"popping" in air intake under load

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andyaddick

Member
Posts
35
Hi all,
my P38 / 2001 / V8 / 4.6 Petrol / Vouge has developed a "popping" in the air intake unit, much like a backfire.

Its not as violent as a backfire , I dismantled the entire pipe from the head and nothing apart from a little smoke came out, and noise.

Ive change all the plugs as thought it maybe a misfire , my next thought was maybe the coil packs as still have the problem with new plugs ??

Tick over is a little guddery , acceleration a problem with lots of "popping" , once up to say 30 / 40 / 50 speed can be maintained with no issue if the revs are under 1500...

Any help would be very much appreciated

Merry Christmas ,

Andy
 
Worn cam, bent/burnt valve. I would look at the condition of all plugs, if you have one or more washed clean then HGF/slipped liner. I would also do a compression test.
 
I was thinking the same thing as mine (2002 4.6) had a similar sound although mine was more a sort of pinking, rattly sound rather than a popping. Happened in all gears under load as it hit 1500 - 1800 rpm. Followed shortly by a missfire.
Mine was a HG split on left bank between middle cylinders & it looks like a liner has moved. Had HG replaced & head back on & it appears to be fine now but expecting the inevitable sooner or later.
Compression test is simple so would try this first.
 
thanks guys, will have a look at the plugs in the next few days , (if the wife allows !!) .

I was hoping for coils, any ideas of a HG fix ? £££££'s ??????? if so then time to scrap , which would be a shame as I love the thing !
 
I would say first thing is to get it compression tested - this will tell you if its the HG. Mine cost £600 (with head skim) & would be a couple of days. It would be a shame to scrap a 2001 over a HG fail but i guess it depends on the overall condition.
 
thanks for all the helpful advise,

Ive now noticed I have some oil spillage, as you look at the engine from the front the oil is on the right hand side, splatters on the air intake pipe.

Could a "camshaft gasket leak" be causing the oil loss AND the popping / banging ?

Many kind thanks , merry Christmas !
 
right had another look at new spark plugs, the left hand side, 2-8, are all sooty, the left 1-7, not so bad, one was quite clean.

I don't have any oil in the coolant, nor do i have any "white" substance in the top of the oil cap when taken off, or significant oil loss.

All leads are giving a decent spark , some better than others, but I still have this rather loud popping and loss of power when under load.

One thing i did do was take a plug out and start up , the "popping" come out of the spark plug housing rather then back down the air intake.

any ideas much appreciated !
 
hi, thanks again for the info , sorry , quite "green" to the innards of the P38.

What i did was remove the spark plug from where it screws in then started up , the noise then seemed to be coming from the chamber.

I've removed each lead 1 by 1 and no difference, cant see any arching either.

Had the MAF go before but didnt get this popping / backfire noise, tho the power reduction is pretty similar.
 
With the plug out, you will get a chuffing/popping noise....

Maybe if the plugs are sparking OK, and all the sooty ones are on the same bank of 4....maybe it is a blowing exhaust manifold gasket....this can sounds like a chuffing, popping or ticking type noise depending on the severity of the blow....

If you can, get it running and when it is dark get a high power torch with a thin beam and see if you can see traces of exhaust gases coming from the sooty bank....or if your careful and the exhaust is cool, put your hand over the exhaust outlet from the block (don't actually touch the manifold) but see if you can feel a blow.....

Had similar noise on my 93 Classic, turned out to be a single exhaust gasket had split!
 
many thanks, definitely have gasses coming up from somewhere !!!

looks like a complete pain in the arse to change :-(

rather this tho than a head gone .... will up date with findings !
 
update-
plugs and leads all replaced, no change still have the "popping"

car now with garage, they "cant" find the problem but it is a backfire down the air inlet .

Has anyone had a similar problem or know of a possible cause ?

They dont think its the head but its not been ruled out,

many thanks
Andy
 
andyaddick said:
update-
plugs and leads all replaced, no change still have the "popping"

car now with garage, they "cant" find the problem but it is a backfire down the air inlet .

Has anyone had a similar problem or know of a possible cause ?

They dont think its the head but its not been ruled out,

many thanks
Andy
Click to expand...

If it's back firing down the inlet either you have glowing embers in the cylinder igniting the incoming charge which would be a really big bang or an inlet valve is sticking/bent or burned can't be a lot else actually.
 
Last edited:
Saint.V8 said:
With the plug out, you will get a chuffing/popping noise....

Maybe if the plugs are sparking OK, and all the sooty ones are on the same bank of 4....maybe it is a blowing exhaust manifold gasket....this can sounds like a chuffing, popping or ticking type noise depending on the severity of the blow....

If you can, get it running and when it is dark get a high power torch with a thin beam and see if you can see traces of exhaust gases coming from the sooty bank....or if your careful and the exhaust is cool, put your hand over the exhaust outlet from the block (don't actually touch the manifold) but see if you can feel a blow.....

Had similar noise on my 93 Classic, turned out to be a single exhaust gasket had split!
Click to expand...

andyaddick said:
update-
plugs and leads all replaced, no change still have the "popping"

car now with garage, they "cant" find the problem but it is a backfire down the air inlet .

Has anyone had a similar problem or know of a possible cause ?

They dont think its the head but its not been ruled out,

many thanks
Andy
Click to expand...
Did you check as described above....could be a exhaust gasket....

You said is was a chuffing popping noise - you didn't mention a backfire through the intake....!!

Follow Wammers advice...!!
 
cheers chaps, will get onto the garage again today and advise they follow all mentioned above, will post an update when I have it, many thanks again !
 
Andy,
I had a similar problem with my 1995 4.6.

My popping sound happened under heavy acceleration, but got worse and worse.

Finally found what was causing the problem - one of the cam lobes had worn which was then not operating the exhaust valve it was connected to. As the gases couldn't go out via the valve they burst the H/G and got out that way. Once the cam was replaced and the heads skimmed the engine was lovely again.
 
here is the news ,,,,

head gasket ok , water tested and ok, compression also ok.

Garage been quite good, they say whats already been posted, either a worn cam or blown value as "its blowing back down the air inlet".

They said the next step id to strip BUT have recommended I take it to a Range Rover specialist in earlswood (solihull).

Off to garage in morning then down to earlswood ! keep you all posted ! and thanks again for the help and advise
 
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