My 98 Marquis revs up and down intermittently. This will only happen when the car is in idle but in drive AND the heat is on. It does not rev when in park. It seems to subside when temperatures outside are below freezing. I've had a lot of repairs done in the last 2 months. New thermostat from an overheating incident. Had some trouble with misfires, so I had a tune up and intake manifold replaced when the tune up didn't do the trick. Heat wouldn't blow hot after manifold job and then this revving thing started to happen, so I took it back to the mechanic who did the manifold job and tune up. They tightened the PCV valve and found a loose hose with a vacuum test, but din't think those things should have been the cause of the mysterious revving. They also suggested a heater core flush if the heat did not start working after driving it a while longer, which I have since had done. The tightened hose and PCV valve seemed to do the trick until it was above freezing outside, then the revving when idle in drive with the heat on began again. I have a theory about the IAC valve based on Googleing some stuff but I really know very little about cars. The more repairs I go through, the more I'm learning, but it's been an expensive 2 months.

but had put a rebuild kit back in there and now it wont move.

You can start it by tapping the key and won't start in park. Its sounds as if its hitting the flywheel and is always engaged.
Took the old starter off it was burnt up put new one on still does the same thing. Any ideas?

My 98 Grand Marquis voltage gauge started intermittently dropping and the lights would dim. I replaced the alternator and the 3 pin pigtail since it was cracking. I still have the same problem with the voltage intermittently dropping. I tested the battery, charged it overnight and even tried a new battery in it. The alternator is working sometimes, so I don't think there is an issue with the replacement.

I saw a comment in another thread:
"Turn on the ignition switch to the on but not run position do you see an icon on the instrument panel representing a battery, if you do not see this battery icon the alternator is not seeing power to allow it to charge."

So after reading that, I looked at the dash with the key on and engine not started. There is no battery light. What causes this to happen? What should I be looking for?

Thanks for any help.

It doesn't hesitate long or often, but there none the less

My batt light comes off and on and the car is running rough almost as though it

Car started but will not let me put gear in drive. I have a automatic transmission.

the low pressure measures 150 when compressor runs for about 10 seconds pressure drops to 125, is there a high pressure switch on the high pressure side?

my heater blend door needs to be replaced how do i do it?

The # 5 15 amp fuse position.This has begun recently. I have gone through 5 fuses. The fuses only last about 1 minute then I don't have any trun signals.The 4 way hazard flashers work fine.

it blows hot air only throught he vents and the compressor is on and the lines under the hood air cold.

What is the best method to repair this problem?

98 gr Marquis when initially started it is hard to steer. Very tight unlike normal. After a bit it loosens up. What could cause? I just had maintenance done an oil chafe with all fluids checked. I'm stumped!

Need time and price for heater blend door replacement on a 1998 Mercury Grand Marquis

i have replaced coils, spark plugs