tommytwo Posted December 27, 2016 Share Posted December 27, 2016 I have been running a 92 Rover 820si (T16 engine) as my daily driver for the past 15 years and it has been super reliable up to recently. Now it has got a normal or high idle (1500 and up) So far I have checked for vacuum hose leaks, and poor electrical connections and drawn a blank. Today I had the throttle body off. It was very dirty and all I could find wrong was a slightly sticky stepper motor plunger. The TPS gave a smooth variable resistance up and down. I have changed the CTS sensor but no joy there.Switching off seems to reset everything to normal but then the revs will rise slightly, fall back, rise a bit more, fall back less and soon the idle is back to 1500 or higher again. I need to find a solution to this problem ASAP as my test is due in two weeks. Anyone got an answer for this problem? Don't want to scrap the car but it may come to that. Link to comment Share on other sites More sharing options...
Guest Hooli Posted December 27, 2016 Share Posted December 27, 2016 Dirty throttle body or idle control valve (if it's got one) is almost always the answer. Link to comment Share on other sites More sharing options...
DodgeRover Posted December 27, 2016 Share Posted December 27, 2016 Idle control valve, find it and give it a really really good clean out with a decent solvent/ carb cleaner/ electrical contact cleaner. Occasionally they stuff up completely and need replacing but it's not often. Link to comment Share on other sites More sharing options...
Squire_Dawson Posted December 27, 2016 Share Posted December 27, 2016 I'm no expert but wouldn't have thought the idle speed would come into the MoT test, it would only become a problem if the exhaust emissions were affected by it. Seems a bit strong to scrap it for it idling too high. Link to comment Share on other sites More sharing options...
scaryoldcortina Posted December 27, 2016 Share Posted December 27, 2016 High idle is an emissions fail, even if the cat test was fine. Having said that, the allowed range is 450 to 1500 so you're at the top end of that. Link to comment Share on other sites More sharing options...
Junkman Posted December 28, 2016 Share Posted December 28, 2016 The symptoms make me believe MAP sensor more likely. Link to comment Share on other sites More sharing options...
tommytwo Posted December 28, 2016 Author Share Posted December 28, 2016 Thank you gents, your input has been much appreciated. Have tried the reset process many times. Seems to work until the engine is warm, then idle is way above normal. Switch off and restart and the idle is normal until it isn't. There seems to be a drilling behind the butterfly that is there for idle purposes. The idle screw sits under a nylon blanking plug and the book says that to reset this screw, you need a gas analyzer. That's why I have left it alone. I am going to try soaking it with carb cleaner and see if things improve. Will get back to you if I solve the problem. Thanks again. Link to comment Share on other sites More sharing options...
tommytwo Posted December 28, 2016 Author Share Posted December 28, 2016 I think that I have found the problem that caused my high and variable idle problem. My car is an early MK2 multi injection type. According to my books, this does not have a throttle switch by the pedal, supposedly deleted. Single point injected cars all have it, and it seems, early MK2 multi point injection models can also have it. A signal from this switch alerts MEMS to implement the idle map. No signal, and no idle map is implemented! So things go a bit haywire. Early in the the year, I had the screen finisher off and found a rust hole under there, must have been directly over the switch. Also had a problem with damp drivers floor which I put down to the sunroof drain.. So I think my problem was down to excessive moisture. Just been on a 30 mile run and everything seems back to normal. Many thanks for advice received, much appreciated, it gave me the will to persevere and fix the problem. Skizzer, KruJoe and SiC 3 Link to comment Share on other sites More sharing options...
Squire_Dawson Posted December 29, 2016 Share Posted December 29, 2016 Good, personally I do not trust any of this witchcraft and consequently stick to carburettors with a simple screw. Link to comment Share on other sites More sharing options...
Wilko220 Posted December 29, 2016 Share Posted December 29, 2016 I had a similar problem on an 820 and it turned out to be a temperature sensor which needed replacing. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now