ITR DC2 running slightly rough

[aspen]

My 98 UK DC2 has started to sound and feel very slightly rough over the past week or so. There are no noticable changes in the way the engine revs or pulls but there is a definite but faint roughness audible from outside the car at idle.

I intend to get the car checked out by my local indy as soon as possible but wondered if anyone had any experience or ideas as to what it might be?

[havoc]

Lots of things, from minor to

Simple & cheap things to try first:-
- Injector cleaner in the tank;
- Open dizzy up and check condition of the contacts;
- Take spark plugs out and inspect condition - they're supposed to be platinum, so are longer-life ones, but that's no guarantee;

Then if you want to start spending money, I'd look at stuff like valve clearances and MAP sensor.

Might also be worth checking stuff like the AFR, see if it's running richer or leaner than usual ('plug condition might tell you that), which would give you a clue...

[aspen]

havoc said:

Lots of things, from minor to

Simple & cheap things to try first:-
- Injector cleaner in the tank;
- Open dizzy up and check condition of the contacts;
- Take spark plugs out and inspect condition - they're supposed to be platinum, so are longer-life ones, but that's no guarantee;

Then if you want to start spending money, I'd look at stuff like valve clearances and MAP sensor.

Might also be worth checking stuff like the AFR, see if it's running richer or leaner than usual ('plug condition might tell you that), which would give you a clue...

Thanks Havoc,

Some good ideas there to get me started. Will see how I get on.

[andye30m3]

I'd might be worth cleaning the idle control valve, I think there's a guide on www.itr-dc2.com

Also might be worth checking for air leaks on the induction side, with the engine running spray WD40 around gaskets on the inlet side, If theres a leak the rev's will pick up. My E30 hunted quite badly and it turned out to be the gasket between the throttle body and the head had an air leak.

[hifihigh]

Could it just be the exhaust is blowing a bit?

[aspen]

Finally found time to take a look at the weekend. Took off the distributor cap to look for any potential moisture or dirt, nothing visible but gave the contacts a quick clean and the roughness has gone. I couldn't believe it was such a simple fix.

I am now noticing a fairly high frequency rattle at around 2000rpm which i may have missed before due to the roughness. I checked I had put the cap back on properly and tightened the screws. I certainly wouldn't rule out this new issue being my own fault though. I'll have another look and check the screws later.

[havoc]

Check the heat-shield is screwed-in tight...that's the most common cause of any 'rattle'.

[aspen]

havoc said:

Check the heat-shield is screwed-in tight...that's the most common cause of any 'rattle'.

Will do. Thanks for the replies Havoc.

Not usually a fan of yellow cars but your NSX looks fantastic. I was disappointed when I sat in one at a motor show to find I'm far too tall for them Couldn't even get in and shut the door!

[vz-r_dave]

Alomost certainly the heat sheild, sound terrible when under the bonnet.

[aspen]

vz-r_dave said:

Alomost certainly the heat sheild, sound terrible when under the bonnet.

Guessing the only way to get to it is by getting the car up on a ramp?

[vz-r_dave]

No its the heat shield on the exhaust manifold, get under the bonnet and rev the car up to the 2-3K mark. You will hear it straight away if its the problem. Most just remove it and dont bother putting it back on. Also you may start to hear a slight whistle low down in the rev's. Again nothing to worry about, its the airfilter and the design of the intake pipe.

[Dave_ITR]

I loose count of the times I have cleaned up the dizzy cap, the difference is amazing even when it looks as though it doesn't need it.

[aspen]

Dave_ITR said:

I loose count of the times I have cleaned up the dizzy cap, the difference is amazing even when it looks as though it doesn't need it.

There was nothing visible in mine but it certainly made a big difference. What do you recommend for cleaning it? Just a dry microfibre cloth?

Not had a chance to sort the rattle yet, will try and sort it at the weekend using my dads garage pit.

[aspen]

Located the source of the rattle, its not a heat shield. Its a spring bolt that connects the downpipe to the exhaust. Rusted through at one side so its rattling around. The other bolt seems to be fine for now. Unfortunately not something I can fix myself as it will probably need some welding.