S1 rb25 IDLE problem, need fast answer.

[Fibre guy]

My RB has been acting up, Idles fine one start up then like bad the next. After 2k rpm it revs fine. Holding the throttle down in one spot it changes about 200 rpms every 2 or 3 secs. IACV screw doesn't change the idle.Laptop not working so I can't use my consult.CAS adjustment doesn't change bad idle condition.Exhaust tone has small skips.Tested for vac/boost leaks...Possible problems:Failing coilFailing O2 sensorBad IACV

I just want opinions on what you all might think it is... Thanks Damn gnomes got into my engine again!

[Darius]

Sounds like you are describing a misfire. Is that right?

[Fibre guy]

Correct. All injectors fire but I'm unsure of the coils. They all test "good" but if its a failing coil it will only fire sometimes but test ok. I have no way to tell which cylinder it is if that the problem...Also, I've tried unplugging individual coils to see if any change happens but to no avail.

[Fibre guy]

BUMP!I'm investigating the possibility of a grounding problem due to trunk mount battery, ordering wire to make more ground wires...The more help the better. Opinions please!

[Fibre guy]

Update! Any suggestions to shoot me in the right direction would be great.Relpaced:O2 sensorEngine coolant temp sensorUpgraded:Grounding more that 15' of grounding straps added. Cant seem to find the problem....After it has been on for awhile sometimes it will behave perfectly normal.Does anyone know if this sounds like a bad coil?

I would also like to add that when I unplug the coolant temp sensor when it first starts the idle and rev instantly returns to normal until it warms up. The sensor is brand new and I tried another one just in case, still no fix.

[Darius]

Typically coils act the opposite. When they get hot, they are more likely to misfire and a weak coil will expose itself under high load/boost as a misfire.

Grounding kits, etc. seem to be band aids for other harness grounding issues. Relocating the battery to the trunk shouldn't make any difference unless the battery ground is poor or the paint was not removed to expose bare metal.

Since you mention that the problem goes away after the car warms up, it sounds more like a sealing/gasket/coupler issue that goes away when the material expands. Have you pressure tested your piping to check for leaks?

[Fibre guy]

It holds 15psi on a boost leak down. At 20 I get a pinhole leak at the TB shaft. I decided to pull the coils and re-test them and while I was at it I also pulled off the spark plugs.#2 is BLACK and has heavy residue that smells like gas.#6 is white with a little bit of black and smells like gas.The rest are tan and perfect. They are NGK's with the heat range of 6. Buying new ones with heat range of 5.

The grounding straps I was talking about are off of a roll of 1" tin coated copper braid straps. I attached them to every area that could possibly have a grounding problem. I even have one long strap all the way from the trunk battery to the back of the head with multiple merges into the chassis.

[Darius]

Does #2 look wet with gas (i.e. shiny)? Could it be an injector leak?

[Fibre guy]

Hm... I havn't thought of that. I'll check.

[foulplay]

Any update? I'm in the exact same boat as you, I have had all the exact same problems since I swapped in my S1 RB25DET.

[Fibre guy]

Yeah, actually I pulled the fuel injectors and found out that one was crooked but looked strait. It was firing into wall making it drip down onto the intake.Also, the #2 coil pack may be bad. I swapped it out with the #1 coil. When I get all the injectors back in and seated right I'll see if the problem go's to cylinder one.

FoulPlay, I'd start with coils. To test if its a bad coil just unplug the coils one by one and see if the idle changes. For some reason when a RB's cylinder go's out you can't tell the difference by sound. That's how found my #2 might be bad.