Help... New Plugs and Leads... Engine very rough
Thread Starter
Track Day
Joined: Aug 2011
Posts: 17
Likes: 0
Help... New Plugs and Leads... Engine very rough
Hi
Firstly I have to say what an amazing forum this is, I'm a new proud owner of a 97 C4 993 with a very low 50k miles on the clock (took me a long time to find).
Having trawled through the service history I decided the 60k service would be a good idea and having worked on cars before I had a relatively good idea what i was in for, thanks to Jackel and a number of forum posters i had a good walk though doc.
NOW to the problem: having changed the spark plugs and the leads when I start the car it's extremely rough and won't idle, lots of smoke.
I thought possibly I mixed the leads on the dizzy's but no the numbers on the cap and the leads correspond all the way to the upper and lower plugs.
I really don't know what else to do I have taken the car apart again checking for loose vacuum leads or a power connector but everything looks ok (to a complete amateur that is)
I removed 2 of the lower plugs this evening and they are completely black already, now I know that should not be the case but I haven't interfered with timing or jetting so why should this be?
Could moving the MAF have caused this?
Please help I'm desperate to get back in and go driving, a Porsche should never be left sitting on axel stands!!!!
Thank you to eveyone who reads this.
Firstly I have to say what an amazing forum this is, I'm a new proud owner of a 97 C4 993 with a very low 50k miles on the clock (took me a long time to find).
Having trawled through the service history I decided the 60k service would be a good idea and having worked on cars before I had a relatively good idea what i was in for, thanks to Jackel and a number of forum posters i had a good walk though doc.
NOW to the problem: having changed the spark plugs and the leads when I start the car it's extremely rough and won't idle, lots of smoke.
I thought possibly I mixed the leads on the dizzy's but no the numbers on the cap and the leads correspond all the way to the upper and lower plugs.
I really don't know what else to do I have taken the car apart again checking for loose vacuum leads or a power connector but everything looks ok (to a complete amateur that is)
I removed 2 of the lower plugs this evening and they are completely black already, now I know that should not be the case but I haven't interfered with timing or jetting so why should this be?
Could moving the MAF have caused this?
Please help I'm desperate to get back in and go driving, a Porsche should never be left sitting on axel stands!!!!
Thank you to eveyone who reads this.
Drifting
Joined: Aug 2010
Posts: 2,359
Likes: 26
From: Hales Corners, WI
I would double check the plug wires. If they are in the right location, make sure they are fully seated into the distributors and plugs. There are pics somewhere on this forum for correct locations if your not sure. Not sure if this helps, but I would start with the simplest things and look at what I changed (although I bet you've already done most of that). It was good to post here. This forum has been invaluable for these kind of things for me.
Courtesy of IXLR8:
http://edelweiss.smugmug.com/Cars/Po...154003_Rdktg9c
Courtesy of IXLR8:
http://edelweiss.smugmug.com/Cars/Po...154003_Rdktg9c
Last edited by ble2011; Sep 16, 2011 at 08:18 PM.
Thread Starter
Track Day
Joined: Aug 2011
Posts: 17
Likes: 0
Ble,
Thanks for your comment, I’ve been very busy at work so i haven’t had a moment to spend on the car but I got out last night to the garage and again checked the HT leads and all are definitely on correctly.
I removed the ignition supply lead from the lower dizzy (supplies the upper leads) and the engine remains the same. I also checked the rotor and it does not move on it’s own and the 2 rotors point to the same cylinder.
I have tried to check all the vacuum leads because when you thread the new leads past the variocam intake they can get caught in the many wires but they all look ok.
I am totally at a loss and I really need some help, NO engine codes from the Durametric tester either.
HELP!!
Thanks for your comment, I’ve been very busy at work so i haven’t had a moment to spend on the car but I got out last night to the garage and again checked the HT leads and all are definitely on correctly.
I removed the ignition supply lead from the lower dizzy (supplies the upper leads) and the engine remains the same. I also checked the rotor and it does not move on it’s own and the 2 rotors point to the same cylinder.
I have tried to check all the vacuum leads because when you thread the new leads past the variocam intake they can get caught in the many wires but they all look ok.
I am totally at a loss and I really need some help, NO engine codes from the Durametric tester either.
HELP!!
Instructor
Joined: May 2008
Posts: 163
Likes: 0
From: sussex United Kingdom
Hi did you change the plug leads one at a time, ie old one of new one on or did you take all the leads out then put the new ones on using a diagram from a manual or some other source? The reason I ask is I saw someone follow a plug lead diagram that was incorrect and 180 degrees out.
As someone else said really does sound like ht leads on the wrong cylinder plugs.
I take it you have checked all your vacuum pipes, electrical connections in case you inadvertently pulled any off while whilst working on the car.
Regards
As someone else said really does sound like ht leads on the wrong cylinder plugs.
I take it you have checked all your vacuum pipes, electrical connections in case you inadvertently pulled any off while whilst working on the car.
Regards
Burning Brakes
Joined: Mar 2004
Posts: 1,151
Likes: 0
From: Calif
disable the lower distributor by pulling the HT lead. set upper distributor to point at some cylinder that you can pull the plug from - check that the piston is near TDC, if not, rotate engine until that piston is at TDC and see where the rotor points.
When I changed wires, I had no problems, just connected wires to the proper plugs and to the distributor - as I recall the wires were numbered. If you are using non OEM wires, then that may not be the case.
you can also try pulling one wire at a time with engine running to see if the associated plug is firing at right time - what is most likely is that the distributor is rotated by 15 degrees or something like that, presuming you connected everythign in the way the Porsche manual says you should.
When I changed wires, I had no problems, just connected wires to the proper plugs and to the distributor - as I recall the wires were numbered. If you are using non OEM wires, then that may not be the case.
you can also try pulling one wire at a time with engine running to see if the associated plug is firing at right time - what is most likely is that the distributor is rotated by 15 degrees or something like that, presuming you connected everythign in the way the Porsche manual says you should.
Instructor
Joined: May 2004
Posts: 224
Likes: 0
From: London England UK
Hi
This job should be no problem, the only thing you may want to check is that the upper and lower values of the distributors have not been reversed, ie upper leads on lower dizzy and visa versa
Good luck I'm sure it's something straight forward
https://rennlist.com/forums/attachme...1&d=1316899479
This job should be no problem, the only thing you may want to check is that the upper and lower values of the distributors have not been reversed, ie upper leads on lower dizzy and visa versa
Good luck I'm sure it's something straight forward
https://rennlist.com/forums/attachme...1&d=1316899479
Thread Starter
Track Day
Joined: Aug 2011
Posts: 17
Likes: 0
d ward
I changed the leads one at a time from old dizzy cap to new, I had in fact done the upper cap a week previous and had no issues. This all started when the leads and lower cap was replaced (lower in engine bay = upper spark plugs). The caps are bosch and therefore numbered and so are the HT leads (beru).
william_b_noble
I re-did the entire job again today and the car will now idle with no help from me but at 4oorpm and sounding very unhappy. how will rotating the engine to TDC with the plug pulled yield me any information? sorry Im a little green on this stuff
ASH.PALIN
I agree with you this job should be no problem, I have completed it on a V8 with no issues again by removing one lead at a time and replacing with new. The image you supplied is what I'm working from and with everything numbered it really should be walk in park. I know it's something simple, that’s what’s killing me!!
The car when running is very rich and the exhaust smells very strong of petrol (un-burnt fuel) could there be an issue with the injectors?
If the leads were on incorrectly would that not throw a code in the diagnostics?
I changed the leads one at a time from old dizzy cap to new, I had in fact done the upper cap a week previous and had no issues. This all started when the leads and lower cap was replaced (lower in engine bay = upper spark plugs). The caps are bosch and therefore numbered and so are the HT leads (beru).
william_b_noble
I re-did the entire job again today and the car will now idle with no help from me but at 4oorpm and sounding very unhappy. how will rotating the engine to TDC with the plug pulled yield me any information? sorry Im a little green on this stuff
ASH.PALIN
I agree with you this job should be no problem, I have completed it on a V8 with no issues again by removing one lead at a time and replacing with new. The image you supplied is what I'm working from and with everything numbered it really should be walk in park. I know it's something simple, that’s what’s killing me!!
The car when running is very rich and the exhaust smells very strong of petrol (un-burnt fuel) could there be an issue with the injectors?
If the leads were on incorrectly would that not throw a code in the diagnostics?
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Pro
Joined: Mar 2005
Posts: 745
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From: Charleston, SC
Redman - where are you? I know there are parts of the country where there is a high concentration of Rennlisters, and you might be able to get someone more experienced to come by and lend a fresh set of eyes. Hope this gets figured out..
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Drifting
Joined: Aug 2002
Posts: 2,083
Likes: 5
From: USA
Just to throw this out there..
You might be looking in the wrong area.
Being a 97 and thinking that you may have had the battery disconnected for some time during this project.
It is very possible your ECU is off the charts and the car needs to be driven and re-adapt.
I have been thrown off by 96-98 cars stalling on decel, rich and rough idle, to find later it was this simple.
You might be looking in the wrong area.
Being a 97 and thinking that you may have had the battery disconnected for some time during this project.
It is very possible your ECU is off the charts and the car needs to be driven and re-adapt.
I have been thrown off by 96-98 cars stalling on decel, rich and rough idle, to find later it was this simple.
Thread Starter
Track Day
Joined: Aug 2011
Posts: 17
Likes: 0
deekay911
I think that’s exactly it, a fresh pair of eyes, I know from experience that when its a simple issue the more you delve into the issue the less likely you are to fix it and then someone comes along and spots the issue immediately. Now the unfortunate bit..... I’m living in Ireland!!!
CalvinC4S
This did cross my mind and I had read that if the battery is disconnected for a period the ECU needs to re-adapt. I took the car for a very short run and it was just un-drivable, kept cutting out so I don’t think that’s it. It almost sounds as if the timing is out.
I have a new theory, I disconnected the O2 sensor and it threw a code in the Durametric system (oddly enough only in the version 6 and not in Version 5) I reconnected the sensor and the car wouldn’t start but I'm getting a strong smell of petrol. I think there might be an issue with the Bosch Coil Pack, does anyone know a way to test this prior to ordering a new one (Durametric Not displaying a coil error code)
I think that’s exactly it, a fresh pair of eyes, I know from experience that when its a simple issue the more you delve into the issue the less likely you are to fix it and then someone comes along and spots the issue immediately. Now the unfortunate bit..... I’m living in Ireland!!!
CalvinC4S
This did cross my mind and I had read that if the battery is disconnected for a period the ECU needs to re-adapt. I took the car for a very short run and it was just un-drivable, kept cutting out so I don’t think that’s it. It almost sounds as if the timing is out.
I have a new theory, I disconnected the O2 sensor and it threw a code in the Durametric system (oddly enough only in the version 6 and not in Version 5) I reconnected the sensor and the car wouldn’t start but I'm getting a strong smell of petrol. I think there might be an issue with the Bosch Coil Pack, does anyone know a way to test this prior to ordering a new one (Durametric Not displaying a coil error code)
Instructor
Joined: May 2008
Posts: 163
Likes: 0
From: sussex United Kingdom
You said it runs fine on one distributor, so run out on just that good one, then take the center ht lead off of the coil pack its on at mo and plug it on to the one you think is duff, if it continues to run fine you know its not the coil pack.
As a thought I know you got all new bits, but its not unknown for new bits to be faulty, maybe one of your new distributor caps if mis manufactured.
If your car has done a lot of miles, maybe worth changing your one lamba sensor as a matter of course, as they dont last forever and dont always show up as a fault coding on durametric as your car only runs obd1 and only had the one lamba sensor
As a thought I know you got all new bits, but its not unknown for new bits to be faulty, maybe one of your new distributor caps if mis manufactured.
If your car has done a lot of miles, maybe worth changing your one lamba sensor as a matter of course, as they dont last forever and dont always show up as a fault coding on durametric as your car only runs obd1 and only had the one lamba sensor
Thread Starter
Track Day
Joined: Aug 2011
Posts: 17
Likes: 0
Ok back again with an update, I did a voltage test on the low tention cables at the 2 coil packs and recorded on voltage on 1, this according to posts I have read here on reenlist suggest an ignition switch failure. I decided to also repace the coils and the DME relay
The DME and coils are easy instals but the ignition switch is impossible to get out. It's the top screw that causes the real problem, has anyone any tips on getting it out?
The DME and coils are easy instals but the ignition switch is impossible to get out. It's the top screw that causes the real problem, has anyone any tips on getting it out?
Thread Starter
Track Day
Joined: Aug 2011
Posts: 17
Likes: 0
More update....
Following some further investigations the ignition switch was ruled out. I have now replaced the ignition module (under seat) but this has not resolved the problem.
To recap: car will not start but will turn over on the starter motor.
I am in dire need for help before I give in and send her packing to the Porsche specialist.
Following some further investigations the ignition switch was ruled out. I have now replaced the ignition module (under seat) but this has not resolved the problem.
To recap: car will not start but will turn over on the starter motor.
I am in dire need for help before I give in and send her packing to the Porsche specialist.
Drifting
Joined: Aug 2002
Posts: 2,083
Likes: 5
From: USA
Just to double double check..
Disconnect the battery over night, start the car in the AM and be 100% sure not to touch the throttle on start up. Let it idle for 10 min, then drive it.
I have had them so far out of wack they barley run. I attributed it to possibly having the TPS out of calibration due to possibly taping the throttle on start up.
My symptoms where terrible idle and instant stall when car came off load.
Disconnect the battery over night, start the car in the AM and be 100% sure not to touch the throttle on start up. Let it idle for 10 min, then drive it.
I have had them so far out of wack they barley run. I attributed it to possibly having the TPS out of calibration due to possibly taping the throttle on start up.
My symptoms where terrible idle and instant stall when car came off load.