1990 8v digi strange revving

[panzer]

Need help!

I am accelerating and at around 3700rpm, suddenly power is lost for a split second whilst the rev needle shoots up to 4250rpm +. It also seems to be kangaroo hopping occasionally.

Any advice would be much appreciated as i am starting to get p****d off having just forked out ?500 on other bits. (Could the injectors be dirty?)

Cheers :'(

[mk28vpb91]

Only a suggestion but this could be a problem with the ignition system. Rev counters are often driven by a signal from the low tension side of the ignition. The behaviour of the needle may be related to something going wrong in the ignition circuit. Maybe the HT lead from the coil is breaking down and causing problems.

[Blue MK2]

Could be a clogged Idle Stabilization Valve. Spray some gunk down it to wash the dirt out

[Hammy]

Could be a clogged Idle Stabilization Valve. Spray some gunk down it to wash the dirt out

Just curious, does the ISV come into play when the revs are off idle?   I would have thought it only cut in when the throttle was closed and was used to maintain a stable idle when lights are switched on etc ?..

This might be related to the same problem I had recently.  It didn't increase in revs, but it did misfire quite badly.  This was eventually found to be the MAF (Mass Airflow Sensor) which had dirty tracks on the potentiometer (see Bad misfire)...

Might be worth taking a look at it to see if it is contaminated with carbon deposits etc..

Paul....

[Blue MK2]

Need help!

I am accelerating and at around 3700rpm, suddenly power is lost for a split second whilst the rev needle shoots up to 4250rpm +. It also seems to be kangaroo hopping occasionally.

Any advice would be much appreciated as i am starting to get p****d off having just forked out ?500 on other bits. (Could the injectors be dirty?)

Cheers :'(

Must be the obvious 'idle' needs adjusting ?