Hi all,

If you've read some of my threads you'll all see that I've been having a problem with various issues over the last couple of years.

One problem I just can't get rid of is an engine vibration at about 1400 to 1800 RPM. It's not throwing any codes at all at the moment but I can feel it and it just does not feel right and sometimes the car feels underpowered at the same time.

Some of you guys have suggested changing the inlet manifold gaskets and have commented that the car is running rich. I have had rich fault codes before but at the moment I've not been getting those codes.

However, after doing some research I can see that the upper manifold also has some gaskets (8 individual ones). These I cannot find a supplier for in the UK.

I have found the gaskets that I would need for the lower section of the manifold but not the top.

If the gaskets are causing the problem would the rich running and engine vibration likely to be being caused by the upper (the 8 gaskets) or lower (the 2 gaskets strips) gaskets?

If it's likely to be the upper gaskets then does anyone know a supplier in the UK that I can get them from? I can only seem to find suppliers in the US which has a £60 delivery cost ontop. I don't want to go and spend nearly £120 on just some small gaskets if the problem is with the lower gaskets which are only £12 each.

I am going to get some fuel trim figures from the car when a get some time as well.

My car is an NA as well so I'm not sure if the manifolds are different to the SC.

Thanks,

Chris

 

They really do take advantage of you over there on the price of things.

 

There are some here and they want to clear them:
https://www.ebay.com.au/itm/Genuine-...frcectupt=true

Shipping will be less than US shipping

 

Those are not the ones i used, they have black pieces that fit a curve in the manifold.

Those fit the earlier models i believe, or the six cylinders.

 

Thanks all. Yes you are correct Wingrider, they are for the V6 engines and I have seen those available in the UK and they are cheap also here. It's the ones with the black moulding on the gaskets that are for the V8 that I can't get from the jag suppliers here in the UK.

Wingrider - is the rich running usually a cause of these upper gaskets or the lower ones leaking internally? I've done smoke tests etc and can't find a leak externally on the manifold.

Thanks,

Chris

 

Jag doesn't offer them. Go figure. We quote the Land Rover 4526549. Same 4.2, fits like a glove, and readily available. Let me know if you need a set.

 

Thanks 310Jag. That's the bad boys. I'll use that part number to find them in the UK. Yes I too can't believe that Jag nor the Jag suppliers have them listed on their sites.

 

The Land Rover is used mostly as a family grocery & kids transportation?
Need to keep them on the road.
But the Jaguar with it's racing heritage, will often need new parts to keep it running.
As well as lots of service apt's for maintenance, & minor repairs.
Or not

 

Yes post #6, and yeah they fail

 

Hi all,

Thanks for all your help with this.

I've now had a chance to get some fuel trim readings from the car.

All the below readings where taken with the car stationary and with the engine at full operating temperature.

Do these fuel trims look like a vacuum leak or a problem with these manifold gaskets?

I now have the rev counter surging when using cruise control or when coasting along and it's especially evident when coasting down a hill. The car surges up and down the rev range by about 300rpm when it does this.

Thanks,

Chris

 

Fuel trims for both short and long term on both banks at idle and at full operating temperature:


Fuel Trims at Idle

 

Fuel trims for both short and long term on both banks at 1600RPM and at full operating temperature:



Fuel Trims at 1600 RPM

 

Fuel trims for both short and long term on both banks at 2400RPM and at full operating temperature:


Fuel trims at 2400RPM

 

Fuel trims for both short and long term on both banks at 3000RPM and at full operating temperature:



Fuel trims at 3000RPM

 

Fuel trims for both short and long term on both banks at idle after capturing data at different rev ranges and at full operating temperature:


Fuel trims at idle after capturing data at different rev ranges

 

If I'm correct, ltft look maxed out -15% (rich not lean). Ltft at -15% still keeping stft close to acceptable but not great. Your real close @ 20% average to popping cel codes at 25%. Have you started by checking your O2 voltages? If they are not reporting correctly the whole system will be off. This might explain why your first STFT are different than you last STFT at idle. Make sure your O2 sensors are reporting correctly or your data/corrections to the injectors will be wrong. This whole forum helped me chase what looked like a lean/vacuum leak condition, when it turned out to be a bad/lazy O2 sensor giving us bad data and leaned the motor out intermittently. As your maxed out with rich LTFT, see if you can clear the adaptations (ltft), then check trims again. Your Stft's look like a vacuum leak at all but the first idle read. If the 1650 readings were actually at idle (650) it would be textbook vac leak conditions from there on. What sticks out are the rich ltft (maybe left over, but not at -15%).
Also you stated that your issue was at 1400 to 1800 RPM, at 1650 you go lean which would make sense.

 

Hi Mark,

Thanks for your info. I can get the voltages from my diagnostics tool for the O2 sensor. What would I be looking for to identify that they are lazy/bad? Should I test the same as I did for the trims ie stationary and readings taken at various revs?

Like you, I've been chasing this problem for ages.

Thanks,

Chris

 

You should be getting a slow to resond cel if so. I see those codes and when you look at trace yeah lazy. Remember 02 sensors are similar to spark plugs. They get lazy and wear out with time.

 

450 mv is normal. 900 mv is rich, 100 mv is lean. This has to be taken after FULLY warmed up and in closed loop. They will jump around when cold, and stabilize when engine is fully warmed up.
Idle and 2k. also check at 1400-1800 as that is where you felt the issue worst. Report back to us.If you can add O2 voltage to the dashboard of you reader, it will show RPM, O2 voltage, LTFT, STFT, left and right. This will give us a great snapshot to work with.

 

Thanks for all the help guys.

Mark - will do. Thanks for the pointers. I'll get some readings. I can change the diagnostic dashboard so no problem.

Cheers,

Chris