TBI Question

[greg0380]

I swapped an 87 tbi onto my engine. It runs great except I think it is running rich because it smells rich and if you get anywhere near the exhaust it will make your eyes water. Vac. sensor is new, O2 sensor is new, I have the correct injectors for the 5.0L, IAC is new. Any ideas? If I look at the O2 reading with the scan tool what types of readings (voltages) should I be seeing. With the scan tool I don't see anything unusual but I am not 100% sure of what to expect with the O2 readings. TIA.

[ChevyTech]

With the engine warmed up:
Watching the O2 voltage, you should see it bouncing all over the place between 0.1-0.9 volt. It should be constantly moving.
If it is only varying between 0.3-0.7 volt, this is what is refered to as a "lazy" O2 sensor.

The quality of the scan tool may effect how often the Voltage is captured by the tool. If you watch it for a while even with a cheaper tool you should still see it move to the extreams.

Good luck

[greg0380]

Those are the kinds of numbers that I am seeing (.1 - .9V). It is a brand new Bosch sensor. What could make it run rich? My exhaust tailpipes show black and it stinks. I checked the plugs a couple fo weeks ago and they didn;t show black. Mostly tan and gray but I am not an expert at reading plugs...

[ChevyTech]

The first thing that comes to mind for running to rich is a bad coolant sensor.
Being you looked at it with a scan tool I would assume you are getting no trouble codes and the coolant temperature looked believable.

Are you runnig a 195 degree thermostat?
Does it seem worse cold (open loop) or warm (closed Loop)?
What are the block learn and integrator readings?
Are the computer and prom (chip) for your vehicle or from another vehicle? What is your vehicle?
Excessive hydrocarbons (unburnt fuel) will make eyes water. Do you have a big cam (long duration)?
What is stock, what is not?

[greg0380]

The engine is stock in an 85 1/2 ton 2WD. The TBI is off and 87 suburban 350, I located the correct injectors and tried 2 proms. One PROM I was able to burn myself (downloaded a bin file off the GMECM site, the other I bought from a site "TBICHIPS"). They both seemed to run the same as far as running rich. The TBICHips prom gave the engine alittle more power though.

THermostat is 195, the ECM shows 188 when fully warmed up. Definitelyh seems worse when cold but still stinks when running warm.

When running BLMs vary between 108 and 140. I thought they should average around 128, right? The BLM values really didn't change when I swtiched Proms.

INT vlaues show alot of 128, but vary from 122 to 140.

No trouble codes are set. I should point out that I am not using a catalytic converter.

[ChevyTech]

Originally Posted by greg0380

When running BLMs vary between 108 and 140. I thought they should average around 128, right?

Yes, 128 is the center point between rich and lean.

Things don't seem to be far off if you can get these readings.

You said the block learn did not change much when changing chips. Did you give it considerable run time to change? The block learn changes slow. The integrator changes fast.

Coolant temperature is critical and directly effects the mixture. The electronic spark timing does not run its self test until it sees the sensor temp cross 194 degrees. If you do not see 195 during warm up or driving I would try another thermostat.

Are you running the 1987 distributor so you have electronic spark timing controlled by the ECM?

A warmed up catalytic converter would burn the hydrocarbons that make your eyes water.

[greg0380]

I have been running the Prom for about 3 weeks. I logged that data during a drive to work and i can see that the coolant sensor never got above 190 deg. I do know that the t-stat is 195 (I put it in). Since I never before had an opportunity to see what the actual engine was running at temp-wise, I wasn't sure how closely the thermostat would regulate the temp. I didn't know that the temp had to cross 194. Is that what contols closed loop? I can see that the closed loop flag gets set and stays set.

Yes, I am using the 1987 esc contolled distributor.

[ChevyTech]

No you do not have to cross the 194 temp reading to get in closed loop. When the ECM detects active voltage activity on the O2 sensor (for a specified time) it goes into closed loop.

It's a good thing your using the 1987 distributor.

Resistance on your coolant sensor circuit will also give you a colder than actual temp reading.

Being you are not crossing the 194 temp threshold for the self test of the electronic spark timing, it could have a problem without setting a code. If you did have a problem with that circuit you would probably be asking about more drivablity issues.