Yet again problems... engine stutters and nearly stalls

[NRS]

I really think I have a lemon now. There's been nothing but problems with this car. Around a year ago I changed the engine due to some burnt valves (long story short it involved an amazing roadtrip for a similar price of getting the work done in Norway). There's been a few of the usual MX-5 problems over this time.

I went out to the car yesterday, tried to turn it on a just got a click. Have cleaned the connections on the battery and got a jump start. However it's now nearly stalling whenever I brake to a halt (drops to 500rpm) and stays there for around 5 seconds before coming back to normal. It seems to be when I have put load on the engine, not just if I stay still and have revs. Also it's feeling a bit rough, particularly below 2000rpm and stutters too. When changing gears the revs seem to drop quite a bit quicker than usual. Any ideas as to what it is? It feels a bit like it did previously when it lost compression in one valve, but I've kept an eye on the oil, changed it regularly and there's been no low oil at any point. It was stuttering once or twice before I had to jump start it.

[feef]

That there's more than just a hint of electrical issues suggests it might not be compression or mechanical related.

Does it idle okay once it's settled down?

[GravelBen]

The idle dropping and stalling is fairly common with Mk1s, there is an idle control valve on the throttle body which sometimes needs to be cleaned and adjusted. Maybe the Mk2 has something similar?

When I did mine I gave the throttle body and butterfly a good clean at the same time as it was pretty filthy, seemed to sharpen up throttle response but it could have been partially placebo effect. Certainly sorted the idle droop problem.

Edited by GravelBen on Tuesday 17th June 11:26

[SamR380]

I'm fairly sure it'll be the ICV too. Will it pick up revs if you open the throttle?

[NRS]

From reading around the description of what has happened seems to match a lot of the complains. I've now taken it off and cleaned it to letting it dry now. However when taking it off it was really stuck after removing the screws. It eventually released, but has ripped the gasket between it and the trottle body. If I try running it will it damage anything? It's my only car so will be without one until a new one arrives if it's going to damage things.



Thanks for the help so far!

Edited by NRS on Tuesday 17th June 19:39

[feef]

If it allows a little air to leak in it shouldn't be too bad in the short term. The gap will be fine enough that I'd not worry about it being unfiltered and the increase in air won't be so significant that the ecu can't compensate so it won't lean up. I'd still get a new gasket ASAP tho.

Is it a MK2? I'm considering fiddling with that valve and it's handy to see it off without taking it off myself. Out of interest, do you think it could go on upside down?

[NRS]

Thanks for the input - sent a request for some new parts to the local dealer today, so hopefully it will arrive soon! Also will clear the trottle body while changing the radiator and hoses since the coolant will be drained already. So far the car seems to run a bit better. When cold the revs don't drop as much, but after warming a little (although not fully) it goes back to dropping to 500rpm when in neutral. I am wondering if there is some other problem though - on the last start it almost decided not too again. So perhaps there is some other issue than corroded battery terminals. I'll need to check the battery next!

It's a Mk2 (1999 1.6l model). In regards to the valve - how do you mean upside down? If you mean on the top with the holes facing down I don't see a reason it wouldn't as there doesn't appear to be loose parts that would fall out. However I'm no expert mechanic so best to get a response from someone who knows better!

[feef]

Thanks. That's all I needed to know.

I've moved the throttle on my car, and there's a chance the icv connector would foul the intake pipe. Flipping it upside down would ensure it clears it.

[Darkdice]

I had a similar issue with my mk2.5 (idle drop) and it turned out to be a vaccum leak. That cured the lumpy running too. Lim surprised it never threw a code it was that bad.

With the bonnet open when I turned the engine off there was a loud hiss for 3 or 4 seconds (it was always hissing with the car running).

[NRS]

Yes, it seems to be a problem with the air system from the symptoms. Judging by the work on the valve helping it seems to have been that. So now just waiting on the gasket. However I may need to wait slightly longer for the part. I asked the local dealership for the new gaskets for this and the throttle body, plus a few screws and bits for the radiator (as in screws and rubber rests for it to sit on). Got the quote today for £260 or so!!! I wonder if there is a wrong part code I have used (no idea of the names in Norwegian so tried to find the part numbers) or if it's just the price here. To be honest I wouldn't be too surprised. So may need to wait on parts from the UK/ USA. I'll stop by tomorrow and check what parts they've added there!

Glad to have helped with the question!

I also need to investigate the back of the car - just discovered one side of the original rear bracing bar is tied on with a cable tie, Have to admire the genius who thought that would fix the problem!

Edited by NRS on Thursday 19th June 17:28

[Darkdice]

Mx5 parts have them, inlet one was around £8 - not sure hoe much delivery would be though