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1989 Lincoln Town Car Feeling on/off engine power loss with

Tiny
DEATHSTRYKER
  • MEMBER
  • 1989 LINCOLN TOWN CAR
  • V8
  • 2WD
  • AUTOMATIC
  • 108,000 MILES
Lately, when I've been running my car with the A/C or heater on, I'll feel a continual on/off power loss in the engine about every 2 seconds. My A/C and Heater seem to work fine (it takes a couple of minutes for the A/C to put out cold air but it IS cold when it does come out) but I just don't like to run it due to me not knowing what it's doing to my engine.

Any help would be greatly appreciated and of course, I will donate once more.
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Monday, August 31st, 2009 AT 1:20 AM

17 Replies

Tiny
MERLIN2021
  • MECHANIC
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Two things, 1.) Check the frequency of the compressor cycling from off to on then off again, how long does it run b4 shutting off? 2.) Check compressor pulley without the fan belt on. Does it spin freely or is it dragging and binding? If it binds, the bearing that is pressed into the pulley is no good!
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Monday, August 31st, 2009 AT 4:09 PM
Tiny
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How do I check the frequency of the compressor?
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Wednesday, September 2nd, 2009 AT 9:34 PM
Tiny
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Start the car, and the a/c, then open the hood, when compressor starts, count the seconds until it turns off, then count until it turns back on, frequent cycling on hot days means it's low on r134a or the low pressure cutout switch is defective.
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Thursday, September 3rd, 2009 AT 2:30 AM
Tiny
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Well, I took off the A/C belt today and the compressor pulley moves freely.

While the car was standing still, I didn't notice the compressor doing anything that would indicate that it was shutting off or on. No noise or anything.
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Thursday, September 3rd, 2009 AT 4:13 PM
Tiny
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So when you turn the a/c on the compress clutch pulls the plate and the compressor spins, or pumps out the a/c?
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Friday, September 4th, 2009 AT 2:56 AM
Tiny
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Ok, I've finally gotten some time to check this out. I turned on the A/C and finally understand how to tell if the compressor is on (by the middle of the pulley spinning) so I left the A/C on for a little bit with all settings on high and the compressor never shut off. I watched it for about 15 minutes and it stayed spinning.

I also decided to check if it was low on refrigerant however I was slightly confused as my car's pipes are set up a little different and I don't have a looking glass.

Most instructions say to check the line that goes from the receiver/drier to the condenser for coldness yet I have no line like this.

On my car, I have a big pipe going from the compressor to the receiver drier and then at the top of the receiver drier, the big pipe continues to the top of the evaporator. Both of these lines are equally cold to the touch. At the bottom of the evaporator, a small line goes from it to the condenser. This line is warm. And finally, I have a medium-sized line that goes from the condenser to the compressor. This line gets very hot.
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Friday, September 11th, 2009 AT 4:15 PM
Tiny
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If air temp is 85-90 compressor should run continuosly. Yor problem probably lies elswhere, a/c is cold inside the car? This on offf feeling is called "bucking" or "fishbite" and can be caused by bad plug wires/plugs, fuel filter, air filter, or even a carbon build up under the EGR. The port under it gets clogged up and the port needs to be cleaned out all the way to the trottle body, I use TBI cleaner and a wire coathangar to do it. Vacuum leaks are another problem, inspect the grommett at the top rear of the engine where the PCV plugs into it, theses harden and allow vacuum to escape, replace that rubber grommet.
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Saturday, September 12th, 2009 AT 8:15 AM
Tiny
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I will check the EGR and for vacuum leaks.

I know it isn't the fuel filter or the plugs/wires because I just had all of those replced along with the distributor cap and rotor. I also was checking on the air filter the other day and it didn't look that bad.

I also know it isn't a fuel related issue because I had the car in the shop for an unrelated issue and they said the fuel pressure was perfect.
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Saturday, September 12th, 2009 AT 8:36 AM
Tiny
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OK get a can of spray TBI cleaner, spray around the grommet and if idle changes, there is a vacuum leak there. You would also see oil leaking around it.
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Saturday, September 12th, 2009 AT 10:00 AM
Tiny
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I looked at the EGR valve today and it really didn't seem all that bad. It had a little bit or residue on some of the edges but really didn't seem clogged anywhere. I cleaned it up anyway with some TB cleaner.

Also, I wasn't completely sure where the PCV was at on my car but I did find a part under my upper manifold that looked like it could be it. It was also completely covered in grunge and fresh oil. I sprayed TB cleaner on it while the car was idling but there wasn't any change. Here is a pic of it (after I cleaned it off a little):

EDIT: OK this part is NOT the PCV but I still can't find it. I looked everywhere on the valve covers for it.

EDIT: I did find a definite vacuum leak elsewhere though. There is a small vacuum hose that comes out of the air bypass valve and this hose is connected to it with a small rubber coupling. There was fluid coming out of this connection and when I went to touch it, the rubber piece simply slipped off it was so lose. Unfortunately for me, I can't find this piece anywhere on the internet so I'm not sure how to replace it.
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Monday, September 14th, 2009 AT 5:43 PM
Tiny
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Buy some rubber tubing and make a loop if you need to. Also while your at it remove the IAC from the throttlebody, the pintle is another problem spot for carbon. Ford recommends replacement rather than cleaning!
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Wednesday, September 16th, 2009 AT 3:05 AM
Tiny
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Ok, I finally found the PCV valve. It's very difficult to see on my car because it's behind the motor buried under some vacuum tubes.

That last picture I posted is actually part of the system on down the line. There is also oil around the the PCV valve. And it seemed to come out too easily so I'm going to replace the grommet, PCV valve, and the hoses since the hoses have cracks in the ends of them and they are hard.
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Friday, September 18th, 2009 AT 7:13 PM
Tiny
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Ok let me know how it is after vacuum leaks are fixed.
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Saturday, September 19th, 2009 AT 8:40 AM
Tiny
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Ok, so I've had a little bit of time to mess with this:

I replaced all the PCV stuff and I've got good suction on the PCV valve. Also, my IAC failed on me in an unrelated incident so the shop replaced it along with the TPS.

However, the problem still persists. But I was noticing today with the heat on and the car idle that the compressor is turning on and turning off. It will turn on for about 12 seconds and stay off for about 8 seconds. I'm not sure why it didn't do it before when I checked it. Probably because my engine wasn't warm at the time.
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Friday, October 16th, 2009 AT 4:35 PM
Tiny
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Would you describe your symtom as bucking? If so, two parts could be causing it, the EVR which controls the EGR opening and closing may need to be replaced, the sponge under the fat end cap is clogged, and the other possibility in the MAF, this is at the air filter box, either one can be slightly out of range, and wont set a code. Follow the vacuum line from the EGR, it will lead you to the EVR.
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Friday, October 16th, 2009 AT 6:15 PM
Tiny
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I'm not sure exactly what "bucking" is as I have never encountered it before but it just feels like a slight loss of horsepower to me. Not enough to change the speed or anything. Just feels like a higher strain on the engine that only happens when the heater or AC is on.

I'll check some of this stuff out when I get a chance.
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Friday, October 16th, 2009 AT 7:33 PM
Tiny
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Try checking the diode and WOT cutout relay:
A/C COMPRESSOR CUT-OUT RELAY TEST 1. Relay is located in relay panel on left side fenderwell in engine compartment. Remove relay from panel. Check for continuity between relay terminals 30 and 87A (relay is normally closed). If no continuity, replace relay. 2. If continuity is okay, apply battery power to relay terminal 86 and ground terminal 85. Relay should click, and there should be no continuity between terminals 30 and 87A. NOTE: Compressor clutch diode is located in compressor clutch harness above compressor.


https://www.2carpros.com/forum/automotive_pictures/62217_relay_3.jpg

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Friday, October 16th, 2009 AT 8:23 PM

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