Lumpy running 2.4i petrol Maverick (Terrano). Need help!!

[markandjulie]

Our maverick (terrano) 2.4i petrol 1996 has been off the road for nearly 6months while we constantly try to fix this problem.
Basically it is a lumpy running issue. Imagine the beat of the engine as chug, chug, chug, chug, and then add in some random pop, pop sounds and this is all that is wrong with it! Trouble is, it is not clean running enough to pass the MOT emissions. So, as mentioned, all it does is run lumpy, very snatchy at low revs but quite unoticeable at speed on the road, although when free revved at stand still to say 3000 revs, you can still detect the popping sound in the exhaust note. Dealers and mechanics are all pretty useless with much advice followed but no remedy to date. Since fitting all the parts below, the car revs and pulls much better, in fact it is quite amazing the transformation. However, the popping is still there so no MOT pass possible.
THOUGHTS: It has been suggested it could be air leak on the intake side but have checked all possibilities and found nothing yet.
I cannot work out what the device is on the inlet manifold to the left of the throttle unit. It has a pipe coming from the exhaust manifold, round the back of the block which thens attaches to this device. From the top of it are pipes that join in to the rubber pipes that seem to lead back in to the inlet manifold/throttle body. Is this an egr valve and if so can it fail and cause this problem? Is it easy to remove? Can I service it or is it a replacement part?

In order of repairs to date:
Full new exhaust system, front pipe and catalytic
New engine oil, Oil Filter, Air Filter, Fuel Filter
New Spark Plugs
New Distributor Cap and Rotor Arm
New Lambda sensor
Injectors removed and ultrasonically cleaned by ASNU machine. Flow tested. All okay.
New Ignition Leads
New Air box seal
Second user throttle body fitted with Airflow sensor, throttle sensor, stepper motor, etc all on it. Used genuine new gaskets.
Compression tested and fine, engine only done 55k miles

I have just joined the club and am getting quite hopefull that some other owner might be able to help us. So far very impressed with the how it looks.

Mark Savage

 

[Terranosaurus]

The 2.4 petrols are prone to cracking the exhuast manifold, this would allow air in to upset the lambda sensor, the cracks appear to develop on the upper side as you look down on it under the heat shield.

Where abouts in North Yorks are you?

 

[markandjulie]

Thanks hummingbird. As always, I will be spending this afternoon under the bonnet so will look carefully at the exhaust manifold. I had previously taken the heat shield off to fit the front pipe and did not notice any cracking but will check anyway to see if it is a fine hairline. Location is northallerton area. I am still at a loss as to what that thing is that seems to tap in to the exhaust manifold and then run back round to the inlet manifold. I see some people saying egr valves are only on diesels but maybe they are on some petrols?
Thanks again, will respond re your cracking comment after checking it today pending the wind slowing down to let me get the bonnet up!

 

[Deleted Member S]

EGR valves are now fitted to most petrol cars & it's the only thing I can think of from what you have described :roll:

 

[markandjulie]

I have just checked over exhaust manifold and no cracks there.
With reference to Sweety's reply, maybe this unidentifiable bit is an EGR valve. To date no one else in the dealerhips and garages that I have talked to have even mentioned the EGR. In fact it is a quite a mystery as many posts that I have checked out do not give much away as to where it is and what it does.
When I consider all the other factors in this, if this valve is pulsing, or sticking and it can affect the mixture for running, then this seems to be the thing to look at. Next question is, how much and how easy to replace?
I will start poking around to see if i egt anywhere.
I wonder if it can be bypassed altogether with fixing it if it is a sod to get off. It sure is in an awkward place and those nuts look well rusted.

 

[Deleted Member S]

The EGR valve is I remember right opens up at tick over & lets some of the exhaust gas to entre the inlet to be reburnt for a second time & in doing so lowers the emissions. I could be wrong on the time when it opens but thats it's job. Hope this may help if only a tiny bit :roll:

 

[markandjulie]

Thanks for your input At least its another thing to check out. Will have a word with the dealers tommorrow re costs and availability. If anyone else out there has had experience of this, comments much appreciated.

 

[Deleted Member S]

I don't know if it helps but I priced 1 up for my old mondeo about 16 months back & I think it was about £60-80 for the valve :roll: I wonder if it would be poss to block it of like the TD's :roll:

 

[markandjulie]

Considering the cost of £80 if it was this i would be super happy seeing its cost so much to date. Quite interesting is the possibility of bypassing, even if it just gets me going and I replace it at a later date.
If anyone has bypassed one please let me know even if it was another car altogether.
Thanks again to sweety

 

[Jocky]

I had a 2ltr Primera and it had EGR valve.

Try the partsgateway for a 2nd hand unit. http://www.partsgateway.co.uk/



:smile:

 

[Terranosaurus]

Sorry, forgot to add earlier, yes it is an EGR. If you've had a new front pipe recently than that end should be easy enough to remove, I haven't got any ideas what you could use to bung up the resultant hole though, if you work something out please let me know as I'd like to have a go at removing my EGR. With the exhaust end removed and suitably sealed the EGR will be inactive so you can at least rule that out. Also try a turn on the downpipe to manifold nuts, these tend to work loose and again could cause a small air leak, as theres stainless steel sealing rings not a gasket it doesn't "blow" as bad as other motors cos nothing burns away to make the gap bigger.

 

[markandjulie]

Thank you for all responses so far.
I have been back under the bonnet for the afternoon and the odd bit which I was wondering if it was an EGR valve is definitely that. Cleaned the muck off and it is stamped on the top 'EGR VALVE'. So, it explains a possibility for the lumpy running because it is apparent that this part also has an affect on the inlet side of things.
As well as being awkward to reach the fittings at the inlet manifold, especially the pipe securing nut that secures the pipe that goes round the back of the block, the flange that secures it to the exhaust manifold also look worryingly rusted. The sort of thing that even when you have your new part sat ready to fit, breaks off just where it shouldn't.
When I changed the front pipe this was with the manifold remaining in place. The outlet for the egr pipe is higher up on the casting and as such has probably never been off in 10years.
Next step will be contact nissan dealer for a price on monday.
If any body else has any opinions on whether this part would or would not cause my lumpy running problem, please let me know. I hope I am spending money and heading in the right direction.
One other thought, is, if I bypass as Humminbird suggests, at the exhaust manifold by blanking, what state does that leave the valve. I am guessing if it is not an inlet anymore then whether the valve is stuck or not, there will be no effect. Why does looking after your car always involve mystery??

 

[Jocky]

Before you buy a new unit.

Try to block the rubber hoses exiting the egr. This should render it inoperable!!!!!

Try shutting the hoses with tie wraps. I'm sure that this is what some of the guys with a TD did to good effect.

:smile:

 

[Deleted Member S]

Before you buy a new unit.

Try to block the rubber hoses exiting the egr. This should render it inoperable!!!!!

Try shutting the hoses with tie wraps. I'm sure that this is what some of the guys with a TD did to good effect.

:smile:

Or if you have a bit of rubber pipe the same size you could put a bolt into the end of the pipe & secure it with a hose clip. Do it on the inlet manifold & on the EGR valve. I had to do this on an old weber carb as I did'nt have a fuel return pipe fitted & it worked :smile:

 

[markandjulie]

Thanks for more suggestions. I was looking before at how the egr system appears to work and had thought myself, why don't I block the small hoses off. Then when I looked at the location of the egr valve, it looks like it also inputs direct in to the inlet manifold at the point where it bolts on. That would mean that it inputs a bit in to the lower part of the manifold as well.
Considering there is also two small pipes coming out of the egr unit, my theory (to be questioned or advised) is that the egr valve splits up the gases three ways. A bit seems to go through one rubber pipe and end up being fed in to the side of the throttle body to input just below the throttle butterfly, and the other rubber pipe seems to end up at the large black plastic canister over near the air filter housing, presumably the charcoal canister. So, if I block up the two rubber pipes, if there is a direct input to the inlet manifold where it is bolted on then there is still exhaust gas entering the system if the valve is failing.
What I really need is someone to tell us if my description of how it functions is correct.
It just looks strangely mounted on the inlet manifold. If it only operated externally then it could just be on a bracket. The fact that it looks 'plumbed' in to the manifold makes me think that it does go direct in to the manifold also.
The previous suggestion of isolating it from the exhaust manifold where the gasses first start on their journey probably is the ultimate answer but a pig to try and sort as it involves cutting and blanking the steel pipe.
If any one has any further comment re its direct input to the inlet manifold, it will bring me closer to deciding on what to do.
Thanks again everyone.

 

[Terranosaurus]

For details on the EGR system try this manual HERE Page 144 onwards for the KA24E petrol engine

 

[supertaff]

As for the EGR valve on turbo diesels - look in Workshop downloads for WO3 . If the setup on the petrol engine is similar to this , you could try doing the same to yours..... Matt.

 

[Jocky]

My thoughts put simply are the hoses are under vacuum (engine intake) and its the vacuum that opens and closes the EGR valve. No vacuum valve stays shut and exhaust gas goes straight out tail pipe. No exhaust gas recycle.

If I'm wrong one of the guru's will correct me :smile:


:smile:

 

[mav]

Hello again Markandjulie,

Welcome to the club.

Take a look at the first post in the link below as it may be worth giving Mark a ring if you need any genuine, new and boxed Nissan parts at upto 30% off new prices.

http://www.nissan4x4ownersclub.co.u...topic&t=5025&postdays=0&postorder=asc&start=0

How much does it cost to send a private message to Mark and reclaim some of your membership fee in discounts.

User name is Hammond1027.

---------------------------------------------

Mav.

 

[markandjulie]

Wow, everyones input just gets me closer to believing that we now maybe have the answer.
Thanks Gego for explaining the way it works. It makes sense now.
Thanks Hummingbird for the excellent manual link. The manual pages you provided are fantastic, no more guessing!
I have certainly got enough to get my teeth into now. Have asked dealer for prices but still waiting for reply so not sure yet on costs. If I get the chance after work during the week I will start trying some tests now that I grasp what it all does.
Watch this space as I am back on course for believing we can get the old girl back on the road. It really is an excellent car in good nick with only 55k so have never wanted to give up on it. Thanks to the club and everyones input.
:smile: