Revs Jump Up When Starting

[Veero 1]

Yet more issues with the old Mi that used to work so well.

 

I have refitted the inlet and properly blanked off the unnecessary take offs, but now when I start the car instead of taking ages to nurse it to idle, the revs jump straight up to 3.5k and then fall slowly to 1k where it then idles perfectly. Not insurmountable I thought, so took it for a spin and now it starts to misfire under load above 3k revs on the road. Still at least it vaguely starts properly.

 

I have recently replaced the entire ignition system, coil, leads, plugs, amp, cap, arm and crank sensor. I'm wondering if the twunts sold me the wrong amp. Might try my old one and whip it round the block to see if it misfires.

 

Any ideas what causes the revs to jump up? Idle switch appears to be operating correctly. I am right in thinking it should click, just as you start to move it off the stop?

 

Thanks

Veero

[pablo 0]

airleak? Then the ICV compensates it back to an idle?

[Carbs4me 45]

if you took off the inlet before it miss fired youve probly caused a air leak on the gasket? try a new gasket and give the inlet and the head where the inlet bolts on a good rub, and try again

[S@m 156]

I know im always on about it, but misfiring above 3k rpm reeks of ignition amp to me, i had this problem with a brand new intermotor one once, as soon as i changed back to the old bosch one everything was fine, and make sure you use the heat conductive paste on the back of it aswell!

 

Sam

[Ryan 99]

Check the throttle position switch. Without it the ECU doesn't know to use the ICV to control the idle speed.

[Veero 1]

Tried lots of combinations of unplugging things and not. WIth the ICV and TPS unplugged you can start it with helping with a little throttle and the revs don't jump up. At the end of the day it works. Ish. A little rev jumping isn't the worst of it at the moment.

 

The inlet mating surfaces were clean and had no s*ite on, still bright from when I put the inlet on before and gave it all a good clean.

 

I know im always on about it, but misfiring above 3k rpm reeks of ignition amp to me, i had this problem with a brand new intermotor one once, as soon as i changed back to the old bosch one everything was fine, and make sure you use the heat conductive paste on the back of it aswell!

Sam

 

Gah curses! It's an Intermotor one they sold me, I had a long drawn out argument with them about how aftermarket ones are crap but he wouldn't have it. I'll try my old and possibly not working once warmed up Bosch one tomorrow. Yes I used the heat compound.

 

The TPS is set to just click as it comes off the stop. With it all plugged in it seems to work ish, when driving it takes a little while to come off throttle so driving on low revs at slow speed is really jerky. I may try another TPS, seem to be building a pile of knackered ones.

[chicargo 0]

hi, i could be totaly wrong as im no expert, but im sure there was a post on here about a guy who had the same problem (i think) and it turned out to be a after market inlet manifold gasget blocking the path of the petrol from the injectors, when he removed the gasget he could see impressions of the injectors in it, might be worth a try ???.

[Veero 1]

Yeah will have a look, gaskets only been on a few days and not warmed up properly yet so should come off all right.

 

How does the stepper motor work? Is it a spring loaded stepper valve which requires a 12v feed to open the desired amount and once the feed is turned off it springs back? Or does it just spin when powered and the ECU fine adjusts it? Was thinking about it this morning and it does sound like it could be an air leak and the ICV slowly adjusts the intake down to compensate.

Edited November 25, 2009 by Veero

[welshpug 1,657]

TPS may click, but does it actually work?

[Veero 1]

Well with it unplugged the revs rise and stay high. With it plugged in, they blip up to 3k then settle back down. I haven't put the multimeter across it to see if it works as it should but it worked 100% before I put it on the car not long ago and it's barely done any miles since.