JB-) Posted November 2, 2014 Share Posted November 2, 2014 In my 2007 HR, 1. When sat idling, give it a rev and as the revs drop it momentarily stops at 1500 revs before the revs then slowly drop to normal idle speed. Normal? 2. Driving along and take your foot off the gas and allow the car to coast, it won't drop below 1250 revs. This can catch you out when slowing down say from a 60 to a 30 limit as you don't expect it. Drop the clutch and the revs drop to normal idle, it just doesn't drop when it in gear clutch up. Also have a small problem with the cruise control 'hunting' when going down hill and set to a lower speed, say 50mph. Set it at motorway cruising speed and it seems to work fine, but set a lower speed (therefore lower revs) the throttle on/off is very snatchy when you go down hill. When it's pulling on the flat or up hill it's fine. Both throttle bodies were a bit gunky so they've been cleaned and reset using a G-Scan machine. Idle speed is around 500rpm or 800 with air con on (by the tacho not properly measured) Next thoughts were check for air leaks and clean the MAF's. Anyone had a similar issue? Quote Link to comment Share on other sites More sharing options...
KyleR Posted November 2, 2014 Share Posted November 2, 2014 1. clean the MAF 2. I'm a bit confused about what you mean. If you just coast in gear then the revs won't drop any lower than the speed/gear ratio dictates. 3. Sounds normal. If the car is going down hill it can accelerate and if cruise control is set then the car will dab the brakes to slow you down to the chosen speed. Quote Link to comment Share on other sites More sharing options...
JB-) Posted November 2, 2014 Author Share Posted November 2, 2014 1. clean the MAF 2. I'm a bit confused about what you mean. If you just coast in gear then the revs won't drop any lower than the speed/gear ratio dictates. 3. Sounds normal. If the car is going down hill it can accelerate and if cruise control is set then the car will dab the brakes to slow you down to the chosen speed. If you just remove your foot off the gas, then normally a car would drop right down to normal idle speed if you let it. In my car it's as though it keeps some throttle on. The cruise control problem can't be normal. It's quite violent as it goes on and off he gas. It only has to be a slight decline and as the car starts to pick up speed it comes of the gas, then as it slows down it gets back on it and this is all very jerky. It goes on/off throttle every second or so. I've never heard of normal cruise control applying the brakes either. Quote Link to comment Share on other sites More sharing options...
Toon Chris Posted November 2, 2014 Share Posted November 2, 2014 Cruise control can apply the brakes, but not the system in the Z as its not a forward sensing system. Sounds like dirty throttles (which you have sorted) and then you haven't reset the idle. Do this first before you start to look for leaks. Quote Link to comment Share on other sites More sharing options...
jimboy2 Posted November 2, 2014 Share Posted November 2, 2014 Are you sure? The revs should drop right down when clutch peddle is pressed. But just letting off the gas in gear, the revs will stay the same and slowly drop. Right? Quote Link to comment Share on other sites More sharing options...
Toon Chris Posted November 2, 2014 Share Posted November 2, 2014 Actually on mine the revs will never drop below about 1250 if the car is moving - i.e. just dropping it out of gear, but as soon as I draw to a halt they will drop. That said, and idle reset is always a good idea after throttle body cleaning. Quote Link to comment Share on other sites More sharing options...
JB-) Posted November 2, 2014 Author Share Posted November 2, 2014 Cruise control can apply the brakes, but not the system in the Z as its not a forward sensing system. Sounds like dirty throttles (which you have sorted) and then you haven't reset the idle. Do this first before you start to look for leaks. Both throttle bodies were a bit gunky so they've been cleaned and reset using a G-Scan machine. Quote Link to comment Share on other sites More sharing options...
JB-) Posted November 2, 2014 Author Share Posted November 2, 2014 (edited) Actually on mine the revs will never drop below about 1250 if the car is moving - i.e. just dropping it out of gear, but as soon as I draw to a halt they will drop. That said, and idle reset is always a good idea after throttle body cleaning. Well that's one thing that might be normal then (even though it's odd). As above, the reset was done. EDIT: Typo Edited November 2, 2014 by JB-) Quote Link to comment Share on other sites More sharing options...
JB-) Posted November 17, 2014 Author Share Posted November 17, 2014 Just for anyone following or searching, cleaning the MAF sensors sorted this. Quote Link to comment Share on other sites More sharing options...
ZMANALEX Posted November 17, 2014 Share Posted November 17, 2014 Dirty MAF sensors are the usual demon for this issue. Glad to hear that you are sorted. Alex. Quote Link to comment Share on other sites More sharing options...
steve916 Posted November 17, 2014 Share Posted November 17, 2014 Well timed. I noticed mine was pausing at 1500 revs tonight. Off to look for a 'how to' now Quote Link to comment Share on other sites More sharing options...
JB-) Posted November 17, 2014 Author Share Posted November 17, 2014 Well timed. I noticed mine was pausing at 1500 revs tonight. Off to look for a 'how to' now Ignition off, Philips screwdriver, take out the two screws, pull out the MAF, don't disconnect it, spray the sensing wires through the holes with carb cleaner or electrical cleaner, put it back Don't rub it with anything, just let the spray to do the work. And it won't necessarily look dirty, but it will be Quote Link to comment Share on other sites More sharing options...
steve916 Posted November 17, 2014 Share Posted November 17, 2014 Well timed. I noticed mine was pausing at 1500 revs tonight. Off to look for a 'how to' now Ignition off, Philips screwdriver, take out the two screws, pull out the MAF, don't disconnect it, spray the sensing wires through the holes with carb cleaner or electrical cleaner, put it back Don't rub it with anything, just let the spray to do the work. And it won't necessarily look dirty, but it will be Cheers Joe. I'll give that a go tomorrow lunchtime at work, if it's dry Quote Link to comment Share on other sites More sharing options...
The_Lord Posted November 17, 2014 Share Posted November 17, 2014 But I heard that this may cause the engine to run lean and could cause more problems in the long run. I have the same problem and my MAF sensors look like new..... Quote Link to comment Share on other sites More sharing options...
steve916 Posted November 17, 2014 Share Posted November 17, 2014 But I heard that this may cause the engine to run lean and could cause more problems in the long run. I have the same problem and my MAF sensors look like new..... What could cause this? Cleaning the sensors? Quote Link to comment Share on other sites More sharing options...
The_Lord Posted November 17, 2014 Share Posted November 17, 2014 Incorrect A/F ratio after cleaning Quote Link to comment Share on other sites More sharing options...
JB-) Posted November 17, 2014 Author Share Posted November 17, 2014 But I heard that this may cause the engine to run lean and could cause more problems in the long run. I have the same problem and my MAF sensors look like new..... They will look OK but will be dirty if they've never been cleaned. Mine looked like new but cleaning has worked. Just spraying them with the correct cleaner isn't going to hurt them. Just don't go rubbing them with anything. If it really worries you, buy new ones. Quote Link to comment Share on other sites More sharing options...
JB-) Posted November 17, 2014 Author Share Posted November 17, 2014 The other thing you could do is buy a can of one of the so called 'proper' MAF cleaners like CRC Mass Air Cleaner. To be fair, they do contain different ingredients than carb or electrical cleaner. However I do think that stories of damaging the sensor is more likely down to people not treating them with proper care though. Quote Link to comment Share on other sites More sharing options...
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