Rough again......

[z3steve]

Hi all.....

Got another problem which is similar to what I had last year which turned out to be the CCV needing replacement.

Right, the car idles absolutely fine. After warming up for a few mins I give it some gas and it stutters. Its not confined to first gear but all of them. I've changed the fuel filter to no avail as thought it might be that. The cvv was replaced less than a year ago. All the intake hoses were replaced a year ago and there are no splits or anything loose. No fault codes either. Ive tried disconnecting the MAF and it makes no difference whatsoever.

Im kinda convinced its an air leak but I dont know where else to look apart from the main pipes from the MAF to the throttle body. Anyone have any idea what or where i can look next? Or what to do bar taking it to a garage?

Any questions fire away.......

cheers, Steve

[Southernboy]

Have you considered one or more spark plugs may need replacement, or you may have dirty injectors....Injectors can be treated with a fuel additive specifically for petrol engines...plugs will need removing and close inspection. If any one or more plugs are fouled, it's important to identify the cause as they generally have a "deeper" rooted origin...eg. oil fouling a plug will indicate problems with valve stem seals or cylinder head issues etc etc...Injectors can get fouled up and require a specialist to service them...removing them is fairly simple though, but you will need a decent manual to follow the removal / installation procedure or someone with prior experience and some odd items like fuel hose clamps to prevent petrol escaping onto the engine etc etc..

[z3steve]

Hi Southernboy

Changed the spark plugs too the other day (sorry forgot to mention that I did) and the ones that came out were fine. No sign of anything untoward. I did do the fuel treatment too with some redex stuff but no difference.
I'm thinking its something very simple or hoping at least.

I've got all day today to get my hands dirty so will let you know what I find if anything!

Cheers

[Del]

Another guess to consider = ignition coil issue. Have seen instances on this forum where coils on the blink haven't even evidenced themselves by throwing a misfire code. Vacuum leaks typically cause a rough, cold idle. A sensor problem would tend to throw a code.

[z3steve]

How would I test the ignition coil? Is there a way without purchasing a new lot and are they what goes on to the spark plugs? Excuse my ignorance!!

Thanks for the replies so far

[z3steve]

Just thought, would a hole in the exhaust cause any of the symptoms I'm getting?

[Del]

The attached may be helpful - not your actual car - but broadly similar concept for a 6-cylinder car with 6 individual coils.

https://www.youtube.com/watch?v=z37jl4HXQjg

[z3steve]

Cheers Del, i tried out the coils but they all work as they should.

What i did find was the 'secondary air pump' was knackered. I took it apart and it was orange or full of rusty type crap inside. Also, the main black rubber pipe from that to the engine was all coked up. I cleaned it out but didnt make any difference.

But with the engine running you can here a low rumbling sound (bit like if you listen to the exhaust) and if you crimp the pipe from that secondary air pump it dissappears. what is that pump for and should it suck air in to the engine or be releasing it? currently its releasing it but its very clear the pump doesnt work whatsoever.

I'm clueless and gonna be heading to a garage soon lol

Cheers, Steve

[pedro20001]

hi, I think gookah has covered the removal and blanking off of what is a contraption which isn't really needed here in the uk. I am sure gookah will be along shortly

[bowei001]

The secondary air pump works for about 30 seconds after start up to pump air into the exhaust to lean out the exhaust gases for emissions. The ECU sends a signal to an electrically operated valve to open and allow vacuum to the valve (attached to the cylinder head) to which the secondary air pump is attached by a large diameter black hose. The vacuum opens this valve and allows the air pump (which has, at the same time, been sent a signal to start pumping) to pump air through the valve and into the exhaust port on the cylinder head. After about 30 seconds, the ECU signals stop, the valve closes and the pump stops. What tends to happen is that this vacuum operated valve gets clogged up/fails and jams open. This is OK whilst the air pump is operating but once it stops pumping air into the cylinder head, the exhaust gases go out through the still open valve and straight into the air pump and eventually corrode it into a solid mass. You can replace the air pump (expensive) but you must replace the valve as well otherwise the new pump gets the same treatment. You can just remove the valve, make a solid blanking plate to cover the hole into the cylinder head (use the base of the valve as a template) and replace the valve (need to keep the vacuum line sealed using the valve) and disconnect the lead to the bottom of the pump. All it will mean is that at start up your exhaust gases will be a little richer than they were designed to be.

[gookah]

hi, I think gookah has covered the removal and blanking off of what is a contraption which isn't really needed here in the uk. I am sure gookah will be along shortly

The pump was noisy on my son's car so I disconnected it. However doing that alone will cause problems as it is meant to pump cold fresh air into the exhaust on startup via the diaphragm valve (Pictured)


This valve opens when the pump runs to let the air in and reduce emissions on startup, (USA requirement).
If the pump is disconnected or seized, The diaphragm valve still opens but actually allows the hot exhaust gasses out, and melts the hoses. hence I made a blanking plate to go on the manifold under the diaphragm valve. This way no gasses out and no useless noisy pump.








Blank fitted and then diaphragm valve bolted back on to hold it in place..
By the way , it's been through several MOT's since then with no emission problems.