UPDATE 1/10/2013 Car is running at 100%. In fact it's running better than it has ran in years due to the lack of the vacuum leak that's plagued me. The conclusion I've came to is that I'm an idiot and didn't realize where I tapped for my boost gauge was the vacuum line from the FPR to the IM nipples (see Prior History below). This whole time I had been sucking air into the fuel system which had progressively gotten worse over time and was always more violent with higher rev's. This was then really present when the vacuum line came off the IM causing a TON of air to be sucked into the Fuel system. Only by purging the air out over time was it able to finally start to run normally again. So if anyone out there has a similar issue, air in your fuel system maybe what's causing it. I do love the fact that I was able to fix this WHOLE issue with a 2 ziptie's and a new vacuum hose costing me about 2 bucks total. As for the compression test, that is a little alarming. I plan to report back on the results of an additional dry test followed by a wet test to confirm rings or valves. I'm leaning toward rings but we'll see. Thanks to all that responded to my plea for help and to all the articles I read here at EVOM, thanks for taking the time to share your experiences here.

UPDATE 1/7/2013 Car has finally given me a CEL code of PO304 Misfire in Cylinder #4. Car runs strong mostly but then misfires and sends the car into a stutter which is only corrected by completely letting off the accel and coasting for a bit. Then I'm able to continue driving normally. I only did this twice and then limped it back home. NOTE: the car runs great if you just cruise at > 40mph @ 2.5K rpm. Only when you get on it a bit (4K or so) will it misfire.

UPDATE 1/5/2013 Car is running and I drove it home from my friends garage which was about 20min's keeping rev's below 4K and didn't break 40mph... read more

Specs:
My car is a '04 EVO VIII GSR with 128K miles.
Mods: Perrin intake, Perrin BOV, Perrin TBE, Perrin EBCS Pro.
Other mods are suspension, rims/tires, and brakes.

Prior History:
I have had issues with my Evo cutting in and out around 4K in any gear for about a month. I've also had an issue with a low boost reading on my Autometer gauge of only 7lbs WOT in any gear. Seems like the cutting in and out has gotten progressibely worse for a few years now. Recently I recently conducted a boost leak test and found that my T tap connector for my Boost gauge had a crack in it and I went ahead and replaced the connector and fixed the boost leak that had plagued me for a few years now just the other night before The Incident happend...

The Incident:
Then the other night It was doing it's normal cutting in and out thing, then I started into a corner and went WOT, car cut out a bit harder, but I continued on. This was immediately followed by the car just misfiring badly, then eventually dying. I ended up pulling the car over with no power sterring onto the shoulder. I tried to fire it up again, no go, wouldn't stay running, wouldn't even idle. I then decided to tow it to a friends garage. Since then, the car will run (very rough for about 5 seconds) then die or will just crank without starting at all. Upon inspection I've found that the vacuum hose from FPR to IM had come off the IM nipple. I also checked plugs and found that #4 was loose and once removed, found that it had bent strap but no visible marks on the strap (not sure what caused this, possibly detonation but I'm not an expert on the topic). I've since replaced the bad plug in #4 with no difference to the running, or lack-there-of condition. There has also not been any additional damage to this new plug since being replaced.

Some things I've tried since:

• Replaced the bad plug on #4 (I usually use the NGK 7's but in a pinch I switched to Autolite XP Iridium XP3924 from Autozone)
  
• I have a Innovate Motorsports LM-2 which isn't throwing any codes. One thing I've just read (related to a bad Crank sensor) is to view the RPM's as I'm cranking it to see if that leads to a value of 0. If so it appears that the Crank sensor might be the bad guy here.
  
• I can hear the Walbro fuel pump and the cylinders are getting fuel. I'm not familiar with how much fuel the cylinder should have in it but my assumption is that the plugs aren't getting proper spark. This conclusion comes from a strong gas smell on each plug and visible fuel on the piston in each cylinder viewed through the sparkplug hole with a flashlight.
  
• Completed a compression test (150,150,130,110)psi. I haven't tried to add oil to the cylinder to see if it's the rings or not. Even if it is an issue I don't see this being the source of this issue. Don't get me wrong, I'm worried about it

Conclusion:
Leaning toward bad coil or possibly a bad sensor (Crank or either Cam). I would like to test the coil for spark but am unsure how this would be tested. I've researched it and looks like I may need an oscilloscope. This scope could also be used on the sensors as well. Is there any other ways you can test these sensors? I've read that you can swap the intake and exhaust sensors to see if that makes a diff. Might try that next.

A side note is this very similar issue:
https://www.evolutionm.net/forums/ev...5-evo-8-a.html. I was hoping for a conclusion but it appears we're held in suspense.

 

I am leaning to no or low compression on #4.

Sorry dude, it's time to pull the head. Hopefully you just popped the head gasket. check for oil and coolant contamination on the dip stick and check for oil in the radiator.

 

Well the cylinder does have a compression reading of 110psi. What leads you to think it's the head gasket? Couldn't it just be bad rings or buildup on the valves?

 

Id try the cheap options first like restore oil treatment and fuel injector cleaner, might be able to clean valve deposits and help the rings. If that doesn't help then head pulling time !

 

Well heres a major update. Car is running now, here's what I did.

About 3hours ago I decided to go wrench on the EVO for a bit. I went ahead and checked the dipstick as chrisw mentioned and absolutely no signs of milky or discolored oil on the stick.

I then decided to check the resistance of the plug wires. The long wire read 615ohms while the short one read 315ohms ??? not sure why their different or what value their supposed to be. This post seems to be way different then my readings https://www.evolutionm.net/forums/ev...ires-test.html.

After that analysis I decided to take some advice that I read a day or two ago in regards to swapping the two coils positions. Low and behold the car fires right up It ran fine, then would all-of-a-sudden idle and sound like a gocart or subi, then it would go right back to idling super smooth. I let it run for some time without it dying. humm... So now I'm scratching my head and thought well, let me switch the coils back to the 'bad' config and see what happens. Low and behold won't idle or stay running anymore, just like before. So I switch them back...runs the same (super smooth then randomly gocart style). I realize this could be complete and total cooincedance however the fact is it runs with them in one position, and not in another. I will mention that I do have the plug wires in the correct order. As I'm typing this I'm giving the impression that I swapped the coils and cables as one unit, this is not the case. [#1 goes to coil on #4] and [#3 goes to coil on #2].

Next I dare to take it around the block for a test run. I start to go and it runs and idles perfect, then on my way to the end of the street it starts the gocart style, then back to normal. I press on to the next corner, no prob, the next corner, as I'm approaching the car runs like crap then dies. Uh oh, here we go again. I crank it over and it fires right up and has been running ever since. I decided to chance it and drive it home (about 20min drive not exceeding 4K rpms or 50mph the whole way). Ran perfect and is safely home in my garage.

No CEL codes have been thrown this entire time (either on my Innovate LM-2 or the engine light in the car).

Anyone have some thoughts? Seems like a temperamental sensor or coil since it isn't exhibiting this type of behavior 100% of the time.

 

Car is running at 100%. In fact it's running better than it has ran in years!

This is due to the lack of the vacuum leak that's plagued me. The conclusion I've came to is that I'm an idiot and didn't realize where I tapped for my boost gauge was the vacuum line from the FPR to the IM nipples (see Prior History). This whole time I had been sucking air into the fuel system which had progressively gotten worse over time and was always more violent with higher rev's. This was then really present when the vacuum line came off the IM causing a TON of air to be sucked into the Fuel system. Only by purging the air out over time was it able to finally start to run normally again. So if anyone out there has a similar issue, air in your fuel system maybe what's causing it. I do love the fact that I was able to fix this WHOLE issue with a 2 ziptie's and a new vacuum hose costing me about 2 bucks total. As for the compression test, that is a little alarming. I plan to report back on the results of an additional dry test followed by a wet test to confirm rings or valves. I'm leaning toward rings but we'll see. Thanks to all that responded to my plea for help and to all the articles I read here at EVOM, thanks for taking the time to share your experiences here.