Hi guys,
I'm not even sure what I really seeing here.... It looks like I'm stuck in open loop for one thing.
The car is misfiring severly.
'93 ECU with a TBI chip, but it was running terrible befor the chip. I swapped the ECU as a trouble shooting step
Please help, tell me what you see
I tried to upload an excel table but couldn't, I can email one if it helps.
Thanks

 

I took a quick look at your data logs. It appears as if your O2 Sensor never warms up. This is evident from your idle log when Where is your 02 located? Is it a single wire or a heated sensor??

//RF

 

I'm seeing some error flags on both logs. Is your check engine light coming on?


MALFFLG1:23 IAT / MAT low (Air Temperature) (Code 23)

MALFFLG1:15 CT low (Coolant Temperature) (Code 15)

MALFFLG3:44 O2 lean (Oxygen sensor) (Code 44)


Are your coolant and air temp sensors hooked up? Are the sensors good? If your ECM isn't seeing the correct coolant temp, you'll never get into closed loop. Your fueling will also be affected.

I'd get these resolved first then take some more data.

 

Those malfunction flags do not match data. CTS data appears to be reasonable - starts at 69F and warms up to 180F. IAT data is not available. Idle TPS appears to be high 34 counts..

IMHO, WinALDL definition may not be entirely correct for this ECM. For 1991 to 93 B-Bodies used 16136965 ECM for both 5.0L (L03) 5.7L (L05) TBI for which there is no support in WinALDL. Data stream $62 definition (ADS) for 16136965 is supported under TunerPro-RT.

//RF

 

It's a new single wire, I installed a heated O2 sensor a while back because I have headers and I suspected the same thing, but the heated o2 sensor had no effect so I went back to single wire.

All the sensors are new, I have thrown every logical part at this and have nothing to show for it.

Here is the thread I posted awhile back

https://www.thirdgen.org/forums/tbi/...-mis-fire.html

You might be right about the flags being wrong. after warmup, if I unhook the CTS it acts like it switches into open loop.

 

I went back to original post for further reading on your current problem. Couple of thoughts on your lean misfire.

Have you re-verified your fuel pressure??? How did you measure FP (at TB, at fuel filter and what kind of FP gauge was used to measure FP) 9 PSI is a border line low. FWIW I like to see FP between 13 to 15 PSI.

Depending on the header design heated sensor is almost a requirement. O2 needs to be around 600F to be able to provide valid output voltage. 450 mV is a bias voltage provided by ECM.

Here is my theory on your situation: a combination of low fuel pressure and cold O2 sensor will keep ECM from entering close loop. Low fuel pressure will result in lean start condition and since O2 is cold ECM may not see true O2 levels in the exhaust gas stream. Take a look at SENSOR:rich / lean counter - ECM is trying to alter fuel, but there is no O2 change and after 300 seconds it gives up.

Steps

1) Get that FP to 13-15 PSI
2) Heated Delco Sensor (AFS-74) (3-wire)

//RF

 

I checked the FP at the throttle body inlet using a TBI Chips adapter and my cheap a$$ Harbor freight gauge. According to my FSM 9psi is bare minimum. I have been told to replace my fuel pump. Probably a good idea. I sold the 3 wire o2 sensor because it didn't seem to help me. Probably should try it again after getting the FP up

 

So.. I checked my FP again, now I'm showing less than 5psi.

Looks like it's time to do the pump.

 

Did the pump,
I installed a TPI pump and sending unit...

WOW! I had forgotten what throttle response felt like. It still has a small stumble at idle. My FP gauge is only showing 12 PSI, which means either my cheaps a$$ harbor freight gauge is not accurate or my factory regulator needs help. I have a CFM-tech adjustable regulator that need to stick on this TB.

 

The little of idle stumble maybe a TPS/MAP AE issue. The only sure way to get rid of this is to have WBO with both TPS and MAP coupled to it (unless you have EBL ECM) and extensive data logging. With higher pressure the TPS AE maybe dumping a bit too much fuel and causing that of idle stumble. I would suggest that, if you have the budget, to invest in a WBO unit (ZT2, TT-1, etc).

//RF