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Need help! Stalling problem and more!


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:help: Dear everyone,

I really need some help here. I am encountering some problems with my 996 and am wondering if you guys can help me to find the answers.

Problems:

1. Ticking noise from the dashboard area - The ticking noise is not continuous. The noise from the dashboard area seems to come from some faulty electrical wiring or connections and is not speed related. It seems that if I turn off the A/C, the ticking noise from the dashboard will stop. The ticking noise only happened when the car is warmed up. Someone suggested that the noise may be from a bad A/C drop-out relay or a bad A/C heating fan or auxiliary cooling fan. Do you think this ticking noise may be from a bad cooling or blower fan which is located at the right front of the car (as mentioned in Q2 below, my car may have a faulty cooling fan)?

2. Groaning/Moaning noise from the back of the right front wheel - The noise continues even when the car is parked/stationary (with ignition on). The groaning / humming echoing noise is from the back of the right front wheel near the fuel tank area. It creates a humming echoing sound like “Won ... Won ... Won ...”. This noise only appears when the car is warmed up. Someone suggested to me that the noise might be from a faulty fuel pump or cooling fan. Any views?

3. Stalling problem - my car is a Tiptronic (stock without modification). The stalling of the engine happens when I press on the brakes, what actually happened was that when braking to stop (during the first 5 mins after start-up), the idle will drop to where the car is about to stall, then bounce up and around until it finds the idle. It won't happen once the engine is warmed up. Also, if I have the A/C turned off, the situation seems to be better. Any views?

4. Clunking noise at the engine area - Sometimes when I start the engine in the morning, I can hear a pretty loud "clunking noise" from the engine area. Moreover, I have noticed that sometimes there will be some white/grey color smoke coming from the exhaust pipes with the smell of gasoline when I start the car (it only last a couple of seconds). Is this normal?

5. Loud plastic rubbing noise from the middle of the engine area when I start the engine in the morning, it sounds like “Boo…Boo…Boo…” - could this noise be from a bad fuel pump (does the 996tt have two fuel pumps - one at front and one in the back)? Howabout a bad alternator or engine belt? Any idea as to what that is? It goes away when the car is driven for a couple of mins.

6. Battery - I just have my battery changed. When the radio and A/C is off, the battery level is around 13.5. But when the radio and A/C is on, the battery level drops to around 12. Do you think this is normal?

Best regards,

Superfans.

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Dear Loren,

Thanks for your reply. Actually the car is a 996tt, early 2002 with about 7500 miles. It is an UK model (RHD). I understand this is a 996 board but since I've heard some 996 owners have also encountered similar problems so I am hoping that you could help me to find out the answers to the questions listed in my first post.

A little update on the stalling issue, actually if I don't turn on the A/C, headlights and radio (with the battery level slightly below 14), then the rpm will only drops a little (still above 500) and stalling will not happen even when braking. Only when I have all the electrical items turned on (especially the A/C - with the battery level drops to slightly above 12), then the problem will appear. I am wondering whether there is anything to do with the possible faulty A/C fan (which draws a lot of electricity from the battery) coz the ticking noise from the instrument panel area seems to be from a faulty A/C fan. Yesterday, when I have the A/C turned on, the ticking noise appeared after the car is warmed up. Once I turned off the A/C, the ticking noise also disappeared. I've tried a couple times (ie turn on and off the A/C) and the same has happened so I guess the ticking noise must be A/C related. Furthermore, I also heard a loud squeaking noise from behind the instrument panel when I turned on the A/C. Any views?

Edited by superfans
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  • Admin

I would start by checking all the cars ground points for loose, rust or other corrosion. With all the weird electrical problems it sounds like low voltage to several components. I'll send you a drawing via PM here that shows all the ground points for a RHD 996 - it ought to be close to a TT.

The problem could also be a battery that is not holding a charge. How old is your battery? Most only last 4-5 years. Have someone check the specific gravity readings and make sure all the cells are good.

Third possibility is the alternator is not putting enough current out to charge the battery and run the electrics. Not unheard of but it would be last choice.

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Thanks for the tips. Actually, the battery is brand new (OEM). I just have it changed by the dealer a week ago.

As mentioned in point 5 of my first post, there is always a loud plastic rubbing noise from around the centre of the engine when I start the car. It will last for about 5-10 seconds. Do you think this may be the sound of a faulty alternator or bad alternator belt?

If the battery is running low, then will it affect the engine rpm? Is it possible that when applying the brakes, more electricity will be drawn from the battery to operate the vacuum pump, brake booster, etc. which sort of causing the engine to cut-off?

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There is only one belt even on a turbo - worth a check to see if it is slipping.

Well, from all the symptoms you describe... if the voltage is too low then the fuel pump will not run right - which will make the motor run rough which will lower the vacuum to the brake booster. Also, when you run the AC both front fender radiator fans go to high speed and stay on until the AC is turned off. What happens if you turn the lights on? Same, better, or worse?

If there were an air leak at the motor then I suspect you would have a CEL by now. If you have a scanner it might be worth a look to see if there are any codes. Does your CEL light up when you turn the ignition to on? (or is the bulb burnt out).

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There is no CEL in my case. There is no aftermarket electrical items added to the car. There is no modification of the car either. Everything is OEM.

Can the computer detect a minor vacuum leak? I've heard that one can actually try testing the brake pedal to see if there is a leak. Isn't it that when you step on the brake pedal a couple of times after the engine is off, the brake pedal will become hard due to the release of vacuum in the booster. I've tried that but my brake pedal did not get harden and I can continuously press onto the brake pedal as if the engine is running. Does it mean that there is a vacuum leak in the brake booster?

As to the alternator, it seems that it is still working alright (although the plastic rubbing noise continues for the first 5-10 seconds after start-up). Everytime when I start the engine, the battery level will be around 12V before ignition is on and 14V after ignition is on (of course, with A/C, lights and radio off). Once I turn on the lights, A/C and radio, then the battery level will drop to around 12-12.5V gradually. I am not sure if this is normal.

The frustrating thing is that the dropping of the rpm while braking only happens during the first 5-10 mins drive after start-up. Once the engine is warmed-up, this problem will disappear (at least it won't be as bad which causes the engine to shudder or stall).

Edited by superfans
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There is no CEL in my case. There is no aftermarket electrical items added to the car. There is no modification of the car either. Everything is OEM.

Can the computer detect a minor vacuum leak? I've heard that one can actually try testing the brake pedal to see if there is a leak. Isn't it that when you step on the brake pedal a couple of times after the engine is off, the brake pedal will become hard due to the release of vacuum in the booster. I've tried that but my brake pedal did not get harden and I can continuously press onto the brake pedal as if the engine is running. Does it mean that there is a vacuum leak in the brake booster?

As to the alternator, it seems that it is still working alright (although the plastic rubbing noise continues for the first 5-10 seconds after start-up). Everytime when I start the engine, the battery level will be around 12V before ignition is on and 14V after ignition is on (of course, with A/C, lights and radio off). Once I turn on the lights, A/C and radio, then the battery level will drop to around 12-12.5V gradually. I am not sure if this is normal.

The frustrating thing is that the dropping of the rpm while braking only happens during the first 5-10 mins drive after start-up. Once the engine is warmed-up, this problem will disappear (at least it won't be as bad which causes the engine to shudder or stall).

Yesterday, I placed my foot on the brake pedal when starting the engine but the brake pedal did not depress or drop. Does it mean that the brake booster is not functioning properly?

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