Dennis, One bad tank of gas in four years would be more than sufficient to cause cold startup hesitation due to restricted fuel flow when your lambda circuit is in its fixed rich mode as it is when cold. Try the filter as it's cheap enough to do on a regular maintenance schedule. The omission of a heat stove is probably not the problem as my green car is set up similar to yours without this hesitation. Let us know if the filter works should you decide to change it. As for your friend he's overdue time-wise to change the accumulator as I know of few if any cars that are still using an original, and functional, accumulator. Another strong possibility is that the distributor reg. valve o-rings he replaced are not suitable for use with today's gas and I would suggest he pull the valve and recheck them as it's a 5 minute job (longer if he,s mechanically challenged:). Rob Grady P.J.Grady Inc. -----Original Message----- From: dmcnews@xxxxxxxxxxxxxxx [mailto:dmcnews@xxxxxxxxxxxxxxx] On Behalf Of dmc_5180 Sent: Saturday, October 22, 2005 3:19 PM To: dmcnews@xxxxxxxxxxxxxxx Subject: [DML] Re: Strange acceleration problem ( For Rob Grady) Rob, I too have a very similar experience when I Start my engine cold and then immediately try to take off at a quick pace without letting the car warm up for a minute. As I get to a certain rpm under acceleration the engine will suddenly fall off and backfire pretty loud. I let up on the accelerator a bit so it stops and continue at a less agressive pace. it usually only happens once when cold. it generally goes away a half mile further down the road. I replaced my fuel filter 4-5 years ago and even then my fuel system was quite clean inside the tank. I was in their this spring and everything was quite good. I could understand changing the filter if you went into the tank found rust and disintragated rubber everywhere. But mine is clean. I won't rule out changing it, but I would like to know what the other things are I should look for the other 40% of the time. One thing I should also point out is that I have the Houston exhaust which does not have provisions for the heat riser duct . I just have the pipe tucked loosely on top of the right header so it can draw in any heat heat generated in the area. Other than this, the car runs perfectly. It always starts instantly and idles smooth @ 775 unless it is really cold say less than 50 degrees out then it might idle hunt a little for 3-4 ups and downs before being constant. On a diffenet note: I have a friend who's car will not hot start, even if he just turned it off and goes to restart. Although it will restart if you do the CPR connector swap on the cold start valve. I was under the car a month ago and did a test where we ran the car with the small return line running into a jar to see if the accumulator was bad. After the initial start-up pressurization of the system, which of coarse pushed fuel out of the spring side of the accumulator, the flow almost stopped but did continue to drip albeit very slowly but was constant. I just can't imagine that this would make the car not restart after shutting it off 5 seconds earlier. He has replaced the fuel pump and the O-rings in the fuel distibutor. The only thing left is the accumulator ,which he has, but hasn't gotten around to changing yet. Are their any other possilities? He also has cold weather hesitation although it is much different than my symptoms. His car will stumble slightly when when accelerating say for the first 10 minutes after the car has been started cold. it feels more like a mis in the engine than an all out lean situation he's done an ignition tune up with no change. He runs a can of B-12 thru it every few months, with no change. I even swapped my CPR for his to try see if that might be the problem. no change their either accept he thought the car didn't accelerate as well with my unit than his. so we switched them back, and his car ran fine again. My car runs fine with my CPR so I'm not sure what the deal is their either.Many times he has to depress the accelerator half way to the floor and then it will eventually start. His car has been that way since he's owned it (5 years) it almost acts like it's flooded. On the other hand my car always starts immediatley by just turning the key. We have been chasing this mystery quite some time now. Rob, any suggestions would grately appreciated. Dennis [very long quote trimmed by moderator] To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/