1984 Grand National - Cold weather issue

[edfiero1]

I've got an 84 Grand National, converted to 87 ECU and using an LT-1 MAF with Translator.


For a few years now I have had an odd problem that shows itself in cold weather. When the outside temp gets below 55 degrees, I get an engine miss when the engine is under load.


The car will idle fine, but when you give it throttle before it is fully warmed up, the engine cuts out randomly for a second or two. This is not like a misfire on just one or two cylinders. Its more like a complete loss of power. After the car is fully warm, then the problem mostly goes away. There is no backfire. Just loss of power.


Since the problem began I've changed the fuel pump and ECU for other reasons, and the problem is still there. Fuel pressure is good. Also, just checked the throttle position sensor with a multi-meter and it is working fine. Voltage increases smoothly without interruption as the throttle is moved up to about 4 volts.


Anyone got ideas on where the problem might be? What troubleshooting I could try, or what to replace?
Thanks

[WASyL]

Sound like it need tuning on after start and warmup enrichment, tables and scalars regarding fueling vs IAT and ECT on temps where issue occurs

[edfiero1]

Sound like it need tuning on after start and warmup enrichment, tables and scalars regarding fueling vs IAT and ECT on temps where issue occurs

I have a chip in the car. The IAT is not used. Tuner hard coded the temp to 71 degrees. I checked with him and he said didn't sound like a tuning issue to him and lack of the temp sensor is not causing the problem.

I am thinking more of sensor problem. Like MAF, Crank Sensor, Cam Sensor??? Would any of them cause a problem like this?

[WASyL]

Cam, crank and MAF sensor don't know what engine or air temp is, so if it is temp related it must be one of temp sensors or tune issue. Only swapping MAF and using incorrect calibration might cause this issue but still it is because if tune not sensor by it self. If it would be one of sensor you mentioned car would run like crap all the time not only when cold. So my bet is that tune is wrong.