I've owned my 96 850T since 02 and it's developed a new problem. When I first drive the car, it feels like one cylinder is not working for the first 2 min or so. The care runs very roughly and shakes - also low power. After about 2 min, it starts running on all 5 cylinders and never returns to rough running. Note that it is about 95F out here, so I'm not sure that I would call this a cold-start problem.

Plugs, wires, dist cap are now new.

Thanks
Greg

 

I'd suggest you do a compression test. There is a chance you have a vacuum leak but you may have a sticky valve or something.

Better yet, you should check your fuel injectors. Have you run any injector cleaner in the tank lately? I usually run Lucas fuel treatment in the tank every 10,000. They suggest every 2,000 but I alway run band name fuel and 93 octane.

 

Thanks for the suggestions.
If the injectors have some clogging, would they clear up when they get a little hotter?
Also, it is possible that I have some crud/carbon on my valves as I rarely drive more than 30 min.
Do you have a suggested product for dissolving carbon - other than removing the head and scraping, or blasting with walnut shells, etc.

Thanks again
Greg

 

It's not injectors. Injectors wouldn't magically self clean every start. Even a leaking injector will clear the cylinder in 10-15 seconds tops.
Most likely causes are a stuck valve (unlikely if it clears) , a fouling plug or compression loss/coolant leak.

 

In addition to cold compression test also ck the fuel pressure when cold...

 

Greg, I would start with the injector cleaner. The bottle claims that it cleans sticy gummed up valves as well. As for driving over 30 minutes, a lot of people don't. The hard thing on a motor is the first few miles. My wife use to drive her jeep 6 miles to work and 6 miles back. Took 4 miles to properly warm the thing up. As long as you're driving past the 5 minute mark the car is at temp and should be fine.