Your symptons sound almost identical to mine. When warm the engine doesn't idle completely evenly, but I don't really expect it to given the age. There are no warm start problems and in all other respects the performance is very good.

I don't see how the lambda sensors can be affecting this. As I understand it the car starts in open loop and the oygen sensors have to warm up before the engine uses their values. Started from cold the engine is using a default map based on the airflow, with an offset to increase the idle if the coolant is in certain temperature ranges.

I wonder if we could trick the engine management software by changing the resistance value of the coolant sensor at cold start up, so it thinks it is already over 30`C?

 

The engine coolant temperature sensor (ECTS) provides a decreasing voltage signal to the ECM. If you want him to manipulate the ECM's cold start behaivior the voltage supply should start with no more than 1.8 volts. Good luck.
Fritz

 

Thanks for that. I haven't really looked into this, but I assume the temperature sensor is a resistance value that falls as it gets hotter, so it would just need another resistor in parallel to fool the ECM for 30 seconds or so after start up.

 

Most all obd2 controlled engines idle high for a bit no matter what the temp because that gets the oil pressure up quickly and fully circulating to offset the start and immediatley go driver....colder temps will prolong the high idle some....right now it is 32 to 45 F where i live at sun up and my idle goes from about 1400 to under 1000 rpm in about 30 seconds

 

What car is that? Personally I hate that it revs a cold engine like that - totally counter intuitive to me at least.

 

2006 s type r....just drove it today and it was more like 1200 then down below 1000...bad guess on the 1400 in previous post....one of the main reasons i use 0-40w synthetic

 

 

does anyone remember the old carburetor with the automatic choke control engines. even in perfect factory tune and adjustment as intended they would rev high until choke kick-down. some later Japanese and American cars like my 82 Honda Prelude had a two stage depending upon how cold where initial high idle was intended to be about 2100 if very cold. it would kick down to around 1400 until it warmed up sufficiently which would take some time.

 

^^^^^ +1

sure do. you can go over on the Vintage Mustang Forum and every day some of the old timers are trying to explain to a newcomer how to adjust the cold fast idle setting. Before I bought my XKR last year , my daily driver was a '65 K code HiPo Mustang with 4 Weber IDA carbs, and prior to that , a '66 Shelby GT 350with a vintage Paxton ball drive supercharger. I mention these cars because they are good examples of how well engineered the 1960's era induction systems could be given the lack of computers and sophisticated engine sensors.

the '65's engine bay:



the '66's engine bay:



Z

 

As a yoof I had one of these with carburettors and an autochoke:-



Not quite as exciting as zray's Mustang, I admit. I was rather hoping that in the decade or two after my XR2 was produced, Ford would have solved the problem with the fully electronic throttle body on my XKR - not so it seems.

 

You're probably right, but I still don't like it.

 

@Zray -- my compliments on the vintage hardware. very nice.

 

thank you !

The 2002 XKR is the most modern car I've ever owned. I've been hooked on '60's era cars ever since they were new cars, and just never moved on to the subsequent decades of automotive progress. If my back was not crumbling I'd probably still be living in the past.

Z.

PS here's the full view of some of my old friends:

 

hopefully you have kept the horses in the stable. even though i am gen x, grew up in 60s cars. the 67 was a daily driver for 24 years and then kept as a functioning heirloom until 2007, first month of production of the Firebird. learned to drive in that car. other family car until 91 was a 67 Oldsmobile 442, bench seat. what a heavy clutch with that Hurst shifter extending over the bench seat. after a bad experience with a new 85 GM product, purchased a used 82 Honda Prelude out of desperation and developed an appreciation of how well they were designed and built. great materials and quality components and nice driving. reminded me of the 60s cars that i grew up in, that simple solid design leading to exceptional longevity. kind of glad my family fortunes caused us to miss the cars of the 70s. the fun thing about the 82 Honda was the complexity based upon the same principles of the 67s. obtained a service manual and it was a real joy rebuilding the Honda's carburetor and understanding every function that they would later achieve with fuel injection and ECUs. people should experience the basics to fully understand what is happening in the modern systems.

hope that you can take care of your back.

 

dibbit…..
Concerning your problem with the elevated RPMs when you crank her up.....I'm on my 4th XK8 - XKR and each and everyone of them do or did exactly what your 2001 XKR does.....The Heck with all that ambient Temperature stuff, they all do that fast idle when they are started up! Most of them go up to 1500 RPM for about the count of 10 and then slowly drop back to 650 or 700 RPM.....That's just part of It dibbit...that's life in the Big City! as it's built into the ECM.....! That's the way Jaguar wanted it...…It pressurizes the Oiling system and lubricates the bearings quickly to have it avoid dry Bearings and such…….Anyway, that's what the "Old Man" told me and he wasn't wrong very often!!!! When it came to Cars and such......

Billy Clyde in Houston