logray

Near Auburn, CA. Santa Rosa is a nice place to visit, I wouldn't mind living there.

After letting it sit for a while, then starting it again and driving it around, the car is once again back to stumbling on idle, nearly to the point of stalling and performance is down. Rough running is all over the place. FRA is 1.07 and TRA is -0.08 for both banks. I'm 100% positive now that if I reset the DME and fuel trims back to default it will once again run like a pro and not stumble at idle. But that doesn't seem to be a reasonable way to operate the car every 30 miles, or to drive around without a MAF. So, since I replaced the MAF, tested the MAF wiring, replaced the O2 sensors, what's next? I'm going to try to read about the EVAP system and see if perhaps the intake is somehow sucking excess vapor in, causing the fuel trims to skew out of place so rapidly. Does anyone have any good links on this one? I'll search around some. I'm wondering if I can just temporarily clamp off the evap purge valve at the intake. Here's some O2 data, looks normal to me. (click to enlarge)

New MAF arrived and installed. About 40 miles on the car with a full DME reset. First started out and LTFT were are 0.98 and STFT at 0.00 After some miles, the STFT went to 0.02 and LTFT to 1.02. After more miles, the STFT flipped to negative and the LTFT positive. By the end of the 40 miles, the STFT went to -0.08 and the LTFT to 1.06/1.07. The car still seems to be performing well, although possibly not as good as it did when I reset the DME again and it was using the default fuel maps for a while, I need to drive it more to find out for certain. Could this just be due to the fact that the stock map thinks this should be a 3.4L and because it is now 3.6L, requiring more fuel, that it's sensing it's running leaner than the stock fuel map in the mid/long term range, and therefore dumping more fuel (positive LTFT) and then at idle/short term pulling it back to compensate? It's too soon to tell though because running without the MAF and after a DME reset the car ran great too. I'm wondering if there is something else going on like too much fuel vapor being sucked into the intake skewing the fuel trims or perhaps a back pressure issue? The engine is basically stock at this point, aside from upgraded 3.6L cylinders and pistons, fabspeed headers and stock 3.6L mufflers. Stock intake, air filter, etc. etc. etc. All new Bosch 02 sensors were installed a few thousand miles ago, and the 02 graphs look spot on. I'll post some more data later on. Fuel injectors were cleaned and tested, and all performing well by the tester and report.

If the needle goes past the 0 in the 180 and approaches the next line, that is certainly getting on the hot side. It's probably worth checking your high speed fans are working once the needle reaches or goes past the right edge of the 0. Also, if you've done any work on your cooling system, ensure that it has been bled properly. Using a vacuum fill method is the best way to accomplish that. Also, check that your radiators are cleaned of debris. Nice day for a drive here too, crisp upper 40's into low 50's makes for a cool engine. ;)

Well at least you caught it before it became a total loss. Good luck with the rebuild.

Hi there, certainly you can use a regular spanner. Be sure to use the correct size. As for torque settings and a step by step, pelican parts has a good write up located here: http://www.pelicanparts.com/techarticles/Boxster_Tech/17-ENGINE-Idler_Pullies/17-ENGINE-Idler_Pullies.htm

Also if it hasn't been mentioned, any time work is done on the cooling system where coolant is drained it should be bled properly or refilled using a vacuum system. Otherwise there is risk of air pockets which cause hot spots and abnormal temperature readings.

Sometimes its just the filler tube has come out of the tank, try some duct tape to keep in in place. :)

I spent a few minutes with search and dug up these threads:

I also had the full fabspeed kit. It was great for a while, but grew tired of it being "always" on. I've since downgraded to fabspeed headers and stock 3.6L mufflers and the sound is dramatically improved. Still get the agressive sound I'm looking for, but it's no where near being over the top and absolutely no droning. I've also read a lot of good things about the fister sport muffler mod.

No you don't have to flush the coolant, in the instructions you clamp the hoses going to the core before removal. When finsished you do need to bleed the coolant system. Thermostats run around $100-200, h20 pumps about $300 and I don't have the latest prices on heater cores sorry, but you are probably looking at about 2-3 hours of labor including vacuum refill of the coolant system. I would spend more time with diagnosis before diving into removal of the heater core. This is just a guess, there could be many other reasons for this, like I mentioned above, such as the flaps. Search is your friend here. Have a read through this entire post, it has a wealth of information about this problem: http://www.renntech....ide-of-boxster/

From reading many many threads about this here and elsewhere, if the needle is pointing to the very right edge or left of the 0 in the numbers "180" on the gauge this is considered normal operating temps most 986 and 996 cars. Track drivers will usually get it much hotter, closer to the next line between the 180 and 220 or whatever it is. (remember those numbers are not at all accurate, go back a few posts above where I describe how even with the needle straight up, that is actually more like 200F coolant temp sensor). About the time the needle hits the right edge of the 0 in 180 it is starting to heat up, but it's still no where close to overheating. That's usually about the point where your high speed fans will kick on and either maintain that temp or cool it down some. ANd if not, youi're driving it really hard and it needs to be watched closely or there is some other problem with the car. edit: sorry forgot to add some smileys to denote lightheartedness. :) :) :)

The original poster states he has observed a temp of 190 F degrees. The question is, where did he get that temp reading from? The dash? A/C hack? OBD2? External sensor? There's not any real way to tell from the dash gauge what 190F is unless he knows where his needle must point in order to reach this temp. Also what temp was that, coolant? oil? 190 F degrees coolant temp is just about perfect for most cars. Not even close to over heating. The 986 and 996 like to run hotter than 190F, more like 200-212 F for coolant is considered normal. Oil can be anywhere from 0 to 20 degrees hotter than the coolant depending on how it's driven. So I'm not quite sure what the issue is here, since there doesn't seem to be a problem - what was described in the original post is perfectly normal and there isn't a problem to solve that I can tell. Overheating on this car is going to be coolant temp over 245 F and oil over 265 F ish. The best thing to do to get a feel of how hot your specific car is running is to plug in an OBD2 reader and observe what the actual oil and coolant temp is and compare that with the reading on your own dash gauge. Then you'll have an idea of what the coolant temp dash gauge is really telling you. There are plenty of aftermarket solutions for reading and displaying data from the OBD2 port in a driver friendly format and in real time (not just sitting at idle), from things that mount to your dash, to software that connects to your iphone, even aftermarket stereos are starting to display this data. Hope this helps!

Yes, thanks I had it backwards in the posts above and edited for accuracy.

Maybe you could try disconnecting the fuse or wire harness for the power seats, and see if the current leeching stops. Also were the main power leads checked for corrosion? Ground and power.

It sounds like your engine is certainly getting hot enough, but perhaps your heater core is due to be replaced, maybe the heater flap could be the problem? I'm not sure if the procedure to access the heater core on the 986 is the same as the 996. http://www.renntech....moval-996-99-c2

In a low voltage situation, all sorts of strange things can happen and you can throw predictability and reason out the door. I would properly test and charge the battery, then monitor for these conditions again. How old is the battery? Perhaps it is due for replacement.

No it doesn't bother me at all. I should have added more smileys. :) :) :) Just sayin. AC hack otherwise known as "climate control diagnostics". Porsche eliminated the AC hack in 2001 if I remember right. The information is not programmable. Yes it is a little frustrating that it's not accurate, but that's what we have to live with. It turns out the only thing that is accurate is reading the sensor data directly from the DME using an OBD2 diagnostics reader.

You can swap the relays and ballasts between sides. If the fans start working again, then you have isolated the relay or ballast causing the issue. If swapping relays and ballasts does not solve the problem, then it is probably the fan motor or wiring, but those don't seem to be as common as a ballast or relay going out.

This has been covered many many times here. The figures from the AC hack are simply not accurate, they are an extrapolation of the real figures. In other words, you can use them to get a ballpark, but to get the real temps you need to read the OBD2 data directly.

I reset the fuel trims back to default 0.98 LTFT and 0.00 STFT. In other words, no longer lean long term (requiring more fuel/positive) or rich short term (negative short term), but instead using the default fuel maps. I unplugged the MAF before even starting it. Then drove the car around for a while, and it seemed to run smoother and have similar power to when I reset the computer earlier, but maybe not at it's best when it had time to adjust the map somewhat. Warm/hot idle seems to have dramatically improved as well, rough running values went back to normal and it's not stumbling at all and having trouble holding onto 680 rpm idle with high rough running values constantly spiking. Now it sounds like it's getting the fuel it needs. I hope all this rich or lean driving I've been doing during break in hasn't hampered the ring seating process. Bad news is, I need to buy another MAF now. :( Good news is, I think it might be a bad MAF. :) edited for accuracy

Back to MAF troubleshooting again. Still original MAF (78k miles). I already returned the new MAF since it sounds like the high IAT is perfectly normal for other cars (even though whne you read the tech manuals they say a coolant temp over 90C and IAT over 30C will cause a lean condition). After the DME reset 200 miles ago things are slowly going downhill. At cold startup and idling the engine runs very smooth, since it's getting what seems to be the right amount of fuel. At first after the reset the engine was running great, warm idle was very smooth and power was great. While the car still pulls harder than I'm used to with the increased displacement, it seems to be slighly down on power in the mid-high RPM range, and at warm/hot idle it's back to rumbly and stumbly rough running again, almost like fuel delivery is wrong. I bet if I reset the DME again it would run fine for a while. I pulled out the trusty fuel pressure tester, hooked it up to the fuel rail and got a solid 3.3 bars at idle and 3.8 bars engine off/fuel pump on. Did some more MAF testing. Since I had already completely tested the wiring I did some more data logging. The more I drive it, the more the TRA (short term idle fuel trims) seem seem to keep pulling back to negative/rich, about -0.1 beyond spec at idle, currently reading -0.19 on BOTH banks. The set point at idle is 0.00 +/- 0.1 for TRA. But it's not throwing a code, not sure with the upper end is to throw a code. The FRA (long term mid/high range fuel trims) are leaning towards lean, FRA of 1.05/1.06 for bank 1 and 1.06/1.07 for bank 2. The set points for bank 1 is 1.02 +/- 0.04, and 1.03 +/- 0.05 for bank 2. So still within spec, but just barely. I've been doing some reading about MAF failure affecting fuel trims. In my reading, when a MAF over estimates air flow, it will cause short term trims to go negative and long term to positive. "When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows. Short term fuel trims will run even more lean (negative) at idle as well as they are the quick-acting fuel trims so to speak." Here's where it gets strange... The MAF, at no load idle is pretty much steady at 17-19 kg/hr, 1.35-1.45 volts. At no load 3000 rpm it's pretty stead between 65-75kg/hr. Both of which are pretty much on spec. So, could it be that the MAF is bad after all, despite these numbers, because of what's happening to the STFT and LTFT? And it is misreporting the air flow, even though it thinks it's seeing the right amount of air, perhaps it is actually mis reporting it, which explains the poor running? edited for accuracy

Serial number perhaps? If you look on the side of the oil sump plate on passenger side, there is a small plate with the engine serial number.

There is an aftermarket head unit upgrade I'm looking at for my old Pioneer AVIC-Z3. If I remember right it has the capability to display OBD2 values on screen.

This is what I've found... Speedo is generally about 4mph too fast. Tach is spot on. Rest of the gauges are pretty good, voltage is a little off too, towards the low side.