Hey MC, My 1989 Turbo smells like fuel and I am worried that a spark could ignite it. I narrowed it down to the front trunk area. Eric
If the fumes are that strong, you bet it could ignite and in the garage, it could take your house with it. First, if you smell this, do not start your car to pull it out of the garage, push it out and look for signs of dampness. The three most common sources that I have seen are a cracked fuel cap gasket, loose screws on the fuel sending unit, or vent hose clamps that are tightened to their limit without securing the hose.
For the fuel cap it’s easy. Just pick up a new O-ring for it and you are all set. You don’t need to buy a new cap. The part number is 944 201 553 00. The fuel sender screws often take a sixteenth of a turn and usually this fixes them. If you still get dampness or smell odor after filling up the tank, try to blot the area around the fuel sender and see if you can detect fuel or vapor. The sender gasket is inexpensive as well and easily replaced.
On the vent hoses, there is a special type of clamp called “Oetiker”. I suggest that you cut them off and replace them with worm gear screw type clamps which can be purchased a any auto parts or hardware store. –MC
Hi MC, When I started my Carrera this morning I heard a loud “pop” then the car would not run. It will start but it stalls right away. Chuck
Chuck, That pop you heard was probably due to an intake system backfire. On an early Carrera, a lean fuel mixture can cause parts to break or hoses to blow off. When this happens, the car will start (on the “cold start valve”) but as soon as you release the starter, the cold start valve shuts off and the engine stalls.
If you have the earlier CIS fuel injection used on normally aspirated cars up to 1983, this can indicate (or cause) a significantly expensive problem. On these models, a plastic plenum directs air flow from the air flow meter to the intake runners. If the car backfires, usually an “anti backfire” flapper valve opens and relieves pressure. This can prevent damage but the backfire can be violent enough to actually break the plenum. Sometimes, the plenum may be leaking air and the backfire is just the “straw that broke the camel’s back”. Some cars have the original plenum, the fuel/air mixture weakens the plastic and it can come apart or fractures. In a best case scenario, you find that the glue which secured the flapper valve has failed and it just needs to be re-glued. While you are checking this, see if all the screws are still tight which hold it together. If you find screws loose, tighten all those you can reach and plan to do a more thorough repair since the ones you can’t reach are probably also loose.
If yours is an 84 to 89 Carrera, there is a hose that usually pops off near the rear of the engine (where you can’t see it). It connects the main air flow meter to the intake throttle body. If you are fortunate, the only thing to do is reinstall the big air hose. The hose is located directly in the middle and top of the engine. Check the clamps that secure it and you may find one loose. If you do, loosen it more and try slipping the hose back on then tighten the clamp. Another source of intake leaks on the later cars involves the breather hoses. These rot due to age, heat, and oil. They are located where you cannot see them unless you remove the air flow meter assembly and If you are willing to go to that extent, plan to replace them since they are now over 20 years old.
On the Carrera 2 & 4, the latest problem that I have seen was an entire intake plenum assembly blown right off the top of the engine. The client said “I think the entire rear of the car lifted up when it happened”. This one was a little tricky. Turns out that when the car had been serviced four months earlier, two of the exhaust side spark plug wires were switched on the right bank. This ignited the intake charge while the intake valve was open. This “human induced” problem that was undetectable during driving the car but on that fateful day, BOOM. There were no apparent long term effects of this problem but it points out the need to mark the things that you remove when servicing your car. –MC
Q — In spring of 07 I traded my boat for an 88 930 slant nose coupe from Arizona. For the first couple months, I had no problems. Then leaving work one day, it would not start. After 30 minutes of jiggling wires it finally started. After that, sometimes it would start and quit after a couple miles but sometimes it would turnover but not fire at all.
It sat all winter then started right up (but with major exhaust smoke) then I shut it down and left it a couple days. It started again that following weekend, (2 weeks ago) not as much smoke. I pulled it out into the drive and gave it a little throttle (about 4000rpm) just to go to the end of the drive, but when I let out the clutch, I heard (and felt) a very loud backfire and it stalled. When I attempted a restart it turned over like no compression. So now I’m thinking something blew inside the engine. I wait 1 sec. I try it again and WOW Hey MC she started right up!
I want to get out to some club events but I’m still afraid to drive it. A local Porsche mechanic said he thinks it may be the 6 pin cd box, another said computer. What would be your guess without seeing it?
Is there anyone in SEM/PCA near Mt. Clemens area that could stop, look at and possibly fix this without charging an arm and a leg. These days can’t afford to lose an arm or leg let alone both. 🙂
I’m very disappointed with this car so far, maybe I should just get rid of it while I’m still BEHIND 🙂 So brings one more question to mind 3) What is this car worth (if it was running) in fair cond. and almost 100,000 miles
Thanks Barry
A — This must be the month for intermittents. Have faith, I am a stubborn German who enjoys a challenge. Over the last few years, a half dozen or so fearful folks have begun to venture far from their “AAA Plus” limit. To me the acid test is taking that long road test myself. To verify intermittents, I built a jumper box that allows me to monitor power to both ignition and fuel circuits and if one should drop out, supply power to the circuit that needs it. You might want to borrow it.
The CD box is not the first place I would look. Usually these fail totally, not occasionally. Far more common is a fuel pump relay failure or ignition cut relay. The turbos have an extra relay in the engine compartment that cuts ignition power slightly after you turn off the key. If you do not feel adventurous in the realm of electricity, I would give up early on this one however. What you can do, is follow the fuse box servicing process that I mentioned to Gary in the answer above. Even if that does not help, always start with the source of power and work your way in.
As far as smoke after sitting, don’t worry about it. The engine contains a large quantity of oil that will settle into the crankcase when it sits all winter and that first start up can be very disconcerting. Start to worry when it smokes every time!
Backfiring on this particular Porsche is a particularly troubling and perhaps costly problem. This model uses an archaic fuel injection design that is very sensitive to vacuum leaks in the intake system. Even if a vacuum leak did not cause the backfire, the event itself can CAUSE a new leak. During start up and warm up, the electronic fuel trim components are disabled. In this mode, the engine relies on mechanical fuel mixture control adjustment and vacuum leaks cause the mixture to go lean (not enough fuel) which can cause backfiring.
You might notice the large radiator-like device that dominates the engine compartment when you open the deck lid. This component, the intercooler, is removed during most services and the intercooler is sealed to the intake piping with large silicone rubber O-ring that get oil soaked, broken or squashed. These O-rings are a source of leaks that can cause backfiring and a loss of boost pressure during acceleration too.
As far as selling it, why give up so easy? Once you get it sorted out, you are going to have a ball. Compared to a boat, you are going to have a lot more fun with your Porsche since every weekend there is a driving or social event where you can sport around in your new toy. Besides, what did it cost last season when you filled up your boat? Now double it. Doesn’t that Porsche look better? –MC
Q — The AC blower motor on my 1980 Carrera has been working very erratic lately. It will work one time when I drive but when I stop the car to go shopping for a while, I come back and it won’t work. If I let it sit for a few days it will work then and then not work. It even went out for a few minutes then came back on while driving. What is your opinion on the problem??? Motor going??? Control Switch?? Ground??? So just where is the motor located??? I assume it is in (what is commonly called) the smugglers box. I have a part # of 901 624 901 00 for the motor. Is this correct??? What is the cost of new motor??? Thanks Gary
A — Intermittent problems are the most challenging and all too often, do-it-yourselfers fire the “parts cannon” in desperation. Don’t do that yet. There are some things you can check and even if they do not cure the problem, consider routine maintenance instead.
First check the fuses, but not to see if one is blown, that would be far too easy and the blower wouldn’t work at all. With a strong light, notice the appearance of discoloration on the fuses and the wiring at the fuse block. Notice the different color of the fuses (which corresponds to their load value) and make yourself a diagram with those colors noted. If you find that some of the fuses have shrunk, you have fallen victim to plastic, third world fuses. The original fuses were ceramic and they do no melt or shrink. F.Y.I. Yellow is 5 amp, white is 8 amp, red is 16 amp, and blue is 25 amp.
Next, disconnect the negative battery cable and inspect the fuse box for integrity of the plastic base and then check all the screws securing the wires to the fuse holders. To check the screws, hold the base of the wire holder with needle nose pliers as you try to loosen then retighten the screws. If power flows through an overheated circuit, the screw might seem tight but be partly seized in place due to the heat generated. Typically, I find some screws loose, most of them tight and occasionally, a heat damaged terminal or fuse box. On many older cars, an auxiliary fuse box contains the AC fuses and I have found these broken.
While you are working on the fuse box, mark then remove the relays and look for melted sockets. These sockets can be purchased from Porsche and although not a simple job, they can be replaced. At a minimum, I suggest that you clean the sockets and fuse box with electrical contact cleaner while protecting the surrounding area. After cleaning, a light coating of Dielectric grease (non conductive) is useful for corrosion protection.
At the battery, there are a number of positive wires and grounds that should be inspected and tidied up. The grounds also warrant a good look. And finally, don’t forget connections under the dash and in the center console where the controls reside. The AC system draws a lot of power and every place where a main wire plugs into a component should be felt and if needed, tested for voltage drop between the battery and that point in the circuit. –MC
Q — The leather in my car is very hard from many years in the Florida heat and the seams are starting to pull apart. I tried some leather creams and treatments but the leather is still hard and the little perforated holes in the seat cushions got clogged with the treatment. I paid my son and his friend $10.00 just to clean all those little holes with toothpicks. Got any ideas? Bill
For this cure, you will need to practice patience. Remember it took years to dry out so don’t expect it to soften up overnight. I have had old leather come back to life with repetitive coats of “neatsfoot oil”. You can buy it at the hardware store but I get mine at the local saddlery (Horse people definitely know how to take care of leather.)
It will take a while for the treatment to soak in so plan to do it when you know that you won’t be using the car for a day or so. Paint it on with a natural bristle paint brush. You will notice how it soaks into the leather at different rates. Expect to recoat the neediest areas and wipe the excess off the places where it does not soak in. In some cases, you might discover that it does not soak in at. It is possible that your leather seats may actually be part vinyl. Don’t worry, it won’t hurt vinyl.
After a few applications you will begin to notice the difference and in a few months, your hard seats will soften up again. Incidentally, if you want to apply a more intensive heavier coat, you can cover the seats with plastic for a day or so. This also allows you to drive the car if you can’t wait for it to soak in. –MC
Q — I have been considering a muffler bypass on my 1997 Carrera but wondered if it would be too loud. Have you heard one? Chuck
I really love the way a Porsche sounds without a muffler. Motorhead heaven is sitting in the infield at Daytona when a half dozen or so thunder by. I wish there was a switch that would allow you to select “muffler” when you need to be discrete and “bypass” when you want your Porsche to sound like one. Until then, if I had to live with the bypass pipe, I might drive my car less and I would be nervous about getting caught. Consider one of the sport mufflers instead. Most of them fit well and sound mellow compared to the muffler bypass.
The next time you are at an event, listen to some of the cars that have a sport exhaust or the muffler bypass. Ask if you can go for a ride in the car to see how it sounds. If you hear an exhaust that you particularly dislike, politely inquire as to the brand and eliminate that one from your list.
The price of experimentation is not too great when you consider the residual value of your first choice. If you buy something that doesn’t suit you, you can always sell it in the newsletter and try something else. There are always deals on used parts through the club. –MC
Q — I just bought a track car, a one owner 88 Carrera and I am looking forward to this year’s DE without sweating the damage I could do to my GT3. So I have a number of questions.
1) The former owner installed headers and has the oxygen sensor still installed in the left header but it is unplugged. Should I leave it unplugged or should it be connected.
2) The sway bar mounts in the rear are showing signs of cracking and I was told that a revised bracket is available. What should I do about it?
3) The AC does not work and I need to replace an oil line underneath the compressor anyway. Can I just remove the compressor and leave it off? Mike
Wow Mike, this is what I call “living large”. While you are at the track with the Carrera, I would gladly exercise the GT3 for you. You really should not let these cars sit around.
But seriously, on item 1, the OXS sensor is an electronic “nose” that constantly monitors the fuel mixture and adjusts it based on “smell”. Do you notice that funny odor that you detect after a hard run at full throttle? That is raw un-burnt fuel. And although $4.00 a gallon gas is a factor, there are other considerations.
With the sensor wired into the fuel injection system, the amount of fuel compared to oxygen is constantly adjusted by the Motronic computer for peak engine efficiency except at full throttle. At full throttle, the computer ignores the sensor signal and uses a different “computer map” to give you maximum power. Or you might say “engineered maximum power”. This is where chips come in. A chip will give you more power by re-engineering the map to provide more advanced spark and a richer fuel mix. Simply unplugging the sensor causes the fuel mix to go “full rich” without the benefit of advanced spark timing. So the engine runs great at full throttle and ironically, it would do that anyway if the sensor were plugged in.
The other considerations have to do with increased engine wear by dumping all that extra gas into the engine when it does not need it and the comment by your better half: “why does your car stink?” My dear old Dad also claimed up to 10% better fuel economy in both of his chipped Porsche’s (when he drove for economy).
My advice: Chip it, adjust the fuel mixture to base settings, plug the sensor back in, have it tested, and enjoy the best engineering that Bosch and Porsche built into the car.
On question two, the sway bar mounting brackets were poorly engineered from the start. By my rough guess, they are broken or cracked on better than half the cars I inspect. There are three methods of dealing with this: 1) If the bracket is completely broken, Porsche offers an updated stronger design that is priced at under $100.00 each (plus labor) 2) If the bracket is cracked, it can be reinforced before it breaks and this is equal to the updated bracket at a much lower labor cost. 3) There are aftermarket brackets that attach to that large round tube called the torsion bar housing. Although I consider these ugly, they work and they are cheap.
On question 3: Should you delete the AC compressor? On this model there is no down side to removing the compressor. There is only one wire to disconnect, the compressor is heavy and who needs it at the track? Before you remove it however, make sure any remaining coolant (Freon) is recycled. I suggest that you cap the AC hoses if you ever want to reinstall it. If you want to take this project a step further, that AC condenser under your turbo tail is not improving air flow to the engine either. –MC
Q: I have a 924 that I take to the track and I am concerned about my rear wheel bearings. I think they feel loose even though I have replaced them. I have checked out some of the later cars and they do not have this problem. – Gary
A: You are right, your bearings do feel loose, but how loose is “loose” anyway? First a little history, in 1969, VW Beetles began using the same rear suspension and wheel bearings as your 924. (This is worth noting when you need spare parts.) Beetles and vintage 924’s have a suspension load rating that is rather low. The inner (ball) bearing acts as the thrust bearing and the outer (roller) bearing only carries vertical load. They feel a little loose when they are brand new. As the cars became more powerful and Porsche upgraded the suspension, a heavier duty sealed double roller bearing was used. These later bearings should never feel loose.
When inspecting the wheel bearings, one needs to be familiar with the engineering, specifications, and the torque specification of the nut. If you are not sure of the torque on the axle nuts, check it. – MC
Q: I just bought a 2007 Carrera 4 and I plan to take it to Drivers Ed this year. I wondered what I could do to get more power. Is it possible to install a turbo or a supercharger? – Jim
A: The quick answer is: sell it and buy a turbo. But I understand, this is the car you have and you want to have as much fun as you can. I feel the same way about my car, and I want more power too. For more power, very little is available that does not involve a huge outlay of cash. For my money, I would start with a sport exhaust and a cold air intake. You can expect modest gains in power but more importantly, your car will feel faster.
For the turbo or supercharger option, there are companies that develop kits for newer cars but it is getting difficult to improve on Porsche engineering. Another factor on a new car is warranty. Porsche backs their products with an excellent warranty as long as the car is maintained and operated in accordance with their standards. If you modify a car under warranty, they can always tell you to “take a long walk on a short pier” if something breaks.
For Drivers Ed, find out how much fun your car can be with only a few only minor swaps, and next fall, after a season of fun, pose that question again. Some summertime seat time may change your perspective. – MC
Q: I just went out to start my car and the battery is dead. If I can start it with a jump, is it OK to let the car run for a while and charge up? – Justin
A: It is a widely held belief that the car’s charging system is for charging the battery. Oddly, the folks who designed, built and supplied your alternator do not think so. I know it doesn’t make sense but Bosch warns against trying to charge a dead battery with the car’s charging system.
The alternator’s mission is to replenish the electricity lost during starting and maintain the charge of the battery by powering all the vehicle accessories. A dead battery can send the alternator into thermal overload by delivering too much electricity. Bosch clearly states this on the installation instructions provided with every alternator. It certainly doesn’t seem intuitive does it?
Alternators are designed to produce their rated load for relatively short periods and then taper off. Alternators that produce maximum output continuously are used on commercial vehicles such as police cars, ambulances, etc.
If you have the time to wait, your best bet is to charge the battery at a low rate to charge it up fully. I use a 2 amp manual charger for the first 24 hours then an automatic charger at the 10 to15 amp setting for another 24 hours. To fully charge a stone dead battery may take a couple days and it is best not to rush the process. If you are going to try this however, please note the following paragraph.
If you notice the odor of rotten eggs or see liquid bubbling out of the battery, unplug the charger at the wall socket and sprinkle a little baking soda on that bubbling liquid (which is probably acid). Leaking battery acid will damage the trunk of your Porsche and that nasty odor indicates the presence of an explosive gas (hydrogen). A spark can ignite the hydrogen which is why it is wise not to simply unclip the battery clamps.
If you are in a hurry and you can’t wait to drive your car, connect the jumper cables and let the running car send power to the dead battery for about 15 minutes before you even try to start your Porsche. Once your car is running, rather than letting it idle, drive the car to charge it up. At higher rpm’s, the alternator runs cooler as it charges.
When you park the car that night, put the battery charger on at the 10 to 15 amp automatic setting. Usually one overnight charge will bring it back up to snuff if the battery is healthy. Please note: If you have a charger with both manual and automatic modes, I suggest that you only use the automatic setting. Keeping the battery in a proper state of charge will save your alternator and your battery tray. – MC