poor idle after warm restart

[grimreaper]

I suppose the thinking is that the fuel pressure is low during this rough idle, although that is not confirmed by anything I read above.

That said I don't understand the following post. The fuel pressure should be constant under steady state conditions like idle. What is all this jumping around from 32 to 25 psi? Maybe I just don't understand what he is saying or doing!

while starting it spikes, when idling it is steady

 

[grimreaper]

ox to bat (-) stayed around .01-.02 v.
when i unplugged the o2 sensor, it did nothing to change the af ratios or idle quality.

i had to reset it so ill compare the idle vf to the o2 after a drive... is this heading in the right direction?

 

[3p141592654]

Do you see it cross-counting when it is idling properly in closed loop after the idle problem goes away? Also, is the sensor heater drawing current?

 

[grimreaper]

ill have to check the cross count.
The ecu supplied 12.3v (exactly what the battery measured at) with the key in the on position and 13.84v. right after startup. heater circuit showed the resistance to be at 8 ohms when it was warm/hot to the touch. Resistance has increased more then 2X from when it was dead cold, normal? it should increase but is the extent that mine showed correct?

 

[Nick M]

Do you see it cross-counting when it is idling properly in closed loop after the idle problem goes away? Also, is the sensor heater drawing current?

Is cross count an input when the IDL contacts are closed? I don't see where it is. But then again, I have no refrence in front of me, only the interent. http://www.autoshop101.com/forms/h26.pdf

It is hard sometimes to diagnose a car you aren't looking at. I think he has a small mechanical hiccup. Like a dashpot that is hanging open just a bit. When he opens the throttle and speeds the engine, the bad idle goes normal. The air reseats the dashpot, and throttle plate.

I know that in OBDII, closed loop happens as soon as the engine is warm, and does not come out unless you decelertate with the throttle closed or hard accleration.

 

[grimreaper]

o2 is good. Tested per tsrm.

i will check the dashpot, however it was allowing the desired 1 second close rate and the TP fully closes when i had the tb off.
Noticed something odd. I started it up and let it idle for a few minutes in near freezing temps. Wideband starts at 12.0 and over the course of 2 minutes works it way to 17.7. I thought cold start enrichment was supposed to stay involved until 176 degrees F and the car was not even at a 100 degrees yet.

Can a crimp in the ecu temp sensor wire (wire broke off due to heat/ age at connector) create enough resistance to affect what the ecu reads? The sensor ohms out perfectly per tsrm. Is there a way to see what the ecu is reading for coolant temps and not just the gauge?

 

[jdub]

Not only the crimp, but the old wiring may be an issue as well.

Did you read ohms by referencing the chart in the TRSM? You have to heat the sensor up in a pot of water using a thermometer and read K ohms per the chart left side.

Is your WB O2 calibrated?

 

[grimreaper]

I used a laser thermo gun along with the aftermarket coolant gauge to verify the ohms-temp range that the chart specifys. Ill pull the sensor and boil it this evening to double check it.

Ill test the circuit wiring as well and see what i find for resistance.

WB is an AEM and cant be calibrated. (4 months old, with maybe 2000 miles on it...)

 

[Nick M]

i will check the dashpot, however it was allowing the desired 1 second close rate and the TP fully closes when i had the tb off.
Noticed something odd.

That is only an example, but worth checking.

Can a crimp in the ecu temp sensor wire (wire broke off due to heat/ age at connector) create enough resistance to affect what the ecu reads?

Yes, but it will read colder. The thermistor is NTC.