Hi all.

Just bought a 2wd 1990 cosworth with an idle problem. The idleing goes up and down plus when you put your foor on eccelerator pedal nothing happens until about half way down the travel of the pedal then it revs up slowly. Could this be the throttle positioning sensor. Any suggestions welcome.

Cheers.

 

had this with mine, it was hunting like mad, turned out to be a combination of things.

TPS was broke
ISCV (idle speed control valve) was clogged up, its the one that sits on the airflow meter
Lambada/HEGO sensor was broken (the one on the exhaust)

After replacing them it still had a slight hunting issue, turned out it was a tiny tiny vacumn leak on a bolt in the inlet manifold.

So id say its most likely one of them 4 if not a bit of all!

May also be worth taking out the idle adjuster and cleaning it, as even a tiny bit of shit on this can cause these issues.

type in "hunting" on the search my old thread and quite a few others should pop up on there!

 

Thanks for that Lee. I will change the TPS first as i have a spare one and then i will go through the rest of these items. Thanks.

 

I would if it has not had one in the last 2/3 years change the CTS, clean the iscv on the throttle housing(there is no airflow metre), check co level.
The tps is easily checked in situ, just identify the signal wire and do a check for any patches or dead spots when you slowly open it, it should be very smooth reading.
You normally find these are missing abit up to about 1/3 throttle as this points wears more than others, as in that position more often, you will have to reset the tps when/if you put a new one on.
tabetha

 

Sorry i ment the throttle housing, was thinking of My Series one for some reson when i tried to think or the word

Oh also i replaced the map sensor, (on the escos its upside down on the ineerwing near the throttle housing).

Let us know how u get on, just be carefull cleaning the ISCV, cos these are about Ł300 if i remember correct!?

 

Ive taken off the idle speed control valve and changed it with the one on my other cossie, it made a very slight improvement. I will change the tps tomorrow. I didnt know that you have to reset the tps when putting it back on, does anyone know how to do this before i take my old one off.
Lee, where is the idle adjuster.

 

The easy way to do this is just while the throttle housing is off connect a dig metre up and rotate the tps so that it reads the correct idle amount, which on 2wd is 5 volts, and when opening the throttle should decrease to around 0.5 volts when fully open.
The metre should be connected between the centre pin on tps(live) and earth.
tabetha

 

its a pain it the arse to get to (well on the escos anyway)

hard to describe but its on the throttle housing sort of underneath the ISCV.

To see it properly you need to be underneath the car.

tho i doubt very much this is causig you a problem.

get that TPS changed and see it it makes any difference, My mate helped me change mine, hes a fod technitial, i can ask him about the set up i u like.

so have you checked properly for vacum leaks, get some brake cleaner and spray it systematically around the engine and all the pipes, if the revs rapidly climb then u have found the air leak, as it sucks the brake cleaner in which is then burnt increasing the revs.
i know its hard to tell with the hunting going on, but it worked for me and mive was hunting from 800-nearly 2000rpm every 3-4 seconds

 

[quote=Lee Ivatt;3641318]

get that TPS changed and see it it makes any difference, My mate helped me change mine, hes a fod technitial, i can ask him about the set up i u like.

Yea Lee, can you ask him, i thought it was just a bolt off bolt on job. Thanks.