HELP! Weird driveability problem

[releese78]

I have a very strange problem that is making it quite unsafe to drive my car. Sometimes (usually within the first 15 minutes of driving on any given day), my car will feel like it's going to stall and eventually does. The throttle does not respond at all and it sounds like misfiring cylinders (bubbling, back-fire sound heard). The worst part is that there is no rhyme or reason and when I'm about to cross traffic, sometimes I can't go anywhere and force others to slam on their brakes as to not hit me. Usually I can tell this is going to happen because on that particular day, it will start and immediately stall. I have to rev it a few times to get going. This is somewhat rare though, usually it starts flawlessly and runs like a bat out of hell.

Since this problem has started, I have changed the fuel filter, K&N air filter, belt, plugs, and routine oil changes, and cleaned MAF. All have had no effect. There are no other engine mods other than de-snorkle (done after the problem started). The car runs at a steady 180-185 degrees, coolant bottle and cap have been changed.


The vehicle is a 98 Box, TipTronic with 102k miles. No CEL light or codes present.

Another bit of information that may or may not be related, sometimes when slowing down (entering a toll booth for instance), it seems to downshift very hard, then when accellerating out, the trans seems to have a "dead hole" and almost slip for a few seconds. I am not the original owner, and am not sure as to wether the trans fluid has ever been changed.

Any help would be greatly appreciated!!

[Lil bastard]

I think your tranny problem and rough running/stalling are unrelated.

With 102 on the clock, I would change the tranny filter and fluid - s/b done around every 45k mi. according to the tranny mfr. Same with the O² sensors - bosch rates them at 100k mi., but I've rarely seen any go that long.

As for the stalling issue, it could be so many things and anyone here can only venture a guess without actually seeing the car.

My suggestion is to get it to a dealer or indy with the appropriate diagnostic software to zero-in on the cause instead of throwing 'fixes' at it willy-nilly.

[releese78]

Will do, I appreciate the feedback. I have just put off the diag because with it being intermittent, I'm sure I'll be "going to the doctor when I have no symtoms"

[idheaton]

Although you cleaned your MAF, it may beyond cleaning and need to be replaced

I have a 99 and although it's a manual, I had some intermittent issues the one about starting out being similar to what you describe.

Some of my symptoms were:

• RPM surging at idle.
• Poor take off - Pulling out from a stop was a crap shoot. At times it just seem to want to die and I would have to feather the clutch/gas to get it going with it backfiring and when it decided to go it sometimes wanted to just take off which made me fear ending up in someones trunk. and any thoughts of jumping out into traffic were non-existent for fear of it suddenly stalling out. It was most noticeable on upward slopes where a little more gas was required. It felt like the car was either flooded out or running out of gas.
• Deadspot in the powerband - Once it was up and going, everything was fine, no hesitation or roughness except it had a tremendous dead spot at 5k rpm.

Fixes I tried were:

• Swapping out oxygen sensors
• Cleaning the ICV
• Cleaning the MAF

All of which seemed to help initially but shortly afterwards the car would go back to running poorly.

It got so bad that I was afraid to drive the car as well for fear of stalling out and I always made sure I had way more than enough room to pull onto a busy road in case it decided not to go.

I eventually had the MAF changed (as opposed to cleaning it) and all my issues went away. The strangest part of this is that as bad as the car was running it never once threw a CEL.

Goodluck with finding out what's causing your issue.

ian

[releese78]

Hmmm, sounds like a good idea. I'll change the MAF. $3-400 is definately worth the risk of getting plowed by another car!

[pk2]

Sounds kinda like fuel starvation. In that it craps after 15 minuets (about warmed up) it's no longer running rich and maybe regular lean mode is just to lean. I had this problem exactly in a BMW. Mine was always the fuel filter .

Given you've covered that base, you might take look at the fuel pump. Tests usually involve flow and pressure (2 tests).

Good luck, PK

[pbanders]

I'm with PK, first thing I thought when I read this was fuel starvation. I'd check pressure and supply, fuel filter, fuel pump, fuel pump control, and if the Boxster has one, the tank sock (mesh filter in the bottom of the tank).

[2000SoCalBoxsterS]

Have the CATs ever been replaced? They must be fired by 102K miles.

[releese78]

Dont think the cats have ever been changed, but I doubt its them since its only intermittent. The problem happens within the first 15 minutes of driving, after it warms up, it seems fine. The fuel filter has been changed recently, this didnt help. I also changed the plugs, and they old ones looked very good, nice brownish color, no oil burning or over-lean seeming condition. I'm not sure about the MAF or O2's, I havent changed them. I have cleaned the MAF though.

[idheaton]

Yes, it did feel like fuel starvation. Like when you run out of gas and the engine dies out only to catch when the fuel sloshes back to be picked up.

I had changed my fuel filter @ a 60k service so it wasn't that and also tried numerous things (as stated in my previous post) before changing my MAF. The reason I did that last was I never once has a CEL so thought, 'It's not the MAF'. Ended up changing it as a last resort and it fixed my issues.

This might not be the cause of your problems, just do not rule it out.


Releese,

if you do decide to get a new MAF, you can find them online for 200-300 as opposed to 300-400. You just have to do a little searching.

http://www.********************************************************************************************/search/?N=11567+1698+4294967268+9359

http://www.drivewire.com/products/porsche-boxster/air-flow-meter/133/

http://www.aboveallmotorwerks.com/product.aspx?year=1998&make=40&model=986&maketext=Porsche&modeltext=Boxster&CategoryText=Fuel%2fAir+Intake+System&Category=F2***&SubCategoryText=&SubCategory=***

Quite a few online discount autoparts places that have it cheaper do not list it as a Mass Air Flow Sensor but mix up the name calling it a Mass Air Meter, Air Mass Meter, Air Mass Sensor...the word jumbles goes on.... ... just make sure you order the correct one.

[Lil bastard]

Again, like I said, too much room for speculation here and that's all it is - speculation.

Others may have had similar symptoms which were corrected by changing 'X', but that doesn't mean yours is the same problem. Though it may be (emphasis on may )

Lots of different things can manifest themselves as similar symptoms. For instance, as mentioned, it may well be the cats. What you describe is exactly how a failing cat might work - takes longer to warm up, until then, the DME selects all sorts of screwy maps resulting in poor drivability. Could be the secondary air system which prevents the cats from warming up properly, or timely - same effect.

My point is, get the car on a PIWIS or PST2 and find out what's really going on before throwing mucho dinero at a problem which may not cure your car's ills.

[releese78]

I definately appreciate all of your help and feedback. Thanks everyone!

[releese78]

The problem seems to be getting worse!

Tonight, when I first left the house, I got about a mile before it started sputtering, I pulled off the road and it stalled.

Later on, well after it being warmed up (about 20 miles after it driving great), I was accellerating in 4th gear at around 70mph when it just choked. I put the throttle to the floor and it was completely unresponsive. From there, I drifted to a stoplight and when it turned green, I went no-where. I pressed the throttle and heard sputtering and backfiring, barely moving at all, it did this and all of the sudden...BAM, it woke up and ran like a bat outta hell again.

I'm about ready to just start throwing parts at it (starting with MAF and O2's). I've been through and heard many horror stories of vehicles being at the dealer for weeks at a time and thousands of labor dollars only to be told "we can't duplicate the problem" or "this should fix it".

Any other suggestions or input would be greatly appreciated. Fuel pump? vaccum issues? AOS?

[Lil bastard]

I cannot believe you're having problems to the extent you've described and are still driving the car !!

I presume you know the definition of a person who keeps trying something, each time expecting a different result?

These motors have been known to implode with little provocation and to keep driving one that is signalling to you all is not right ain't the brightest tactic.

You can pull out the 'ol Mechanic's Dartboard and throw hundreds here or hundreds there in hopes of serendipitously curing the issue.

Or, you can take the logical approach and get it to a qualified person with the proper diagnostic tools and actually find out what's gone wrong and target your $ to the proper fix.

Everything posted here is speculation to one degree or another, and advice is cheap - it's not our car! Someone may have suggested what could turn out to be the proper fix, but until you either buy and install all these parts, or get it properly diagnosed, it's all just guesswork!

Talk to the Service Advisor, ask him how much it would be to pull the codes and records and inform him not to proceed until you have given him the OK. Have him put the service charge on the service order beforehand and sign it, retain a copy. That will protect you from all your fears about a dealer.

[hjkim550]

r78,

I would listen to Lil if I were you. Sound advice if you ask me. Your adventures are starting to get pretty dangerous.

If you are concerned about reputable dealers, you should look at the thread: Find your local mechanic/ porsche specialist. It is a long thread but the last page has a convenient list and links to other helpful threads.

In my line of work, people would think I was nuts if I suggested treatments and cures before a careful and thoughtful diagnosis. Just my two cents.

[insite]

if you want to know for sure if it's the MAF, unplug yours and go for a drive. the car will use a default fuel map rather than sensor driven maps. if the MAF is the problem, your drivability issues will go away.

that having been said, if this were the MAF, O2 sensors, etc, you'd be getting codes left and right. when you put your key in the ignition, turn it to the ACC position but don't start the car. make sure the CEL lights up; it's possible the bulb is bad.

if still no codes & MAF is good, take it somewhere. throwing parts at the car is an expensive proposition. it's cheaper in these circumstances to pay the guy. i'm with the others; fuel starvation sounds likely. stop driving the car if you can.

[insite]

you know, another way the car can starve for fuel is if you have a vacuum leak. check to make sure the intake tubing is all connected and not torn. listen for any hissing in the engine bay. i usually wave around a propane torch (unlit of course) in the engine bay; if there's a vacuum leak, the RPM's will jump.

[releese78]

***UPDATE***

Well, I took your advice...almost.

I checked for vaccum leaks, found none. I did find something very weird though. On the passenger side, coming out of the rear firewall (near the coolant and oil hoses), I see what appears to be a vaccum hose (approx. 1/2 inch outside diameter). This hose has no vaccum and doesnt have any type of fluid coming from it. I looked all over for a place this could possibly go and didnt find any open ports, nor could I tell what it is connected to on the other side. When fully extended, it almost reaches the vent fan, and also has a black "half-moon shaped holder" that probably kept it against the side wall somewhere. Weird?

I think I fixed the driveability issue though! Keeping my fingers crossed! I pulled the MAF again and noticed that the sealant (on the side which holds the rectangle plastic cover in place) to be cracked almost all the way around. Rather than chance it, I purchased a new one, which wasnt cheap since mine is a 98 without e-gas. It's been over a week, approximately 200 miles driven and all seems well. Only time will tell though.

As for the tranny problems, I purchased a filter, gasket and fluid from the dealer, (still waiting for the gasket to arrive, it was backordered) and I'm going to do a service on it. Speaking of gasket, has anyone had any good or bad experiences just using the gasket, or RTV, or a combination of both?

On another note, I've been seriously considering purchasing the ZEINTOP, I've spoken to them on several occasions and although I'm not rich (actually quite the opposite!), I think I'm going to drop the cash to do so. I'll be sure to post pics on here since my car is white and I havent seen one in that color yet. I'm told that it will take approximately 6 weeks for delivery.

One last off-topic question, can Durametric turn on the OBC? or is there any "home tool" which can? I was thinking of buying an inexpensive scanner, and want to kill two birds with one stone.

Thanks again for all of your help and input!

[Lil bastard]

Well, as far as a gasket sealer, I would NOT use any type of RTV or such. These provide a hard cure seal which can then be broken by heat and vibration - exactly the environment you're using it in.

When I did my Filter/Fluid change on my Tip S it was only at 25k mi., but the gasket was leaking. Since there is no dipstick for the ATF, there was no way to know what the level was at. Since I needed to remove the pan to replace the gasket, I swapped the filter and fluid while I was in there. See my DIY in the DIY section.

I used Hylomar as a sealant rather than RTV. Hylomar is a polyester/urethane sealant originally developed by Roll Royce as a sealant for their Jet Turbine Engines. It is a non-setting, non-hardening sealant and so is both vibration and thermo-expansion resistant. It is also a zero-tolerance sealant which means that in some applications where you would need to account for the thickness of any sealant, you can use Hylomar and remain at factory specs - it does not alter spec tolerances. I have used Hylomar for many years and have never used RTV Silicone since - it works that well.

It was licensed to PermaTex, but I understand they now longer produce it as it competed with another of their products. But, Hylomar is available from Hylomar USA marketed as Hylomar Universal Blue. At $28.50 for 100gm (3.5oz.), it's not cheap. But, you use very little when using it as a gasket sealant and 1 tube will last for years - it has an indefinite shelf life. Plus, used as a gasket sealant, it will NEVER leak again, unlike RTV, so that alone makes it worth the cost. See it at: http://www.hylomar-usa.com/

Also, the Durametric will not activate the OBC, only a PIWIS or PST2 can be used. My dealer did it for free when I had the car in for some other work. Others I have heard have charged $60 or $100 to do it while still others have outright refused to do so. Seems the best tactic is to ask them to turn on the temperature display, never letting it slip that you're planning the OBC Hack.