1999Porsche911

I'm wondering if it is a software problem because when I come to a stop, it's like something resets and the idle drops to normal. If it was a vacuum leak or sticking throttle or pedal, it would stay at the higher RPM. Unfortunately, it's so intermittent, I can't seem to ever make it happen when I have someone checking it. It seems to be happening less and less and the symptoms are changing a bit. Now I can go three or four days without it happening and then suddenly I'll clutch and the engine will stay at whatever RPM it was at when I hit the clutch and remain there until I put it back in gear and continue to behave that way until I come to a stop. Then once I've come to a stop, it usually resets and behaves normally. I've been avoiding taking it to Porsche since the holidays had my budget so tight, but I may finally give in if I can't figure it out within another week or two. So, when are you going to try seeing if the coolant temperature sensor is causing the problem? I already pulled that connection and cleaned it as you suggested. I haven't replaced the actual sensor, but I'm assuming it's ok since the temp gauge on my dash is working correctly. I am not saying the sensor is deifinately the cause, although it is a common one, but a bad sensor will still povide accurate readings to the dampened down display.

I'm wondering if it is a software problem because when I come to a stop, it's like something resets and the idle drops to normal. If it was a vacuum leak or sticking throttle or pedal, it would stay at the higher RPM. Unfortunately, it's so intermittent, I can't seem to ever make it happen when I have someone checking it. It seems to be happening less and less and the symptoms are changing a bit. Now I can go three or four days without it happening and then suddenly I'll clutch and the engine will stay at whatever RPM it was at when I hit the clutch and remain there until I put it back in gear and continue to behave that way until I come to a stop. Then once I've come to a stop, it usually resets and behaves normally. I've been avoiding taking it to Porsche since the holidays had my budget so tight, but I may finally give in if I can't figure it out within another week or two. So, when are you going to try seeing if the coolant temperature sensor is causing the problem?

When yoou remove the oil cap, the idle increases "ever so slightly" which as you explained earlier, eliminates the noise.

You would have to put a stop on the pedal so it would not rise off the floor as much as it does now. I have not had a problem with the pedal height so I haven't had to adjust it, but if you find a way to to install a 1/2 inch stop above the pedal, you would have full braking power and lower pedal height. You would also have to extend the nipple on the cruise control switch which can easily be done by installing a rigid hose on the sleeve that extends it 1/2 inch. Obviously, elimination of air in the brake hydraulic system is even more important when dereasing the brake pedal travel.

Would you lift the front of your Chevy Chevelle by hoisting the car up by the engine? I didn't think so. Porsche specifically states in the owner's manual to never lift the car by the engine. Lifting by the engine can cause the mounts to leak and extend. Nothing more than common sense here. There are numerous ways to safely lift the back of the car.

hello there, ive search the entire forum and this seems to be the only post which relates to the problem im having. basicly, ive a 98 3.4 996, it has 114,000 miles on it, 10k of which ive put on it myself. ever since i bought it the engine has ticked, but only when warm and the presure drops to around 1bar. by increasing the revs ever so slightly it disapeares entirely. to me it sounds like a valve lifter, but its not as i have replaced all the lifters on the right hand bank from where it is coming. ive also tried various oils, it practicly disapeard when using 15w-50, but the oil presure was very high and so i changed it back to 0w-40. has anyone any suggestions to point me in the right direction? i dont think it would be a piston bearing as surely it would have gave up many miles ago, and get louder with engine revs. something to do with the timing gear/chain perhaps? Change back to 15W50.

It's all about tank design. In most cases, the fuel pickup in new cars is NOT at the the lowest point in the tank. This portion of the tank is reserved for sediment (which is minimal due to better filtering of today's fuel delivery systems). More and more tank designs are also engineered to reduce or eliminate disturbance of sediment at the lowest part of the tank when filling it with fuel. All pumps also have a screen to eliminate intoduction of large debris into the system and most, if not all, smaller particles will be stopped by the fuel filter. The cleaning of your injectors is not to remove debris that is stuck in them but to reduce any varnish that has accumulated in them. This problem has all been elminated for people who use an ethenol based fuel. In most cases, using a fuel additive to clean injectors is nothing more than a "feel good" approach only and serves no real purpose. It is still a good idea not to let your tank get too empty because of floating debris as well as your electric fuel pump is cooled by it's submersion in the gas.

The gasoline you put in your car has the same chemicals as these after market additives do. So I wonder why you don't change your oil after every fillup? There is NO WAY, I repeat, NO WAY for any additive to get from the cylinders into the oil without also having gasoline get into the oil. If this is the case, your engine is doomed anyway. But, marketting is very powerful on some people.

Don't know what year your car is but there is a cotter pin that holds the clutch pedal to the bracket. Often, this pin interfers ever so slightly with the pedal movement causing a clicking sound. Look under the dash and push the pin inward towards the center of the car.

No confusion here. Just a different and more conservative approach. Not an issue of "right" or "wrong". Everything I have read recommends an oil change after the use of a fuel cleaner. The operative word being"recommended". I would love some examples of what fuel additive companies recommend changing your oil in relationship to using their products. I have never come across any in the past 40 years. As a matter of fact, many of them recommend using the additive every 1000 miles or so. That would be alot of oil changes.

Hi 1999Porsche911, everything I have read from the "oil experts" recommends using a fuel cleaner just prior to your oil change. I think the main issue is the fuel cleaner disrupts the oil viscosity. First of all, as I said earlier, if fuel injector cleaner or the dirt is washes away was able to get into the oil, then your gas would also get into the oil. You would then have a major problem with your engine and any investment in injector cleaner would be best used by putting it into a cookie jar to help defray the cost of a new engine which is sure to be needed. You may be confusing a gas additive with an oil additive.

Why? The theory is that the fuel cleaner dislodges small particles from whatever areas it washes down and all of those contaminants end up in the oil. YMMV. Regards, Maurice. So, IF that theory was true, then that means that gas regularly gets into the oil too. And if that was the case, your engine would grenade in a very short time. :lol: Using a fuel additive does not effect the oil and there is no need to change the oil after using it.

Why?

Check for loose parts first. broken guts of a cat, loose muffler/bracket/tailpipe/heat shield, back license plate frame, etc.

No way.... so since I am running a straight 3 inch Maf housing and intake pipe all the way to the throttle body a single resistor or rheostat would have done the trick?? so are you saying all I had to do was add a little resistor inline on my maf signal to the ecu similar to like this photo?? http://www.houseofrage.com/tundra/rrtun33.jpg Or run a single rheostat inline before the ecu and just dial the rheostat down to get the desired 15.5 kg/h reading at idle?? That makes a lot of sense since the smaller 3 inch maf housing piping has globally offset the the voltage. just turning down the voltage globally to the levels that a 3.5 inch housing would produce would be enough to trick the ecu. ****, your good. wow, should have had this dialogue a week ago. I would have loved to try this out, but at this point I have already committed to, installed and dialed in the AFC-SELECT unit... I am still very pleased with the results I have and the fine tuning flexibility the AFC-select +/- 50% correction it gives you makes it a really fine tuning gadget. Plus it has a lot of cool flashing lights... haha... One last question... so is an AFR of 13 flat across the board the most ideal setting or is 12-12.5 a better bet??? Thanks so much for your input. I learned a lot! I am sure this dialogue will help a lot of members. Bill Changing the size of your plumbing and the flow of air past the MAF accomplished the same thing a 5 cent resistor does, only with alot more work. All each acomplishes is to reduce the output signal of the MAF to coincide with the maps of the computer. An A/F ratio of around 12.5 would work well. Look at your after cat O2 sensors while at WOT near redline and make sure that they read 0.88 - 0.90 volts and chances are, your A/F is pretty close to that. Higher numbers would be richer and lower would mean leaner.

Before you go with the vacuum switch, what is your MAF signal right now at idle. It should be around 15.5 kg/h. If not put around a 560 ohm resistor inline on wire #5. Check the idle MAF signal again. Add or subtract resistance as required to get it to 15.5. Once completed, I suspect your WOT A/F ratio will be pretty close to what you are looking for. The variable MAF control is what I use because I also have a variable intake system which increases intake air at higher rpms. In your case, since all your air is going through a constant sized intake, a single resistor will work. If your A/F ratio is a little high or low at WOT, either increase the resistor size slightly to make it more lean or decrease it to make it richer. If, for some reason, your ECU was tuned incorrectly, the variable MAF control may be the answer. Using the vacuum switch as I described will provide a seemless, instant transision between signals. Set the switch to be off with ANY vacuum and on without.

The unshielded cable is the emergency release cable. The other end of it should be behind the left taillight. The way I adjust the lock is to lossen the 2 bolts and raise the lock to the top of its travel, then just snug the bolts up a little, close the trunk and see if the lever will open the trunk. It should open up fine but the trunk will be too high. I then press down steadily on the trunk against the lock until the trunk is down completely. Confirm that the trunk opens unassisted and then tighten the 2 bolts. Make sure that the cable is properly connected to the lock before doing any adjustment.

hey 1999-911 and Todd, I have read a lot of your posts on conversions and Thanks for all your input and knowledge...you guys rock! I actually got my hands on a stock 996 air box with the intention of cutting out the MAF housing to use with my cold air intake... well, as you already know... not so easy. I then tried to find some 3.5 inch tubing and create my own MAF housing to mimic this as well, but gave up. The idea of fine tuning won me over in the end. You both have great ideas and options with the similar idea of controlling the MAF signal, but how exactly do you rig it to be able to do that? How do you control when it switches from "closed" to "open" loop calibration? Is it a throttle position or rpm?? Is it a unit you buy and splice into the maf signal wire at the ecu? what's it cost? The AFC-select works a bit like that. 4 wires are connected at the ecu to monitor Throttle position, power, MAF signal, knock sensor. The maf signal wire is the only wire altered so that the signal is sent to the AFC-select unit and then a "new corrected signal wire" is sent back into 996 ecu. What I was impressed with on AFC-select is the ability to designate exactly which rpms to correct voltage % on and at what throttle position I wanted to adjust the signal on. For example: If on the dyno my MAF signal at 70% throttle position (tp) is already giving a rich afr of 10. Below 70% tp the afr is ok. So in this scenario by throttle position 70% I wanted the the voltage corrected by -20%. I can create the parameters for the throttle position like this: at 20% tp = 0% voltage correction...correction would ramp up smoothly so that by 70% throttle position and above = 100% preset voltage correction is reached. (voltage correction being preset at -20%) This allows us to have a nice smooth linear correction on MAF signal output. then we fine tuned every few hundred rpms to smooth out any bumps or dips in the AFR readings.. After all was said and done we made about 15 runs on the dyno as we adjusted the signal correction little by little to make sure of never running too lean. Is there a way to do this type of callibration with a simple resistor to alter the MAF signal? I am all for any solutions or ideas to help. Especially since a lot of us have gone down the bolt on mods and conversion routes only to be disappointed when things are not running properly and as expected. After a couple hundred miles this weekend I am very pleased. Now I have to just keep my fingers off from tinkering with the computer to get that last little .01% correction ;) I also find myself watching my afr reading like crazy whenever I accelerate at wot. It has been great though and holds 12.0 afr pretty solid. Sometimes too many gauges are a distraction! :o What AFR's do you find to be ideal and safe?? Thanks again for your input. it is greatly appreciated. Bill The easiest and most effective way is to simply get an adjustable vacuum switch similar to the one shown in the link below. The MAF signal #5 wire would be cut with the DME side of the wire going to the common on the switch and the MAF side of the cut wire to BOTH switchable leads on the switch. The switch is activated by vacuum, switching from one lead to the other depending on whether vacuum is present or not. The default lead (vacuum present) would be connected to the MAF side of the cut wire without resistor and the other lead would be connected to the MAF side of the wire with a resistor the size which will give you the A/F ratio you want at WOT. You could also put a rheostat inline to make it easy to test different settings Using the above method, you maintain the current tubing configuration of the intake and it allows an easy way for fine tuning in a matter of seconds. The easiest and most effective way is to simply get an adjustable vacuum switch similar to the one shown in the link below. The MAF signal #5 wire would be cut with the DME side of the wire going to the common on the switch and the MAF side of the cut wire to BOTH switchable leads on the switch. The switch is activated by vacuum, switching from one lead to the other depending on whether vacuum is present or not. The default lead (vacuum present) would be connected to the MAF side of the cut wire without resistor and the other lead would be connected to the MAF side of the wire with a resistor the size which will give you the A/F ratio you want at WOT. You could also put a rheostat inline to make it easy to test different settings Using the above method, you maintain the current tubing configuration of the intake and it allows an easy way for fine tuning in a matter of seconds. http://images.google.com/imgres?imgurl=htt...l%3Den%26sa%3DN

i disagree! you should not sit with foot on clutch and in gear. that just wears out the clutch mechanisms like the pressure plate,disc and throw out bearing. i think the problem you are having is the first signs of clutch drag and hence when you remove foot from clutch and reapply then it slips in! when you release the pedal does it return fully? if not then you have air in the hydraullic system or a faulty cylinder. The clutch mechanism, including pressure plate and release bearing are deisigned for use and keeping the clutch disengaged at a light or stop sign will not prematurely wear them out. If you are worried about things wearing out, why would you choose to wear out the transmission rather than the inexpensive pressure plate and release bearing? Your's in another old and incorrect argument. I guess maybe we should turn the engine off at the same time to keep the injectors, fuel pump, spark plugs, serpentine belt, water pump, etc. etc. from wearing out?

Just drive like you are supposed to do and keep the car. in gear at all times. Sitting at a light in neutral is not only unsafe buy can cause problems such as the one you have as well as puts unnecessary stress on the syncos. The explaination that Barry gave is right on, so just keep it in gear. You should be able to downshift into first gear at any speed under 30 mph.

Nice job, but it would be alot easier to simply make your MAF have a variable signal. Maf would be calibrated one way in closed loop which would allow the O2 sensors to properly managed the a/f and then would switch to the another calibration in open loop. You then have a fully adjustable MAF signal and full control of your a/f ratio in a matter of seconds.

I do not know if it will fit in your car, but the primary reason to use a sprung disc with a solid flywheel should not be to reduce noise, but to save your shafts and bearings from destroying themselves.

Your goal is to keep the engine from getting to that temperature in the frst place. You can do my fan mod which allows you to turn the fans on full speed with a flip of a switch and you will be able to control engine temps in stop and go driving. Radiator Fan and Engine Compartment Fan Switch Mod The 3.4 996 runs extremely hot when driving around town in temperatures higher than 75 degrees. This mod is a way to reduce coolant temps back to a safer level, helping to reduce oil temps and improving performance. The mod consists of installing a switch that will allow you to turn on the high speed radiator fans at any time, while maintaining the automatic operation of the fans. We do the same for the engine compartment fan. Radiator Fans Connect a wire to the ground (Pin #85) of the 2 high speed fan relays located on the relay carrier located in the driver’s side foot well. The relays are #20 and #22. Feed this wire to where your switch will be located. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and then connect the other end of this wire to a chassis ground point. With key on, this switch will now immediately turn on both radiator fans providing maximum cooling. When you turn the key off, the fans will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. Engine Compartment Fan Connect a wire to the ground of the relay located in the relay carrier behind the passenger seat, driver’s side. Relay #8. . Feed this wire to where your switch will be located. I simply fed the wire along the driver’s side of the car and under the door sill. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and connect the other end of this wire to a chassis ground point. With key on, this switch will now immediately turn on the fan drawing air into the engine compartment. When you turn the key off, the fan will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. This mod helps keep the engine compartment much cooler when driving around town and is particularly beneficial to any engine that draws its intake air from inside the engine compartment. It will also help keep engine temps down. If you are adventurous, you can automate the operation of these switches so they will switch off at a specific speed, or operate when vacuum is present only, etc. You can choose any style switch you want and even use Porsche switches. I simply used 2 toggle switches that I installed in the batwing, Jim Very useful write-up! I installed the 3rd radiator but in stop-and-go traffic, temps (even now that we're entering winter) still reach 100C and higher, so I guess I am going to do your mod soon. Any input as to which of the two mods gets you the biggest bang for the effort? I have a hunch that the high speed fans provide more cooling than the engine compartment fan. Correct? Joost Running the radiator fans provide the most cooling.

My car DOES have a throttle cable- it's attached to the throttle body that I removed when I did the oil filler tub fix. What a HUGE HEADACHE. Then you are not talking about a 1999 C4 as they do not have a cable. What kind of car DO you own? a 1999 c4 :) The whole EGAS thing drove me nuts since I ordered one new maf sensor from ebay- it was the wrong one. Then went thru pelican- it was the wrong one. And finally took the old one out and took the part number- NOT EGAS :( It is surely a C4 thou, according to both the title and the way all 4 wheels spin :) And you are telling us that the throttle is controlled by a single cable from the pedal to the passenger side of the throttlebody? If that is the case, there is something suspicious about your engine. Are you the orginal owner and was a different engine put in the car?

My car DOES have a throttle cable- it's attached to the throttle body that I removed when I did the oil filler tub fix. What a HUGE HEADACHE. Then you are not talking about a 1999 C4 as they do not have a cable. What kind of car DO you own?