Very High CO levels-Car stalling
Thread Starter
Racer
Joined: Jan 2002
Posts: 252
Likes: 11
Very High CO levels-Car stalling
Hi all,
My ex car (964 C4) started exhibiting some strange problems recently. Basically the new owner is getting some very high CO level readings (in excess of 9%!). Coupled with this is that it is has become very hard to get the car to idle properly as it keeps stalling on morning starts and the owner has to keep his foot constantly on the throttle to keep it from dying. Even when fully warmed up it will occasionaly stall when coming to a stop. This was happening with a APE (Autothority) MAF sensor installed. Out of desperation the owner refitted the original vane type sensor which resulted in the co levels coming back down to normal and the car idling beautifully. However performance is down from the MAF setup. Any one with any tips or ideas as to what to check for/ replace/adjust etc? Have tried talking to Autothority and their service is disgraceful to say the least. Got some token answers intially as to what could be wrong but then their responses to my pleas kept taking them longer and longer to reply with the last email to them unanswered for two weeks.
Would appreciate any and all advice.
Note, when I swap the sensors over I swap the chips in the ECU as well; stock chip-stock sensor; Autothority chip-autothority MAF.
cheers,
Krish
'97 993tt
'89 964 C4 (just sold)
My ex car (964 C4) started exhibiting some strange problems recently. Basically the new owner is getting some very high CO level readings (in excess of 9%!). Coupled with this is that it is has become very hard to get the car to idle properly as it keeps stalling on morning starts and the owner has to keep his foot constantly on the throttle to keep it from dying. Even when fully warmed up it will occasionaly stall when coming to a stop. This was happening with a APE (Autothority) MAF sensor installed. Out of desperation the owner refitted the original vane type sensor which resulted in the co levels coming back down to normal and the car idling beautifully. However performance is down from the MAF setup. Any one with any tips or ideas as to what to check for/ replace/adjust etc? Have tried talking to Autothority and their service is disgraceful to say the least. Got some token answers intially as to what could be wrong but then their responses to my pleas kept taking them longer and longer to reply with the last email to them unanswered for two weeks.
Would appreciate any and all advice.
Note, when I swap the sensors over I swap the chips in the ECU as well; stock chip-stock sensor; Autothority chip-autothority MAF.
cheers,
Krish
'97 993tt
'89 964 C4 (just sold)
Race Car
Joined: May 2003
Posts: 4,240
Likes: 103
From: SoCal
Leave the 964 engine alone. It has enough
potential problems w/o putting questionable mods
on it.
Your other option is to totally strip it and
make it a race car. Then you don't have to worry
about an idle problem or a CO level.
As I mention on my website,
most chips and mods for later cars are
problematic.
Don't get taken down the "path" with
performance mods.
Good luck
Loren
potential problems w/o putting questionable mods
on it.
Your other option is to totally strip it and
make it a race car. Then you don't have to worry
about an idle problem or a CO level.
As I mention on my website,
most chips and mods for later cars are
problematic.
Don't get taken down the "path" with
performance mods.
Good luck
Loren
Rennlist Member
Joined: Jun 2001
Posts: 3,695
Likes: 69
From: Arizona
Check the idle position switch before you do anything else. I have this problem occassionally, to solve it I reach down and pull the floormat back so it dosen't rest on the pedal. The slightest pressure on the throttle causes the position switch to open and you loose throttle stability. Chasing the idle with your right foot is impossible you're fighting the DME, best to keep your foot off it unless you plan on using it.
FYI, I have the autothority MFS kit as well, it does tend to be more sensitive to the off idle stall, particularly with the AC on.
FYI, I have the autothority MFS kit as well, it does tend to be more sensitive to the off idle stall, particularly with the AC on.
Thread Starter
Racer
Joined: Jan 2002
Posts: 252
Likes: 11
Thanks Richard <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" /> . I did check the idle switch but it checked out okay. The thing is it idles fine when the original air flow sensor is back in the car but with the Autothority MAF setup it just runs way too rich- 9% co levels at idle 
! This according to my mech is what's causing the stalling.
Any other ideas?? Anyone??
cheers,
Krish
'97 993tt
'89 964 C4 (just sold)
! This according to my mech is what's causing the stalling. Any other ideas?? Anyone??
cheers,
Krish
'97 993tt
'89 964 C4 (just sold)
Race Car
Joined: Aug 2001
Posts: 4,922
Likes: 1
From: London, UK
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Lorenfb:
<strong>Leave the 964 engine alone. It has enough
potential problems w/o putting questionable mods
on it.
Your other option is to totally strip it and
make it a race car. Then you don't have to worry
about an idle problem or a CO level.
As I mention on my website,
most chips and mods for later cars are
problematic.
Don't get taken down the "path" with
performance mods.
Good luck
Loren</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">How do I find your website?
Thanks for your opinion on upgrades - I'll remember not to ask your opinion in the future.
<strong>Leave the 964 engine alone. It has enough
potential problems w/o putting questionable mods
on it.
Your other option is to totally strip it and
make it a race car. Then you don't have to worry
about an idle problem or a CO level.
As I mention on my website,
most chips and mods for later cars are
problematic.
Don't get taken down the "path" with
performance mods.
Good luck
Loren</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">How do I find your website?
Thanks for your opinion on upgrades - I'll remember not to ask your opinion in the future.
Thread Starter
Racer
Joined: Jan 2002
Posts: 252
Likes: 11
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> Thanks for your opinion on upgrades - I'll remember not to ask your opinion in the future.
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">My sentiments Christer. Don't remember asking for an opinion but I got one instead of help.
Car's still stalling and still running rich at 9% CO levels with the Autothority MAF/chip setup. Anyone with any ideas as to how I can bring the CO down? I have sold this car to a really decent bloke and want to solve this problem for him and would appreciate all help and advice.
cheers,
Krish
'97 993tt
'89 964 C4 (just sold)
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">My sentiments Christer. Don't remember asking for an opinion but I got one instead of help.
Car's still stalling and still running rich at 9% CO levels with the Autothority MAF/chip setup. Anyone with any ideas as to how I can bring the CO down? I have sold this car to a really decent bloke and want to solve this problem for him and would appreciate all help and advice.
cheers,
Krish
'97 993tt
'89 964 C4 (just sold)
Trending Topics
Race Car
Joined: May 2003
Posts: 4,240
Likes: 103
From: SoCal
I apologize for my strong statements about chips.
I really hate to see Porsche owners waste money
on things that cause problems for their cars.
In the last month, I've converted three 964 DMEs
and one 3.2 DME to stock.
With regard to my website, Rennlist asked that I
not mention it in my posts. If you are interested
use Google and search "Porsche fuel injection".
My website will be on the first page on the right.
Good luck
Loren
I really hate to see Porsche owners waste money
on things that cause problems for their cars.
In the last month, I've converted three 964 DMEs
and one 3.2 DME to stock.
With regard to my website, Rennlist asked that I
not mention it in my posts. If you are interested
use Google and search "Porsche fuel injection".
My website will be on the first page on the right.
Good luck
Loren
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Race Car
Joined: Aug 2001
Posts: 4,922
Likes: 1
From: London, UK
Loren
No offence taken on my part, I do the same thing to other people occasionally (although I try not to!).
Everything I do to modify my car is researched and tested as far as possible beforehand and shared as far as possible with the group. Both the good and the bad. Hopefully this way we can all benefit and share knowledge. Perhaps you can join in as well. If you have experience, we'd like to hear about it..
No offence taken on my part, I do the same thing to other people occasionally (although I try not to!).
Everything I do to modify my car is researched and tested as far as possible beforehand and shared as far as possible with the group. Both the good and the bad. Hopefully this way we can all benefit and share knowledge. Perhaps you can join in as well. If you have experience, we'd like to hear about it..
Thread Starter
Racer
Joined: Jan 2002
Posts: 252
Likes: 11
No worries Loren 
. Can understand where you're coming from I guess. Like Christer I try and research everything beforehand before making the attempt (and this does not just apply to cars!)
The problem has been identified yes in that it's definitely the MAF that's causing this, but why?
The Autothority MAF setup works great especially on full throttle application, it's just the idle and the new owner is loathe to ditching it after noticing the loss of performance with the stock setup.
Again if anyone has any ideas or fixes I coud try to bring the CO levels down.......
cheers,
Krish
'97 993tt
'89 964 C4 (just sold)
. Can understand where you're coming from I guess. Like Christer I try and research everything beforehand before making the attempt (and this does not just apply to cars!)The problem has been identified yes in that it's definitely the MAF that's causing this, but why?
The Autothority MAF setup works great especially on full throttle application, it's just the idle and the new owner is loathe to ditching it after noticing the loss of performance with the stock setup.Again if anyone has any ideas or fixes I coud try to bring the CO levels down.......
cheers,
Krish
'97 993tt
'89 964 C4 (just sold)
Rennlist Member
Joined: Jun 2001
Posts: 3,695
Likes: 69
From: Arizona
Krish,
I wasn't saying the throttle position switch would affect c/o, but in my case it definately affected the stalling.
I had the same problem bringing a car from out of state that didn't require emissions to mine that does. I had to refit the cat, and could not get it to pass the idle test (too rich) rolling test was fine. There was no way to tweek it to pass. I called autothority who had a remapped chip for the MAF setup that solved the problem.
In terms of modifications I think that most on this forum are trying to extract as much as they can from their cars, that includes putting up with more tempermental engines, harsh suspensions, noisy exhaust and squeeky breaks...kind of what a porsche is all about...
For rolling around town a mercedes is a wonderful car.... <img border="0" title="" alt="[Wink]" src="wink.gif" />
I wasn't saying the throttle position switch would affect c/o, but in my case it definately affected the stalling.
I had the same problem bringing a car from out of state that didn't require emissions to mine that does. I had to refit the cat, and could not get it to pass the idle test (too rich) rolling test was fine. There was no way to tweek it to pass. I called autothority who had a remapped chip for the MAF setup that solved the problem.
In terms of modifications I think that most on this forum are trying to extract as much as they can from their cars, that includes putting up with more tempermental engines, harsh suspensions, noisy exhaust and squeeky breaks...kind of what a porsche is all about...
For rolling around town a mercedes is a wonderful car.... <img border="0" title="" alt="[Wink]" src="wink.gif" />
Thread Starter
Racer
Joined: Jan 2002
Posts: 252
Likes: 11
Thanks Richard. Looks like I might have to opt for a remapped chip as well. That Mercedes down the road is starting to look real good <img border="0" title="" alt="[Wink]" src="wink.gif" />
cheers,
kris
'97 993tt
'89 964 C4 (sold)
cheers,
kris
'97 993tt
'89 964 C4 (sold)