Cold Start Issues - Engine sputter (77 280z Auto)

[Yarb]

I had the same issue your experiencing and I basically set it to the factory idle speed after the aar closed.

[MH77280Z]

On 2/5/2022 at 11:22 AM, Zed Head said:

Pumping the pedal will only have an effect if you get the TPS to full throttle "full enrichment".  This will increase the fuel through the injectors by 27%.

Kind of sounds like you have low fuel pressure or a leaking FPR or fuel pump.  Pumping the pedal adds some fuel, keeping the engine going until fuel pressure builds up to where it should be.  You could probably just hold the pedal wide open and get the same effect, except it would be scary when it finally takes off.

The AAR will be just like holding the throttle pedal slightly open, except that you'll lose "idle enrichment", which probably isn't much.

@Zed Head and all I am back to start. Today I had my AUX Air Reg still bypassed (waiting for the rebuild to arrive) and cranked the engine and had the same uneven sputtering issues. Once it warms up it runs and idles fine. But cold start is EXTREMELY terrible. I dont think i should change any settings of the air bypass screw on the AFM as the engine idles fine when it is warm.

I have not pulled the throttle body for cleaning like @siteunseen has suggested. I plan to do that.

What should be the logical next step?

 

 

[Zed Head]

2 hours ago, MH77280Z said:

cold start is EXTREMELY terrible

Need details.  Without the AAR you would need to hold the throttle pedal down with your foot to keep RPM up.

[siteunseen]

My original AAR had the electrical coil windings break loose. The part that has the electrical connector would slide out if I remember right. I found a good one at an old junkyard locally. I've read where people put them in boiling water to see if they close but I don't think that's good since there are electric windings. Maybe a hot hair dryer or a heat gun would let you test it?

I could have glued the innards back in I guess but found the better one.

[siteunseen]

Here's what I'm talking about. That flat blade heats up and turns the metal disc inside the housing. Opening and closing it.

Edited February 25, 2022 by siteunseen

[MH77280Z]

8 minutes ago, siteunseen said:

My original AAR had the electrical coil windings break loose. The part that has the electrical connector would slide out if I remember right. I found a good one at an old junkyard locally. I've read where people put them in boiling water to see if they close but I don't think that's good since there are electric windings. Maybe a hot hair dryer or a heat gun would let you test it?

I could have glued the innards back in I guess but found the better one.

I tested a second used AAR i bought of ebay which is also about 1/4-1/3 open etc. The car had same issue. Once it warms up the engine is more smooth on idle as well. Once it warmed up in 10 mins i took the AAR out and inspected and it was fully closed. After 15-30 mins at room temp it does opened up 1/4-1/3.

Initially i thought the car was too rich due to AAR closed and hence the bypass. Now with the AAR as well it has same issues.

 

 

 

[siteunseen]

Has anyone mentiond the cold start injector? Sometimes they add too much fuel on warm up. The fuel sensor bullet connections are also suspect.

[Zed Head]

On 2/4/2022 at 8:06 PM, MH77280Z said:

Cold start is giving me issues, the engine sputter and try to die. If you pump the gas it is uneven, sometimes it suddenly jumps to very high rpm, i mean u really have to keep pumping the paddle to get it running.

3 hours ago, MH77280Z said:

cold start is EXTREMELY terrible.

Same thing?

[siteunseen]

Have you cleaned all the brass sensors in the thermostat housing? That helped mine.

[MH77280Z]

18 minutes ago, siteunseen said:

Has anyone mentiond the cold start injector? Sometimes they add too much fuel on warm up. The fuel sensor bullet connections are also suspect.

We installed a new Standard Motors cold start valve. I can clean the bullet connectors but what does that mean? do u suspect the injector is not working due to corroded connections etc.?

[MH77280Z]

17 minutes ago, siteunseen said:

Have you cleaned all the brass sensors in the thermostat housing? That helped mine.

Where are those brass connectors? do I have to drain the coolant and open the thermostat housing to clean it? what will that effect?

[siteunseen]

5 minutes ago, MH77280Z said:

Where are those brass connectors? do I have to drain the coolant and open the thermostat housing to clean it? what will that effect?

Post #2 shows them. They get corroded over time and loose their sensitivity. You can remove them and sand them down until shiny, steel wool works best.