roaring in airbox

[jctilingservices]

Showing complete ignorance here so one for John to comment on first really.

EGR valve operates, I thought from manifold, so was just thinking if this was faulty, such as faulty diaphragm, is it possible for say exhaust gasses to go where they shouldn't go, or inlet to be sucked from a place it shouldn't be sucked(!), either of which could cause, my theory goes roaring noises when passed through damaged diaphragm connected, eventually, to air inlet which might then form a trumpet effect accentuating the noise.

Don't even know if this vehicle is fitted with said valve, or a similar device.

As said this is total ignorance but as Sherlock Holmes (or Dr Watson) once said (or words to the effect) when all the possibilities have been eliminated its time for the impossibilities.

Thanks for the input mate, appreciated. Yes my car has an EGR valve held in place by 2 torx bolts, not sure if this can cause the problem or not.

 

[jctilingservices]

ok guys heres an update.

Had a friend look at the car, who says he is a qualified mechanic, I don't know if he is as I have only known him about 6 months, anyway, at first he said blocked cat, until he heard the engine, then he said definite misfire. he plugged in a hand held code reader, and started the car and done what he called a live test. he said the sensor in the front pipe was spot on, but the sensor in the cat, the readings were fluctuating all over the place, then he started to take the leads off 1 at a time and got a shock off number 2 lead.

however, the car was registering no faults or faults pending on his machine

suspected cures he recommends,
1,new set of leads
2, compression test to see which cylinder is down then replace valve
3, change sensor in cat
4, change cat

if none of these work, look elsewhere at sensors, but he agrees it is roaring through the airbox but as misfire ?????????????

 

[Burnerman]

Hell this has got me stumped.....I have had collapsed cats before, but the symptom was no power. Removing the down pipe or even just taking the lambda sensor out restores power, so proving that one.
Getting a shock from a plug lead isn't the best, so its a good move to replace these.
I like Alans idea about the egr - at least its in that area - but I've never had an issue like this with these.
I don't know if you are familiar with Bank Top garage, near the airport on the Dinnington road, but the guy there is first rate.
John

 

[jctilingservices]

Hell this has got me stumped.....I have had collapsed cats before, but the symptom was no power. Removing the down pipe or even just taking the lambda sensor out restores power, so proving that one.
Getting a shock from a plug lead isn't the best, so its a good move to replace these.
I like Alans idea about the egr - at least its in that area - but I've never had an issue like this with these.
I don't know if you are familiar with Bank Top garage, near the airport on the Dinnington road, but the guy there is first rate.
John

tomorrow i will take the cat out, as the cat is between manifold and downpipe, so my attempt the other day by removing the downpipe was a waste of time, seeing as the cat was still connected and could be at fault.

new set of leads tomorrow

not sure how to check EGR valve but will take it out and clean it, see if this makes a difference

Thanks for the time and patience John and the rest of the lads who tried to help, really is much appreciated, will keep yous updated as i go on lol

 

[Belle427]

ok guys heres an update.

Had a friend look at the car, who says he is a qualified mechanic, I don't know if he is as I have only known him about 6 months, anyway, at first he said blocked cat, until he heard the engine, then he said definite misfire. he plugged in a hand held code reader, and started the car and done what he called a live test. he said the sensor in the front pipe was spot on, but the sensor in the cat, the readings were fluctuating all over the place, then he started to take the leads off 1 at a time and got a shock off number 2 lead.

however, the car was registering no faults or faults pending on his machine

suspected cures he recommends,
1,new set of leads
2, compression test to see which cylinder is down then replace valve
3, change sensor in cat
4, change cat

if none of these work, look elsewhere at sensors, but he agrees it is roaring through the airbox but as misfire ?????????????

The after cat sensor jumping all over the place is a sign the cat isnt doing its job correctly, so you may be on to something there

 

[Mursal]

The after cat sensor jumping all over the place is a sign the cat isnt doing its job correctly, so you may be on to something there

Never say this problem CH427, so when you say jumping all over the place, do you mean the voltage trace on the scope or can you see it on a voltmeter?

 

[jctilingservices]

The after cat sensor jumping all over the place is a sign the cat isnt doing its job correctly, so you may be on to something there

Never say this problem CH427, so when you say jumping all over the place, do you mean the voltage trace on the scope or can you see it on a voltmeter?

sorry mate but I cant answer your question in all honesty as I don't know, my mate used a hand held fault code reader, and did what he called a live read with the engine running, he said the sensor in the down pipe was stable and at the right voltage, but the one in the cat he said was bouncing all over, i.e readings going up and down, not settling as the other sensor did. hope this makes sense to you

 

[Belle427]

The after cat sensor jumping all over the place is a sign the cat isnt doing its job correctly, so you may be on to something there

Never say this problem CH427, so when you say jumping all over the place, do you mean the voltage trace on the scope or can you see it on a voltmeter?

On a scope or using live data readings on a hand held more sophisticated fault code reader. Voltage should more stable on the after cat sensor at around 0.45 volts, the pre cat will be switching between roughly 0.2v (lean) to 0.8v (rich)

 

[jctilingservices]

The after cat sensor jumping all over the place is a sign the cat isnt doing its job correctly, so you may be on to something there

Never say this problem CH427, so when you say jumping all over the place, do you mean the voltage trace on the scope or can you see it on a voltmeter?

On a scope or using live data readings on a hand held more sophisticated fault code reader. Voltage should more stable on the after cat sensor at around 0.45 volts, the pre cat will be switching between roughly 0.2v (lean) to 0.8v (rich)

don't know mate, I have just done a compression test as someone mentioned a burnt valve, my readings are as follows
cylinder 1, 15 bar.........220psi
cylinder 2, 16 bar.........230psi
cylinder 3, 16 bar.........230psi
cylinder 4, 15 bar.........220psi.

I don't think there is a problem with the valves but my mate who is supposed to be a time served mechanic recons I have problems with valves on cylinders 1 and 4. what do you think ?

 

[Belle427]

they look ok a 10% variation is acceptable

 

[Mursal]

Thanks CH427 for the information

I don't think compression readings down 10psi flags any problems.
Can you put a plate (cut from a bean tin can) to blank off the EGR valve? Just encase its leaking into the inlet manifold when ever it feels like it

Just found this nugget of information
http://www.rac.co.uk/forum/showthread.php?14361-Astra-1-6-8v-2002-going-into-limp-mode


By the way, other tin cans are available

 

[jctilingservices]

Thanks CH427 for the information

I don't think compression readings down 10psi flags any problems.
Can you put a plate (cut from a bean tin can) to blank off the EGR valve? Just encase its leaking into the inlet manifold when ever it feels like it

Just found this nugget of information
http://www.rac.co.uk/forum/showthread.php?14361-Astra-1-6-8v-2002-going-into-limp-mode


By the way, other tin cans are available

will try the bean can tomorrow, after I take the cat out and see how the car revs then, unless I can find a tomatoe tin, then I will do that first as the egr is much easier to take off hahaha

 

[jctilingservices]

here goes again lol
new plugs, still same problem
EGR valve, still same problem
disconnected the cat, still same problem
disconnected manifold,still same problem.
compression ok on all cylinders, another 2 trains of thought for me are

1, timing belt stretched, reason for thinking this, idles ok, revs pick up nice and slowly, but upon putting ya foot down the misfire appears, could it be that there is stretch in the belt and that the belt is not keeping up with cam and crank if you understand my meaning

2, is it possible I may heave wear on one of the cam lobes ?

 

[jctilingservices]

further update

live read o2 sensor bank 1 active
o2 sensor bank 1 sensor 1 the readings fluctuate between 100 and 785, this is with the car running at standstill, any ideas, also is is sensor 1 bank 1, the sensor in the cat or underneath in the front pipe

 

[Belle427]

further update

live read o2 sensor bank 1 active
o2 sensor bank 1 sensor 1 the readings fluctuate between 100 and 785, this is with the car running at standstill, any ideas, also is is sensor 1 bank 1, the sensor in the cat or underneath in the front pipe

That will probably be 0.100v and 0.700v which looks normal switching to me
i think your going to have to start with the basics and as you said examine the timing area etc as this is a weird one!