View Full Version : 4.0 L searching when cold

disco stu
07-28-2008, 09:30 AM
Hi everyone, I'm new to the forum due to my recent aquisition of a 97 Discovery 1. I have had it on the road for about 3 weeks, and since I replaced the y-pipe with the cats the engine seems to be hunting/searching, as it was running smooth before. This only seems to occur when its cold... at idle it will surge up and down about 200 rpm either way... same when driving, as soon as the engine warms up no more surging... the speedo also jumped to zero stuck for a drive or two and jumped back into action, and it seemed to effect the tach revs when the speedo jumped (it also idled at like 1500 when the speedo was kicked out, but only in neutral and park) I have the sneeking suspition it is the IAC valve... but figured that any opinions would be a great help. Oh and its an auto tranny. I am a mechanic myself so i do most all my own work, this site is great, and those cats were wayyyy cheaper through rovers north than the OEM! Thanks guys.


07-29-2008, 08:34 AM
REset your adaptive values. The new cats probably flow better and the ECU is confused.

disco stu
08-02-2008, 07:14 PM
I reset the adaptive values, didnt seem to change too much, possibly slightly less surges. however i then fixed the 3 vacuum lines at the t.... which were all split. now there is no more surging when driving, mostly only when it is up to temp and sitting at idle, sometimes when cold. so my next guess was the IAC valve. i looked and looked yesterday and could not find the bloody thing ANYWHERE. i had schematics from rovers north magazine, as well as a picture from another forum. it seems my AIC valve is hiding. any help on trying to find that sucker would be appreciated muchly. oh and the cruise control still didnt work after the vacuum lines were fixed... the only portion i couldnt get to was the charcoal canister under the left front headlight area... and i cant find any easy way to get my hands in there even to check... the master kill for cruise lights up, and my steering column buttons still 'click'... could it be the line going to the canaster? or maybe a short in the column. thanks for the tip on the reset ptschram.


disco stu
09-24-2008, 11:42 AM
the problem that is persisting has been moved to the thread titled MAF?