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The check engine light comes on from time to time

(1990 Ford F-250)
in Mill Valley, CA on May 12, 2011
The check engine light comes on at random times. Sometimes it will last for the entire drive, and sometimes it will turn off on its own. It used to be only on occasion, but now it occurs more frequently. What might it be?
Displaying 3 answers & 4 comments
Popular Answer
on May 12, 2011
Many things can cause the check engine light to illuminate.

For a 1990 7.5L V8, I would think emissions controls items. Have a diagnostic test performed - codes will be available from the engine's processor that indicate what system failure is causing the light to come on. Then testing can be done to find out what exactly caused the light. Good luck.
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on May 13, 2011
OK, thanks. Do I need to go to a Ford dealer for this, or do independent shops usually have the instruments to do the diagnosis and repair?
on May 13, 2011
A good independent shop (along with a good tech) will have the tooling and expertise, as well as a dealership.

Funny enough - it's getting harder to find more mature pros who remember the function and operation of a 21 year old truck...even at a dealership (i'm not entirely sure about Novato Ford - nearest to you). So definitely look well and make sure you have a good place you trust.
on May 14, 2011
Thanks Dave, I appreciate your help. I'll call Novato Ford and a couple other shops I like to see what they can offer. By the way, my truck is 21 years old, but only has 100, 000 miles. I take good care of it and plan to keep it a while longer.
on May 14, 2011
The age of the vehicle comment refers to more of the progressive skill of technicians today. Many of today's techs can be entirely competent with a 2010 vehicle, but if you give them a 1990 - they are lost. It's a different diagnostic architecture, and there are fundemental differences in operation. Consider that most of todays engines are overhead cam engines, and this is an old fashioned big block push rod engine. Many technicians today don't have any idea what a MAP sensor is or does, for example, and you have one.

I think the truck is probably fantastic - low miles, nice engine -- just need a little help getting it restored to proper working order.
on May 12, 2011
The Check Engine is an indicative of a malfunction detected in the emission control system of your truck. It is absolutely necessary to retrieve the trouble code(s) stored in the computer to diagnose and fix the problem. For more info visit;

Use the Directory to find a technician near you;
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on May 13, 2011
I agreed with everything said. Take the vehicle in and get the code pulled.
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