The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support Morrison Fabrications
Please Support Fuel Injector Clinic

Lean condition that has me stumped

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

turbo tim1

10+ Year Contributor
163
5
Sep 16, 2010
Pine lake, AB_Canada
A friend of mine brought me a 90 talon in pieces, I put in a new engine and am now at fire up stage, the car starts but idles lean (brand new aem wide band guage) it has the a/f pinned lean at idle, it revs up fine but idle is so lean that it almost wants to stall out.
here is what I have done so far.
1. put a fuel pressure gauge on it to see fuel pressure which is at 45 psi.
2. I have installed a 400 lph walbro fuel pump, changed nothing. tried changing the fp reg aswell, still lean.
3. put the return fuel line in a bucket, that fuel pump is moving a shit ton of fuel through that rail and regulator so flow is not a problem.
4. I have slowely pinched of the return line watching the pressure on the gauge climb to 100 psi essenstially dead heading he pump and no change in A/F which I find very odd, usually that will make a car go rich.
5. swapped ecu's no change
6. checked the wiring at the ecu to see if some one at some point switched pin 6 and 14 around, and for shits and giggles I switched them around, no change so I switched them back.
7. swapped out the incjector resistor pack, no change.
8. found that some one had wired the top coolant sensor wires to the ecu coolant sensor located next to the single wire sensor thats for the gauge and they had tied off the ecu coolant sensor wires, so I fixed that, the car starts better but still lean.
9. car gets a little richer with air meter unplugged but still pegged lean.
10. car has maf translator and 550 cc incjectors, maf translator is backed off as if it has the smallest injector size. I tried a factory air meter and factory injectors, car is now really lean, so I swapped back in the 550s with the factory air meter, it richened up a bit but still pegged lean on the new wide band gauge.
11. checked the voltage supply going to the injectors, tested out at 11.9v Key on engine off, while running it has the same voltage that the alternator is kicking out. 13.9v

I have been around these cars for a long time, but this problem has me stumped.
t belt in time and timing is set at 5 degrees total at idle, firing order is correct.

any advice would be much appreciated.
 
Do you still have the stock o2 sensor installed? If so what is it reading. I dont think your wideband is reading correctly though cause full lean on that gauge and your car would be misfiring and stalling
 
Do you still have the stock o2 sensor installed? If so what is it reading. I dont think your wideband is reading correctly though cause full lean on that gauge and your car would be misfiring and stalling
the car does miss at idle, and the plugs are white, I havent driven the car yet, I want this part sorted out first.
 
Sounds like your intake manifold gasket to me.
the intake mani gasket is new, plus I smoke tested the entire system for leaks, there are no leaks.

Does the car still have the oem oxygen sensor installed? What is the Vacuum at idle ? What tuning device (ecmlink safc or just maft)
yes the car has an OEM botsch o2 sensor that is brand new.

Confident in maf translator version and setting? Re read on full throttle tech to be sure
when I tried with the maf translator the AUX set to 0 and base is set to 0, this is the setting for the smallest injector size and with stock or 550's the a/f should be retarded rich.
 
the only thing I havent done yet is check all the grounds on the wire harness, I dont know the history on this car, it is possible that some one has monkeyed around with the wire harness.
 
Bosch 02 sensors arent the greatest. Theyre hit and miss working even when new. Im going to assume the car is running off the bosch o2 sensor and youre just using the aem for tuning. You need to check the o2 sensor. Make sure you have power and ground and at the right wires. Also check the maft wiring and set up( set up for correct maf 3" or 3.5" ) . Do you have anything for logging? Fuel trim, airflow, and o2 reading at idle to help you
 
Bosch 02 sensors arent the greatest. Theyre hit and miss working even when new. Im going to assume the car is running off the bosch o2 sensor and youre just using the aem for tuning. You need to check the o2 sensor. Make sure you have power and ground and at the right wires. Also check the maft wiring and set up( set up for correct maf 3" or 3.5" ) . Do you have anything for logging? Fuel trim, airflow, and o2 reading at idle to help you

yes the car runs of the factory narrow band o2, I have tried running it unplugged, the car should run off a default map when it doesnt see a sensor. I have played with the dip switchs on the maf t, every variation of air meter size, seems to run a little richer when on the largest maf air meter setting.

there is not logging on this car, I am littererally going off aem wide band o2 gauge in real time and plug color. I believe the wide band to be correct because the plug color is white and it intermitantly miss's while idling

I am going to go through all the grounds on the harness again on the week end and see if there is one or more that are not hooked up.
 
so I tried a different smoke machine and found a bad intake mani gasket, I feel like an idiot now cause I didnt find the leak before when I smoked it with a different machine. also the leak was not audible and the car did not idle high, I suppose had I used a vac gauge that also would have told me somthing was up.

any way I replaced the gasket and now the car runs good.
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top