RBP

Anyone experience rough engine performance when first out in the morning on a cold engine? I am always under 3,000 RPM and try to operate at around 2,500 until it warms up a bit. The manual says not to idle for warm up, just start it up and drive. Seems to go away when warmed up so maybe this is normal. Any comments?

d ward

Is it worse when its damp or wet outside, had this on a 993 and it was the ht leads breaking down and was far worse when damp as the ht leads were arcing on the engine

Leon993

To me, it seems that engaging the gears and running a cold 993 is a bad idea. I have always let the car idle of like five minutes and then take it slow. But on winter, when the oil is thicker, I would even let it idle longer.

I wonder if the manual says not to idle for emission reasons....

NC TRACKRAT

Have you checked/cleaned your ISV lately? If not, do a forum search and you'll find plenty of info. and DIY instructions. At start-up, I'd idle for 30 sec. or so, then not exceed 3k-3.5k rpm until oil operating temp is reached. Extended idle just contributes to clogged SAI system and tends to foul plugs.

RBP

Presently I do start-up and let idle for say a minute, then drive very conservative at around 2500 until the engine warms up a bit.

What is the ht lead?

vincer77

Anecdotal info here seems to point to cars that are idled before driving are more prone to problems like oil leaks. I think that a 1 minute warm-up with under 2500 rpm operation until the temp is up to the first mark is good advice.

Ed Hughes

That's what multi-viscosity oil is for. 5 minutes of idle is just goimg to let part of your motor warm up. Best to drive under 3k and move the oil aroumd, thereby warming the motor up consistently.

Leon993

All interesting points. Ill follow Ed's and Vincer's advice on the one minute warm up before going. However, in minus freezing weather, I notice the temp gauge takes much longer to warm up, so perhaps a bit longer on idle when freezing outside?

M. Schneider

I've practiced the above ^ "cold engine" start since new which was 11 miles at delivery. Noted 911 expert Bruce Andersen once offered the 911 engine's was various metal types which expanded at different rates - best practice is to warm the engine by driving easy/moderately and not to exceed 3000 RPM until at full operating temps.

Fast forward by 12 years and 65,000 miles, my 993 when starting from cold will softly stumble ever so slightly - not unlike the original post's concern. The full monty 60k service was done at 57,000 or two years/8-9k miles ago- which included new Beru wires, boots and all. And yes, #5 & #6 spark plugs were changed as I did the 60K work myself. Removed the 2 distributor's for the belt service because of age. The stumble I'm experiencing goes away after the initial 1st - 2nd gear shift. I've practiced since new using a 20oz Techron dose into a full tank of fuel, then driven to empty or so, before each oil/filter change in an effort to combat carbon deposits. Never cleaned the SAI ports though....

vincer77

I need to share my recent experience. I have been experiencing a stumble on acceleration for a few months now. It has been worst when cold, then after warm up almost indeiscernable. But when warmed up, the engine had some slight misses under acceleration that I would characterize as "dirty acceleration". I have also been experiencing rough shifts. I have cleaned the ISV a couple of times and was looking at maybe replacing the distributor caps. The PO had already replaced plugs and wires.

While getting tires (subject of another soon-to-be thread). at CPR here in Brentwood TN, I explained the problem to Matt and he suggested that I use Techron. He added that the ethanol in the fuels these days leaves "alchohol crystals" (at least that is what I remembered) that the Techron cleans up. So, the next day I saw the Techron on sale thread so stopped by Advance Auto and picked up 4 bottles. After the first 1/4 of a tank, the stumble is about 80% gone. The car accelerates smoothly and it is easy to switch gears. It is really amazing how well it worked. Now, I am a Techron believer. Thanks Matt!

1pcarnut

+1 to the warm it up while driving. This has been advocated for years by people who know their stuff. I learned this back in the '70s on cars and motorcycles with carbs. Within 30-60 seconds I'm gently on my way. No hard acceleration, no revving the snot out of it and no fast shifts, just let it warm up while moving.

axl911

993s are not rough when cold. It's a sport car and a product of the 90's, but it's not rough when cold.

Check you cylinder head temperature sensor (CHT). Plenty post on how to do this when you search. Checking it is easy with a voltmeter. Replacing it is another story!!!!

Ed Hughes

Be sure and change your oil soon.

M. Schneider

+1. I hear that.

Fuel additives such as Techron, BG, etc., wash into the oil during combustion. It's recommended to go easy on the "snake oil" for the greater good of the engine oil; all 10 quarts in the 993. While not critical, I mean no 3.6l ever died from a 20 oz Techron overdose that I'm aware of, do an oil & filter change after using these types of fuel additive products. I'm just saying.....

kjr914

HT= High Tension, which is another way of saying High Voltage. Here he's referring to the high voltage plug wires.