Corrado Running Lean...Need Help

[popeye775]

Hi all,

I am new to this forum. I am apart of Vortex and The-Corrado forum as well. I am trying to get as many opinions as I possibly can. Here is my issue: My 1990 Corrado G60 is running lean. I have a wideband installed and am getting 16-18 AFR while idling after warming up a couple minutes, 14.5-15.5 AFR while cruising, and the lowest it will go at wide open throttle is 13.5 AFR. When I come to a stop, the AFR will be at 14.8 for a couple seconds and slowly creep back up to that 16 range. Here are the things that I have done recently:

- Spark plugs

- Injectors (stock size)

- 268/270 Cam

- BBM stage 3 chip

- 3.5 bar pressure regulator (currently set to 3 bar because fuel pressure gauge freaked out at around 3.5 bar)

- All new vacuum lines (the ECU vacuum hose is exactly 1m and OEM spec long as per the bentley/the FPR vacuum is not the braided factory spec though)

- Smoke tested

- Fuel pump replaced 5k miles ago (along with the fuel filter)

- Fuel lines replaced

- Timing checked

- Spark plug wires replaced

- CO Pot set to 250 ohm

- Fuel injector wiring replaced

- Intake Manifold Gasket replaced

- New ground wires

- New relays and new CTS as well

The other thing that I have done is done a leak down test. To which I did find bad piston rings (or worn piston rings in two cylinders) but was not sure if this could be the cause of the lean running conditions or not. Valves are good, and head gasket is also good. The other things that I also have are new 30lb injectors that I can put into the car whenever needed. I do have plans for the piston rings already, but again I am not sure if this can be the issue to the lean issue or not. Any recommendations or tips would be greatly appreciated. I am not sure how many people are on here anymore, but if there is anyone still on here, any recommendations on things to look at?

[ps2375]

Is the WB installed in addition to the ECU's sensor? If so, are both sensors in the same general location on the exhaust?

[Butcher]

How does the engine run?

How do you know your wideband controller is even working properly? Small exhaust leaks can cause issues.

[TDCTDI]

Sounds like too much shit has been done to “improve performance”. In my experience, only but so many modifications can be made before they stop playing well together. First & foremost, are you running a stand alone engine management or just a rechip/tune on a stock ECM? The stock ECMs are designed to run lean & oddly have a way of running home to momma to override any sort of performance tune overwritten onto them. This also tends to cause the ECMs to just take a shit & quit altogether.


Definitely do a smoke test on the exhaust side as well.
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[popeye775]

Hey guys,

So the wideband is installed next to the ECU sensor. I got a bung welded on right where the wideband requires. The reason i say it runs lean as well is by looking at spark plugs throughout this process. I’ve been pulling plugs and looking at them to make sure that it actually is running lean. I can post a photo of the spark plugs as well. As for ECU, i am running stock ECU. I’ve been working with BBM when it comes to tuning my Corrado. I attached both photos of the spark plugs.

Thank you all in advance for the replies as well!

[ps2375]

Is that plug pulled after some idle time or was the motor shut down during a WOT run and pulled? IT makes a diff when trying to read the plug.

[popeye775]

[ps2375]

When you "read" a plug, you shut the motor off at the point you want to read it for. Anything else is hit or miss for reading the plug.

[popeye775]

[ps2375]

[popeye775]

Hey guys,

For anybody still following this thread, i made some headway. I replaced the ECU vacuum with OEM vacuum hose. It helped a bunch actually. Cruising around 2k RPM the car runs at ~14.8 AFR. When I’m driving and come to a stop, it will stay at about 14.5-14.8 AFR for a second but then slowly creep up to ~16-17.5 AFR. WOT is around 13.5-14 so still a little lean. I haven’t pulled plugs at WOT in a bit so I’m unsure if it’s just an exhaust leak causing my wideband to freak out or not but any opinions from anybody still following this thread?

[ps2375]

Get some quality vacuum line at Silicon intakes .com. They have a thick wall hose that won't collapse and will last longer than the car. Sounds like you might be making head way.

[popeye775]