928 S2 idles jumpy between 600-800 rpm
01-05-2005, 05:27 PM
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928 S2 idles jumpy between 600-800 rpm
Dear rennlisters,
Long story:
Last year I had several problems with my 928s2, first it had some problems with power loss (it felt like the ignition/fuel injection was a bit off) under 2000-3000 rpm when wet, when driving and if the car dried up the rpm with which the problem occured got lower till there was no problem anymore.
The MAF was "diagnosed" faulty (got a remanufactered unit) and the ignition cables were also replaced by the mechanic.
Troubles started again when the wheather got worse (wetter)
Again power loss under 2000-3000 rpm.
My girlfriend had a crazy 928 when taking it to a schoolreunion 150 kms, it just stopped working 150kms away, switched cars and I took it back, new problem, when warm it won't idle and sometimes shuts off above 2000 rpm. Ran higly irregular, extremely rich and had detenations in the exhaust. (One positive note: my girlfriend won't take the 928 for long rides anymore <grin>)
Mechanic replaced the temp II sensor then... all seemed well...
Still got the problem, try driving 10 miles in heavy slowdriving traffic, rain , with a shark that won't idle and is irregular on gas (jumped forward all the time)
I then replaced the cranksensor+the 2 ignition modules in front, the problem still was there.
After scratching myself on the head several times, I decided to check the LH jetronic , and specifically the connector which turned out to be the culprit, there was corrossion on the lower 3 pins (temp,maf,idle). The water probably got there because I've got a leaking sunroof and I'm almost always parked nose down (water running down via window style).
My problem was with the connector having corrosion on it, so I probably did't need a new MAF temp II or ignition cables, ignition modules, I always like to donate money to charities
, this is the reason why I will do some more work on the car myself 
I cleaned the connector last monday and the car ran beautiful, but..... one problem: when warm it idled very jumpy (loping?) between 600-800 with 2 jumps every second. MAF is connected so it isn't in limp home mode, acceleration and driving is ok.
When placing the crank sensor I noticed some clean oil lying in the intake under the maf.
Can the clutch problem posted in another thread (clutch chirping sounds) be of any influence ? (when idle is jumpy the clutch noise is heartshaking, more pronounced , which is very logical )
I haven't checked anything yet, because it's been a busy week , but any insight would be appriciated...
Regards,
Long story:
Last year I had several problems with my 928s2, first it had some problems with power loss (it felt like the ignition/fuel injection was a bit off) under 2000-3000 rpm when wet, when driving and if the car dried up the rpm with which the problem occured got lower till there was no problem anymore.
The MAF was "diagnosed" faulty (got a remanufactered unit) and the ignition cables were also replaced by the mechanic.
Troubles started again when the wheather got worse (wetter)
Again power loss under 2000-3000 rpm.
My girlfriend had a crazy 928 when taking it to a schoolreunion 150 kms, it just stopped working 150kms away, switched cars and I took it back, new problem, when warm it won't idle and sometimes shuts off above 2000 rpm. Ran higly irregular, extremely rich and had detenations in the exhaust. (One positive note: my girlfriend won't take the 928 for long rides anymore <grin>)
Mechanic replaced the temp II sensor then... all seemed well...
Still got the problem, try driving 10 miles in heavy slowdriving traffic, rain , with a shark that won't idle and is irregular on gas (jumped forward all the time)
I then replaced the cranksensor+the 2 ignition modules in front, the problem still was there.
After scratching myself on the head several times, I decided to check the LH jetronic , and specifically the connector which turned out to be the culprit, there was corrossion on the lower 3 pins (temp,maf,idle). The water probably got there because I've got a leaking sunroof and I'm almost always parked nose down (water running down via window style).
My problem was with the connector having corrosion on it, so I probably did't need a new MAF temp II or ignition cables, ignition modules, I always like to donate money to charities
, this is the reason why I will do some more work on the car myself I cleaned the connector last monday and the car ran beautiful, but..... one problem: when warm it idled very jumpy (loping?) between 600-800 with 2 jumps every second. MAF is connected so it isn't in limp home mode, acceleration and driving is ok.
When placing the crank sensor I noticed some clean oil lying in the intake under the maf.
Can the clutch problem posted in another thread (clutch chirping sounds) be of any influence ? (when idle is jumpy the clutch noise is heartshaking, more pronounced , which is very logical
)I haven't checked anything yet, because it's been a busy week , but any insight would be appriciated...
Regards,
01-05-2005, 05:47 PM
#2
928 Collector
Rennlist Member
Rennlist Member
Air leak?
Keesje, the sunroof is not likely leaking. Its gutters are likely plugged. Use weed eater line or shark fishing line and snake it through ALL FOUR the holes. Front ones obvious, rears visible if you lift the rear hatch and look at where they exit the roof.
Als van die beste,
Heinrich
Keesje, the sunroof is not likely leaking. Its gutters are likely plugged. Use weed eater line or shark fishing line and snake it through ALL FOUR the holes. Front ones obvious, rears visible if you lift the rear hatch and look at where they exit the roof.
Als van die beste,
Heinrich
01-08-2005, 08:52 AM
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Heinrich,
One of my suction hoses is broken in the middle, it's barely hanging on a thread, could it be that when the engine is warm, it takes in too much hot air (but this shouldn't be a problem at idle I think) ?
Regards,
One of my suction hoses is broken in the middle, it's barely hanging on a thread, could it be that when the engine is warm, it takes in too much hot air (but this shouldn't be a problem at idle I think) ?
Regards,
01-08-2005, 05:17 PM
#6
Nordschleife Master
Could Be -
Weak Spark - weak battery
MAF going BAd or getting Wet
Maf not seated properly
Bad SPW (Spark plug Wires)
When was the last you checked the belt for the twin distributors?
Air filter?.
Just a BRain storm on my Part
Weak Spark - weak battery
MAF going BAd or getting Wet
Maf not seated properly
Bad SPW (Spark plug Wires)
When was the last you checked the belt for the twin distributors?
Air filter?.
Just a BRain storm on my Part
01-08-2005, 05:55 PM
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1. Check your throttle position sensor, specifically the idle pot [?]
2. After you replaced your MAF...was the CO set? Try leaning it out. There is a round hole near the connector; insert 3 mm allen wrench and turn counter-clockwise about one turn- see if that helps.
N!
2. After you replaced your MAF...was the CO set? Try leaning it out. There is a round hole near the connector; insert 3 mm allen wrench and turn counter-clockwise about one turn- see if that helps.
N!
