My 1991 SHO (112k miles) is currently in the shop with some failures that are difficult to diagnose. The mechanic is reputable and competent, but is hesitant to start swapping out parts until he knows where to start, which has repairs at a stand-still. I am contemplating getting rid of the car rather than repairing it at this point. The problems all started 2 years ago when the Ford garage (last time they saw the car!) replaced a failed crankshaft sensor (CPS) after the car left me stranded (the reason Ford had the car to begin with). After this work, the car had no low-end power, but it still got me too and from work reliably. Not once have a I seen the check engine light with the car running, but the ignition problem has gotten much worse recently. Car runs fine at times, but it can begin to buck severely. That lasts only a few seconds. When this happens, the car can be driven, but has no power at all, and the exhaust smell is unusual. The tach can also be a little erratic at times, showing RPM readings that are not consistent with running conditions.
Here is what the mechanic has observed:
The car will not complete the engine running self test. The only consistent code is from the fuel injectors (I forget the error code). I observed the same thing when I ran the test: the engine always stalls out at a point after the "goose" test.
The wave form from the crankshaft sensor is the expected square wave. However, it appears that this wave form is bleeding over into the camshaft sensor wave form, and the deviation from the expected signal is as much as 0.6 volts.
With SPOUT plug pulled, at idle condition, the timing is 10 degreees BTDC as expected. However, timing advances 10+ degrees with increasing RPM. This should not happen, correct?
When the system is brought to a fault state, the engineering data indicates that each set of 3 should be fired simultaneously. However, the observation is a time lag between the 3.
The engineering data the mechanic has access to says the latter 2 conditions should not be observed.
Has anyone observed this behavior before? I'm on the clock as far as deciding what to do going forward. I hate the thought of parting with this car (only the second car I've driven in 26 years), but I either need it repaired or replaced by early next week.
Thanks in advance.
Here is what the mechanic has observed:
The car will not complete the engine running self test. The only consistent code is from the fuel injectors (I forget the error code). I observed the same thing when I ran the test: the engine always stalls out at a point after the "goose" test.
The wave form from the crankshaft sensor is the expected square wave. However, it appears that this wave form is bleeding over into the camshaft sensor wave form, and the deviation from the expected signal is as much as 0.6 volts.
With SPOUT plug pulled, at idle condition, the timing is 10 degreees BTDC as expected. However, timing advances 10+ degrees with increasing RPM. This should not happen, correct?
When the system is brought to a fault state, the engineering data indicates that each set of 3 should be fired simultaneously. However, the observation is a time lag between the 3.
The engineering data the mechanic has access to says the latter 2 conditions should not be observed.
Has anyone observed this behavior before? I'm on the clock as far as deciding what to do going forward. I hate the thought of parting with this car (only the second car I've driven in 26 years), but I either need it repaired or replaced by early next week.
Thanks in advance.
