Running rich

[buick8791]

Hi,

Our GN 87 is running very rich from starting cold(about 20 celsius degrees). sputtering and black smoke coming out from the pipes

But, when the engine has achieved the normal operation temperature (about 70 -80 celsius degrees, cold thermostat) the car is running fine.

There is some problems with the maftpro(doesn´t keep the monitoring display when started the car, display is the boost control phase), but I always set the display on monitoring display when the car is running, no avail.

I feel, that the problem is not in the maftpro, because the car is running fine when warmed up.

I doubt, that the problem lies in the two wire cool coolant sensor with the yellow and black wire .

So, how to test this sensor properly, take it in to the kitchen and put it into the waterpan with the thermometer and connect the ohm meter on the sensor connectors?

I have the ohm and corresponding ohm values.

So, how to proceed with the problem?

Thanks in forward,

and greetings from Finland!

[maxwedge]

See what the coolant temp sensor is telling the ecu when cold, should read on a scanner. Post back

[Blue Bowtie]

The typical GM temperature sensors (coolant or intake air) should be close to the following table:

[buick8791]

Thanks for the answer!

I haven´t the scanner. Anyway, the bad coolant sensor should give the fault code 14 or 15. I have got only the code 45, running rich with the paper clip system from the aldl connector. But thanks for the good table regarding the ohms and temperatures for the sensor!

So, what next?

BR,

buick8791

[maxwedge]

The ecu may not recognize a bad coolant sensor it could assume 10 below is right, then it is really rich, confirm your cold sensor readings from the chart. Also if original, replace the o2 sensor, cheap enough.

[buick8791]

Thanks for answer!

To day`s measurement:

GN cold as the sensor, the plug off fom the sensor:

Measured: 18C/3700 ohms, table says 20 or 21C/3400 ohms.

The rich condition is intermittent, some days all are ok, some days not.

Is it ok regarding the measuremets/the table values or is it the time for the new sensor?

BR,

Buick87/91

[Blue Bowtie]

If it was reasonable to assume that the coolant was around 65°F, it seems close enough.

A bigger question is whether it is consistent.

[buick8791]

Thanks again!

Yes, I feel same as you wrote. Thermistors are thermistors and are not ever lasting.

By the way, the sensor in the engine is not original. I have renewed it some years ago for some reason, I don´t remember why. I feel it is Standard brand.

I found the original one in my box and it is ok when measured in the table test,
a little bit better regarding the results than in the engine at the moment.

But, old are old and I will look in RockAuto pages, what they have. Recommendations for the brand?

Thanks again,

BR,

buick8791

[buick8791]

To days trip about 10 kilometers everything was well, the car was running very fine from the initial start. Only things what I have done were pulling and pushing back ECM connectors several times and also the sensor connector while testing the sensor. Yes and charged the battery full.


But, anyway I will order the new sensor. RockAuto sells also AcDelco ones, the price is about 45 or so Euros delivered to home door.


BR,

Buick8791

[buick8791]

Hi Maxwedge,

you proposed to renew the O2- sensor if original.

I have renewed it several times. But regarding the running very rich from the initial start, the engine is in the open loop and the o2- sensor doesn´t participate in the mixture ratio then.

But, maybe you meant, that O2 sensor is gone anyway because of the rich condition.

So, it has not gone, because the car is running well during the three trips without any codes and black smoke. let´s see.

Thanks for all!

Buick8791