Fluctuating / bad idle

[AndyW]

So new update.
When the codes cleard, they did mit come back. Today i worked with the mechanic at the car. When we start it, there was the creepy noise again. When we took of the hose from the IAC Valve, we mentioned, that there sucked Air in but also Air comes out. It's like bubbling. Hard to describe.
At first we thought that the catalyst were clogged. So we sepperated them from the exhaust mainfold. Same Problem.
So we put everything together again.
now we suspect a defective intake valve, because when the engine gets warmer, the noise comes directly.
Tomorrow my mechanic want to unscrew the valve cover and do a pressure test.

[David]

The padded hose from the PCV valve on the left hand cam cover over to the throttle body plenum, maybe? Often the rubber elbows at each end can leak or become soft and collapse. The PCV valve itself should be replaced every 80k Miles.

I can confirm the Motorcraft part numbers are:
PCV valve: EV-261 (2C5Z-6A666-AA)
Hose to Throttle-body: KCV-240 (2L2Z-6A664-FA)

Unsure of MGR numbers, if thee are any.

David

[re-tread]

If you separated the catalyst convertors from the manifold and still had the problem then it may be one of the O2 sensors either side of the cats. I had a similar problem, which continued to get worse until it changed to a missfire, which in turn destroyed one of the cats. I replaced the cats and the failed O2 sensor and all was fine and has been ever since.

[AndyW]

@ David: the hose from the IAC valve Plenum Body which goes goes back into the air intake hose after the MAF sensor.
@ Dave: when the o2 sensors are bad, there should not be an Error Code?

[SCP440]

Not always, a small air leak and a lambda that is still giving an out put but wrong might not be enough to put the light on. This is why it is useful to look at live data.

An air leak will obviously lean off the mixture and this should show up as the compensation should be quite high trying to get it back to where it should be. Look at the swing on all of the lambdas, they should all have the same amount of swing. You can move them from side to side if you want to test them.

Steve

[David]

@ David: the hose from the IAC valve Plenum Body which goes goes back into the air intake hose after the MAF sensor?

Not that hose, the other one, rearwards of it and lower, the positive crankcase ventilation valve and hose. It goes from the top left cam cover (the valve itself) just underneath the air trunking, to the plenum right of the tail of the Mustang on the throttle plenum plaque (so between the IAC and the EGR).

Look at the pictures. Here is the hose on eBay at the moment:
https://www.ebay.co.uk/itm/333612093681

... and the PCV valve itself, (a service replacement item at 80k say Ford, 90k say MGR):
https://www.ebay.co.uk/itm/MG-ZT-260...wAAOSwKNpel4p6

Available cheaper from the States of course, under the numbers I quoted in the earlier post.
When mine went bad, I did indeed get lean-mixture error codes after a while, but not straight away.

David

[AndyW]

When we took the hose off, the engine did not stop running.

The hose from the crankcase ventilation valve is okay, also the valve itself.

[AndyW]

Hello all. I think we have found the Problem. My mechanic did a pressure test at the inlet and outlet valve. Everything was fine. Then he looked at the timingchains. One timing chain is loose. The other is tight. it looks like she's skipped a tooth.
Now i order new complete timing Set.

[David]

Hello all. I think we have found the Problem. My mechanic did a pressure test at the inlet and outlet valve. Everything was fine. Then he looked at the timingchains. One timing chain is loose. The other is tight. it looks like she's skipped a tooth.
Now i order new complete timing Set.

You might like to read this old thread. This may have contributed to/explained the death of the engine in #347?
https://www.two-sixties.co.uk/mgoc26...-chain-tension

P.S. If you do replace the chains, chain guides and tensioners, I would be interested in knowing if it was possible to do it with the engine in-situ. Mine is passed its scheduled change date.

David

[SCP440]

P.S. If you do replace the chains, chain guides and tensioners, I would be interested in knowing if it was possible to do it with the engine in-situ. Mine is passed its scheduled change date.

David

It must be possible even if the radiator needs to come out. There are several videos on You Tube showing it being done in Explorers and the like. My guess the problem might be the cam covers in our cars as they look quite tight, a trick I do on the Jensen is to undo one engine mount on one side and put a jack under the sump to tilt the engine a few degrees, this gives enough room to get some parts off.

What is the scheduled change date/mileage on these engines?

On a positive not a mate recently had the timing chains done on his Audi S6, the final bill was just over £5k and less than £1k of that was parts. Apparently if he had left it any longer the engine would have been scrap.

Steve