Rough motor, loss of power?

[BM3MW]

So last night im getting on the highway, gowing through the gears and revs, not more than 6k 6,500k rpms. and after i slow back down to speed limit, the car is running very rough. it will not idel smooth and seems like its lost some power. Any ideas? Did i bend a valve?

[///M3-4Life]

How does your brake pedal feel? Is it really hard? If so it could be a disconnected vacuum line

[hoover]

How does your brake pedal feel? Is it really hard? If so it could be a disconnected vacuum line

exactly that - elbow on inlet manifold near your strut brace? - tick over will be rough as rats if its out

[BM3MW]

So i did a compression test and one of the cylinders has 0 psi.. So whats next to look at? what are the steps i need to take?

[hoover]

So i did a compression test and one of the cylinders has 0 psi.. So whats next to look at? what are the steps i need to take?

i notice your other post to mate - i'd get some other checks done before pulling the head off, like a leak test to see where that one is leaking, could be a piston/ring but may be a valve?

[heysad]

Apologies for hi-jacking this old thread but this seems to be roughly what I'm experiencing, car seems to go well for a time then power seems to drop off, always very careful to leave oil temps come up etc.

I'm not terribly mechanically minded but have checked the hosing that runs from the rear of the inlet manifold which I believe is the vacuum pipe mentioned above and the "looks" OK, any definitive way of checking it?

When looking I can also see a hose coming off the bottom middle of the inlet manifold, has a short bit of hose on there and a little filter of sorts. Not running an airbox (Emerald ECU), just sock filters. Is having this little hose/filter arrangement in place gonna cause any issues?

I don't really understand what's going on, unsure whether something is wrong all the time like a duff sensor or the hose related issue above of whether it's a heat related issue, I've no idea! :(

It's been back to the Rolling Road a few times always showing figures that are very consistent with the numbers that it normally pops out, car hasn't been there for a session for a while since it didn't seem to be getting me anywhere! :(

Looking for things I should, or if complicated someone else, to check to get to the bottom of the problem, getting very frustrated with it all!!!

Thanks in advance!

- Andy

[Jake]

Hi Andy,

So the car usually runs well but sometimes the power drops off? Most likely an ignition problem. Do you have any spare parts to test with? I'd start with the cap, rotor, and ignition leads.

Jake

[heysad]

Hi Jake,

Car generally runs OK from the point I start for say 20 minutes or so....a journey I did the other day exhibitied the problem, drove from Wallingford, Oxfordshire to Theale, Berkshire taking say 20 minutes all seemed OK, didn't get chance to stretch it's legs 'cos of traffic, then drove up the motorway from J12 of M4 to J11 at about 4500 to 5000 rpm which can only be 5 or 6 miles tops, by the time I sitting at the lights at J11 it's sounding pretty dam rough on idle and has no real go:(

I don't have any spare ignition parts to hand, happy to try though! Is the order of items above the order you suggest I test them? Best supplier and rough cost?

Many thanks!

- Andy

[heysad]

I gotta say, in terms of ignition, the only thing that I remember being changed since I've had the car are spark plugs and that's in 10yrs+ of ownership, they may have been changed but certainly not in recent history!:(

- Andy

[Jake]

I would highly recommend C2. I'm not sure on costs off the top of my head but I'm sure they've got everything listed on their website.

Its hard to troubleshoot this stuff over a key board. It would help if you were able to remove and inspect these parts (ignition wires, cap, rotor, plugs). If you're not mechanical and don't want to have someone check it out for you then it only leaves one option, replace things until it goes away.

Jake

[heysad]

Hi Jake, I assume you meant C3 so given that none of those parts have been replaced in forever I've ordered a new coil and cap, I have some new plugs so will try those 3 things first, leads were very expensive so will leave them until last!!

Happy to have someone check it out but want to do the easier and cheaper things that I can do first before I start laying out for labour

I will have a quick look tomorrow and see if any parts do look odd though!

Thx for your help!

- Andy

[Jake]

On those wires, open the cover and look at all the places the wires touch the edges of the covering. Its very common to find the rubber cut or worn all the way through. Or an old trick is to put the car in a dark garage or something, start it up, and then observe the wires. Sometimes if they are cut or worn they will allow little sparks to come from them to the surrounding metal parts. Not snapping arcs of blue flame, just little electrical traces.

Jake

[heysad]

Thx for advice Jake, will check it out for sure!

[EvadM3]

Heysad,

If you can wait a week or two, I could possibly come down and help you out on 15th or 16th feb. I have a few spare S14 parts you could try as opposed to replacing and hoping for the best. We could also do a compression test while we are at it.

Offer of help is their if you want it.

Send me a PM with a contact number and we can go from their. I`m in London so not many miles away.

Regards,

Dave

[TR-Spider]

Hi Andy

I had today similar symptoms (running good cold --> warm loss of power / stuttering / strange exhaust note).
Must have been moisture somewhere within the ignition wires/distributor.
Somehow the engine temperature then made things worse.

I pulled the cables from the distributor, spayed WD40 into, cleaned distributor inside/runner/ housing, now its fine again.

Thomas