Expected alternator behaviour?

[Clan]

Originally Posted by TonyS9

The idle valve and ECU will compensate for carbon build up, this problem only happens shortly after starup. If it doesn't stall the ECU will compensate. Like I say above the ECU compensation isn't kicking in for some reason.

It will compensate for carbon up to a point , it depends how the throttle was set up to start with . Best go back to basic principles and get that right first ...

It Sounds like the constant idle valve isn't working at all to me .

I always checked these and adjusted them on every service that I did , I must have done hundreds back in the 90's .. It only takes a couple of minutes .

[TonyS9]

Originally Posted by Clan

It will compensate for carbon up to a point , it depends how the throttle was set up to start with . Best go back to basic principles and get that right first ...

It Sounds like the constant idle valve isn't working at all to me .

I always checked these and adjusted them on every service that I did , I must have done hundreds back in the 90's .. It only takes a couple of minutes .

There is an idle valve, but the ECU does the measurement and decides what to set it to. I have never seen any evidence that valve dirt cause idle problems.

I'm sure it can get gummed up, but I've seen cars with blocked oil pumps and totall cruded up engines with fine idle valves. It seems to be the component to blame for idle problems.

Its actually a servo, its position is determined by the applied voltage, although it just pushes against a spring. In the auto and AC models it can compensate for sudden signaled loads, it responds immediately to the ECU control signal. They move from closed to fully open every start up and open when moving to closed throttle, its very unlikely for them to get gummed up, too much movement. Its the ECU that takes its time to decide the idle valve position when there are other problems.

[Laird Scooby]

Originally Posted by TonyS9

You don't say what car it is. The LH2.4 will absolutely load compensate during idle. You can drive the car without touching the accelerator if you engage the clutch slowly enough.

The load compensation baggy is talking about is immediate signaling. The auto drive and AC put on huge loads which might otherwise stall the engine, so they are signalled directly to the ECU and it immediately changes the fueling and idle valve setting. For the rest of the loads the ECU uses the rpm feedback from the ignition ECU and this provides a slow feedback.

Either your idle solenoid is stuck or your idle switch isn't working and the ECU doesn't know it is idle mode.

I seem to recall soon after Alan got the car back from Luke he cleaned the throttle body again (Luke cleaned it during changing the engine and also setit up as it should be but given it was a replacement engine things may have altered during what might be considered as running in) so he may have distrubed the idle switch in the TPS.

As you rightly point out the load compensation mentioned is instant because of the reasons stated so should still work instantly.

It is an LH2.4 if memory serves but even the LH2.2 compensates idle speed.

[360beast]

Originally Posted by Clan

It seems your constant Idle valve isn't working or not adjusted properly More likely throttle blocked with carbon around the edges not allowing enough air through.

If this problem has gradually got worse suspect a dirty throttle plate and housing inside .
if it suddenly happened , maybe an electrical problem.
If it happened after you did something perhaps throttle and position sensor need setting up from scratch again.

Not at all, I've removed the throttle body and cleaned it thoroughly with a new gasket.

I found that it had this idle issue once I had replaced the engine, I tried 3 different idle valves on it all of which were cleaned and it made no difference. I then went through the system checking for air leaks and found none, I noticed the TPS was adjusted all the way to one side, so I checked the multiple cars and throttle bodies I have on the shelf and found them all were in the middle. So I did a basic idle setting using the guide on turbo bricks. This massively improved the issue but it would still occur intermittently, unfortunately Alan needed the car back so I didn't have time to sort it once and for all, I personally suspect there is an issue with the throttle body or TPS as why was it adjusted so far out on the replacement engine? So I've said Alan should remove the throttle body off his original engine, clean it up and fit it to see how it goes.

[360beast]

I forgot to mention Alan said it had a high idle issue similar to this before I replaced the engine so this could be an existing issue that has altered behaviour slightly since the replacement engine.

[kiloran]

Yeah, it's just one of her quirks and foibles. Plenty of driving today, lots of stop-start in traffic etc. Idle absolutely fine, even with heated seats, fan, and full beam on. Old TB will go on once I have some time to do it - probably February half term.

[Forrest]

Originally Posted by Laird Scooby

Try to find a Halfords HB096 to replace it with, it's a traditional lead-acid battery without calcium or silver-calcium in it which need a much higher voltage to charge than your alternator puts out.
Also the HB096 is the heavy duty battery for yours so should have plenty of reserve power for starting etc.

I had come to a similar conclusion myself that Halfords was the last UK retail source of traditional, maintainable lead-acid batteries. Galling though it is to pay premium prices for a budget product I bought an HB075 today using their 10% discount code to fit to my Scirocco when I get it out of winter hibernation. There are, however, several clues that it in fact uses calcium technology.

It displays the new EN50342-1/6 performance ratings. A genuine lead-antimony battery would most likely be C1,W1. C2,W3 suggests this uses some calcium technology although I suspect not silver-calcium which I believe is most sensitive to lower charging voltages.

It begs the question why Halfords also sell a maintenance free “calcium” battery for £10 more. The triumph of marketing over technology I suspect. Anyway, this looks to be quite a solid battery and comes with a three year warranty so I don’t regret the purchase.