maddog11

hi, 98 1.8 zetec vert
ive got a problem where my revs can go through the roof, im guna change the pcv valve and see if that helps, its had a new maf which fixed a different problem, the speedo works but im still wondering if there is a vehicle speed sensor that could be a problem ? also i cant see any egr system on the car which i thought strange .

GVK.

Should be a VSS (vehicle speed sensor) in the gearbox, cars of that age will have a normal speedo cable then a 3 pin plug with a lead coming out of it.

Follow the lead up to the bulkhead area then try it with it unplugged.

zs&tas

Yes it has a triangular 3 pin plug I'll try thanks

martysmartie

iTrader: (1)

If the ISCV is increasing the speed then it's something management related, otherwise it's an air leak.

Not sure VSS is the issue, given the speedo is working.

Martin

maddog11

hi, yeah i wasnt sure, when its started it revs a little high . when i drive it it then starts wanting to pull by its self, when stopped at a junction the revs then want to run away. if i turn the engine off then on . it resets and im back to the beginning again. i have some hoses and pcv valve coming as it is cheap enough to replace.
Also , i find it strange that the pcv system is taking in unmetered air and taking it through to the metered side. i realise it was made like this so must work in a as new state but looks like its asking for trouble if you ask me , it dosnt really make sense lol.

GVK.

It was a quirk of a lot of Ford engines of this era where the VSS caused rev hang.

As above they had a normal speedo cable then a VSS going to the PCM.

maddog11

yes they are seperate. the new pcv valve helped a little.
the new maf cured a stutter issue we had between 2k and 3k. so im assuming thats good now , drives nice.
still has rev hang. with the vss unplugged the engine jumps all over the place , its better plugged in but maybe it still is not working , does anybody no the part number for this because i cant seem to find one for this car . when i was looking at parts the other day i had stuff listed under mk7 ? it seems theres a few versions of these zetecs some maf some not same as vss.

i think i will try a different vss and replace some hoses and rebuild the intake of vac leaks . when it stops raining ;(

maddog11

sorry also i thought of the throttle sensor but its measuring .95v up to 4.5v and seems a clean sweep

maddog11

you know what im such a dope , it was only the reverse switch i could see. i need to get it back on the ramps to find the vss ;(
also im thinking out loud here, but it wasnt hanging revs before the maf swap maybe the new maf is causing different problems , this is anoying

maddog11

ive replaced some vac hoses, idle valve, checked tps ok . i have two mafs. maf 1 over fuels car stutters but drives ok , suttery. maf2 drives good hangs revs everywhere. either they are both fcked or maf1 is masking the rev hang by over fueling. or maf1 works and something else is causing the overfueling.
need to check the intake temp and coolant temp sensors.

maddog11

#update
so going through previous owner issues . i have a new speed sensor but its too cold to fit now , ive unplugged the speed sensor for now and the car drives much beter, it does not hang revs anymore which is great.
im not at a point where it idles at 1400rpm warm. and has a stutter on accleration. would this be speed sensor connected ? or something else ?
thanks i wasnt sure if the ecu does not know the car is stationary wether it held the idle revs up or not .

GVK.

I would clean the idle valve out, it maybe sticking open slightly to cause the fast idle, good news on the rev hang!

maddog11

yeah so i have a new speed sensor to fit when its warmer . the idle valve is brand new.
im thinking i prob still have a vac leak somewhere. i hate sorting out other previous owner issues but it has to be done , the car is clean , low milage and very nice to drive