My car idles at between 1500 and 500 rpm even when hot and will suddenly idle faster or slower for no apparent reason I recently had an alternator problem resulting in a completely flat battery I recharged the battery in the car but the next day it was completely flat again. I took the battery out of the car and recharged it on the bench and next day it was still fully charged. So the car went to the auto electrician and they replaced the alternator, problem solved. After each recharge and after new alternator I had to reprogram sound system and clock. The idling problem started after the electrical problem was fixed. In all other respects the engine runs sweetly as normal. There is no noticeable change in power and it runs smoothly. Has anyone got any suggestions as to what might be causing random changes in idle speed?
Check all your small vacuum hoses in the engine bay Especially the ones under the throttle bodies at the front of the motor and around the drivers corner side of the motor etc. if one of these is off it will fluctuate. Maybe this is it ?
is it a constant rev up and down ie hunting? if its hunting it might be a big vacuum leak. if it just randomly idles at different speeds its gotta be something else. have you checked if you have control over the idle speed with the idle screw?
Thanks for feedback The idle speed is most often at about 1500 rpm but will drop back to normal for no apparent reason. If it is at normal around 600-700 rpm it may suddenly rise to 1500 and stay there. It does not hunt and does not idle at intermediate speeds. I have not sat for long periods at idle trying to fix the problem, just at traffic lights. I have not tried to adjust the idle setting partly because it does idle at the correct speed some of the time. I will check for loose or damaged hoses. Thanks again.
I get the same thing occasionally The symptoms are the same but usually it dies down, sometimes it just won't and I turn it off and when I re-start its usaully fine again. I think it is in the ECU. What symptom would ask the ECU to hold tickover at 1500 rpm ? The other thought was it may be the ATCU controlling it, is yours an auto? I have never seen a thread on this before that came up with any solid results.
Have you checked your IACV could be clogged or in need of a IACV SERVICE This unit controls your idle so after checking as mentioned above your vaccum leaks, clean your throttle bodies and check your electrical connections for corrosion build-up. I would check the IACV next.
I have the same problem: Randomly sometimes my car will just keep the ticker on 1.5k and then other times it idles normally at like 700-800. Its like it has a mind of its own on the matter. Sometimes mid way through the trip it sorts itself out or other times its just 1.5k the whole journey then the next day i can drive the car and it idles perfectly?
I'd check and/or replace the water temp sensor and check for vacuum leaks, etc. Also could be MAF related so run a diagnostics and go from there.
It is a manual but It was converted from an auto. It was done before I bought it and I did not find out until I tried to have the clutch pedal and reversing light fixed. So I do not know what else was not done properly. I have had no problems though for the last four years, this is something new. Thanks everyone for the help. Much of the technical advice is beyond my understanding but I can use it to give my mechanic some pointers.
my NA aus spec manual does the same thing as well. i have no hose leaks, but havnt yet checked the IAVC. this problem seems to only occur when the zed is cold. once the motor has warmed up it seems to be fine. but then at days it will randomly not do it.
Your To-Do list. Could be a number of things, most of them suggested previously, but here's how I'd go about it. Check error codes first, could be easy fix. If it's not hunting but randomly jumps between normal and high idle then it's most likely to be either temp sensor, IAVC solonoid or possibly AAC solonoid. The temp sensor is at the front of the motor on the top coolant pipe and is the two wire plug on the right. Jiggle the plug around when warm and see if it causes the idle to jump or relax. If so it's the connector that needs cleaning. Once you rule that out check the IACV and AAC plugs which sit at the back of the plenum on the passenger side. AAC is the one that sits low and horizontal, the IACV is the one that sits a bit higher up. Check the plugs and clean them, see if it makes a difference. Next if you havn't got your answer, then pull the whole IACV/AAC assembly off (4 bolts, not hard to get to) and strip it down and clean in a bucket of degreaser. I leave the parts over night to soak in the degreaser before cleaning them out. Once it's all together touch the contacts of the solonoids with 12v and you should hear them click. If their all working fine then reattach them to the plenum. If you didn't tear the original paper gasket when you removed the unit then you can reuse it, otherwise get a bit of gasket paper from auto1 or similar. With that done you've erradicated any ellictrical reasons bar AFM and ECU for your idle shifts. If it's Hunting consistantly while warm then you've got a leak somewhere. Pressurise the intake system to about 10psi and start hunting for hissing sounds. Find and fix. If there are no leaks and you've erradicated CTS and IACV/AAC unit then you need to grab a datascan or similar and have the TPS voltage showing while driving. A faulty/sticky TPS will not show an error but the voltage shift will show on datascan. It will also show AFM voltage. If AFM voltage is jumping during idle it could mean either AFM or ECU issues. It may not be the AFM as the ecu can still direct other functions like the IACV to pull in extra air. After that it's a case of borrowing a known good one and doing the old swap-a-roo and see if you get a possitive result. There are a few more possibilities which I've run across, although not in zeds, and they are a rarity. Such as blocked injectors and faulty fuel regulators, but like I said, rarity and they show more of a hunting idle and overall poor running, etc. The How-to of all the above is in the tech section and none of it is difficult to do. Hope it helps.
Identical to my zed, generally fixes itself when warmed up, but sometimes doesnt. More of an annoyance than a problem, and the fact that is has so many possible causes puts me off fixing it as im not mechanically minded.
