Help needed - lack of power and very rough engine

I only drive my car every other week or so and have twice now experienced a rough and powerless engine. 1st time was 6mths ago after it had been standing still for 2.5 weeks. Then it was okay until the 2nd time which was last night after a 2 week lay up. Symptoms: - engine sounds as if its only firing on half cylinders. ie engine noise isnt smooth and consistent, its 'bubbly' and sounds normal for a second, then low, then normal, then low - revs seem to be low as well, idleing at 600 whereas i think it normally idles at 800 (both with no air con) - power delivery is very weak and inconsistent - last night the engine light started flashing as well (the yellow one that has 'check' inside the picture of the engine) - on both occasions I only experienced this for one drive. The second drive is fine - e.g. when I drove home last night it sounded okay again and power delivery was okay Anyone experienced this before? Any advice? Booking and taking it in to OPC is a right hassle, but I figured if the engine check light has flashed, then the computer must surely be able to tell OPC whats up? Is that true? Is plugging the diagnostics in a quick thing? ie could I just rock up to Chiswick and ask them to quickly plug the computer in and see what it says? I figured that my first course of action should be to get OPC Warranty RAC man out today. I have OPC warranty.

Sounds like coil packs to me - I had the same and it's aggravated by wet weather (gets into the splits in the coil pack casing). Think it's covered by warranty?

When was the last time it was serviced? The coil packs are checked then. Not sure whether the warranty would cover them as I think they are considered as "wear and tear" but to have them replaced shouldn't me more than a couple of hundred notes & less if the car is being serviced anyway.

I've had cracked coil pack replaced under warranty

Once you replace the faulty parts, it sounds like your car needs a good old fashioned Italian tune up :twisted: 911s need to be driven!

Hi you don't mention the mileage the car has covered, or when your last service was, I agree that coil packs on one bank of cylinders could be the issue, however the description also sounds like the engine is "hunting" which may also point to an intermittent over fueling issue. This could stem from symptoms on the intake side, but as you discern it to be on one bank only, you may be getting a feed back from the Oxygen Sensors in the Catalyser on the affected bank, which in turn affects the fueling. Another check is the engine losing water? Catalysers deteriorate in storage probably faster than in use especially if the storage atmosphere is damp. I think biting the bullet and getting the car into your OPC is what is needed to track down the probable diagnosis more accurately. Depending on the mileage as well as giving the car a good thrashing as another member has suggested, perhaps an Injector Clean with a good proprietary cleaner, and consider whether you are using the best fuel for the car. The top grade Shell V Power is the one I've been recommended when going through problems on my car. Hope you sort it out. Regards Big Bob

Hey Big Bob, welcome to 911uk. What do you drive and whereabouts are you? Say hello to everyone here!

Thanks guys - its going to OPC Chiswick on saturday. I pray that the computer tells them whats wrong. I have had 2 problems that they couldnt fix (1 got fixed after I told them what to do/look for, the other got fixed elsewhere). Also: 54k miles, 6k mileage p.a., OPC minor service in Sept, fuel is Shell V Power. And I will be giving it a damn good workout once its fixed.

Nice one Bob!......and welcome!

Welcome to the forum Bob, I had a similar problem recently on my family car, a GMC Yukon( an ocean going liner with wheels,handles like tectonic plates) I tried all the simple stuff first(plugs and leads) but the problem disappeared after I replaced all 8 coil packs with uprated aftermarket items. I got them tested and 2 had completely failed and 5 out of the other 6 were breaking down under load. Max

Hi Adrien I'm not sure if this is the right way to say hello to the UK911 universe of enthusiasts, but this is it. I drive a 2003 996 Coupe in Speed Yellow, It has a few power mods courtesy of the Porsche Shop, ie REVO, Supersprint Exhaust System , and Fab Speed Full Flow Intake System, upgraded brakes ie Pads, Braided Hoses and ATE Brake Fluid. To go with the Factory Fitted Side Skirts and Aero Kit, I've got a Cargraphics front spoiler fitted that finishes off the appearance. I've also got Victor Equipment 18" Le Mans Wheels in Black for the final bit of bling! I've been a Porsche owner for a year now. See my letter in Frbruary 08 Total 911. I live in Southampton. Regards Big Bob

Welcome Big Bob! Sounds like a great car... without wishing to hijack the thread, have you found the Revo remap's made a difference?

Hi Robert. The Revo made a noticeable difference before I added the Exhaust System and the Full Flow Cold Air Intake. There is a slight dead spot around 4000 rpm on the standard mapping, it loses this. The power and torque increases are very discernable, and you also have the opportunity to adjust the throttle response between 1-9. Paul at the Porsche shop suggested 7, I tried 9 but that was a little too "in your face" for town traffic. 7 is spot on. The advantage of the REVO over other Remap Suppliers is that as you have a Port Switching Device so you can swap back and forwards between Standard and Sport as you desire, basicly by an ignition key, and port insertion action. You also get a security setting that you can insert if you are leaving the car for a time, that prevents the car ever being started again even if the ECU is replaced. Definitely worth a try. They will let you have a 24 hour trial before buying if you want it! If you want to do a bit of tweaking, Paul at the Porscheshop takes a lot of beating on price and quality of parts and service. Definitely worth the trip to Birmingham area. Best Regards Big Bob

Thanks- Porscheshop's not too far from my folks. Interesting thought about the throttle response, I'd not considered that...

UPDATE FROM OPC OPC Chiswick just called me back with diagnosis: - Coils cracking. They will replace all 6 under warranty - MAF might be faulty, they will replace this as well, under warranty (was replaced under warranty 18mths ago at Reading OPC) Also found, but not under warranty... - the heat shield over my catalytic converter is rusting, so the bolts attaching it to the converter arent holding it securely and the heat shield might be vibrating slightly. Recommend: new bolts, nuts & heat shield. Parts cost c.£80 - my silencer has 'split open' but it 'isnt blowing yet, but is on the verge of blowing'. Recommend: new silencer. Parts cost £1000 - total labour for both issues c.£400 - the car was serviced 6mths ago and neither of these issues was mentioned, but that doesnt mean they weren't in existence. So I dont really know how long the rust or the split has been there I have no clue about the above two issues. Can anyone help out and advise what I should do? (BTW, I am not arguing that they should be covered, I figured they arent, its more how I should get them fixed) I never get non-warranty work done by OPC so am getting the car delivered back (very helpful OPC) and will make a decision based on advice from the Oracle that is 911uk.com