help please

[4x4junkie]

Need some help. My 88 bronco 351 dies after about 30-45 min of running. let it cool down and it starts back up but will die again when it heats back up. I love the truck but am tired of the problem. i've already replaced the ignition module, pick up coil, fuel pump and filter, had the alt and battery checked, replaced the air flow sensor. a buddy said its probably clogged converter but new exhaust is up there in price. so here i am. any thoughts. thanks

 

[TheBus]

If you really wanted to test if the cat is clogged all you need is a simple vacuum gauge. Once you tap into the intake manifold vacuum lines with a gauge, rev the engine and snap the throttle shut quickly. The gauge needle should return fairly quickly back to a normal reading of 20in/gm. If it returns slowly the exhaust could have a restriction in it.

An exhaust shop can also test vacuum closer to the cat. The only bad part is it requires drilling a small hole in cat near the inlet to stick a vacuum hose into. They should do it for a small fee (if any). If it is not clogged they can just put a small tack weld on the hole to seal it. Do it seem like its lacking a lot power?

It sounds like an ignition component is getting super hot and stops working in your case. You could narrow it down by testing if you have spark while cracking once it dies on you. Just get a spark plug ignition tester that has a ground clamp on it. Then unhook a plug wire, connect it to tester, and clamp it on a good ground. Then verify you have spark coming out of the wire... That way you could narrow it down to the ignition system if you don't have spark.

 

[Rons beast]

When it won't start check if you have spark. If you do spray some starting fluid in the intake tube and see if it starts, or attempts to fire.

That will tell you if it's a spark or fuel problem.

You won't be the first to get a bad ign. mod either.

A clogged converter will have it running like you're towing a battleship all the time.

I have on occation, placed a baggy of ice cubes on the ing mod and cranced the engine to see if the cool down would have an effect.

It is rare but I have found a fuel pump relay that overheated and did exactly what you describe.

Find out if you are searching for a spark or fuel problem first.

good luck let us know what you find.

 

[miesk5]

yo,

Try a Self Test by our good pal here, BroncoJoe19

An assistant to write the info is helpful

heat the engine up; idle until temp gauge is in normal range you usually see

and when it warms up; shift thru all gears incl Reverse anyway.

Then turn off all accessories/lights, etc.

Make sure A/C is off and transmission is in Park (automatic)

Do Key On Engine Off (KOEO) portion first.

The engine temperature must be greater than 50°F (10°C) to pass the KOEO Self-Test and greater than 180°F (82°C) to pass the KOER Self-Test.

Look Codes up in my broncolinks.com site using the new Search function if in a hurry today.

And Post em here according to

KOEO

& KOER