Engine Cold start problems due to sensor? But which one, no parts cannons!

[AeroCoupe]

You need to check the 5v ref wire to see what the voltage is when the sensor is plugged in. You commented that all the sensors are off brand so it literally could be a bad sensor causing the problem.

 

[beeduckworth]

I've since changed all to motorcraft, still have the same problem. Figured better off to have legit quality sensors even if they aren't bad. I have 5 volts when plug is unplugged. Then when plugged in and coolant is 80 degrees I was around 2.6v so that all checks out.

 

[vferrizz]

I checked vacuum leaks with a smoke machine, nothing. Yes it does still have an egr but maybe it's not functioning well. What confuses me the most is while running poorly, if I unplug the ect then the car runs perfect during cold start/ warm-up. I don't see egr as an issue or it would be an issue with ect unplugged....correct?

If you unplug the ECT, voltage output is 0VDC to the signal return path to the ECU pin 46. Low voltage out of the ECT correlates to warm engine temperature. The TPS, ACT, ECT and EGR outputs all go through the white salt and pepper shaker pin 1, which is the signal return to ECU Pin 46. The way I understand this is all 4 sensors have their output voltages summed together and the total voltage signal goes to ECU pin 46.

 

[beeduckworth]

If you unplug the ECT, voltage output is 0VDC to the signal return path to the ECU pin 46. Low voltage out of the ECT correlates to warm engine temperature. The TPS, ACT, ECT and EGR outputs all go through the white salt and pepper shaker pin 1, which is the signal return to ECU Pin 46. The way I understand this is all 4 sensors have their output voltages summed together and the total voltage signal goes to ECU pin 46.

Ah I see ok, well the only problem I see here then is the egr voltage being an issue because it throws a code. That must be the missing voltage back to the ecu to run correctly. The tps, ect, and act are all correct in spec, only egr is not working, I have no vacuum to the egr so I'll have to sort that out and see what vaccum lines are incorrect.

 

[beeduckworth]

Well I found that the egr is activated on cold start and this is what's causing the bad idle. When disconnected it closes and runs well so I'll need now figure out how the vacuum is routed to fix that up. Is it supposed to be open on cold start open loop?

 

[AeroCoupe]

Does the car still have the two solenoids on the back of the passenger shock tower? If so the source of the vacuum for the EGR comes from them:

 

[beeduckworth]

Does the car still have the two solenoids on the back of the passenger shock tower? If so the source of the vacuum for the EGR comes from them:

Yes but there is another relay above those that has a line running to egr. Looks like the computer opens and closes that relay based on pintal valve on egr reading. I had the rgr off and it can press it in with my thumb so it's not stuck but maybe the sensor doesn't read right and miss informing the computer. I have a new one anyway to throw on and see what happens.

 

[vferrizz]

Well I found that the egr is activated on cold start and this is what's causing the bad idle. When disconnected it closes and runs well so I'll need now figure out how the vacuum is routed to fix that up. Is it supposed to be open on cold start open loop?

EGR should be closed at idle when cold and at WOT. Below are some vacuum routing diagrams:

 

[beeduckworth]

EGR should be closed at idle when cold and at WOT. Below are some vacuum routing diagrams:

Yeah the evr controls vacuum to the egr, it does close when car gets to operating temp(closed loop) why the valve is told to be open by the computer I don't know, so I'll have to figure out what tells the computer to open that. Then I should be good to go.