Generallee Posted June 18, 2017 Report Share Posted June 18, 2017 Hi all, so 2000, 2.7 , manual - have cleaned MAF and throttle body, new plugs and coil packs but still have a rough idle - sometimes it hunts, sometimes it just runs rough on perhaps 4 or 5 cylinders, seems much better when cold too, fine as soon as the loud pedal is pushed and has plenty of power. Cheapo scanner says no fault codes. Any suggestions appreciated. Link to comment Share on other sites More sharing options...
edc Posted June 18, 2017 Report Share Posted June 18, 2017 If it was running ok before you took apart the intake then check for air leaks. Link to comment Share on other sites More sharing options...
Anker BS Posted June 18, 2017 Report Share Posted June 18, 2017 There must be misfire codes if it isn't firing on all cylinders. Check for vacuum leaks. Link to comment Share on other sites More sharing options...
the baron Posted June 19, 2017 Report Share Posted June 19, 2017 My guess as above would be an air leak, I had a similar issue and changed the MAF etc to no avail, take it to a good indy and they will find it if that is what it is. Link to comment Share on other sites More sharing options...
Generallee Posted June 19, 2017 Author Report Share Posted June 19, 2017 Hi, this has been on going for a while, but definitely much worse when hot - initially I thought it was plugs/coils. I think I will have to run it in somewhere to have a check over. Thank you for the suggestions. IAT temp does seem high, it was saying 30 degrees last night when outside air temp was only 24. Yes it could well be a vacuum leak. Link to comment Share on other sites More sharing options...
Tex24v Posted June 19, 2017 Report Share Posted June 19, 2017 Considering what you've checked and replaced so far, I might start to check the O2 sensors, I had some really rough running /misfiring (although not just on idle) back in 2015 which was due to one not functioning correctly. Reading the codes should also point you in their direction if that is the case for you, and either way is probably the best place to start. Link to comment Share on other sites More sharing options...
edc Posted June 19, 2017 Report Share Posted June 19, 2017 A duff O2 sensor normally gives a code. MAF and air leak won't. Link to comment Share on other sites More sharing options...
Generallee Posted June 19, 2017 Author Report Share Posted June 19, 2017 On the limited live data I have on my scanner - one of the oxygen sensors does look like it is giving a duff reading - whether this is the cause or the symptom? One of the clamps onto the big rear silencer is leaking slightly at the clamp. Link to comment Share on other sites More sharing options...
ragpicker Posted June 19, 2017 Report Share Posted June 19, 2017 Agree with the above. If the idle is hunting then you've got a post-MAF air leak bud. Link to comment Share on other sites More sharing options...
Generallee Posted June 20, 2017 Author Report Share Posted June 20, 2017 OK, so can only get readings on 2 oxygen sensors on my scanner but both look fine now - been everywhere looking for vacuum leaks....BUT..... could it be the petrol cap not on tight enough? This would affect the evap system???? It is the only thing I have found - the misses drives it and it was probably half a turn loose. It appears to run/tickover fine now after test runs etc. Anyone???? Link to comment Share on other sites More sharing options...
ragpicker Posted June 20, 2017 Report Share Posted June 20, 2017 Yes indeedy the fuel filler cap not sealing properly can cause an erratic idle Link to comment Share on other sites More sharing options...
Generallee Posted June 20, 2017 Author Report Share Posted June 20, 2017 Oh well - glad I found what it is.... and I suppose the coil packs were all cracked up, but apparently working... and plugs are service parts! Thanks lending an ear everyone - have let 'she who shan't be named' know... Cheers.... Link to comment Share on other sites More sharing options...
Generallee Posted July 3, 2017 Author Report Share Posted July 3, 2017 OK, so.... it doesn't appear to be the petrol cap that is causing the issue (had to apologize to her indoors!). I have been driving it for a few days and it appears only to hunt/rough idle when it is really hot, say drive for 20 mins, stop and let the heat properly soak through, then back into a traffic and off it goes. Got it on my cheapo scanner and all the oxygen sensors seem to be reading ok except bank 2, sensor 2 which is consistently reading low around 0.1V when it is misfiring/hunting. Would a duff Oxygen sensor post cat cause this problem? Is that how these sensors go or do they break down all together? Any help appreciated. Link to comment Share on other sites More sharing options...
Lonewolfgjp Posted July 3, 2017 Report Share Posted July 3, 2017 It does sound like a vacuum leak, I've had a few messing round with the throttle body. The car runs lumpy with hunting idle and it seems to get worse when the engine is warm. Have you tried spraying a bit of carb cleaner round the joints on the air intake pipe? And try it round the plenum t piece and sleeves. If its leaking the revs will shoot up when you spray the carb cleaner? Link to comment Share on other sites More sharing options...
Generallee Posted July 4, 2017 Author Report Share Posted July 4, 2017 Hi Lonewolfgjp, Yes, tried carb cleaner everywhere (I think). The Oxygen sensor reading is the only thing I have found that is measurable and suspicious - if the pre cat sensor is reading correctly and the post cat one is low won't that mess with the mixture? It reads fine, flipping every half second but then goes a stable voltage when really hot. Link to comment Share on other sites More sharing options...
Lonewolfgjp Posted July 4, 2017 Report Share Posted July 4, 2017 I'm not sure, I had trouble with the pre cat sensors and it ran like a bag of nails and the revs were up and down. When you tried the carb cleaner did you squeeze the rubber joints a little? I didn't first time round and thought I was ok. Then I went for a run and got the engine warm and vacuum leak was back. I got back and tested again and all seemed well but when I squeezed the joints slightly and sprayed the cleaner it shot the revs up so I tightened the clamps some more! Also are you using a ratchet and socket? I started off using a screwdriver but found I got far more purchase with the socket ? Link to comment Share on other sites More sharing options...
That986 Posted July 5, 2017 Report Share Posted July 5, 2017 Check the oil filler pipe as well, if that thing is cracked up then it will be drawing air in. Link to comment Share on other sites More sharing options...
ooid Posted July 5, 2017 Report Share Posted July 5, 2017 I have to say this looks like 99% MAF. Similar symptoms with mine, it needed a new MAF, cleaning did not help. ( Link to comment Share on other sites More sharing options...
Generallee Posted July 21, 2017 Author Report Share Posted July 21, 2017 Still not got to the bottom of this - just so busy - if I unplug the maf, it still continues to hunt so shouldn't that discount the maf being at fault? Link to comment Share on other sites More sharing options...
wasz Posted April 6, 2018 Report Share Posted April 6, 2018 I had a high idle on a 996. I made a smoke machine with a soldering iron, uncle bens jar, a tyre inflator and some baby oil (seriously) and found an air leak at the AOS (just replaced and seal was dodgy). http://911uk.com/viewtopic.php?t=124928&postdays=0&postorder=asc&start=140 But the high idle remained. Mine is a cable throttle car, and it was down to the idle control valve that was stuck. http://www.911uk.com/viewtopic.php?p=1391891 Link to comment Share on other sites More sharing options...
wasz Posted April 6, 2018 Report Share Posted April 6, 2018 On 7/21/2017 at 12:00 PM, Generallee said: Still not got to the bottom of this - just so busy - if I unplug the maf, it still continues to hunt so shouldn't that discount the maf being at fault? If there is no change on pulling the MAF plug...... then the MAF is not having an effect and may be duff. Try swapping with the friendly owner of a car of the same spec, or buy new. Make sure you get a genuine Bosch one from a trusted supplier (not eBay etc) as there are many fakes out there that just do not do the job. Link to comment Share on other sites More sharing options...
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