8 cylinder front engine iconic vehicle
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By hessank
#154496
Cold start: no problem. Car idles strong until I drive off

Hot start: after car is fully heated up and I shut it down, do my errands etc car will start first turn of the key.
However, the idle sucks and I have to feather it until I drive off. Otherwise, it will die.
So I've been doing my hot starts with the AC on to boost the RPM. This works but obviously not the solution.

I suspect a part(s) needs replacement etc. What should I look at?
No fuel found in any Damper or Fuel Reg hoses. Last year all vacuum hoses replaced and smoke test showed no leaks in system.

Please and thanks
Fred
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By worf
#154508
Ohm-out the TEMP-II at the ECU plugs. (Directions in my PPI guide linked in my signature.)

Recheck the fuel pressure regulator and both dampers:

- Pull off vac lines.
- Use hand pump with gauge to verify vacuum hold
- Start engine
- Verify no fuel leakage from vacuum ports while engine running.
- Reattach vac lines

Those units can hold vacuum but leak under pressure.

Next questions:
- how many miles since the Mass-Air Sensor was rebuilt?
- how many miles since the injectors were cleaned (by a service.)
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By hessank
#154910
Thanks Worf. Answers inserted in red

Ohm-out the TEMP-II at the ECU plugs.
At 75 degrees F, I got 2.7K Ohms. Temp II Sensor is 5 years old


Recheck the fuel pressure regulator and both dampers:

- Pull off vac lines.
- Use hand pump with gauge to verify vacuum hold. All hold vacuum at 20
- Start engine
- Verify no fuel leakage from vacuum ports while engine running. No drop in pressure
- Reattach vac lines

Those units can hold vacuum but leak under pressure.

Next questions:
- how many miles since the Mass-Air Sensor was rebuilt? Alpha N. Mafless
- how many miles since the injectors were cleaned (by a service.) 3 years and about 5K

So I found a few vac hoses not as tight, you know the ones from the side of the manifold to the Booster and around the Venturi Tube thingy

So I continue to boost the hot idle with the AC
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By worf
#154962
hessank wrote: Mon Jun 13, 2022 4:37 pm Thanks Worf. Answers inserted in red

Ohm-out the TEMP-II at the ECU plugs.
At 75 degrees F, I got 2.7K Ohms. Temp II Sensor is 5 years old
You need to get a resistance reading from both ECU plugs with the engine warm as well as a cold measurement.

hessank wrote: Mon Jun 13, 2022 4:37 pm
Recheck the fuel pressure regulator and both dampers:

- Pull off vac lines.
- Use hand pump with gauge to verify vacuum hold. All hold vacuum at 20
- Start engine
- Verify no fuel leakage from vacuum ports while engine running. No drop in pressure
- Reattach vac lines
I asked you to check that the ports were not leaking fuel. I didn’t ask about fuel pressure.

But, Pressure should rise with no vacuum.
hessank wrote: Mon Jun 13, 2022 4:37 pm So I continue to boost the hot idle with the AC
Low idle is usually a rich-running condition. It can also be due to no idle switch signa.

Ohm-out the idle switch at both ECU plugs.

After that consider o2 sensor.
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By hessank
#154969
Verify no fuel leakage from vacuum ports while engine running. No drop in pressure

Sorry wrong answer input. There was no fuel leaks
My O2 sensor is almost 10 years old so that may be an issue.

I am not returning to the car until Sat. I will report back then.

Thank you for taking the time
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By worf
#155053
hessank wrote: Mon Jun 13, 2022 9:00 pm My O2 sensor is almost 10 years old so that may be an issue.

I am not returning to the car until Sat. I will report back then.
If you are running Alpha N, then you have a Shark Tuner. So, bust it out and see what it says about O2, idle switch, etc.

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