flat spot

[alfa race driver]

can anyone explain why there is a flat spot between 1 and 3thousand rpm. before i bought mine i test drove many and they where all the same.it seems to be worse when warm , anybody any ideas of what the problem is.

[jimbro1000]

Normally I would be inclined to say it was a matter of fuel economy and emissions control.

No idea really though but I can say for sure that it isn't present on my friend's V6 running on a MOTEC management unit.

[Wombat Rick]

What engine is it?
I'm assuming it's a Twin Spark because most have flat spots but shouldn't have. It will be one of, or a combination of...

1) Engine temp to ECU sender. £10. Easy DIY fitment. Just on thermostat. Especially likely if it occurs about 5 mins after setting off. Like driving a proper car with the choke still out!

2) Mass Air Flowmeter. £140. DIY job. Easy to check though. From the air filter box, follow the trunking round towards the engine. You will find an electrical connector sticking vertically upright. Unplug it. Then go for a drive. If the flat spot has gone, then your MAF is jiggered. Most are so don't worry. It's a really fine wire that dangles in the air flow and if it gets hit by dust or a bug, it goes all to pot. German part you see. Totally unreliable.


3) Lambda sensor. £110. Nasty DIY job. Needs to be up on a ramp.