Irocw89

iTrader: (1)

I have a 89 Iroc, 350 TPI. it has been running rich for about 10 months it is also giving me the lean exhuast code and I have done all i know and still no progress. it is spitting out billows of black smoke out the back and the mpg is at 10-12, used to be at 18-20. i have changed the spark plugs 3 times each time they are covered in black sut. last time i put a msd blaster coil, taylor wires, and a heated O2 sensor, still gatting lean exhuast. i have long tube headers, no cat, borla rear, Apr adjusted as low as it can go (40psi), ported valves, modified mass air, no screens, k&n filter.

If any one can help me please do

Thanks

arec2001

I have the same problem did you figure it out?

Irocw89

iTrader: (1)

I havent figured it out yet, I'v talked with a couple of freinds, and since all 8 are running rich we think the problem might be a bad computer vs leaking injectors. I plan on taking it in for a diagnostic next week and possibly changing the computer. I will let you know how it turns out.

let me know if you get it figured out first.

arec2001

I actually suspected my injectors at first and had them cleaned and flowed. They were fine. Then I suspected the fuel pump (thinking it was pulsating and causing erratic operation), but changing it didn't help. The computer is only 2 years old, so I don't blame it yet, although it is a reman...

My latest theory is that it could be a large vacuum leak.

Vader

You should check for exhaust leaks. Also check the air injection diverter valve operation and A.I.R. plumbing, check valves, etc. If you are admitting air into the exhaust in front of the O² sensor, you've just discoverd the problem.

Do you have a running O² voltage reading? If the exhaust is rich but the O² is indicating lean, you likely either have a problem with the sensor, sensor circuit, or leakage.

If that doesn't help, check the MAF output voltage at a known steady RPM. Your's wopuldn't be the first time a MAF reading got FUBARed by screen removal. They exist for a reason, you know, and it ISN'T just to keep leaves and insects out. You can get an incorrect readign without setting a DTC, which could be part of your problem.

arec2001

I don't have the smog pump connected but do have the air tubes (edelbrock headers) plugged up. Maybe air is getting in somewhere? I'll check.

What baffles me is that before I used a heated o2 sensor, I always read lean (hovered around 200mv +- 40) but now with the heated o2 it starts up at 1024 for about 3 minutes, then it drops to around stoich, does 200 or so crosscounts, and oscillates between 0 (for 30 seconds or so) and 150-200 (for 8 seconds or so). This is at idle and while driving.

My MAF is totally stock, and I believe it isn't working right because when I go WOT, it only reads 55-60gps. Shouldn't it read more? For the past few months the car won't go over 4000rpm, no matter how long you hold it at WOT, whether while in neutral or through the gears. It acts like it's not getting enough fuel, yet the fp, regulator, and injectors have been changed or serviced. Add't, the base PW rarely exceeds 7ms. Maybe the MAF is clipping the signal?

Vader

That MAF reading sounds really low. Is that scan data from teh ECM, or are you reading the DC voltage from the MAF and scaling manually? I'd suggest getting the voltage from the MAF to see how it compares to the 0-5V (0-255 g/S) scale.

And, are you getting the O² mV reading from the ECM serial data or directly from the sensor lead?

arec2001

I've obtained all of my readings from serial data. I'm using Craig Moates' ECM845.

I'll see if I can get the MAF reported vs actual voltages tomorrow.