Firstfives.org

I know this is a 5's board but I was hoping some of you knowledgeable M30 guys might be able to help. I have a 1976 3.0si that is driving me crazy. The car runs fine when it is cold. As soon as it get up to temperature it starts to miss, sputter and backfire.

Here's a little background.... The head was replaced by a previous owner with one from a 1986 model. I have converted it to electronic ignition(Pertronix). Removed all the emissions controls including the "thermal reactors". I've replaced every temperature sensor in the car. Replaced all the vacuum lines that remain. Replaced the cold start valve (and have by-passed it to make sure it isn't flooding the car when warm). Replaced the MAF sensor and set the valves and timing to spec.

I'm not sure if it pays to try replacing the ECU and / or the fuel injection control unit. I'm running out of ideas and patience.

Any help would be greatly appreciated.

Scott

Until an expert answers you can check the FAQ's or Google search previous posts here. There's a cross over parts list, etc.

Probably know about realoem.com for exploded views to see what goes where.

Lenny D. is going to remind you to check all grounds (brown wires) clean and shiny, and check connectors the same.

Thanks for the reply. I've searched a multitude of forums and sites looking for answers. I'm familiar with BMW's but primarily E30's and E36's.

I've cleaned all the grounds and am puzzled because it really seems to be engine temperature related. It runs great when cold but as soon as it comes up to temperature is when it starts to stumble.

I had almost the exact same problem on my E12 - you should check the coolant temperature sensor and also check that you don't have a short in the ground wire to the AFM.  I stumbled across this by putting my hand on the AFM and leaning against the car body.  The AFM needs to be grounded to the body, and I was acting as the ground. 

On Mon, May 17, 2010 at 10:39 AM, Kneedrager <gbinc@comcast.net (gbinc@comcast.net)> wrote:

Thanks for the reply. I've searched a multitude of forums and sites looking for answers. I'm familiar with BMW's but primarily E30's and E36's.

I've cleaned all the grounds and am puzzled because it really seems to be engine temperature related. It runs great when cold but as soon as it comes up to temperature is when it starts to stumble.

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I had almost the same problem i had change everything you said except the spark plug wires and one night it was pitch black and i had the hood open and i could see the current coming out of two wires that were too close to the engine bay and it miss fire every time it happened hope this helps