This is not a mass air flow 302 but it has a maps sensor so its speed density. Lately it has been running horrible. Very rich. Black smoke out the tail pipes. I don't get any codes with my scanner. The issue is it won't start unless you put your foot to the floor with the gas pedal. It runs rough on initial start up but then smooths out. If you shut it off then go to fire you have to put the gas pedal to the floor again and black smoke out the pipes. I realize it has to be running rich but how and where do I start to correct this issue. It was running fine until the last month were it started doing this all the time. Previuosly it might do this once and a while but it was rare. Please help thx in advance.
Starting blues
- Thread starter 86bluecobra
- Start date
Fuel pressure was what I was thinking. This is on a EFI 302 however. I am getting black smoke and black liquid comming out of my tail pipes. I just don't have a fuel pressure gauge to check on the shrader valve. I changed the o2 sensor the old one was completely carboned up, coated completely. It has to be running way rich but not getting codes.
I wondered about that but I had one fail on a v-6 tarus and the thing just quit. I don't know if they work poorly or if they just give up the ghost. I always kinda thought they worked or they didn't.
I agree with checking the MAP out further. Ensure the vac line to it is good and that it doesn't have holes, etc in it.
I have experience with a sensor failing. It ran a bit like your car is.
Just something I'd really go over.
Good luck.
I have experience with a sensor failing. It ran a bit like your car is.
Just something I'd really go over.
Good luck.
Hot start problems characterized by black smoke and rich running after startup are usually a ECT that is borderline.
Dumping the codes will normally show a faulty sensor. The ACT & ECT may be on the outer limits and not set a code but cause problems. Use a DVM or multimeter to check them.
Pin 25 ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.
Pin 7 ECT signal in. at 176 degrees F it should be .80 volts
The ACT & ECT have the same thermistor, so the table values are the same.
Here's the table: The values are +/- 15%, so don't get worried if your readings vary a little bit.
Voltages are measured across the two connector pins of the sensor with the sensor connected. Some safety pins used to probe the connector from the rear will be helpful
50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v
Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms
Dumping the codes will normally show a faulty sensor. The ACT & ECT may be on the outer limits and not set a code but cause problems. Use a DVM or multimeter to check them.
Pin 25 ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.
Pin 7 ECT signal in. at 176 degrees F it should be .80 volts
The ACT & ECT have the same thermistor, so the table values are the same.
Here's the table: The values are +/- 15%, so don't get worried if your readings vary a little bit.
Voltages are measured across the two connector pins of the sensor with the sensor connected. Some safety pins used to probe the connector from the rear will be helpful
50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v
Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms
I'd check the ECT signal output. If it looks good at the sensor, check it at the puter.
If it doesnt look good at the sensor, check the incoming voltage and then disconnect the sensor and check resistance.
If it doesnt look good at the sensor, check the incoming voltage and then disconnect the sensor and check resistance.
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