Air-con cut in/out?

[Chillidoggy]

My air-con works a treat, cuts in and out, just as it should. I noticed that when air-con is running, and the engine is idling, the engine stumbles and threatens to die for a few seconds before picking up to a normal idle. Cutting in is perfect, the engine revs up slightly to compensate for the additional load, and it's a smooth transition. It's when the load is taken off that the stumble happens, before it recovers.

Looking a the Service Notes, it's ECU-controlled but by the thermistor which switches the pressure switch on the receiver/dryer and sends a signal to the ECU, which in turns signals the IAC to move. There is no mention of any fuelling adjustment, though. Given the IAC is a brand new unit, and appears to work as it should otherwise, any thoughts on this one?

 

[temple]

Do you need air con in Margate? or is the car filled with hot air from occupants 

[Chillidoggy]

It's only for when we travel to the posher areas of the country, like Brooklands.

[Chillidoggy]

Could it be the ECU is having to 're-learn' what it should be doing with the IAC valve because the air-con has not been in operation for so long? Clutching at straws, really.

[Bibs]

While the IACV is new, did you reset it's position once it was installed in the car via Freescan? Might be worth doing that anyway in case it's a notch or two off...

[Chillidoggy]

I may have checked it with Freescan but TBH it was a while ago and although it's done very few miles since then, I cannot really remember as I'm getting on a bit (399 in dog-years). I'll have a look in due course.

Of course there is a remote possibility that it is faulty in some manner, as was the previous one which had fallen apart inside.

[Chillidoggy]

Checked the IAC value last night, it was 170, which is normal. When I started the engine, it ran for a few seconds at idle, then died, but when I started it up again, it continued to run without a problem. Never had that before. There were 3 Code 26 up, which could be a multitude of things by the looks of it, so I reset both them and the IAC and will see how things progress.

This morning however I came across this section if the Freescan manual which may offer a solution, so I'll give that a shot when I get around to it:-

 

1. Poor Idle

The way the ECU handles the idle condition is to reduce the injector pulses to every other cycle at low loads and rpm.

However, during the "learn" phase, this is usually not the case, and the engine runs smooth, but once that phase is over the engine tends to get rough at idle unless the injectors/gas/spark plugs etc are all "perfect" and the learn process was done correctly. The idle air controller is usually the culprit, as the idle swings down past 1000 and the "every other pulse" seems to kick-in, then the system rises above 1000 and the mode changes back... rough as hell.

If the IAC is disconnected when the idle is below 1000, the car may run rough (shows injector or plug problems), but if it is disconnected at a higher rpm the car will be smooth. The change across modes causes the roughness. The other main issue is that although the car tries to learn idle as soon as you reconnect the power and start the car, it does not learn the correct position of the IAC valve until you drive the car over 20mph.

To get a stable idle (as best as possible with this ECU on any 4 cylinder Esprit), try this. The Idle tables are virtually the same in all the chip variations

(a) Before anything else, run FreeScan (engine OFF) and use the "Reset IAC position" button. This ensures the IAC is in the right spot. Shut off the car and it will go to 170 counts (home).

(b) Disconnect the battery entirely (or pull the fuse), and make sure the charge is full before continuing. The car should be COLD! (otherwise it will not learn correctly and stall on cold days!)

(c) Reconnect it and keep the charger connected to trickle charge the battery.

(d) Start the car, A/C ON and fans on (at least the lowest setting, A/C clutch does not work if the fans are off) and let it idle for 15 minutes. It should start right away, no stalls. If it stalls, check the throttle air bypass.

(e) Turn off A/C, and idle for another 5 minutes. It should start idling a little high then work its way down.

(f) Drive, at least over 20mph to reset the IAC. Idle should now work correctly with A/C and no A/C. If there is still a problem with idle jumping around, too low, or "hunting", check the throttle air bypass. To do this, connect FreeScan and check the IAC counts and ensure it is from 5-40 counts with A/C off. If it is lower, there is too much air passing the throttle and the engine cannot reduce it, if too high, there is too little air. This is the stop screw on the throttle body. It shouldn't normally need adjustment, but after 10+ years, things do change!