Mechanics

ENGINE RUNS ROUGH

1994 Lincoln Continental • 45,000 miles

> Engine runs rough.

> Replaced both Cylinder Head Gaskets …
Included Exhaust Manifolds Gaskets, Upper & Lower Intake Manifold Gaskets.

> Tested Cooling System Constant Control Relay Module (CCRM).

> Tested Engine Coolant Sensor.

> Replaced Valve Stem Seals. Umbrella type.

> Rebuilt Fuel Injectors.

> Cleaned, lapped, and reseated Valves.

> Replaced Spark Plugs.

> Replaced Spark Plug Wires.

> Cleaned small amount of oxides from distributor cap (inside) aluminum lugs.

> Distributor / distributor timing has not been disturbed. Distributor housing still set at OEM chisel marks.

> Replaced EGR Valve Control Solenoid. Was activating check engine light and chime. CEL now off.

> Cleaned internals on IAC - Idle Air Control Valve; no difference. Then also replaced IAC; no difference
With IAC connected engine idle is a little rough. Without IAC it is the same; rough, but have to adjust idle stop to keep engine running. Installed temporary slip blind at IAC but found no difference.

> Cleaned internals and tested diaphragm at EGR Valve. Remounted valve w/new gasket. Installed temporary slip blind between EGR and manifold; found no difference in idle quality. Pulled slip blind.

> Tested TPS – Throttle Position Sensor.

> Cleaned and tested MAF – Mass Airflow Sensor 3-times. Even disconnected with engine running and there is only a very slight difference in idle quality... Maybe gets a tiny bit worse.
(1) power circuit good. (12.34 V)
(2) ground circuit good. (12.69 V)
(3) 2nd ground circuit good. (12.69 V)
(4) * MAF electrical “signal” swings a few hundredths of a volt along with engine roughness swing at idle
= approx 0.78 to 0.810 V. Voltage numbers rise and fall fairly smoothly during rev up to 1500 rpm and coast down.

> * When engine rpm is increased (by hand) it will not hold at a steady rpm.

> Idle rpm 510 to 520. Spec calls for 550.

> Have not tested O2 sensor.

> Soaked every imaginable vacuum hose, fitting, component, with carb cleaner; no change in idle.

> Engine vacuum at upper intake manifold 18 to 18.75 in. At idle. Needle bounces within the range.

> Now have trouble codes 56, 35, 63.

> Tired of throwing money at this car / money pit.

> Car only has 45,000 total miles.
Avatar
Keith W
April 2, 2012.



That si why ou always scanfor codes and CHECK fuel Pressure first. Low fuel pressure will causerough runing. Those codes aren't right either they need to be 3 numbers not 2. The code is 563 which means a high fan control circuit failure, check the fuse and relays fuel pressure shold be 35-45 psi.

Hmac300
Apr 2, 2012.
These aren't OBD II codes. (OBD I)
These are BEFORE_OBD II.
This is a 1994 Lincoln Continental
I have an OBD II Scanner but it is not used for pulling codes on this year / model car.

Tiny
Keith W
Apr 2, 2012.
Yes I know it's OBD1, but it's a 3 digit number which is 563 that is directly from FORD.

Hmac300
Apr 2, 2012.
Thank you but I have to disagree.
There are over 80 2-digit codes in OBD I.
I pulled these myself as I have done several times over a number of years. There has always been 2-digit OBD 1 codes along with the 100 thru 600 series codes for Ford vehicles as far as I've seen. Did you read thru the info in the url's I pasted in my 1st reply? This info covers the way I've pulled codes in these older cars. A Star scanner is not needed. This car does not allow the CEL to flash codes. You have to do it under the hood. The easiest way is to jumper the connections and read the flashes on a continuity tester. What do you think?

Tiny
Keith W
Apr 2, 2012.
If I get 5-flashes, a very short pause, then 6-flashes, then trouble code will be 56. A long pause then 3-flashed, short pause, 5-flashed, equals 35. And, so on. I couldn't g

Tiny
Keith W
Apr 2, 2012.
If I get 5-flashed, then a short pause, then 6-flashes, the trouble code is 56. A long pause, then 3-flashes, short pause, 5-flashes, equals 35. And so on. I couldn't conjure a 563 code from any of the flash sequences if I tried all day. I cleared the PCM, ran the car, re-tested several times over the last couple of weeks. Still, I do value your input.

Tiny
Keith W
Apr 2, 2012.
56 MAF circuit above maximum voltage

35 EVP circuit above maximum voltage

63 TP circuit below minimum voltage

Tiny
Keith W
Apr 2, 2012.
What's the fuel pressure

Hmac300
Apr 2, 2012.
Haven't had time to get that yet. The car is outside. It has been raining off and on. And I had med appointments to keep. I will check that soon. Though and let you know.

Tiny
Keith W
Apr 2, 2012.
OK !. Here's what I got. (Fuel Press. @ Rail)
Key-On-Engine-Off = 40 # Fuel Press
Engine at Idle, bouncing between 500-520 rpm = 32.5 # Fuel Press
Pulled vacuum hose off top of press. Regulator and stopped vacuum leak on the hose with finger. Fuel Press. @ Rail went to 40 # and there was no change in the rough idle. Regulator increased pressure w/no vacuum hose as it should.
Any ideas appreciated.

Tiny
Keith W
Apr 3, 2012.
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