Slow idle/engine judder (newbie question)

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2

Hi,

Recently picked up a J-reg mk1 Eunos Roadster in classic red (with a spoiler) - never had an mx5 before, but it seems in pretty good condition, and drives great - can’t get over the way it corners!

Only thing it does do, which I am assured is very common among these cars and not to be considered too worrying, is sometimes idle at a very slow speed and judder slightly when pulling up at junctions etc. I’ve read various diagnoses and solutions to this problem on this and other boards, so apologies if I’m duplicating other threads, but I can’t find any particularly recent ones regarding this, and just wanted to make sure I am indeed experiencing the same thing that many other people have reported.

So far, it’s only done this a few times, and it does seem to co-incide with cold weather/lights on/heating on (factors which I’ve read can exacerbate this problem, but please correct me if I’m wrong). I’ll slow to a halt, and in either 1st with the clutch fully down, or neutral, it will sound and feel almost like it’s going to stall, occasionally juddering quite noticeably. It’s never actually stalled tho, and doesn’t seem to affect pulling off - but it’s a bit disconcerting!

Although, as I said, I have found numerous posts about this problem, I really haven’t found a definitive solution - e.g. some suggestions involve the battery, some the fuel line, some adjusting the idle speed settings… Not being particularly technically minded when it comes to cars, I’m thinking the saftest bet would be to take it in to have the engine tuned at some point - then if it is anything more serious, presumably they’d spot it (…?)

So my question is really, does it sound like this problem is anything I need to be concerned about? Should it be looked at or can I safely just ignore it? And if it is just a matter of adjusting the idle speed settings, is this something that someone who has only rarely opened a car bonnet (i.e. me) should really be attempting to fix themselves? Of course I’ve got to start tinkering around at some point, but having only owned it for about a month I’d hate to end up doing it any damage when I’m not even entirely sure what the cause of the occasional juddering is.

Any advice and tips very welcome!

 

3

 Adjust your “Base Idle”. All you need is a paper clip & screwdriver. That usually does the trick!

There`s a “how to” in the FAQ i believe

Edit…here you go Thumbs up

http://www.mx5oc.co.uk/forum/forums/t/206.aspx

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 Start with the base idle as dave as said,easy to do and cost is a paper clip, but i am going for the batt,or a bloody good service.

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G’day mate Welcome to the forum–

Just signed in for the first of many visits? Please pop your location in your profile, and the year and model of your MX5 in your sig. This helps enormously when we try to answer questions…

Certainly set the base idle, and check the clutch switch, although if it happens in neutral then this last one is unlikely.

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Many thanks for these links - have browsed the site a bit, but hadn’t spotted the FAQ list, looks like it could be very useful.

Also, this procedure for setting the idle rate does sound pretty simple - doesn’t look I can do much damage, and I think I can stretch to the cost of a paperclip! Presumably some of you have had this slow-idle problem and cured it in this way?

Incidentally I’m also intending to take the doors apart in order to clean the electric window mechanisms at some point - they do work, but are kind of slow, and don’t quite go all the way down…

I’ll report back whether setting the base idle does the trick.

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Get a can of halfords silicon lube spray( yellow tin with a gray lid) for this,and while you are in there spray the lock and mech also,will make them work better and no frozen locks in winterWink

8

mine does this too, and when i first got the car found it a bit worrying.  I’ve never had a problem with it though and the engine has been faultless touches wood so it’s not something I’m worrying about!

9

 Just to update on this, I’ve reached the conclusion the low idle speed in this case is something to do with the battery. I was intending to adjust the idle-speed as described in the faq, but was watching the revs the other night, and they seemed perfectly normal - however as soon as I put on the lights, they became subtly but noticeably slower when iding. The times where it’s sounded really slow, it’s been cold so we’ve also had heating/fan on. Therefore it seems connected to extra load on the battery somehow.

If this conclusion is correct, this is actually a relief, as it means there’s nothing wrong with the engine itself.

Does it sound like I should change my battery or check the connections?  Or if it’s not actually stalling (just idling a little slow when the lights and heating is on!) then should I just accept this as normal and ignore it for now?

 

 

 

 

 

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 The engine revs do dip when you put an electrical load on. If the revs drop so low as to give a judder the base idle must be a little slow. If the battery red light does’nt come on at normal tickover and the engine starts OK, I don’t think you have a problem other than the base idle too slow.

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 Thanks for the clarification - sounds like it’s probably worth me tweaking the base speed anyway, I guess it can’t hurt!

 

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 Hi again - first of all, having become a bit more familiar with this forum it looks like this post should probably be in the garage section - don’t know how to move it tho, is this something only admin can do?

Anyway, back to the low idle/judder problem… I tried the base idle setup today, but now only have more questions I’m afraid! 1st of all, there is only one TEN connector, but two GND ones in the diagnostic box - does it matter which GND you use?? I tried the one furthest away (i.e. the one at the bottom on this diagram http://www.mx5oc.co.uk/forum/forums/t/823.aspx). Before doing this, the revs were at around 850. After connected the paper clip, they did seem to drop a little, maybe to just above 750. However a few moments later, it seemed to have returned to around 850, and seemed to be staying there. Waited a few mins, no change. Hence no need to adjust?

So, on driving it today, I monitored the problem more closely (incidentally, no lights/fans/ac were on today). It really does seem totally random. At some junctions, I’d approach, drop the clutch, shift to first ready to pull off - revs would drop to almost zero, engine juddering very worryingly, whole car was visibly shaking. Sometimes I did exactly the same, and the revs were fine. Maybe 70/30 in favour of it being fine, distributed pretty evenly/randomly throughout about a two hour drive. A few times when it was juddering I had time to shift to neutral, and then the revs did seem to go back to around 850. Does this alter the diagnosis at all? I’d have thought that with the clutch down it wouldn’t matter whether I was in gear or not? Someone did mention the clutch switch earlier in this thread - if the idle rate is always fine in neutral, but often low and juddery in 1st with clutch down (but not always!), would this point toward the clutch switch being a problem? Found this FAQ section that seems to back this theory up: http://www.mx5oc.co.uk/forum/forums/t/231.aspx

I don’t want to give up trying to fix this myself just yet, as other people seem to have successfully cured this problem themselves - but I suspect they were already rather more technically minded when it comes to engines. If the base idle speed isn’t the problem, there seem to be a whole range of other possible solutions, none of which I feel particularly comfortable trying. If the info in the previous paragraph leads to any definite diagnosis, I’ll look into the clutch switch thing, but otherwise, I am starting to think it’s probably worth taking it in for a service - does feel like copping out a bit, but might be the most sensible option until I’m a bit more familiar with the workings of car engines.

On that front, any advice about how much I should be looking at paying for them to investigate this erratic idle problem? And should I seek out a mazda specialist (in west london ideally) or should any decent garage be able to handle this? Sorry for all the different questions, but I did warn in the title this was a “newbie” post… Any further advice much appreciated!!

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 …and then today, it didn’t judder once! Kept an eye on the revs, they seems pretty consistently at around 850 at idle, both in neutral or in 1st with the clutch down. Pretty sure I wasn’t doing anything different.

As for the clutch switch explanation, surely it would do the low idle juddery thing all the time if the clutch switch was broken, not just occasionally? If I can rule that out, that would be good - already seem to have ruled out battery or base idle being the problem, at least I’m getting gradually closer to finding the cause… please let me know if it sounds like I can rule out the clutch switch option too!

14

sounds like base idle to me. Take it for a good run then with no engine electrical loads on short the pins. If the idle drops below 800 rpm adjust it up. Then remove the clip and test again. It sounds like you are looking too hard to me.

Try the obvious before you go to a specialist. 

15

 Well I’ll certainly try this again, after a journey in which the juddering has occurred - if this is all it is I will be very happy.

Can anyone clarify two small things:

  1. does it matter which GND socket I connect the other end of the paper clip to?

  2. the “valve” that needs to be adjusted - this involves turning the philips screw recessed into the short metal tube, right?

 

Thanks!

16

 Hi alligatorlizard,

This is my first post on the forum… but I’ve been having EXACTLY the same problems as yourself, and it is irritating how sporadically it happens.

I don’t think it matters which ground you go for, and it sounds like you’ve found the right thing to turn (the instructions in the garage section were good enough for me to find it)

So what have I done:

I had to change by battery anyway (it was leaking!) and that didn’t solve the problem so I doubt it is that.

I have adjusted by base-idle too. I think i tried doing this with no load, then full load (as I had read on one forum). This doesn’t really solve the issue, but is good practice anyway.

I did think this was something to do with the neutral switch… but I noted above someone said this is unlikely since, as in your case, my revs return to normal when in neutral.

I had a look at the clutch switch, it appears to be ‘springy’ enough on the back of the pedal, so I don’t think the spring has broken inside.

I did the LED diagnostic box readout (an LED and a paperclip) incase that would tell me something…it give me no error codes after the initial light, so the ECU see’s nothing wrong.

 

I think my next step is to remove the clutch switch and have a good look at it… I’ll let you know how I get on. I notice this is quite an old thread though, did you fix it in the end?

17

 Ah this is a very old thread! Shortly after this I had problems with the cooling system, took it to a garage, and turned out the car had been running on 3 cylinders since I’d bought it…  So the cause of the strange behaviour mentioned in this thread was one cylinder not having enough compression, exhaust valve needed replacing - don’t worry though, this is (hopefully) unlikely to be the cause of the problem you have.

As it happens, I’m currently having another idle based problem - not a major one, but the idle often droops immediately after startup, although after revving the engine for a bit settles down and will remain stable for the rest of the journey. In my research of this, I’ve found a ton of reasons for idle droop - and there are many kinds of idle droop… so many threads all over the web on this subject, confusing thing is they all seem to have different causes/solutions…

I’m currently investigating the ISC valve and idle air valve - these are key parts of the system that keeps the idle steady at diferent temps etc. Here’s some useful info I found recently on the idle control system (hope it’s OK to link here?) http://www.justanswer.com/mazda/6jih0-mazda-mx5-mx5-mk1-starts-first-time-every-time.html - though as your idle speed seems affected by the clutch, maybe the answer does lie with the clutch switch. Can’t offer any advice on this though, after I had the exhaust valve changed, all ran fine (until my recent idle-droop-immediately-after-startup problem that is…)

Probably best to start a new thread on this, good luck diagnosing!

18

Hi guys, I have set my base idle (with no loads) and the car is idling great when in gear but rubbish in neutral, it’s like a roller coaster lol.