986 CEL on after storage

[Rundtinden]

Hi!
Just fired up my 1999 986 2.5 after almost two years in the garage. It was fine when I parked it. On first startup the red light next to the temp gauge started flashing, and the CEL came on. Not flashing. I checked the coolant, and found it was a little low. Just under min. Added some coolant, changed oil and filter, and both lights were gone. That was yesterday. Today the CEL light came on again. Car pulls strong, and the oil looked fine. No water in it, and no bad signs in the filter either. Will hook it up and read the codes, but what do you think is the most likely cause of the CEL?

[studentwhocantbudget]

Hmm, intuition tells me you should replace all your fluids after sitting for 2 years. Maybe start with an oil change and complete coolant flush.

[Rundtinden]

Originally Posted by studentwhocantbudget

Hmm, intuition tells me you should replace all your fluids after sitting for 2 years. Maybe start with an oil change and complete coolant flush.

Thank you for swift reply. I changed the oil and the oil filter yesterday. The coolant was fresh when I put it away, so I just added enough to make the red flashing light go away.

[mikefocke]

And then the brake fluid flush.

[blue62]

Originally Posted by Rundtinden

Hi!
Just fired up my 1999 986 2.5 after almost two years in the garage. It was fine when I parked it. On first startup the red light next to the temp gauge started flashing, and the CEL came on. Not flashing. I checked the coolant, and found it was a little low. Just under min. Added some coolant, changed oil and filter, and both lights were gone. That was yesterday. Today the CEL light came on again. Car pulls strong, and the oil looked fine. No water in it, and no bad signs in the filter either. Will hook it up and read the codes, but what do you think is the most likely cause of the CEL?

The CEL could be from any number of things.
Read the code then you will know why the CEL is on.

[Stl-986]

Until you know the codes there isn't much help.

[trilobite]

Incidentally, I had something similar happen. Granted, I didn't store it for a year, but I bought it from someone who had.

After I put about 150 miles on it after storage, I threw CEL and blinking coolant light. It was throwing 3 different codes, one of which ended up being a bleeder valve. Fixed that and the coolant system was right as rain. (...except for not having secured the reservoir cap tightly enough and blowing out about a gallon of coolant onto a parking lot, but we're not going to talk about that.)

[Rob175]

You said it threw 3 codes but only told us of 1. So let's start over....what are the 3 codes? Code numbers ONLY please.

[Rundtinden]

Originally Posted by Rob175

You said it threw 3 codes but only told us of 1. So let's start over....what are the 3 codes? Code numbers ONLY please.

Finally found the time to hook it up!
Codes as follows: P0300, P0301, P0302 and P0303. My Bosch Estronic reports them to be ignition faults on cylinder 1, 2 and 3. When I cleared the codes it took about 5 minutes of eventless driving before the CEL came on again. Any suggestions?

[Rundtinden]

Changed the rubber boot between the plenum and the intake. Checked for leaks. Then took it for a test drive. Cel came on again after 80km. Car pulls strong, but seems to have a problem on low throttle settings. New codes: P300, 301, 304, 305 and 306.
Changed plugs and inspected coils. Could this be a fuel problem?
Filter perhaps?

[blue62]

Originally Posted by Rundtinden

Changed the rubber boot between the plenum and the intake. Checked for leaks. Then took it for a test drive. Cel came on again after 80km. Car pulls strong, but seems to have a problem on low throttle settings. New codes: P300, 301, 304, 305 and 306.
Changed plugs and inspected coils. Could this be a fuel problem?
Filter perhaps?

P300 is a general misfire code.
P301 is cyl 1 bank 1.
P304-305-306 ia all cyl.on bank 2.

So You have an issue that is causing misfires on both banks.
Could be a vacuum leak.
Could be a fuel problem.
could be an electrical problem.
Could be a sensor problem like the MAF sensor.
Could be any number of things.

Best thing to do is go with a good automotive diagnostic procedure.
That is: start with the simplest things first and work your way up step by step.??

I assume you have done the basics??
Checked battery condition via a load test?
Looked at plugs and coils??
Has good clean fuel???
Good clean air filter??

After that:
Start with a proper vacuum test with a vacuum gauge.
If you know how to use a vacuum gauge for testing you not only can test for vacuum leaks but it will give you a good baseline for overall engine condition.

Greater engine loads and more throttle create greater fuel demand.
You say it pulls strong: does not sound like a fuel issue to me although it is possible. It doesn't sound likely.


If you have something like a Durametric scan tool you could hook it up and look at fuel trims and O2 sensor response to try to determine if you have a lean or rich fueling condition. If you do this could help in knowing what to look for as the issue.

From the info you have provided my guess is you have an air intake issue:
Vacuum leak
Maf sensor issue
IAC issue
EVAP system leak
Something related to air intake

You stated you had air leaks in the intake. you did some work there.
Do a vacuum test with a vacuum gauge it will help tell you if you have fixed all the vacuum leaks.

Or it could be electrical


Lets try to find the cause of the issue.

Give me more info on the car.

Miles?
Is it all stock or are there mods?
If so what mods?
Stock air filter?

So if you start if and let it warm up how does it idle??
What RPM does it idle at?
Smooth with no issue? or lumpy- rough?
Hunting= RPM moving up and down?
If it idles lumpy or rough or hunts, will it smooth out if you hold the RPM at around 2000-2500 RPM?? Do this in neutral and let me know.

Pull the freeze frame data with your code reader and post it.
That will tell me the conditions when the codes were set.

[Rundtinden]

The car has done 130 000 km.
Stock air filter.
Mods: Plenum is from Pedro with a splitter in it. Throttlebody from an early 996. Stainless steel exhaust and headers. Underdrive pulley. This configuration worked fine until I put it away for two years.
Has changed the plugs, inspected the coils, changed oil, filter and air filter. New waterpump and coolant. Changed a sleeve with a hole in it. Has checked twice with start gas, cannot find any more vaacum leaks.
It was stored with very little fuel in it. Have not changed the fuel filter yet.
Will try clean the MAF and change the filter tomorrow.
The car now idles at around 900 rpm. Up and down maybe 100. When I have driven for a bit the idle seems to rise to about 1200. Then settle down again if I hit the throttle for a second.
At 2500 rpm and above I cannot detect any misfires. With light throttle and below 2500 I can hear and feel less than smooth operation from the engine.
With full throttle it picks up speed fast without any detectable misfires.

[blue62]

Originally Posted by Rundtinden

The car has done 130 000 km.
Stock air filter.
Mods: Plenum is from Pedro with a splitter in it. Throttlebody from an early 996. Stainless steel exhaust and headers. Underdrive pulley. This configuration worked fine until I put it away for two years.
Has changed the plugs, inspected the coils, changed oil, filter and air filter. New waterpump and coolant. Changed a sleeve with a hole in it. Has checked twice with start gas, cannot find any more vaacum leaks.
It was stored with very little fuel in it. Have not changed the fuel filter yet.
Will try clean the MAF and change the filter tomorrow.
The car now idles at around 900 rpm. Up and down maybe 100. When I have driven for a bit the idle seems to rise to about 1200. Then settle down again if I hit the throttle for a second.
At 2500 rpm and above I cannot detect any misfires. With light throttle and below 2500 I can hear and feel less than smooth operation from the engine.
With full throttle it picks up speed fast without any detectable misfires.

Classic intake air issue symptoms.
I believe you either have a vacuum leak.
An issue with the MAF.
Or an issue with the IACV = intake air control valve.
The IACV bypasses air around the throttle body butterfly so the engine can idle properly. They are fairly simple and can stick and hang up.
They can be disassembled and cleaned.

You can try cleaning the MAF use only cleaner spray made for MAF'S
Don't touch any part except the MAF housing.

If that does not work try unplugging it and see if it idles differently.
If it does the MAF is suspect.

If the issue remains look at the IACV.

Also possible is a vacuum leak via the EVAP sytem or the SAI system.

Let me know how you go.

[Rundtinden]

Codes as read by my Bosch Estronic: P300, P301, P302 and P303. What is the most likely cause? I erased the codes, and drove it for a few minutes before the CEL came back on. It pulls strong, but the idle is a bit erratic at times.

[studentwhocantbudget]

Originally Posted by Rundtinden

Codes as read by my Bosch Estronic: P300, P301, P302 and P303. What is the most likely cause? I erased the codes, and drove it for a few minutes before the CEL came back on. It pulls strong, but the idle is a bit erratic at times.

Jesus, that'd be a misfire on four cylinders (you would know this if you took 2 seconds to google!). No clue what could cause that I defer to anyone else or otherwise if it were me I'd consult a shop. That's a lot of failure at once.

[Rundtinden]

Cleaned the MAF. Recalibrated the ECU. Still erratic idle and problems when not under load. Goes well when it got higher revs.
Cel comes back on after a few km. It idles on about 800 when Cold, 1200 hot.
New search for vaacum leaks. None found.
If I disconnect the MAF when it idles it immediately stops.
Also opened the oil filler cap when it was idling. Not difficult to open. But some suction there. The idle jumped up to 1500 With the cap open.
Will change fuel filter tomorrow, just in case.

[blue62]

Originally Posted by Rundtinden

Cleaned the MAF. Recalibrated the ECU. Still erratic idle and problems when not under load. Goes well when it got higher revs.
Cel comes back on after a few km. It idles on about 800 when Cold, 1200 hot.
New search for vaacum leaks. None found.
If I disconnect the MAF when it idles it immediately stops.
Also opened the oil filler cap when it was idling. Not difficult to open. But some suction there. The idle jumped up to 1500 With the cap open.
Will change fuel filter tomorrow, just in case.

Are you disconnection the MAF while it is running??? Or disconnecting then starting the car and it dies?

Unplug it with engine off.
Then start car and see how it runs.
If it runs badly or dies then I would say it is starting to sound like the MAF could be the issue.

Usually when you unplug a faulty MAF the car runs better.
But you have those intake mods so I am thinking the opposite will happen because the DME defaults to openloop fuel maps when you unplug the MAF.

So I would check and clean the IACV first. Just to be sure it is not the problem.
No cost in checking and cleaning the IACV.
MAF sensors on the other hand can be a little pricey.

[blue62]

About how many miles did you put on the car with the current intake modifications before you stored it for the two years???

Did you have any issues with it as modified before the two year lay up???

[Rundtinden]

Deleted the codes, unplugged the MAF and started the car. No difference. Car runs, but with the same symptoms as before. Will clean the throttlebody and valve tomorrow. What other possibilities are there? Random misfire reported on all sylinders. No vaacum leak found. Can it be the AOS?

[Stl-986]

Well if you have no clue then maybe you shouldn't say anything. And if YOU googled you would have known that isn't miss fire on 4 cylinders.

It's actually misfire on cylinders 1-3. I would start with just pulling the coils & plus and replacing the plugs. clear the codes and then take it for a drive.