87 5.0 Troubleshooting & Solutions

Lateralgeez · Sep 11, 2015

Apparently 12x1.175 is not a common nut size

Lateralgeez · Sep 11, 2015

Hey guys a bit off topic but if you ever decide to go hydraulic clutch here is how the builder did mine. I remember once we were going to drive my buddy's 500hp fox up in NY (it had a small fire earlier) and when he pushed in the clutch, pop! Cable snapped. Anyway, there are a few different ways to do the slave cylinder bracket, just search miata t5 clutch etc.

I guess it was easier to do this than swap in a cable setup. Not totally sure.

A new hole was drilled further down the fork to prevent slave shaft binding.

Lateralgeez · Sep 11, 2015

Slightly more on topic is low profile oil pan. Due to the sub frame I don't know, dry sump may be the only option. Reason for this is impact marks on the pan. The car doesn't have adjustable coil overs yet (bilstiens are still on the parts car awaiting re valve) or I would raise it for more clearance.

Excuse the 2010 grassroots budget exhaust. Hoping to go 3" properly in the future.

a91what · Sep 11, 2015

3" is unnecessary at your current level..
2.5 is more than adequate.

Lateralgeez · Nov 23, 2015

Plugs

cyl 2 and 4 are black with deposits. This cyl bank also puffs white, at least on cold start. Cyl 6 leaked a small puddle. Occasionally it misfires (every few seconds) and feels hesitant at light throttle. I believe most of the issue is exhaust pipes flattened in half under the subframe.

Planning for mass air conversion, new wiring harness, and proper exhaust with o2 sensors.

Lateralgeez · Dec 19, 2015

Today I did what I should have done a long time ago. Fired it up and pulled injector wires while listening to the engine. Turns out 4 and 5 aren't working. Got a loaner noid light tester and, to my amazement, they were getting pulse. Now I'm at the parts store swapping out those injectors. If you have a misfire, check your injectors!

I wasn't able to test plugs 7 and 8 due to the intake manifold. Any suggestions?

mikestang63 · Dec 19, 2015

Lateralgeez said:
Today I did what I should have done a long time ago. Fired it up and pulled injector wires while listening to the engine. Turns out 4 and 5 aren't working. Got a loaner noid light tester and, to my amazement, they were getting pulse. Now I'm at the parts store swapping out those injectors. If you have a misfire, check your injectors!

I wasn't able to test plugs 7 and 8 due to the intake manifold. Any suggestions?

if you are replacing injectors, do them all at the same time. Be sure to use new O rings and oil them so they don't tear on installation

Lateralgeez · Dec 19, 2015

Curses. The new injectors didn't help. Either these remanufactured are also bad or injectors aren't the problem. For now I'll be happy with a V6 and loud valve tick.

Ruled out so far:
Distributor and tfi module
Plug wires and plugs
TPS
Fuel pressure
Fuel pressure regulator
Fuel rail
Vacuum
Timing
Compression
Ignition coil
Injectors - assuming both the remans are good

What are the chances an intake valve is stuck shut? That would explain the gunshot backfires...

Lateralgeez · Dec 19, 2015

mikestang63 said:
if you are replacing injectors, do them all at the same time. Be sure to use new O rings and oil them so they don't tear on installation

Thanks, I did this a few months ago but paid a lot for reman injectors for whatever that's worth. Old ones were full of dirt from the tank - dry rotted fuel pickup sock. That's when I replaced the fuel filter, rail, and pressure regulator.

Lateralgeez · Dec 19, 2015

Sounds like I need to remove the valve cover and see if they are moving. Some plugs are black so that credits my stuck shut theory.

Courtesy of ehow
How to Check a Stuck Engine Valve | eHow

Lateralgeez · Dec 20, 2015

How on earth could a valve stick shut. The whole force of the engine is pushing it open via pushrod

Lateralgeez · Dec 20, 2015

Decent amount of oil in the throttle body, guess i need a catch can. This can't be normal. Piston rings shot?

Looking at the headers it's plain to see #4 is not firing.

Ok I'm not sure what to look for here. Seems normal.

Lateralgeez · Dec 20, 2015

Well this is shameful. Turns out I had 4 and 5 plug wires swapped. Still have slight occasional misfire but it's much much better.

stykthyn · Dec 20, 2015

Oil is from the breather tube that runs to the tb. Perfectly normal. Just clean as needed.

Lateralgeez · Dec 20, 2015

stykthyn said:
Oil is from the breather tube that runs to the tb. Perfectly normal. Just clean as needed.

Ok thanks! Good thing I run 93 octane it's probably 87 in the combustion chamber lol. Seems like both valve covers should have a breather.

a91what · Dec 21, 2015

For giggles, what plugs are you running? How do they look when you pull them? What cam, firing order are you using?

If you keep fouling plugs a hotter set could help..... especially if your burning oil.

Lateralgeez · Dec 21, 2015

They are stock replacement motorcraft. 4 and 5 are dark from the plug wires being swapped. The rest are ok except #2. It's nasty but not sure why.

Pretty sure it's stock HO cam and definitely HO firing order.

It's pretty wild to drive now! Especially with the 4.1 rx7 rear end. Poor tires.

a91what · Dec 21, 2015

Ok. What's the timing at?

Lateralgeez · Dec 21, 2015

a91what said:
Ok. What's the timing at?

About 12 degrees at warm idle. I didn't rev it to check higher rpms.

a91what · Dec 22, 2015

This was set with the spout pulled?

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