[Zombalot]

Issue has been resolved, thanks forum.


THIS IS THE CULPRIT, THIS WAS ONE BACKWASH OF INJ 3

Heres what I know:
I purchased this car from someone I know that let it sit for about a year due to his purchase of a C6 and a HellCat, he assumed it had a bad tank of gas and the rare stutter was just the gas not completely ran through. It drove fine with a very rare stutter around 80 and I drove it for about 500 miles, then let it sit for about a month (its not my dd) then rapidly got worse to this point in about 75 miles.

At idle or low rpms it sounds like a Subaru. I drove it to O'reillys to scan the code and getting up to speed or keeping it about 3k ish would clear it up. I intended on getting meth and a dyno tune but obviously thats on hold. I'd like to get this sorted before I tow it over Kozmic, save me some $$ on labor.

Mods: Been on car for past 30k miles
GSC S2, valves, and springs | Ported head and exh mani | DW65C | FIC900cc | FP Red
AMS IC and Turbo back. Tuned by Kozmic.

Heres what I've done:
Visually inspected wires and plug, nothing of concern.
Brand new NGK #1422 (factory) gapped at .021 (old set looked dirty, nothing of note)
Only ran Exxon or Shell 93 since ownership.
One bottle of seafoam.
Compression test: 95 on every cylinder using harbor freight tester (this is what I have, its done me well, new orings). Tested warm, right after drive. 5 Cranks. Same numbers as when first purchased.
Ohm tested wires and coil pack.
Cleaned injectors. SOLVED ISSUE

 

[Kooldino]

95 on the compression test? how many cranks do you give it? Can you try another tester?

 

[razorlab]

Yea, get a different/ better tester. 95 is below minimum spec:

Evo 10:
Standard: 158psi
Minimum: 109psi

 

[Jabo]

You pull one plug at a time or all four ?

 

[stEVOlution Z]

for compression test, I just crank until the needle stops going up, which is about 10 seconds worth of cranking or so... :shrug:

 

[Zombalot]

You pull one plug at a time or all four ?

Both. 1 at a time before my new plugs arrived when I initially inspected old ones, then pulled all plugs on second check when I replaced the plugs. Just to see if it made a difference. Same results.

 

[Jabo]

Both. 1 at a time before my new plugs arrived when I initially inspected old ones, then pulled all plugs on second check when I replaced the plugs. Just to see if it made a difference. Same results.

You should not see the same values with all plugs removed at the same time and only one removed at a time. The former should see markedly lower values than the latter.

How does the plugs look like?

Borrow a different compression tester to make sure the one you are using is not dud.

 

[Yxd68]

The ONLY way to accurately do a compression test is with ALL spark plugs removed and the throttle plate blocked wide open with a freshly charged battery (minimum cranking speed of 325 RPM).

Anything else or any other way is weak tea and results are meaningless.

 

[Zombalot]

I haven't had an issue with it and nobody sells them near me, so I'll have to wait on the compression tester verification unfortunately. I did pull injectors and cleaned them out. I did not test the original spray pattern but I got some gunk out. I even blew some crud out of the bowl on accident!

These are what the old plugs looked like.

This gunk I cleaned from injector 3. Spray pattern is now on point (didn't check first)

 

[Jabo]

So, did cleaning the squirters help?

 

[Zombalot]

Close, delete, do what you need to do mods. The injector was the culprit. Issue has been fixed.

 

[Jabo]

Excellent .