Idle issues

[TBD]

So I. Was finally able to resolve my high idle when cold issue (the car was idling at 2.000 revs). Turned out two vacuum lines had been interchanged above the left fuel tank, The air injection solenoid was pulling air from the charcoal canister when cold.

But I still have an issue when hot. The engine idles rough, swinging between 1200 and 600 rpm. I've tried to search the web, but with diverse results:

- IAC (Idle Air Control)

- Injectors (these are new upgraded)

- Throttle position sensor

- Another vacuum leak

What do the experts here suggest? How can I narrow it down without throwing parts at the car?

It should be noted that I also still have the issue of long cranking to start the engine.

[Erikl]

Is this a late 4 cyl -S4?

 

if so I would try looking at the sensors with esprit mon or free scan

 

and post up a driving and idling data dump

 

folks might be able to see what is going on.  Do you have a CEL

Check all those vac lines for splits or if they have slipped off

 

[Thartje]

If you're not getting an OBD II check engine code then you're going to have to go through some trial & error. I would start with O2 sensors if its only doing it once the engine is hot. Could also just be bad wiring. The ECU and wiring on the Esprit is one of the main reasons I decided to swap to something more modern for engine management. Not sure how the wiring harnesses usually hold up but mines was frayed throughout.

[Escape]

On 10/06/2024 at 01:57, Erikl said:

Is this a late 4 cyl -S4?

It's a V8 😉

Checking for error codes and getting some live data is still good idea of course.

[TBD]

Yes, it's a V8. The engine harness is from 2019 (wehen the engine was exchanged) and the O2 sensors are new (and working).

Also, the Throttle position sensor is reading correctly (0%). Intake temperature was 49°C, so also reasonable and seemingly correct.

I am going to log these values (plus O2 and Manifold pressure) to try to see if anything unexpected is happening.

From the web the symptoms seem to lean towards the Idle Air Control Valve.