Scratching head after installing new heads. (Sorry for the pun)

[1991ExploderXL]

Incorrect info from manual

Here's the first schematic that came up when I searched online. It cranked right up!

Mystery solved!!

Turns out the Chiltons manual I was using had the firing order and spark plug orientation way off.

So it should've fired up the first time...
Well, there's $40 worth of gaskets that I didn't have to change.

Anyways, I drove the truck about 20 miles this evening and it's running great! Not a huge difference to be honest, just rock steady coolant temps and more torque than before, a little smoother too I'd say. Tomorrow I'll change the oil and filter, switching to 5w-30 from here on out. I'll also flush the cooling system and refill with fresh prestone.

Thank you guys so much for your prompt replies and your patience, I can't express my gratitude enough!

 

[974X4BLACKSPORT]

Glad to see your up and running!

 

[1991ExploderXL]

I can't tell you how glad I am! I'm just about to head out to the shop and change the oil now. Thanks again for the patience and persistence!

 

[MrQ]

Incorrect info from manual View attachment 167834 View attachment 167835
Here's the first schematic that came up when I searched online. It cranked right up!View attachment 167836 Mystery solved!!

Turns out the Chiltons manual I was using had the firing order and spark plug orientation way off.

So it should've fired up the first time...
Well, there's $40 worth of gaskets that I didn't have to change.

Anyways, I drove the truck about 20 miles this evening and it's running great! Not a huge difference to be honest, just rock steady coolant temps and more torque than before, a little smoother too I'd say. Tomorrow I'll change the oil and filter, switching to 5w-30 from here on out. I'll also flush the cooling system and refill with fresh prestone.

Thank you guys so much for your prompt replies and your patience, I can't express my gratitude enough!

Wow that is way off, no wonder that engine ran like crap. Glad you found the solution.

I have found stuff in my Alldata files that are wrong too. It had the return signal wire being the same from the TPS, CTS and IATS and 3 different 5 volt circuits going to them, which is exactly backwards

Never hurts to verify the data when it seems wrong.