[fasterthangas]

While idling; I've pulled cylinders 5 and then 6 plug wires individually and there's no difference in idle speed. Both cylinders have 150psi of compression. Plugs have been changed twice. Plug wires, coil and tfi have been changed as well. I tested spark on all cylinders with the tool that goes between the plug and plug wire. Spark is orange on all cylinders. I haven't done a leak down test. Car ran great right up to this point. It's weird that two cylinders side by side are affected and they also fall in line in the firing order. Valvetrain?

 

[Dwain]

if its got 150psi compression, i doubt the leakdown would be an issue. I also doubt the valvetrain would be an issue because you have compression. I would use a noid light to verify you have injector pulse on those 2 cylinders. How do the plugs look in those 2 cyls?

 

[fasterthangas]

if its got 150psi compression, i doubt the leakdown would be an issue. I also doubt the valvetrain would be an issue because you have compression. I would use a noid light to verify you have injector pulse on those 2 cylinders. How do the plugs look in those 2 cyls?

I performed an injector pulse test via TunerStudio. All are pulsing. There's wet gas on plug 6. Plugs barely have any color.

 

[Nitrous SSC]

You'd think with 150psi of comp the valvetrain and cylinder compression would be fine. Maybe it's not throwing a hot enough spark? It's ******* but did you try a screw driver trick to visually see how much spark is going to each wire? Could be cap/rotor?

******* is stared out?! Come on. How am I supposed to type "you might be a *******" jokes.

 

[Blown85GT]

Crazy thought, if an intake or exhaust valve wasn't opening (but other was), could you still get full compression?

 

[fasterthangas]

You'd think with 150psi of comp the valvetrain and cylinder compression would be fine. Maybe it's not throwing a hot enough spark? It's *** but did you try a screw driver trick to visually see how much spark is going to each wire? Could be cap/rotor?

*** is stared out?! Come on. How am I supposed to type "you might be a ***" jokes.

Are you referring to pulling a wire off the cap and jumping the spark to a screwdriver?
I used this to test spark:

 

[fasterthangas]

Crazy thought, if an intake or exhaust valve wasn't opening (but other was), could you still get full compression?

I'm not the best at visualizing things like that. Tight valve, loose valve, sunken seat? My brain hurts.

 

[96pushrod]

Pull the valve cover off and look for something weird.

Plug wires in the proper place? Lol

 

[fasterthangas]

I took a flashlight and shined it into the cap while in total darkness. I found no cracks for what it's worth.

 

[fasterthangas]

Pull the valve cover off and look for something weird.

Plug wires in the proper place? Lol

Plug wires have been triple checked for firing order. I had the valve covers off and gave the valvetrain a quick look. There was no odd wear on the rollers or what I could see of the pushrods. I told myself that I should check lash but I didn't. I'm wishing I did now.

 

[Blown85GT]

I'm not the best at visualizing things like that. Tight valve, loose valve, sunken seat? My brain hurts.

I'm sure my thought was off the wall and rediculous.
But, I was thinking if you wiped a cam lobe (or 2), or broke a rocker, collapsed lifter.......something that would prevent a valve from opening.

Could you still get good compression results if only one of the valves was opening/closing?

 

[fasterthangas]

I just started the car in pitch black and didn't get a light show around the cap, wires or plugs.

 

[fasterthangas]

I'm sure my thought was off the wall and rediculous.
But, I was thinking if you wiped a cam lobe (or 2), or broke a rocker, collapsed lifter.......something that would prevent a valve from opening.

Could you still get good compression results if only one of the valves was opening/closing?

Good question. Usually if there's a wiped lobe; I hear popping out of the tailpipes at idle. I don't have that.

 

[jim bourne]

Try a leak down test, its possible head gasket between cylinders has failed.

 

[fasterthangas]

Try a leak down test, its possible head gasket between cylinders has failed.

Would there be coolant in the oil or vice versa?

 

[kjb302ho]

Try a leak down test, its possible head gasket between cylinders has failed.

he has compression.

loosen the rockers on the cylinders and close the valves. apply air to the cylinder. listen for a massive leak out of the intake or exhaust pipe. orange spark is a weak spark. should be bright blue

take the plug out and verify the spark is actually happening.

 

[Blown85GT]

Would there be coolant in the oil or vice versa?

Not if it's between the cylinders.

I had that happen (gasket between 2 cylinders), but the 2 adjoining cylinders had minimal compression.
Odd that you would have good compression and popped gasket.

 

[fasterthangas]

he has compression.

loosen the rockers on the cylinders and close the valves. apply air to the cylinder. listen for a massive leak out of the intake or exhaust pipe. orange spark is a weak spark. should be bright blue

take the plug out and verify the spark is actually happening.

I think the orange spark is due to the type of bulb in the tool shown above. When I pull a wire off of the cap; the spark is blue and jumps quite a gap.
Can't I rotate the engine by hand to close the valves?

 

[fasterthangas]

Have bright white spark at plugs. Just checked.

 

[kjb302ho]

I think the orange spark is due to the type of bulb in the tool shown above. When I pull a wire off of the cap; the spark is blue and jumps quite a gap.
Can't I rotate the engine by hand to close the valves?

as long as you can verify the rockers are loose meaning there is no pressure in the spring and that means the valve is completely closed. verify the plug is actually firing. ive seen too much anti seize cause plugs not to fire.