VtexGt3

iTrader: (14)

Been having this problem for over a month now and it's got me pretty stumped. Hoping the collective experience of evom can shine some light on it.

The story:

Car had no issues and then suddenly one day out of the blue, after an hour of driving, it sounds like it's got nasty drag cams. Now it'll happen after just 5 minutes of driving.
Car starts up fine, no issues. Thermostat opens and no issues either. At some point after the car is fully warm, it will develop a super lumpy idle; I mean greater than 280 cams kind of lumpy. A lot of rattling from under the car as well, I imagine due to the rough idle. The idle was dipping below the 800 target and doing small bounces to try and maintain the target rpm, but more on that later. The car holds boost and will drive however this is a noticeable power difference when the lumpy idle thing starts to happen. The symptoms go away after the car has cooled down. Most annoying part, it's not throwing any codes or a CEL.

What the car has:

Car has 113,xxx miles on it

• Turbo back exhaust
• mbc
• drop in filter pretty much it's entire life.

2,000 miles ago the oil pump failed so the engine was rebuilt 18 months ago

• H Beams
• Wiseco 9:1 pistons
• ams balance delete
• arp studs
• mishimoto rad

What I've Tried:

• Cleaned the Throttle Body
• Replaced MAF
• Checked fuel pump... working fine as far as I can tell
• Replaced idle air control valve. This was an issue for a lot of people, thought it might do it for me...nope (this fixed the bouncing idle issue. Now it'll idle at 800 sounding like it's got nasty *** cams)
• Burped the Radiator... there were bubbles, but that didn't fix the issue
• Logged the car... No knocking, NO CEL or Codes, when the car is idling like sh*t the actual rpm still matches the target idle rpm in the log.
• Pulled the spark plugs, all the tips look good. #2 & #3 had oil on the threads, I guess the valve cover is leaking a bit.
• Car isn't burning any oil
• No oil in the coolant
• No coolant in the oil
• Last oil change was 100 miles ago no issues
• OEM map, did not fix the problem either.
• Have not found any obvious leaks like a loose IC pipe or popped off hose

Anyways, any help would be greatly appreciated!
Thanks!

VtexGt3

iTrader: (14)

Bump

kaj

iTrader: (60)

What's a drag cam?

Unrelated, but Did you clean all the black stuff out of the throttle body?

Have you tried a different O2 sensor?

VtexGt3

iTrader: (14)

lol just some big cams

I've cleaned all the deposit from the throttle body, but didn't scrub it so the seal isn't damaged.

I have no replaced either of the O2s, I figure if it was a O2 sensor failure it would throw a code

illbill

iTrader: (1)

Had the same issue on my high mileage IX that got progressively worse. Idle was fine when first starting up but would be terrible once the car was warmed up. It ended up being my EGR system. A quick test is to loop the vacuum lines from the throttle body back into itself and drive for a day to see if the lumpy idle goes away. You'll throw a code for the EGR but if the idle is back to normal, you'll know it's something in there like a bad EGR valve or vacuum leak in the system.

VtexGt3

iTrader: (14)

Interesting, will give this a shot. Thanks

kaj

iTrader: (60)

What happens to the AFRs when idle goes crazy?

VtexGt3

iTrader: (14)

Don't have a wideband so no clue. This was a pretty much stock car until the motor blew due to the dead oil pump... it's essentially now a stock car with a built motor ... the irony

CeliOnce

iTrader: (3)

You should bare minimum get an oil pressure gauge.

kaj

iTrader: (60)

My car does a weird thing when I start it after it's warmed up. It idles super lean for about 30sec or so. I wonder if our issues are related somehow.

VtexGt3

iTrader: (14)

Isn't the cliche "boost gauge bro"?

I have a boost/oil press/oil temp gauge pack

Oil pressure is normal during cold start and once warmed up and oil temp is normal as well.
Car also holds boost as far as I can tell... it's not capping out at 14 or what not like when the recirv valve isn't connected right

VtexGt3

iTrader: (14)

I wouldn't be surprised if in the end I have a vac leak somewhere and it's throwing things off switching from open/close loop... which would be in line with why it starts up fine and then has diarrhea once the ecu makes the switch.

timing jumping a tooth or two? anyone with experience when that happens? That would manifest itself from initial startup and not after the car warms up only right?

I checked to make sure none of the EGR hoses popped off, or really any hose, and they all seemed okay. Will do a smoke test tomorrow and like the other guy suggested loop the EGR sensor.. The struggle continues

kaj

iTrader: (60)

A vacuum line sold be noticeable in closed and open loop. Have you sprayed carb cleaner on the lines, yet?
If it's only when warm, it should be a bad sensor, somewhere.
The MAF is plugged in?

Just tossing out ideas. Sometimes it's the simple things we miss LOL

MR. EVO MR

iTrader: (9)

Spark plug wires are all tight?
If you loose one cylinder it'll sound like big cams.

josh_evo9

iTrader: (1)

Egr may be sticking, or you may possibly have a faulty egr solenoid. You can get a vacuum hand pump and test the egr valve in about 30 seconds. My car had a faulty egr solenoid, after some driving at operating temp, the egr valve would stay open and my car would idle very rough.