I’m trying desperately to fix an intermittent problem. I think it is electrical by deductive reasoning only.


‘85 E150 with a 302 engine.

From a stopped position, with the throttle depressed and held in one position, the engine will increase rpm to where it should be then immediately loose power as if I had released the throttle, then resume power and loose power, resume power and loose power. This cycle continues at approximately 1-second intervals. Most times the engine will eventually “kick in” and run properly until the next stop but other times it will just continue or even die completely.

The problem only occurs when the engine is warm and has been running a while.

The problem only occurs from a stopped position when the throttle is applied. It never begins to happen while moving.

The problem occurs intermittently. The vehicle may drive fine for several days then the problem may suddenly appear. Just as it suddenly appeared it may then clear up the next day.

New long block
Rebuilt carburetor
New fuel pump
New fuel filter
Fuel tank inspected and cleaned
1-year-old spark plug wires
1-year-old spark plugs
1 year old distributor cap and rotor

The EGR valve works but there is no vacuum applied. This was traced back to a solenoid control that has power but is not switching and allowing the vacuum.

This vehicle has the EEC IV computer and the TFI module is mounted to the distributor.

Can anyone help point me in the right direction? I've posted in other sections without succes. I'm becomming a little disheartened.

Joe

 

Sounds like a fuel related problem to me. Could be a loose connection on the fuel pump, dirty "sock" on the fuel tank pickup, plugged fuel filter.....maybe even a dying fuel pumpor a sticking needle valve in the carb.
Not saying it isnt electrical though.

Sparky

 

The fuel pump is mechanical (and new). The fuel filter is new. I took the gas tank out and cleaned it and I checked the sock which looked OK. The carb was just rebuilt. This problem was also present before all the new stuff. Is there anything else in the fuel system I could check or is it reasonable now to eliminate the fuel system as the problem?

Also, when the engine is warm and just at idle, the idle will rise about 200-300 rpm (my guess) for 2 seconds then drop back for 2 seconds then rise again and drop back etc. etc. Could this be related to the first problem? Could this be caused by a bad sensor sending information to the computer or does it sound more like a vacuum leak?

Joe

 

When TFI modules die , their dead. If you know your getting spark
You might want try taking a gatorade bottle and sticking carb fuel input filter into it and have someone crank the engine over. It should squirt every time the, "eccentric", or cam hits the pump. Watch for sparks and don't smoke.
If that's good, it will eliminate the fuel problem getting to the carb.
Good luck with it.
If you figure it out tell me what you found.

 

I have a '95 F-250, just started doing about the same thing. Started minor, getting worse. I am going to put a new fuel filter on it tonight and see if that helps. I had a friend of mine tell me that the TPS might be doing it. Any possibility of that, or suggestions on the TPS part??

 

One of the things that is considered a Valuable tool for these EFI or computerized trucks is a CODE READER.
These are reasonably priced and do a great job in determining carb & monitored systems.

The EQUUS company is one manufacturer.
In Canada,they are available at Canadian Tire Stores.

[link:www.canadiantire.ca/assortments/browse_product.jsp?FOLDER%3C%3Efolder_id=377831&AS SORTMENT%3C%3East_id=166971&bmUID=1011997665744|EQ UUS Code Readers]


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