Rough idle, surging at up to about 3.5k

[Guest highboy_coupe]

Hi,

I have been trying to eradicate an erratic idle, my X hunts a bit (a couple of hundred rpm over idle speed then back down again), and it will never sit dead on 1100rpm like the proverbial sewing machine. It also feels a bit snatchy and surges below 3.5k, which can make traffic a little tiresome.

I have changed air filter and spark plugs which has made no real difference, emptied the tank in case it was bad fuel, and checked all the vacuum hoses for cracks etc.

Now from what I can find, it could be the throttle bodies need balancing, the fuel pressure regulator, the full filter, or I need to run some decent injector cleaner through it. Does any one have a dead steady idle, or do they all do this?

To put it in perspective, the X idles like my 91 VFR750, that's done 55k miles...

[Guest highboy_coupe]

Going to try a lambda eliminator as have read alot of similar posts on blackbird forums, we're the ecu leans out the mixture too much on closed loop for emissions purposes.

Cheap enough to test the theory anyway.

[fast_eddy 712]

Do the throttle bodies (starter valve synchronisation). I found it  best @ about 1800 rpm.

[Guest highboy_coupe]

That is on my list to do, I need to find a cheap carbtune first though, I don't really  want to shell out £50 for a one off job!