[flash]

unfortunately, while those bottles do help, they really are more a preventative thing than a curative one - worth a try, but i wouldn't count on it



yanking and sending them away is really the only way to get them right - usually takes a couple of days plus shipping



i use RC Engineering - pete uses Marren - others use Witchhunter - all seem to be fine

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[Cloud9...68]

I would put the MAF cleaner in the same category as the Technon - good, inexpensive maintenance, and something everybody should do periodically, but I'd be shocked if it smoothed out your idle.

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[astroede]

Cloud9...68: Correct! The MAF cleaner did not change the idle speed variation. Think I'll pull the injectors and send them out for cleaning and balancing as recommended by many.

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[jaap]

[quote name='astroede' timestamp='1296335131' post='104295']

... Reassembled and started the car. Immediate difference: the car idled higher (cold) and idled much smoother than on previous cold starts. ...[/quote]



What should the idle speed at cold startup be? I think mine just start idling at the the normal 825-850 range. Is this an indication that the idle control valve is stuck? By the way mine also has a slight variation at idle warm or cold.





Jaap

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[Cloud9...68]

I'm not sure what the idle speed should be cold - that's a good question. I've done everything covered in this thread except cleaning the idle stabilization valve (which I'll do as part of the huge rebuild project I'm working on), including sending the injectors out for cleaning and balancing, and none of it had any impact whatsoever on the smoothness of my idle, which is comparable to the OP's.

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[flash]

while certainly cleaning the injectors is a very good idea every few years, as deposits get on there and gum up the works, and you may find some more power as a result, i'm not sure it's going to resolve that small idle variation - more than likely it's just a component of engine age



how is the compression in each cylinder? have you done a leak down test?

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[astroede]

Flash: I have not checked the compression yet. I will check this and post result as soon as I can get a compression gauge.



I pulled the fuel injectors this morning. Certainly is a simple enough procedure. One observation: the injectors pulled out of the manifold VERY easily (but were tight in the fuel rail). Makes we wonder how good the seal was.



Photographs of the injectors and injector tips below. I'll be sending the injectors to WitchHunter Performance for clean and flow service.

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[flash]

definitely dirty and in need - worst case scenario, the car will very likely have more power, but given how dirty those are, they could be responsible for fluctuations in idle

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[968norway]

My 2 cents, first, it's a good idea to get the injectors cleaned, makes a difference.



But just a comment, I read somewhere that the DME has adaptive idle control, which can cause it to 'hunt' a bit as it balances the sensor inputs. Mine has always moved a bit, 850 rpm +/-. And before anyone says anything, the top has been done, camshafts, new'ish' MAF, rotor, cap, plugs etc. Though cleaning the idle-control seems like a good idea.



Thanks for the helpful pictures.

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[flash]

indeed - there are a number of idle maps, and readings are taken and adjustments made based on a lot of factors



normal warm idle is 840+/- 40 for the manual and 880 +/- 40 for the tip

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[968norway]

Just another thing, as flash has said in other places, the chassis grounds are a bit of a problem. I thought I had a problem with the cooling system, the temp read too high and the oil pressure read a bit low, turned out cleaning the connection from the battery to the chassis sorted it. Might have an effect on the rpm reading.

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[flash]

good point - the connectors at the back of the instrument cluster tend to have issues as well - any lack of contact there will cause odd things



but, we are now scatter-gunning, so given that the injectors are so dirty, i'd be inclined to think they might be the culprit

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[968norway]

Exactly right, these cars are at least 17 years old, cleaning the injectors is something that should be done. Though sometimes it turns out to be something simple.



Hard won (and sometimes expensive) experience.



Good luck!

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[astroede]

Update: Got my injectors cleaned by WitchHunter Performance for $91 including shipping/insurance. See the performance report below. I finally got around to re-installing the clean injectors today without problems. Video of the resulting idle below. Is the idle variation improved? You be the judge, but I'd say it's about the same.



Roads are snow covered today, so I have not been able to take her for a drive yet.



One thing I noticed in the video is the oil pressure gauge needle jumping around a bit. Should it be more steady at idle?



http://www.youtube.com/watch?v=qTPlkb8sbjQ

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[rl968]

My car does almost the exact same thing. Others have way more experience than me, but I think this is either normal or there is some common condition with the cars that we are missing.

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[Cloud9...68]

Was your engine FULLY warmed up when you shot this video (i.e. at least 20 minutes of driving)? Your oil pressure is significantly higher than mine at idle; mine's a little under 2. This implies that either your engine wan't fully warmed up, or the bearing replacement I'm planning to do soon is past due...



How many miles are on your engine? I have a little over 115K. Thanks.

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[astroede]

Cloud 9: I have 76K miles on my 968. I didn't drive the car today since the roads were covered with snow, but I did let it idle and rev 20 minutes or so. May not have been fully warmed up.

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[jaap]

[quote name='Cloud9...68' timestamp='1298749073' post='105646']

Was your engine FULLY warmed up when you shot this video (i.e. at least 20 minutes of driving)? Your oil pressure is significantly higher than mine at idle; mine's a little under 2. This implies that either your engine wan't fully warmed up, or the bearing replacement I'm planning to do soon is past due...



How many miles are on your engine? I have a little over 115K. Thanks.

[/quote]



A little under 2 seems a bit low (although probably still within specs) and may also depend on oil weight and idle speed. At idle (825-850) and fully warmed up mine (at 130k) sits between 2 and 3 (closer to 3) using a 5w50 oil.



Jaap

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[flash]

when fully warmed up, spec on idle is minimum of 0.6 - 0.8 bar



typically i see anything from 2 to 3 bar at idle on most cars - this varies largely depending on the oil temp, weight, and condition - lighter oils make less idle pressure - cold ambient temps make higher pressure - cold oil is higher than hot oil - you see where i am going here



as for the fluctuations, while i still think they are fairly normal, and i have no idea why i did not ask this earlier, but have you done the obvious of removing the cluster and cleaning the contacts and checking the ground?

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[Cloud9...68]

I know this is a little off topic, so this is the last I'll post about this, but on a hot Texas summer day, with the engine fully warmed up, my oil pressure definitely sits a little below 2, which is within spec, but it seems to be on the low side of the distribution. My engine has 115K miles, but has been behaving this way at least since it turned 100K, maybe longer. I use 5W40 synthetic oil. It sounds like the rebuild I'm embarking on, while maybe not urgently needed, will make a significant difference in the way my car performs.

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