When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Please help to diagnose P0410 and 1411 CEL code & rough idle
Hey all,
I recently picked up a 98 C2S with 50K miles - see thread here. Long story short, because of Covid, I was unable to see the car myself but I had a friend (who owns 3 993's) put eyes on it. Also, I was able to get in contact with the prior owner (who's owned it since new) and get the download of the car from him. I ended up buying the car knowing that it had the P0410 and P1411 CEL code. When I received the car, it drove great... no white smoke, pulls hard, doesn't seem to burn oil after 500 miles. However, the only thing that I needed to address immediately was the CEL and a slight rough idle. So this is what I've done so far:
Replaced the SAI valve
SAI port cleanout (confirmed that the ports have air coming through and is not clogged)
Took off and cleaned out the Idle Stabilizer Valve.
Cleaned MAF with MAF cleaner
New Air Filter
After performing the above, both the P0410 and 1411 CEL and the rough idle is still there (although the idle is slightly better). I'm wondering if I have a vacuum leak? Would a leak cause both issues?
I'm starting to run out of ideas on what is causing these issues. Does anyone have any input? Should I replace the O2 sensors?
FYI, I will be replacing the distributor cap and rotor next week - not sure if this will do anything but it was on my list of things to change anyway. Thanks in advance
Since both codes are "Version 1 Signal implausible / Implausible Component Section / Malfunction" not
"Version 2 Interruption / No Signal = second column in list below", "Version 3 Short to Ground / Below Lower Limit / Lean Mixture Limit"
or "Version 4 Short to B+ / Above Upper Limit/ Rich Mixture Limit' It suggests it may be the Oxygen sensors are simply sending erroneous signals, for example, if their internal heaters are not working properly the sensors will not heat up into their operating range and give meaningful signals.
Normally oxygen sensors have a very long service life but they can drift out of specification or their pigtail connections can get dirty or easily miswired when reattached after an air injection port cleaning.
If you have a reader that lets you graph operating output, like Durametric, from the sensors one can evaluate their output in real-time. Even with a reader evaluating their performance and timing of light-off at startup for a few seconds could be a challenge in capturing meaningful diagnostic data for your problem.
One option is to simply replace all 4 of them. If purchased online (eBay) at a cost of $60~$80 each purchased in BOSCH branded boxes they are extremely easy to replace in your driveway, and just replacing them all may be an economical option.
When checking their wiring or replacing them be sure to install the correct sensor part numbers to the before and after catalytic converter positions ( the Porsche part number is etched on the barrel of each BOSCH sensor, and connect the pigtails from each to the matching color connections on the engine wiring harness gray to gray, black to black, it is possible to have them switched.
Once the oxygen sensors' function installed position and wiring are ruled out.
However unlikely, the fact that the codes exhibit on both sides of the engine suggests a possible air pump supply issue feeding both.
With Durametric or a professional scanner, one can turn the air pump on and off to see if it is working. The pump failing is almost never heard of but the wires to it are a known deterioration point, easy to fix, and may be causing the system to not run the pump.
Also, I believe there is a vacuum controlled valve upstream from the check valve that should be check for being connected to its hose and actually functioning during the air injection cycle.
A quick driveway test:
The air injection cycle runs for just a few seconds at startup with a dead cold engine. If one caps-off the check valve closing it off with a piece of garden hose and a clamp and then feels considerable airflow from the existing hose normally attached to it for a few seconds at start-up from a dead cold (sitting overnight) engine it will validate that both the air pump is working and its vacuum controlled valve is opening during the cycle.
Well your error codes suggest a SAI fault. It can only be three things 1. the SAI check valve problem (which you replaced)
2. The SAI ports are blocked. 3. SAI pump not working
Before tackling the SAI pump/ports, the check valve is controlled by the vacuum system. Check your vacuum system can hold a vacuum when the car is running. A mityvac you can borrow from AutoZone works fine.
Andy's suggestion above is clever to test the pump. The other simple driveway test is open up the airbox and feel if air is being sucked in by the hose feeding into the pump. The airbox has three hoses connected to it and it's the 1/2" round one that feeds the pump. If there is some air flow there, then likely the ports are clogged so air can't move well through the SAI system which throws a fault on the ECU due to the 02 sensors picking up excessive CO due to not enough fresh air being pumped into the cat via the SAI pump on start-up.
There is a procedure on Pelican and here to show you how to clean the ports. Not hard but will require some minor wrenching to remove parts to get to the ports so you can clean them out with compressed air, carb cleaner, and a bike brake wire like you would to snake a plugged drain pipe.
Reality is that the SAI fault has no performance impact other than not allowing you to pass smog if you are in a state that still forces you to retest. Some just ignore the fault or delete the system..
As for the rough idle that can be multiple things... how rough is it?
Also does the car run fine when you are on the gas?
You didnt say there were other ECU codes so since you are not throwing misfire codes, you may have an intake vacuum leak.
The term vacuum leak in our cars means two things for clarity. 1. Leak of the vram vacuum system which is different than what most mechanics define a vacuum leak which is 2. Leak of the intake
The former will cause problems with mid range performance as your vram will not be working correct (and not deactivate/activate the SAI air to be pumped into the exhaust ports).
The later can cause a rough idle. As someone suggested earlier a smoker or a pressure test of the intake will help identify if you have a vacuum leak... basically a small air gap somewhere after your MAF sucking in a small amount of air when the motor is running. The leaked in air causes the motor to speed up, ISV kicks in to slow it down, and then repeats itself at idle which is one form of "rough idle".
Since you said you cleaned your MAF, I would check if your MAF is seated properly on the throttle body and hand tighten the band clamp that is securing it.
Other rough idle problems root cause can be the ignition (which will throw a misfire code)
1. bad wires, incorrect wires connected (common mistake since there are 12 plugs), or wires not seated properly on the caps or plugs
2. old plugs...unlikely as you have a pair of plugs so having both plugs fail is unusual
3. worn caps/rotors
4. broken distributor belt which means only 1 set of twin plugs are firing
After ignition, then the fuel system
1. Clogged/dirty injectors
2. Old fuel
3. Fuel pressure problems
Running a few tanks with techron will help flush the system of old fuel tarnish as a simple measure.
Be methodical and use a process of elimination so you can isolate the root cause. I would advise not to change a bunch of stuff at the same time (throw a bunch of new parts) as it will be impossible to determine a corrective action you do addresses the root cause of the problem.
That's definitely on the list. Just have to figure out where they all are.
Originally Posted by pp000830
Rough idle has nothing to do with these codes.
Since both codes are "Version 1 Signal implausible / Implausible Component Section / Malfunction" not
"Version 2 Interruption / No Signal = second column in list below", "Version 3 Short to Ground / Below Lower Limit / Lean Mixture Limit"
or "Version 4 Short to B+ / Above Upper Limit/ Rich Mixture Limit' It suggests it may be the Oxygen sensors are simply sending erroneous signals, for example, if their internal heaters are not working properly the sensors will not heat up into their operating range and give meaningful signals.
Normally oxygen sensors have a very long service life but they can drift out of specification or their pigtail connections can get dirty or easily miswired when reattached after an air injection port cleaning.
If you have a reader that lets you graph operating output, like Durametric, from the sensors one can evaluate their output in real-time. Even with a reader evaluating their performance and timing of light-off at startup for a few seconds could be a challenge in capturing meaningful diagnostic data for your problem.
One option is to simply replace all 4 of them. If purchased online (eBay) at a cost of $60~$80 each purchased in BOSCH branded boxes they are extremely easy to replace in your driveway, and just replacing them all may be an economical option.
When checking their wiring or replacing them be sure to install the correct sensor part numbers to the before and after catalytic converter positions ( the Porsche part number is etched on the barrel of each BOSCH sensor, and connect the pigtails from each to the matching color connections on the engine wiring harness gray to gray, black to black, it is possible to have them switched.
Once the oxygen sensors' function installed position and wiring are ruled out.
However unlikely, the fact that the codes exhibit on both sides of the engine suggests a possible air pump supply issue feeding both.
With Durametric or a professional scanner, one can turn the air pump on and off to see if it is working. The pump failing is almost never heard of but the wires to it are a known deterioration point, easy to fix, and may be causing the system to not run the pump.
Also, I believe there is a vacuum controlled valve upstream from the check valve that should be check for being connected to its hose and actually functioning during the air injection cycle.
A quick driveway test:
The air injection cycle runs for just a few seconds at startup with a dead cold engine. If one caps-off the check valve closing it off with a piece of garden hose and a clamp and then feels considerable airflow from the existing hose normally attached to it for a few seconds at start-up from a dead cold (sitting overnight) engine it will validate that both the air pump is working and its vacuum controlled valve is opening during the cycle.
Thanks Andy, very helpful. Do you know where the pump is located? I tried to google and didn't have anything pop up. I also have a duarmetric cable so I'm going to hook it up and see if I can get turn the pump on that way. Thanks for that great info!
Originally Posted by SwayBar
My OBD threw an 02 sensor code when bad so I suspect your 02's are good.
That's what I am thinking too...can both sets of O2 sensors really go bad at the same time?
Originally Posted by samurai_k
Well your error codes suggest a SAI fault. It can only be three things 1. the SAI check valve problem (which you replaced)
2. The SAI ports are blocked. 3. SAI pump not working
Before tackling the SAI pump/ports, the check valve is controlled by the vacuum system. Check your vacuum system can hold a vacuum when the car is running. A mityvac you can borrow from AutoZone works fine.
Andy's suggestion above is clever to test the pump. The other simple driveway test is open up the airbox and feel if air is being sucked in by the hose feeding into the pump. The airbox has three hoses connected to it and it's the 1/2" round one that feeds the pump. If there is some air flow there, then likely the ports are clogged so air can't move well through the SAI system which throws a fault on the ECU due to the 02 sensors picking up excessive CO due to not enough fresh air being pumped into the cat via the SAI pump on start-up. - I have taken the airbox out multiple times and agree, there are three hoses. One is where the MAF is, the second is toward the bottom right that connects to the lid of the airbox (right piece) and the third is on the bottom left that connects to the left side of the airbox. Are you referring to the third?
There is a procedure on Pelican and here to show you how to clean the ports. Not hard but will require some minor wrenching to remove parts to get to the ports so you can clean them out with compressed air, carb cleaner, and a bike brake wire like you would to snake a plugged drain pipe. - Thanks. The roto-rooting was the first thing I did to try to clear the CEL.
Reality is that the SAI fault has no performance impact other than not allowing you to pass smog if you are in a state that still forces you to retest. Some just ignore the fault or delete the system..
As for the rough idle that can be multiple things... how rough is it? - It's really not THAT rough. It's nothing that I would consider bad but if it's something that is fixable, I would want to do it. I will try to get a video of it this week.
Also does the car run fine when you are on the gas? - Yes, 100% fine when I'm on the gas
You didnt say there were other ECU codes so since you are not throwing misfire codes, you may have an intake vacuum leak.
The term vacuum leak in our cars means two things for clarity. 1. Leak of the vram vacuum system which is different than what most mechanics define a vacuum leak which is 2. Leak of the intake
The former will cause problems with mid range performance as your vram will not be working correct (and not deactivate/activate the SAI air to be pumped into the exhaust ports).
The later can cause a rough idle. As someone suggested earlier a smoker or a pressure test of the intake will help identify if you have a vacuum leak... basically a small air gap somewhere after your MAF sucking in a small amount of air when the motor is running. The leaked in air causes the motor to speed up, ISV kicks in to slow it down, and then repeats itself at idle which is one form of "rough idle".
Since you said you cleaned your MAF, I would check if your MAF is seated properly on the throttle body and hand tighten the band clamp that is securing it. - I checked and yes it is seated tight on there.
Other rough idle problems root cause can be the ignition (which will throw a misfire code)
1. bad wires, incorrect wires connected (common mistake since there are 12 plugs), or wires not seated properly on the caps or plugs
2. old plugs...unlikely as you have a pair of plugs so having both plugs fail is unusual
3. worn caps/rotors
4. broken distributor belt which means only 1 set of twin plugs are firing
After ignition, then the fuel system
1. Clogged/dirty injectors
2. Old fuel
3. Fuel pressure problems
Running a few tanks with techron will help flush the system of old fuel tarnish as a simple measure. - I ran my first tank with Techron two weeks ago. I plan on running one more the next time I fill up
Be methodical and use a process of elimination so you can isolate the root cause. I would advise not to change a bunch of stuff at the same time (throw a bunch of new parts) as it will be impossible to determine a corrective action you do addresses the root cause of the problem.
Please see my comments in red^. Thank you for taking the time to help me diagnose. I am going to check on the pump next!
When you actuate the air pump with the engine not running you will clearly hear it when you are seated in the cabin. Actuating the pump does not mean the vacuum controlled valve is actuated and opened as well. This is why the test is done by disconnecting the check valve hose. Getting to the check valve is easily done once the intake air filter box is removed. The engine can be started with the airbox out and the airflow sensor reattached to the intake rubber duct without the box attached.
The pump is tucked under/ behind the intake manifold on the transmission side of the engine. One can see it's green & brown power wires and plug connection next to the vacuum controlled valve in the engine overview picture and it is the black plastic thing under hose leading to the vacuum controlled valve and the check valve in the closeup.
When you actuate the air pump with the engine not running you will clearly hear it when you are seated in the cabin. Actuating the pump does not mean the vacuum controlled valve is actuated and opened as well. This is why the test is done by disconnecting the check valve hose. Getting to the check valve is easily done once the intake air filter box is removed. The engine can be started with the airbox out and the airflow sensor reattached to the intake rubber duct without the box attached.
The pump is tucked under/ behind the intake manifold on the transmission side of the engine. One can see it's green & brown power wires and plug connection next to the vacuum controlled valve in the engine overview picture and it is the black plastic thing under hose leading to the vacuum controlled valve and the check valve in the closeup.
Hope this helps,
Andy
Thanks Andy! I remember seeing the plug when I was replacing the SAI check valve.
does the pump run after the engine starts? if not, check electrical components, fuses, relay
if pump runs, implies air not getting into exhaust. you already checked ports were open, next check parts 14 & 19 & hoses. also check the distribution manifold, there are a few core plugs that disintegrate over time. Check the SAI thread on the Pelican 96/993 forum for photos
do your vram actuators cycle if you key on but don't start if engine's been off for at least an hour? if not, look for vacuum leak that could be affecting the function of part #19
does the pump run after the engine starts? if not, check electrical components, fuses, relay
if pump runs, implies air not getting into exhaust. you already checked ports were open, next check parts 14 & 19 & hoses. also check the distribution manifold, there are a few core plugs that disintegrate over time. Check the SAI thread on the Pelican 96/993 forum for photos
do your vram actuators cycle if you key on but don't start if engine's been off for at least an hour? if not, look for vacuum leak that could be affecting the function of part #19
ToSi, to be honest, I'm not sure. That's one thing I will have to test. I have fister 3's in so even if I was by the engine, I'm not sure if I can hear the pump over the exhaust. In terms of vram actuators cycling, when I put the key in and turn to "on", I do hear some kind of buzzing noise. I'm not sure if that's the actuator or not though
08-23-2020, 11:37 AM
Please help to diagnose P0410 and 1411 CEL code & rough idle
