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My 1990 na6 runs like a bucket of bolts on cold start up. basically feels like its running on 3 cyls. after about a minute or so its fine and purr like a kitten if seemingly a little rich. the car is turbo and running an emanate blue . but data logs are fine.

Your ecu could just be adding too much fuel on warmup

its not the ecu. full stop. dont even mention it. data logs are rock solid consistant. its a fault with the car somewhere.

Well, let's get out our crystal ball(s). The limited information is not helpful.
Take it to a mechanic.

4sfed5 wrote:its not the ecu. full stop. dont even mention it. data logs are rock solid consistant. its a fault with the car somewhere.

Well you tell us what it isn't and we'll guess what it could be.

It 100% would be the ecu. If datalogs are saying all is ok then the ecu isn't logging ok

Running on 3 cyl would show up on a wideband clear as day.

Ecu or no compression when could or dodgy injector.

Ignition is paired so should be running on two or four.

Injector could be sticky when cold but unlikely to be never play up at all ever when hot but every time when cold.

Compression - no ring - head gasket seal when cold? Do a cold compression test and a warm compression test and see if one cyclinder is down.

If it does it every single time when cold pull an injector plug / ignition lead off and see if the revs drop.

Or... It could be the ecu seeing false wide band results until the sensor warms up.... And flooding it with fuel and making it drive like crap.

My bets on something ecu related.


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The data logs show injection ms exactly asper logs from when was normal. all other .cu parameters exactly as per old logs when it was fine.
ill do a comp test cold and see what happens.

That's a poor way to confirm that the ecu is fine, but if you think that fuel hasn't changed and all is good with the tune, then it's only spark plugs, coils, injectors or fuel pump. If you had a wideband working we'd narrow it down.

Could be a leaky o-ring on an injector. Fuel leaks around it when the engine is not running and sits in the inlet, it is drawn in at start up and makes one cylinder run rich for a short while.

4sfed5 wrote:My 1990 na6 runs like a bucket of bolts on cold start up.
after about a minute or so its fine and purr like a kitten if seemingly a little rich.

Above symptom is typical of a bad coolant temp sensor (to an OEM ECU) on the NA6 - might be an issue if it's still utilised on yours:

thanks 93 clubman. i changed the temp sensor thinking that might be the issue....it wasnt.

i' think i'm leaning towards leaky injector or head gasket on #1 or #2 cylinder...

Sticking valve or half dead HLA?

Hi guys I'm new here. But the ecu? No when the car starts on 3 syls when cold. First check your coil -sparkplugs and wiring also your valve cover gasket..... That sounds weird but that did it for me I had the same problem. Gr

I pulled the injection plugs one by one at cold start. cyls 123 all made it worse. cyls 4 made no difference at all. so the issue is either a leaking injector or a cold compression issue in 4