1987 Rough Idle
02-27-2005, 09:35 PM
#32
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Just FYI,
I have an 1987 Targa, ROW with n/a engine (930/20) that had a somewhat rough idle with the stock chip. I replaced the stock chip with Steve Wong's chip and now the idle is smooth as silk ( I can *actually* rest a nickel on the engine at idle now).
Now, I have no experience with other aftermarket chips.. I did my homework and researched *every* chip out there and went with SWs chip after reading many, many gushing reviews.... I could NOT be happier with my purchase... ( No Loren, I did NOT get before and after dyno results )
Take the time and read all the info on 911chips.com, specifically http://www.911chips.com/faq.html
to get a better understanding of why his chip is superior to the stock chip...
Re: Loren - don't really know what his deal is, but at least he is consistant in his ranting ( that's the bright side )
Re: your rough idle.. in 95% of cases, it's one of two things ( or both) -
Vacuum leak ( vac hoses intake boots or intake gaskets )
Mixture setting ( set on the air meter )
Unfortunately, if you set the mixture setting *with* a vacuum leak, the mixture setting will probably not stay consistant since the vac leak will probably get worse ( as the rubber hose(s) degrade or gasket(s) degrade ) so check for vac leaks *first, then set the mixture correctly.. To set mixture correctly, you will need a gas analyzer and so is normally out of the DIY catagory. Fortunately, the cost of setting the mixture is NOT high ( < $50 if no parts needed )
Note that you *might* be able to make the idle less rough by fiddling with the base idle speed adjustment
have a look at the bottom of this page for howto http://www.911chips.com/dmeconvr.htm
Good luck
I have an 1987 Targa, ROW with n/a engine (930/20) that had a somewhat rough idle with the stock chip. I replaced the stock chip with Steve Wong's chip and now the idle is smooth as silk ( I can *actually* rest a nickel on the engine at idle now).
Now, I have no experience with other aftermarket chips.. I did my homework and researched *every* chip out there and went with SWs chip after reading many, many gushing reviews.... I could NOT be happier with my purchase... ( No Loren, I did NOT get before and after dyno results )
Take the time and read all the info on 911chips.com, specifically http://www.911chips.com/faq.html
to get a better understanding of why his chip is superior to the stock chip...
Re: Loren - don't really know what his deal is, but at least he is consistant in his ranting ( that's the bright side )
Re: your rough idle.. in 95% of cases, it's one of two things ( or both) -
Vacuum leak ( vac hoses intake boots or intake gaskets )
Mixture setting ( set on the air meter )
Unfortunately, if you set the mixture setting *with* a vacuum leak, the mixture setting will probably not stay consistant since the vac leak will probably get worse ( as the rubber hose(s) degrade or gasket(s) degrade ) so check for vac leaks *first, then set the mixture correctly.. To set mixture correctly, you will need a gas analyzer and so is normally out of the DIY catagory. Fortunately, the cost of setting the mixture is NOT high ( < $50 if no parts needed )
Note that you *might* be able to make the idle less rough by fiddling with the base idle speed adjustment
have a look at the bottom of this page for howto http://www.911chips.com/dmeconvr.htm
Good luck
02-27-2005, 10:30 PM
#33
"now the idle is smooth as silk ( I can *actually* rest a nickel on the engine at idle now)." - ausdilecce -
Actually, ALL 911s from the '82/'83 SC thru the 993 have an "idle hunting" of
about 30 to 60 RPMs, the result of the closed loop emission control system.
Those that don't usually have a problem in the emission system or have it
disabled, e.g. bad O2 sensor, too rich/lean a mixture causing the O2 to not
have an affect. It is also noticeable in other Porsche types and other cars.
Sounds like you might have to have your Porsche diagnosed for a properly
functioning fuel injection system, since yours lacks the normal "hunt".
"Re: your rough idle.. in 95% of cases, it's one of two things ( or both) -
Vacuum leak ( vac hoses intake boots or intake gaskets )
Mixture setting ( set on the air meter )" - ausdilecce -
I don't know where your 95% number (a "ranting") comes from, but it's not accurate!
Maybe you did a sampling of Porsche shops & dealers?
The distribution of problem sources is fairly broad & NOT peaked
on two sources (AFM & vacuum leaks), e.g.
1. bad O2 sensor
2. fuel pressure regulator
3. bad cylinder temp sensor
4. bad grounds
5. too high of alternator voltage
Bottomline: There're many possible problem sources for the words "rough idle",
and that's why it needs to be properly diagnosed without guessing.
Actually, ALL 911s from the '82/'83 SC thru the 993 have an "idle hunting" of
about 30 to 60 RPMs, the result of the closed loop emission control system.
Those that don't usually have a problem in the emission system or have it
disabled, e.g. bad O2 sensor, too rich/lean a mixture causing the O2 to not
have an affect. It is also noticeable in other Porsche types and other cars.
Sounds like you might have to have your Porsche diagnosed for a properly
functioning fuel injection system, since yours lacks the normal "hunt".
"Re: your rough idle.. in 95% of cases, it's one of two things ( or both) -
Vacuum leak ( vac hoses intake boots or intake gaskets )
Mixture setting ( set on the air meter )" - ausdilecce -
I don't know where your 95% number (a "ranting") comes from, but it's not accurate!
Maybe you did a sampling of Porsche shops & dealers?
The distribution of problem sources is fairly broad & NOT peaked
on two sources (AFM & vacuum leaks), e.g.
1. bad O2 sensor
2. fuel pressure regulator
3. bad cylinder temp sensor
4. bad grounds
5. too high of alternator voltage
Bottomline: There're many possible problem sources for the words "rough idle",
and that's why it needs to be properly diagnosed without guessing.
Last edited by Lorenfb; 02-27-2005 at 10:57 PM.
02-28-2005, 12:30 AM
#34
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Originally Posted by Lorenfb
Sounds like you might have to have your Porsche diagnosed for a properly
functioning fuel injection system, since yours lacks the normal "hunt".
functioning fuel injection system, since yours lacks the normal "hunt".
02-28-2005, 01:48 AM
#35
Racer
ROW 930/20 Carreras are not closed loop emissions controlled, and thus cannot have an O2 senor hunt. It would be wise to not disseminate false information and mislead customers into thinking they have a malfuntion becaused they achieved better idle as a result of installing my chips. I will let you in on some technical secrets about why my chips result in a superior idle over the stock chip, or any other chip for that matter.
A couple of years ago, myself along with a good friend of mine at BMW, spent considerable time trying to improve the factory's idle control code. Testing was performed at all temperature extremes, from cold start at -30 degree C to well past 100 degree F. I had also spent considerable time trying to tame different AFM controlled Motronic motors with lightweight flywheels and aggressive cams. Imagine what problems one would face installing something like mod-s cams and a lightweight flywheel in a flapper door meter Motronic 3.2. What was interesting is my friend, a Motronics programming engineer, had located withing the BMW archives, the original '80s Bosch software which displayed and programmed all mapping functions for our Motronic systems, which worked not only for the BMWs, but the Porsche Carreras as well. Some very interesting maps and code functions were discovered that were previouly completely unknown, i.e. rate of change of ignition timing per engine cycle, or fuel enrichment decay per cycle after initial throttle transient.
As a result of our research, our efforts with respect to idle control stability resulted in coding which modulates hunting such as the typical 50 rpm O2 sensor hunt of the stock chip by revising control parameters which dynamically guides the speed upwards within one engine cycle if it were to say, fall below the preprogrammed 880 rpm idle speed. Likewise, if the engine's idle speed tries to shoot upwards past 880, the engine would immediatedly be guided back down to the target 880 idle speed. This function operates independently of the idle control valve, taking away a lot of responsibility from the idle valve in modulating the idle speed, and typicaly minimizes to eliminates idle hunting, as testified by many owners without them even knowing about the feature. The improvement works not only for U.S. spec emissions controlled vehicles, but for ROW euro spec Carreras without emissions controls. The typical 50 rpm hunt from the O2 sensor modulation is minimized to being almost indiscerable. This feature is unique to our chips, and cannot be found on anyone elses without obvious copyright infringement.
The second principle improvement in idle stability comes from controlling the fall rate of the engine rpm as it approaches the target idle on deceleration such as between shifts. Typically with the factory chip, as the driver releases the throttle, the engine rpms fall like a rock to 880 rpm, and it becomes dependent upon the electric motor of the idle control valve to catch the engine speed before it falls too low. However, as this valve ages, or gets gummed up, it's response time slows significantly enough to cause sub idle dipping to 400-600 rpm on throttle deceleration between shifts, or even stalling, and it gets worse with the AC on with the additional load from the compressor. The solution has been to control the rate of fall of the engine rpm to give the idle control valve enough time to modulate the idle speed, instead of catching it by surprise each time. The new behavior is witnessed on release of the throttle with the clutch depressed where the rpms drops like normal to appx. 1000-1050 rpm, after which it floats down to idle at 880 rpm within a second, providing the idle control valve is given sufficient time to take action. It is as if a throttle damper was placed on the throttle butterfly. The overall result is, no more sub idle dipping, an improvement in everyday driveability, cold start running, and is even able to tame stalling and fluctuations as a result of lightweight flywheels and high overlap camshafts.
A couple of years ago, myself along with a good friend of mine at BMW, spent considerable time trying to improve the factory's idle control code. Testing was performed at all temperature extremes, from cold start at -30 degree C to well past 100 degree F. I had also spent considerable time trying to tame different AFM controlled Motronic motors with lightweight flywheels and aggressive cams. Imagine what problems one would face installing something like mod-s cams and a lightweight flywheel in a flapper door meter Motronic 3.2. What was interesting is my friend, a Motronics programming engineer, had located withing the BMW archives, the original '80s Bosch software which displayed and programmed all mapping functions for our Motronic systems, which worked not only for the BMWs, but the Porsche Carreras as well. Some very interesting maps and code functions were discovered that were previouly completely unknown, i.e. rate of change of ignition timing per engine cycle, or fuel enrichment decay per cycle after initial throttle transient.
As a result of our research, our efforts with respect to idle control stability resulted in coding which modulates hunting such as the typical 50 rpm O2 sensor hunt of the stock chip by revising control parameters which dynamically guides the speed upwards within one engine cycle if it were to say, fall below the preprogrammed 880 rpm idle speed. Likewise, if the engine's idle speed tries to shoot upwards past 880, the engine would immediatedly be guided back down to the target 880 idle speed. This function operates independently of the idle control valve, taking away a lot of responsibility from the idle valve in modulating the idle speed, and typicaly minimizes to eliminates idle hunting, as testified by many owners without them even knowing about the feature. The improvement works not only for U.S. spec emissions controlled vehicles, but for ROW euro spec Carreras without emissions controls. The typical 50 rpm hunt from the O2 sensor modulation is minimized to being almost indiscerable. This feature is unique to our chips, and cannot be found on anyone elses without obvious copyright infringement.
The second principle improvement in idle stability comes from controlling the fall rate of the engine rpm as it approaches the target idle on deceleration such as between shifts. Typically with the factory chip, as the driver releases the throttle, the engine rpms fall like a rock to 880 rpm, and it becomes dependent upon the electric motor of the idle control valve to catch the engine speed before it falls too low. However, as this valve ages, or gets gummed up, it's response time slows significantly enough to cause sub idle dipping to 400-600 rpm on throttle deceleration between shifts, or even stalling, and it gets worse with the AC on with the additional load from the compressor. The solution has been to control the rate of fall of the engine rpm to give the idle control valve enough time to modulate the idle speed, instead of catching it by surprise each time. The new behavior is witnessed on release of the throttle with the clutch depressed where the rpms drops like normal to appx. 1000-1050 rpm, after which it floats down to idle at 880 rpm within a second, providing the idle control valve is given sufficient time to take action. It is as if a throttle damper was placed on the throttle butterfly. The overall result is, no more sub idle dipping, an improvement in everyday driveability, cold start running, and is even able to tame stalling and fluctuations as a result of lightweight flywheels and high overlap camshafts.
02-28-2005, 08:38 AM
#36
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1987 Rough Idle
I have fitted a number of 911chips, chips recently in both standard and modified 3.2's all of which have had very good idles with very little adjustment required! For my money there is NO other chip to use, just a 911 chips, chip!
03-09-2005, 10:46 PM
#38
What IS your point, Loren? Big deal - I'm Dave Thomas here and Wavey on the Pelican forum. I have different screen names on the Mercedes and Saab sites. SO WHAT??? Does this mean something to you?
You seem to have plenty of time to chase people around and harass them, which is what got you thrown off the Pelican site. Are you trying to get banned here too? If you have so much time on your hands, how about answering the simple yes-or-no question that you've been asked hundreds of times? That's the only way you'll ever regain any credibility, not by posting stupid comments like the above, which add absolutely nothing to the discussion.
You seem to have plenty of time to chase people around and harass them, which is what got you thrown off the Pelican site. Are you trying to get banned here too? If you have so much time on your hands, how about answering the simple yes-or-no question that you've been asked hundreds of times? That's the only way you'll ever regain any credibility, not by posting stupid comments like the above, which add absolutely nothing to the discussion.
03-26-2005, 06:18 PM
#39
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Rough Idle
OK, I finally got around to checking a few things that would affect my idle, and after fitting a new set of magnacore spark plug wires (RPITA), the idle hasn't improved so I went to the oxygen sensor. After getting the car fully warmed up, I disconnected the sensor and checked the voltage from the black sensor wire to ground and got nothing. The meter is a Fluke digital meter and it was fluctuating plus and minus 0.002 volts dc. I reved the car several times and no change whatsoever in the voltage. Could my problems be a failed oxygen sensor? The car has 78,000 miles and as far as I know the sensor has never been changed. I'm thinking I need a new sensor. Would a failed sensor not provide any change in voltage?
As always, thanks in advance!!!
As always, thanks in advance!!!
