Power loss on 1987 E-150


#1

I’m experiencing power loss on a 1987 Ford E-150 351 4 bbl with 150,000 miles. The air pump and all the associated plumbing has been removed and all the air lines plugged (There are a bunch of those!!) Did this about 2 years ago.



Since then the van has always run rich, especially at idle. This makes the van hard to start in hot weather when the engine is hot - in fact I have to hold the throttle open while I crank it.



The van works fine until the throttle opens more than 10%. Past 10%, I’m getting some kick back through the carb.



It came on quite suddenly. I was towing, then the van started to slow down like I was going up a grade - except I wasn’t.



I’m leaning towards a vaccum leak - the engine starts much easier now, even when hot - except that the leak would be most active under high vaccum situations, and that’s just the opposite of what is happening.



I’m also think the vaccum advance diaphram might be leaking and not working when the engine vacumm changes. I’m also leaning towards coil since the plugs, wires, rotor and cap have all been replaced.



I am sure it’s just a simple, single thing - I’ve experience this type of thing before, but it was so long ago, I can’t remember what the fix was.



Sure would appreciate some help.


#2

[b]That air pump system you removed from the engine is designed to light off the catalytic converter(s). And since there’s no air going to the cat(s), they’re probably starting to plug up.

Tester[/b]


#3

I can think of a few things that could cause something like this, but I do agree with the converter diagnosis by Tester and would probably be the first thing I would check.

You can check for a converter clog with a vacuum gauge. If you do not own one, I would highly recommend it buying one.
They’re cheap, can tell you so much about an engine, and worth their weight in gold IMHO.

Here’s an example of a decent inexpensive one that should last a lifetime.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93547


#4

If you are getting backfire, I’m leaning toward the timing being off. Check the timing and do the vacuum tests. The procedures are in your Haynes, or Chilton’s. Let us lean together.


#5

While I like the cat as a potential problem, it doesn’t fit the symptoms. The engine starts to miss and backfire through the carb even in neutral - car not moving.

The problem seems 100% related to throttle opening.


#6

[b]Well, I’ve seen cats plugged up so much that the engine wouldn’t even start! So don’t discount this as not being a cat problem.

Tester[/b]


#7

For those who are interested, the problem turned out to be:

Ignition Control Module


#8

Yes, we’re glad to get responses. Believe it, or not, some of the suggestions for actions are original. This means, that it’s not been tried before. I/we would like to know so that it can be considered for the next person with a similar problem.