Misfire

[TVRobin]

Hello everybody. I have bought a 95 Chim 400 after lusting after TVR's since my bosses brother had a 3000M when I was 16 and my friends dad had a 450 SEAC when I was 19 (It was brand new)! Can't wait to join in on the local meets.
I have a problem though. My car goes very well until you put your foot down for a few seconds (two gears) when it develops a misfire that sounds (and feels) like it's running on four cylinders. Carry on driving for a minute or two and it clears and runs fine.
To give you some background; it has covered 75k with FSH up to 71k (Oct 04) when it had a major service. It has been parked for almost a year since it failed it's MOT on emissions (I have changed the oil). I got it through with a lambda sensor; the old one was physically damaged on the inside.
I was thinking ignition coil as my boat did something similar when hot but it would only run properly again if I cut the engine and let it cool for a while.
Please help me as the grin on my face is starting to wane. Regards, Robin

[that daddy]

robin dont panic its a minor glitch,have you checked the condition of the dist cap & rotor arm give them a wipe with a cloth inside & out removing any carbon dust or similar,what are your HT leads like are they chaffed on anything metal, have they been bunched together with cable ties,they dont always like that.as your coil got the red top,is it unbranded,are the connections clean on the coil tower,let us know.

Edited by that daddy on Tuesday 8th August 09:20

[chassis 33]

A few more questins to give us something to go by...does it try to backfire/pop and bang down the exhaust? Have you popped the spark plugs out, if so what condition/colour are they? How was the lambda sensor damaged, could one of the pre-cats be failing and breaking up?

If it's been sat for a while there might be sum gumming in the fuel system, a few tanks of clean fuel should clear that up?

Regards
Iain

[Griffter]

If it really is running only on four injectors during misfire, then the problem is with one bank of injectors. Either one bank's earth (located on the back of the n/s cylinder head or on one of the n/s fuel rail mouting bolts) is duff, or your ecu is over or under fuelling one side. On the cat cars I believe the ecu can adjust the fuelling between the banks (happy to be corrected) which would be done on the basis of lamba readings. I have to say, if your old lamba sensor was damaged from inside the exhaust, I'd check to see the same hasn't happened to the replacement. If so, you need to find out what the cause of the damage is. Bits of cat being propelled down the manifold are a likely starting point.
If it's not actually only running on 4, then you need to start looking at the plugs for clues, checking the ignition side as suggested, monitoring sensor outputs, or hooking up a code reader.

[TVRThomo]

TVRobin, as you will no doubt see from previous threads there are a number of possibilities for rough running but if it helps read my post subject heading "Finally!" it's a few pages back but it was to do with a coroded chopper which is under the rotor arm in the distributor cap.

Hope this helps.