disconnect connector at a part called a TPS which is mounted on a Butterfly flap shaft opposite the throttle cable. Use an Ohmmeter on the TPS and check for smooth changes in Ohms as throttle is pressed.
If you get to the warmed up engine running part, use a water spray bottle and spray the seams of the intake and any Vacuum lines or fixtures you see. If the engine stalls or sputters then you have found the leak.

Aug 12, 2013 | 1998 Mercury Grand Marquis

1 Answer

2003 mercury grand marquis misses when warm

How many mi sense last tune up. If around 100,000 plugs and wires should be changed. If it has the the 4.6 they have 2 coil packs. These can short out. Also the EGR valve can stick open causing a small vacuum leak. These can be cleaned sometimes to fix a miss.

Jul 02, 2012 | 2003 Mercury Grand Marquis

2 Answers

1998 Grand Marquis. Start goods. idols low. put in gear, stalls out. Changed fuel filter & had injectors serviced. Problem remains. Could it be the Transmission modulator valve?

I would check the operation of the idle speed control valve, it is what changes the idle speed when a load like the transmission is put on the engine, without it the engine will idle slow and stall out, this is even more apparent when reverse gear is selected or drive or the AC is tuned on. The ISC valve is located on the side of the throttle body top of upper intake manifold. Below is a picture of the ISC (idle speed control valve)

Sep 30, 2011 | 1998 Mercury Grand Marquis

1 Answer

1988 merc grand marquis, vacuum diapram, symptoms? any gear i put it into, i hear a vacuum like sound, is this it?

The 1988 merc has an automatic emergency brake release that has a valve on the steering column under the dash, when you put the tranny in gear it sends vacuum to the valve on the brake to release it. It could be the valve on the steering column that is the problem. Good luck!

Mar 28, 2011 | 1988 Mercury Grand Marquis

1 Answer

Car won't idle without revving when cold and dies when in drive

This Vehicle needs an Idle air control/Idle speed motor. Good Luck

Dec 28, 2008 | 1996 Mercury Grand Marquis

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