Rb20Det Breaking Up Past 3500Rpm, Pig Rich.

[rx-line]

Hey all,

I have been losing my shit while my car is in the paint booth with the weight of it not running right. Currently the car is running pig rich in the 10 afrs with a high idle and is spooling the turbo and stuttering past 3500rpm in the neutral position. It almost sounds like anti lag.

Having discovered this I since checked the TPS and replaced the MAF sensor, the new-used OEM MAF cleaned up the idle a bit and the car no longer died after any amount of throttle but the two-step action is still present. I have a new temp sensor on order, the only other thing that comes to mind is the Oxygen sensor but I cannot see how either would effect it so greatly.

Surely there are others who have overcome this, as I have read about others with the same propblem but with no posted fix,

RX,

[Ben C34]

Boost leak.

[GTSBoy]

Whilst Ben is probably right.........you would be well advised to put the useful bits of information in your post that would actually help people to understand your problem. Things like, what ECU, what ignition, has it been tuned, what were the AFRs under load when it was tuned? etc etc. For example, did you know that RB20s tend to run 10:1 AFRs when teh boost is turned up on the stock ECU anyway?

[rx-line]

Yes that would help, it has a mines ecu, fmic, custom plenum, custom charge piping, bov, fpr etc. Stock ignition

It ran 12's afr's when I first installed the wideband whilst still running the oem o2 sensor. It always ran fine with a slightly high idle as my cold start and iacv share the same vaccum line. And it ran fine, after working on the body for a couple months I started it one day to it going in and out of rich and normal afrs. And now it will not pull itself out of being pig rich and 15 psi vaccum at idle.

Seems to me like it's not a boost leak as it shudders before it builds any amount of boost. Seems like it's running rich with on a retarded map.

Rx

[scotty nm35]

Well something has changed, and it is most probably a leak.

Pressure testing the intake is easier than making a post describing the most common problem on any turbo car.

[rx-line]

You guys are a funny crowd, I've ran the car with no charge piping and it revs through the range fine whilst being pig rich, I'll figure it out sooner or later and post what the actual problem is. Thanks for the help I guess.

RX

[CEF33Y]

Check crank angle sensor, it might be cactus or not plugged in all the way. I've had that happen to me before

[Ben C34]

You guys are a funny crowd, I've ran the car with no charge piping and it revs through the range fine whilst being pig rich, I'll figure it out sooner or later and post what the actual problem is. Thanks for the help I guess.

RX

Your a funny guy, removing the intercooler pipework and refitting it without then pressure testing it.

When you find a boost leak be sure to report back.

[rx-line]

So far I've checked the ecu and have got the 55 "all good", tightened all the silicone couplers for the charge piping but nothing yet, Thinking of loosening the BOV a bit, changing the fuel and changing the oil as there is a slight gas odour.

[Ben C34]

Ok.report back when you have pressure tested the inlet aysyen

[Dose Pipe Sutututu]

so you can't rev it past 3500rpm?

and your AFRs are super rich?

sounds like you need to check continuity between your ECU & AFM.

Also another worrying thing I've noticed.. you've got an aftermarket FPR & re-mapped/stock ECU.

[Ben C34]

So far I've checked the ecu and have got the 55 "all good", tightened all the silicone couplers for the charge piping but nothing yet, Thinking of loosening the BOV a bit, changing the fuel and changing the oil as there is a slight gas odour.

How will loosening the bov or an oil change help at all?

[rx-line]

How will loosening the bov or an oil change help at all?

Changes in vacuum? and oil filled with fuel can create an increased liquid amount could create blowby?

Anyhow I found that the red wire on the oxygen sensor was broken and repaired it, after the repair and having the car warmed up allowed my car to regain proper AFR's and rid itself of the choppy revs. It's quite funny that you were so sure of a boost leak that you went out of your over confident simpleton ways just to prove what you thought was a valid point!

To anyone reading this thread with similar problems besides this stagea fanatic , I would definitely recommend you check your o2 sensor with a multimeter.

BT

[Ben C34]

Thanks for the feedback.

In 90 percent of cases it is a boost leak. It is so easy to check for it should be checked anytime you touch the pipework.

Your suggestion of adjust bov and oil change is far crazier.

So is your car actually fixed? Or just idles nicer now?

[Blackkers]

fixing the O2 sensor won't change anything other than cruising AFRs.

Oil change? seriously man

[rx-line]

Nope I drove it and It keeps proper AFR's whilst under load as well, I know neutrul rev's aren't the best indicator of problems and correct afr's but it worked well as a baseline as I knew where it should be. It runs rich in cold start and then you can hear a noticeable change in idle and then it run's 12's afr's after the O2 was fixed. Run's better than ever.

If your oil level is above normal and contains fuel, I would assume you will get blow by which could cause numerous problems no? Explain to me how this would not effect things please, rather than saying how would that work. I don't attest to knowing everything but I sure won't take your advice without explanation. I figured it was a good idea to change anyhow. I did not once say it was the problem but I new there was a chance it'd help.

Fixing the O2 sure does change afr's, I know for a fact it sends a reading to the o2 and at .5v would be supposed proper afr's at idle. I wouldn't think the ecu would disregard this at idle.

RX

[Blackkers]

You'd have to be burning an absolute shitload of oil for it to be a problem. In that case you've got other issues to look forward to. Yes oil collects blowby gasses but it is a very small portion of the oil itself and even less would make it back into the cylinder.

The thing is that the ECU doesn't even reference the O2 sensor at idle or at decent throttle. The ECU completely ignores what the O2 sensor says unless you're cruising at light throttle off boost. Soon as You've got some boost it goes back to open-loop meaning no correction based on the O2 sensor.

How did you decide that your AFR's are in the 12's again? Do you have an aftermarket wideband?

[rx-line]

Yes I have an innovate wideband running separately from the computer. The old O2 sensor was shorting out, may have caused the problem? Anyhow the new o2 fixed the problem oddly enough.

RX