Expert: Ernest (Ernie) Kenward - 12/16/2007

Question
QUESTION: 1990 mercury cougar 3.8 v6 car appears to idle fine the problem w/the car is it will not accelare over 45 miles an hour slows down to about ten miles an hour pulling hill does not smoke at all the plugs are greyish white put on new fuel pressure regulator the car does not stall thought it was a problem w/ ignition control module but could not locate it under the hood someone pulled trouble codes and said it was low fuel pressure but i dont believe its the pump or fuel filter could it possibly be the map sensor but theres no black exhaust smoke

ANSWER: I can take only a general stab at this because, as I have pointed out before, I do not maintain information databases on any but my own vehicles, and thus have no specifics on ECU-controlled vehicles.  

What I can say is that a problem in which a vehicle idles properly and exhibits no visible emissions problems, but lacks power when power is demanded DOES suggest a fuel delivery problem - if rate of fuel delivery is capped at a low value, the engine will be unable to load beyond that cap.  For that reason, the "low fuel pressure" report sounds like an appropriate avenue for investigation.

The other reason for inability to load could be an inability to advance the ignition timing with load.  In older, non-ECU vehicles, this can cause an increase in emissions as a result of the enrichment brought about by the power valve in the carburetor opening due to the low vacuum present when the engine cannot rise in power to meet the load and thereby restore the proper air/fuel ratio for that condition.  Checking the initial timing and the rate of advance would probably be a good move, regardless of the findings in respect to fuel delivery.

Fuel filters should be changed every so often anyway, of course!  Frankly, in my view, these usually are cheap enough (as are filters in general) that I would replace them on a seasonal basis or after any period of heavy use - a cross-continent trip, for example - anyway, and not wait until problems due to restricted flow begin to occur.

Your problem probably is an easy one to fix.  Carry on!

Regards ... EGK

---------- FOLLOW-UP ----------

QUESTION: i forgot to add that when the car warms up it starts having problems w/ pressure not evev going up hill if you stop and let it cool down it does half alright for another little bit and reckon where the ignition control module is located thank you so much!!!

Answer
Perhaps the ignition modulator is worth a check then.  It is a power semiconductor module, and these can fail in time due to thermal breakdown.  In fact, this is one of the items I regularly carry in the vehicle road tool kit as a spare.  Over the twenty-two years I have driven my Ford E250 motorhome conversion, I have had to replace the unit twice.

The unit may fail suddenly, as from normal function to non-function in seconds, and that is what happened at the time of the first failure in 1989.  The second failure however was a slow onset, with loss of power noted in climbing hills in our area in 2005.  I was concerned at first about a possible timing advance problem, and connected my timing light to check it out.  Finding the number 1 plug pulse signal to be erratic and intermittent caused me to consider that I had a modulator problem again.  Having the spare allowed me to check out that possibility without delay, and verified it.

With my trade discounts, the modulator for my vehicle is only about Cdn$65 or so, making keeping a spare that can be right there if you need it, in the back country or wherever, a wise option.  In point of fact, I carry an alternator diode and bearing kit, carb kit and spare floats, an alternator regulator, replacements for all fuses and lamps, and valve stems in my vehicles at all times, as well as those items I normally use for routine tune-ups: plugs, cap, rotor, and a spare ignition lead set.

These can keep you on the road with little need for shops.

Check that modulator.

Regards ... EGK