Mechanics

CAR HAS IGNITION PROBLEMS

1995 Mercury Cougar • 120,000 miles

My girlfriend has a 95 mercury cougar. And it has an ignition problem, it keeps wanting to stall but dont this happens now and then, not all the time she could go 3 days with no problems then it will act up for 2 days then be fine for 3 days and so on. I replaced ignition switch, ignition module, plugs, wires, coil, iac motor, cap & rotor, fuel pump, tp sensor and checked all wires everthing looks good but still nothings changed, still same problem is it posible that something I changed is bad or defected please help im ready to loose my mind
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WOLFPACK
October 5, 2011.



The crankshaft position sensor is a common fault on these vehicles. It's located on the front of the engine behind the crankshaft pulley.


Dan_K
Oct 5, 2011.
This car doesnt have a crankshaft position sensor


Tiny
WOLFPACK
Oct 5, 2011.
It does. On the 3.8L it's in the front, on the 4.6L it's on the rear. Here's a component locator diagram for the 3.8L. If you need the on for the V8, let me know. You didn't specify which engine yours had.


Dan_K
Oct 5, 2011.
Im sorry its the 3.8 v-6. I replace the front main seal a month ago their was no crankshaft sensor. (My 95 buick pa has one behind the damper pully so I know what it looks like) I wish this cougar had one this probably would be an easier fix this car still has the obd 1 comp


Tiny
WOLFPACK
Oct 5, 2011.
Have you check the Mass Air Flow sensor for contamination?

See below: MAF sensors can get contaminated from a variety of sources: dirt, oil, silicon, spider webs, potting compound from the sensor itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows.

If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. If the MAF sensor is contaminated, the fuel system will actually be lean because of under-estimated air flow. During open loop fuel operation, the vehicle applies Long Term Fuel Trim corrections that have been learned during closed loop operation. These corrections are often lean corrections learned at lower air flows. This combination of under-estimated air flow and lean fuel trim corrections can result in spark knock/detonation and lack of power concerns at WOT and high loads.

One of the indicators for diagnosing this condition is barometric pressure. Barometric pressure (BARO) is inferred by the Powertrain Control Module (PCM) software at part throttle and WOT (there is no actual BARO sensor on MAF-equipped vehicles, except for the 3.8L Supercharged engine). At high air flows, a contaminated MAF sensor will under-estimate air flow coming into the engine, hence the PCM infers that the vehicle is operating at a higher altitude. The BARO reading is stored in Keep Alive Memory (KAM) after it is updated. Other indicators are Long Term Fuel Trim and MAF voltage at idle.

Symptoms: Lack of Power
Spark Knock/Detonation
Buck/Jerk
Hesitation/Surge on Acceleration


Dan_K
Oct 5, 2011.