At my wits end with this issue

[TwistedFish]

Ok maybe this will make it easier. Test the MAF connection with the key on with your multi-meter probes in the locations shown. The approximate voltage for each test is in parenthesizes.

View attachment 319222

This is the MAF RTN voltage chart:

View attachment 319223

Hey, thanks for all your help so far, I made an update with the compression test findings in the OP, let me know what you think!

 

[ChildIdenticant]

I know that you stated you are 100% sure that the firing order is correct but your description sounds very much like an incorrect firing order.

I concur. And watching the video in first post, it looks like the spark cables are swapped incorrectly, further indicating this.

 

[MrQ]

If cylinder 4 is down on compression, there are a few things that could be wrong, from least severe to most severe:


Valve stuck open
Bent valve
burned valve
Head gasket failure
cracked head
broken piston ring

You can check 1 and 2 by pulling the valve cover. 3 can be checked with a boroscope. 4 can most of the time be checked with a coolant pressure test. 5 will require pulling the head and 6 can be checked with a boroscope. Unfortunately, unless you can free number 1 from the top, they will all require pulling the head to fix.

Before you go to far I suggest doing a cylinder leak down test just to verify if the cylinder is actually bad. It can be a more accurate test.

 

[Hyde_Jeckyll]

Go to amazon and buy a new ignition coil pack. Had issues with my gf’s 91 and we trouble shot at very thing and I mean everything twice over and it was a pain. Finally my stepdad and I both came up with the conclusion of the ignition coil pack so we got one out of a wrecking yard and all the problems went away. It can seem like everything from fuel to airintake to misc.. wiring problems. Pull your coil pack and flip it over to see if it looks blown out or to see if it has been leaking. If so that’s your problem .

 

[TwistedFish]

Go to amazon and buy a new ignition coil pack. Had issues with my gf’s 91 and we trouble shot at very thing and I mean everything twice over and it was a pain. Finally my stepdad and I both came up with the conclusion of the ignition coil pack so we got one out of a wrecking yard and all the problems went away. It can seem like everything from fuel to airintake to misc.. wiring problems. Pull your coil pack and flip it over to see if it looks blown out or to see if it has been leaking. If so that’s your problem .

This is good advice, but I think most of my issue comes from whatever's causing my loss of compression in cylinder #4. Thanks for your reply!

 

[TwistedFish]

Hey all, check out the new update if you’d like! Looks like a blown head gasket

 

[TwistedFish]

If cylinder 4 is down on compression, there are a few things that could be wrong, from least severe to most severe:


Valve stuck open
Bent valve
burned valve
Head gasket failure
cracked head
broken piston ring

You can check 1 and 2 by pulling the valve cover. 3 can be checked with a boroscope. 4 can most of the time be checked with a coolant pressure test. 5 will require pulling the head and 6 can be checked with a boroscope. Unfortunately, unless you can free number 1 from the top, they will all require pulling the head to fix.

Before you go to far I suggest doing a cylinder leak down test just to verify if the cylinder is actually bad. It can be a more accurate test.

Hey, not sure if you saw, but I posted an update, looks like a blown head gasket, possibly cracked cylinder head, but it doesn’t look like it’s gonna be something simple haha.

 

[MrQ]

Fortunately the head gaskets on these are fairly easy to change out. Just be patient and make sure you know where everything goes before you remove it. If it is a cracked head you MUST make sure to get the right head. There were differences through out the years and they are not all interchangeable especially since it is a 91. The PN should be stamped on the side of the head. You will need upper and lower intake gaskets as well as the head gaskets themselves as well as new head bolts. You cannot re-use the old ones.

This would also be the perfect time to change out lifters, rocker arms, and pushrods. If you overheated it would also be a good idea to give your cooling system a once over (thermostat, water pump, radiator, hoses, etc).

 

[Centaurious]

Or you could get a Re-manufactured long block.

 

[MrQ]

New heads cost about $300, last time I priced a long block it was almost $2000 which (all things considered) is more than twice what the vehicle is worth.

Granted my brother spent almost $15,000 on his 91 between the purchase price and on-going repairs (new upper end, new transmission, new suspension, new tires, etc), so it's all about what it's worth to you.

 

[sandsprayer]

OP lives in Hawaii, added shipping costs?

 

[TwistedFish]

New heads cost about $300, last time I priced a long block it was almost $2000 which (all things considered) is more than twice what the vehicle is worth.

Granted my brother spent almost $15,000 on his 91 between the purchase price and on-going repairs (new upper end, new transmission, new suspension, new tires, etc), so it's all about what it's worth to you.

Okay, so actually, good-ish news. I'm an idiot. I looked at the radiator (coolant) more closely (what the picture showed), and even stuck a stick in there to see if there would be oil residue, and it turns out all that shiny stuff was actually what looks like metal fragments. So. Yeah. Sorry about the huge alert post.

 

[MrQ]

Okay, so actually, good-ish news. I'm an idiot. I looked at the radiator (coolant) more closely (what the picture showed), and even stuck a stick in there to see if there would be oil residue, and it turns out all that shiny stuff was actually what looks like metal fragments. So. Yeah. Sorry about the huge alert post.

Umm, that's not good news either. Metal shavings or fragments do not belong in the cooling system. I highly suggest flushing the whole system and inspecting or replacing your water pump. When the bearings go out the water pump vane can actually wobble and start digging into the timing cover or the pump itself (stamped steel vs aluminum, steel always wins) causing metal shavings to be introduced into the system.