What to check before replacing engine?

[Joe_SHO]

1993 manual. It puffs out the oil fill with the cap as it rotates, and the exhaust is so restricted that it won't stay running unless I pull the oxygen sensors or disconnect the tailpipe. Here is a link to it running with the oxygen sensors removed:

I bought it with a knock. However, the knock is intermittent and sounds more like clattering to me, so I'm still hopeful. Question is what else should I check or do to confirm I absolutely need to pull the engine? Can I do compression or leakdown test with the intake removed? What could I take a video of that would help you diagnose the noise?

 

[Texas Marauder]

Can I do compression or leakdown test with the intake removed?

Yes you can

 

[SHOdded]

it has the obd1 system, so options are pretty ... restricted ... from a computer diagnostics point of view. you have to get physical with it. check all the usual culprits up top including throttle body, maf sensor, iac, egr nostrils, spark plugs, coil, dis, grounds, oil level and condition, etc.

if these all check out, then it is worth pulling the intake to check compression.

various maintenance procedures

Maintenance - The SHO Phoenix Project

 

[Joe_SHO]

it has the obd1 system, so options are pretty ... restricted ... from a computer diagnostics point of view. you have to get physical with it. check all the usual culprits up top including throttle body, maf sensor, iac, egr nostrils, spark plugs, coil, dis, grounds, oil level and condition, etc.

if these all check out, then it is worth pulling the intake to check compression.

various maintenance procedures

Maintenance - The SHO Phoenix Project

I'm fairly familiar with obd1 and fairly familiar with engines, but I am NOT familiar with fwd or dohc engines. I'm intimidated by the thought of pulling a fwd engine, even though I swapped a 4.0 into my 1987 Bronco II and replaced the heads on my 1993 F250.

 

[SHOdded]

the yamaha heads + ford block works well in combination. but the parts i have outlined can cause common problems, all of which can be found using the search feature on the site. if you can get the ford service manual that would help you a lot so you can learn the layout of this engine. i believe most if not all of the items outlined are fairly easy to access and check. now if you get in as deep as bad rod bearings that's a bit of work.

 

[rubydist]

I don't understand why you are considering replacing the engine if the exhaust is plugged up.

 

[BaySHO Performance]

I don't understand why you are considering replacing the engine if the exhaust is plugged up.

Exactly. What's going on is that the exhaust is clogged and that is creating huge back pressure which is why it's trying to escape through the engine instead. This will be from a blown catalytic converter. So take the Y pipe off and check each end of each cat to confirm. The material is in two halves which is why you need to check both ends as it may be that only one half has disintegrated. I do this with a long flexible pickup tool. You may see black 'sand' come out when you bang the Y pipe on the ground.

It sounds like the rear half of a cat has gone for cat material to clog up the exhaust. Just as well: a blown front half will enable material to get sucked back into the engine and will score the cylinder walls. A compression test might show a problem if so, or you would be able to see the scoring (vertical lines on the cylinder walls) by using a bore scope.

Next up is to try to find where the blockage is and try to get rid of it. I use a drain snake that can go all the way back to the left muffler. Often that can break the material up and unclog the exhaust, but one time it wouldn't do that, so I marked where the drain snake reached and took it to a muffler shop who cut the pipe at that point to remove the blockage.

Next is the mufflers themselves. Bang on each one to see if they rattle. Stock mufflers have three pipes inside which double back on each other. Once stuff gets in there, it is impossible to remove and the mufflers will have to be replaced. Aftermarket mufflers such as Borla are a single straight through design and it's impossible for stuff to get stuck in them.

Last of all it to find out why this happened. Usually from a really bad backfire which causes the fuel explosion to happen inside the cat which blows it. Power washing the engine, allowing water to get in the plug wells will surely do it, but there are several other possibilities.