blilley

I have a 98 with 76,000 miles on it. I was in town last night at a light and my car typically idles at 800 rpm. While i was at the light it would drop down just under 600 for a second pop back up to 800 for about 5 second and continued to do this while at lights.

It was a little better this morning until it got warmed up. Then it started to do it again. Even when it was idling at a normal RPM it still wasn't steady. There hasn't been a CEL as of yet.

Any Ideas?

Thank you,
blilley

Turboflyer

You will have to wait for a CEL so the proper fault can never be reproduced while your actually trying to repair the real problem. Also only stop at stop signs if the lights are causing the problem. Sounds to be like a small air leak induced when things heat up. Now, where is the real question. But we are CPU infested so all bets are off. Drives you nuts I know.

Loren

Sounds to me like a partial stuck ICV (Idle Control Valve).
Many times removal and cleaning will greatly improve the idle. If cleaning it doesn't help then perhaps the solenoid has gotten weak and it needs to be replaced.

blilley

Lol, I have a problem with actually stopping at stop signs. I tend to roll through them. I didn't notice at the signs.

blilley

Thanks Loren, I'll clean the ICV this weekend and go from there.

blilley

Macster

I have no experience with the idle control valve, having never had to do anything to it.

The one time my '02 at around 80,000 miles started acting up, among other things developing a mild hunting idle problem the final diagnosis was a failing air/oil separator.

During my attempts at diagnosing the cause of the engine symptoms (idle as I mentioned above, and a sort of a vague flatness to the engine's take off from idle) I removed the throttle body and found the butterfly valve lower edge wet with oil and no little amount of oil downstream from the throttle body including qiute a bit of oil at the hose connection -- the hose connected to this connection I learned later came from the air/oil separator) immediately after the throttle body.

Cleaning the oil from the valve and the body found things improved, for awhile.

As I continued my diagnosis the engine started acting up more severely.

One last thing I discovered before I called my Porsche dealership's service advisor was when engine idling there was a tremendous amount of engine vacuum, so much so that while I could unscrew the oil tube filler cap I couldn't remove it from the tube. The dipstick I could remove, but with the dipstick removed there was clear evidence from the sound alot of air was entering the open dipstick tube.

Deciding the engine troubles were past my ability to deal with after talking with the service writer who diagnosed a failing air/oil separator over the phone (and had just diagnosed another a day or two before for another Boxster owner) and following his suggestion to not drive the car any more than absolutely necessary I arranged to flatbed the car to the dealership where it was found the air/oil separator was bad.

The other owner failed to heed the advice not to continue driving the car and the engine suffered damage -- not sure how much -- from hydraulic lock because the failing air/oil separator allowed the engine to ingest too much engine oil.

BTW, I can't be sure now but I don't recall any CEL appearing, at least not at first and maybe not at all, other than what I may have caused by for instance early on running engine with MAF disconnected (in an attempt to eliminate a failing MAF) or running the engine with the oil tube filler cap removed which then allowed way too much air into the engine after the MAF.

Check the idle control valve/hardware but keep in mind the possibilty of an air/oil separator being the problem.

Sincerely,

Macster.

blilley

I got the car back out this morning. Idle range is worse that before, it has even stalled out a couple of times when pulling up to lights or stop signs. I have even noticed the smell of blown out matches, almost a sulphuric smell coming from the car.

does this smell, or stalling out help confirm or change any opinions?

thank you very much
blilley

1schoir

Blilley:

Aside from the ICV, have you looked at the throttle body itself to see if it's all coked up/gummed up. If the butterfly valve does not make a good, even seal with the inside of the throttle body bore, the engine will not idle properly.

It's fairly easy to remove the throttle body and give it a good cleaning.

Regards, Maurice.

blilley

describe fairly easy. I will get a chance to get into to look at the car tommorrow morning. as long as the wife doesn't make up something for me to do.

Macster

I was saying the smell may or may not be important.

Given the engine's not running right, is cold, it would not be surprising the converters could smell funny. (Even under good conditions they can emit a rotten egg or sulphuric smell that is no cause for concern.)

The varying idle is more of a concern.

My advice to you is to if you are capable of it or if not have someone who is, but before you do anything else is to unequivocally eliminate the possibility the air/oil separator is ok, is not failing.

If this thing is failing then continued attempts to diagnose the symptoms put the engine at risk of serious damage, maybe even total destruction.

If the air/oil separator is clearly not the source of the problem, then there is likely an air leak or the MAF is going bad. Another possibility is insufficent fuel pressure or supply.

For the MAF, I've been told, and have tried it myself, is to disconnect the MAF from the engine wiring harness and start, run the engine. If symptoms perist or get worse, not MAF.

Check the intake system for any signs of air leaking into the system after the MAF. Use your ears. A co-worker heard air leaking around/past a bad oil filler tube cap on my '02 Boxster. A new cap fixed a nagging/but intermittent problem with various diagnostic trouble codes that pointed to the MAF and in fact caused me to replace the MAF. That the original MAF had over 100,000 miles on it I thought the old MAF had to be due to be changed. In this case I was wrong.

The oil tube itself can leak and the large rubber pleated hose IIRC under the air/oil separator can also devevelop a split or crack and leak.

And then there is the idle control valve and all that help control the idle.

Sincerely,

Macster.

blilley

Great post, thank you Macster.

I replaced the MAF about 6 months ago, I have an aftermarket EVO Intake. I wouldnt' think that it's the problem, but I will most definatly check that. thank you for your guidance.

blilley

Loren

You can unplug the MAF and it will not matter at idle and low speed running.
The MAF has nothing to at idle.
You may have other air leaks - any smoke at start up or idle?

Macster

General rule is last thing touched is first thing suspected when car/engine starts acting up.

I've never tampered with Boxster intake but I've done intakes on other engines and they generally are a pain to get properly sealed and this includes not only immediately after installation but for long time after.

Used to do this to help determine if intake leaking. First with engine idling and ideally warmed up I would spray some carb cleaner (the kind that comes in an aerosol can) into intake -- after 1st removing the air cleaner. ('course if you remove air cleaner and run engine you have to make darn sure nothing falls into the engine air intake 'cause if it does.... oh boy!).

Anyhow you spray carb cleaner into intake and see how engine reacts. Stumbles or speeds up.

Then you spray around where the intake bolts to the heads/engine, a fairly small area at a time. Not too big an area because you won't know where the leak is and you want to put enough cleaner that there's sufficient amount ot cause the engine to react noticably. Give each area a couple of shots of cleaner.

The idea is if an intake leak when sprayed on that area the carb cleaner will get sucked into the intake through the leak and the engine will react thus you know not only the intake is leaking but where.

If intake leaking, well then you have to address that. More bolt tightening is not the way. What I had to do, what I was taught to do, by mech. friend, was to unbolt the intake, check for any gasket surface damage like a nick or a ding or a bolt hole with a pulled thread, gasket damage, etc, anything that could result in the intake not sealing properly.

Also, you want to check the intake mating surfaces to make sure they're not bent, twisted, etc.

Check that all bolts can thread completely into its proper hole that there is not some debris, dirt, oil, coolant, etc, in the hole. If there is this can make the bolt feel like it tightens up properly but it will not hold correctly.

Be sure the bolts are in their correct holes. Some bolts can be longer/shorter than others and you should never assume a short bolt can be used in a deep hole and a long bolt used where a short bolt should be used.

If all found good or whatever was found wrong is corrected, then the next step was to re-install the intake with all new gaskets, etc, following recommended practice, which can differ from what the 'book' says.

Be very attentive to tightening sequences and torque settings. Don't do this by feel.

Mostly when I had to I used some good silicon seal applied to the trouble-some areas. It helps too to note what was used/done when removing the old/original intake.

After buttoning every thing up you get to test/check the engine/intake for leaks again using the engine's behavior and if not up to par again with the carb cleaner.

Sincerely,

Macster.

blilley

I am now armed with fault codes. P0410 & 1411. these two have come on and off since I have owned the car. My assumption is that is from the cold air intake.

The two new codes that I haven't seen before, are P1123 and P1125. Oxygen sensing in cylinders 1-6 below limit/lean mixture. What I don't know is what direction I should go with this. I do have hesitation now, and it sounds as if the car wants to almost backfire. I am going to get into the car now and have a look see, not to mention the top problem I have on another thread to check out.

help please
blilley

blilley

Well I'm happy to say that it was a simple fix I do believe. The air filter was loose from the intake tube, which is a little scary unto itself not nowing what all got sucked in there.

Never the less the filter is back on idled for about 10 minutes normal, took a quick drive around the block and everything seems back to norm.

now if i can just get this effing pushrod off of the damn v-lever

Thank you guys for all your help.

blilley