Poor performance when warm

Kevin Parrilla · 04-22-2012, 04:14 AM

Hello, I have a 1983 911sc with 80,000 miles. The problem I am having is when the car is warm. It is making a fluttering sound when the throttle is pushed more than halfway. When it is cold there is no sound at all and pulls strong.

Thank you,
Kevin

Innov8 · Innov8's Garage

Sorry Kevin, don't mean to hi-jack but I have the same issue on my 82 sc. When the engine is warm, it idles fine but if I give it some gas, the engine bogs down and sputters until about 3k rpm. From there it pulls and runs normally. The problem is intermittent but seems to be becoming more regular. I've checked the control pressures and everything seems to be in spec (from my searches here).
I've replaced the fuel pump, fuel filter, plugs, cap and rotor and injectors and sleeves. Car starts and idles fine otherwise.
I've been told I need to get a "dwell meter" to trouble shoot the CIS further... I don't know what that is but will check the lamda relay too... can you be more specific... is it PCG-951-253-00-M14 from our host? They call it an Oxygen Sensor Relay but do not include a parts diagram or image. Your advice is greatly appreciated. This is becoming a frustrating and costly fix.
Thank too Kevin.

Kevin Parrilla · 04-22-2012, 07:54 AM

Everything is normal during warmup,But it seems as soon as it hits the first mark on the temp gauge it makes the fluttering noise. If I push the pedal past halfway there is less power. If I bring the rpms up slowly without full throttle it redlines without any problems.

If my question helps others, than this forum has
served its intended purpose

Kevin

Targalid · 04-22-2012, 10:57 AM

Kevin,
When was the last time you gave the car a basic tune up: plugs, distributor cap, rotor, ignition wires? I had similar problems, with the engine bogging down around 2500 to 3000 rpm. Changing the plugs made a huge difference. Each of the other component updates then contributed to increased performance, with new ignition wires being the final (and most expensive) thing I tried. That smoothed out the occasional miss during acceleration. Since Innov8 has already updated his ignition system I have nothing to offer for him except to try running injector cleaner through the fuel system. Good luck.

rsscotty · 04-22-2012, 11:18 AM

When it comes to diagnosing your issues, the first thing that comes to my mind is broken head studs, based off your "fluttering" description. This means you'll hear an exhaust leak between the cylinder and the cylinder head. You can check them next time you pull the valve covers off.

Kevin Parrilla · 04-22-2012, 11:51 AM

I am the second owner of the car,the original owner had the same problem and put some money into finding the problem with no avail. The valves were adjusted close to 10,000 miles ago along with a tune up.There were no headstud problems found at the time.

Josh D · Josh D's Garage

Sounds like preignition to me. Check ignition timing. What grade of fuel are you running?

Kevin Parrilla · 04-22-2012, 12:58 PM

Timing was the first thing checked when I got the car.I have tried every brand and grade around with no change

Innov8 · Innov8's Garage

Good news. Installed the new relay (from our host) for the lamda and the car ran like a top. Tested it just before installing, with out the relay installed and the car ran the same as before, backfiring and stuttering when giving a little gas off idle. Installed the relay, started right away and drove for 2 hrs... no problems. $12 fix.