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Engine knocking

skhell

skhell

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Location
Portugal
Car
1.8, 6th gen Accord
As some of you might know, my Accord is converted to run on LPG.

Today, I let the LPG tank go empty, I ended up running on petrol for a few miles, the distance I took to get the the gas station.

While running on petrol, the engine started to make funny noises, mostly on load: 2ª gear at about 3000rpm, or 3ª gear at 2500rpm. I think the engine is knocking.
The funny thing is, it only does this when running on Petrol, while on LPG, there is no noise.

Any ideas of what might this be?
I guess it's something related to the petrol system, right?
Dirty injectors?

Bad or old fuel?I have always used this petrol and never had any problems.

Could it be the knock sensor that it is faulty?
I have already check the ignition timing, and it's ok.

I think I have no error codes, since the check engine light is not on. Still, I am not sure since the car doesn't have an OBD socket.
 
Pedro how long has the petrol been in the tank as it might be very poor quality now.
 
brett said:
Pedro how long has the petrol been in the tank as it might be very poor quality now.
Click to expand...

I am not sure, about 2 or 3 months. I never put too much of it, but it last for some time.
Today I put some 10 liters of petrol, will run on petrol to reach the reserve, and the will put some more petrol of a more reputable make, and maybe a 98 octane, see if it solves the problem.
 
Hi Pedro

I've had some knocking or maybe rattling is closer to the sound on mine around the same RPMs. I have no engine light showing, but monitoring the Timing Advance via the ODBII shows it retarding and advancing pretty much inline with RPM.

I usually just run supermarket unleaded RON95. Usually an idea is to run a super unleaded at around RON98 when you experience detonation to benefit from the higher octane number and therefore the more controlled burn.

As far as I know LPG is rated significantly above RON98, generally above RON100 and maybe closer to RON110 so if you are 'knock' free with LPG it might point to detonation with a lower grade fuel.

I was going to investigate my EGR ports as I haven't ever unclogged them and I am at 86000miles. Have you looked at your EGR ports and Valve recently?
 
I have done the EGR valve and ports about 1 or 2 years, not sure, might look at it and see how it is.
I checked the valves at about 7000km, maybe less, and they were ok.

Although I have a flashlube kit installed to prevent valve seat recession, I tend to keep an eye on the valves in a regular basis, so if there is a problem, I will detect it soon.

I really cant tell the timing advance via obd(don't have the socket), so not quite sure what happens in that rev range.
 
skhell said:
I have done the EGR valve and ports about 1 or 2 years, not sure, might look at it and see how it is.
I checked the valves at about 7000km, maybe less, and they were ok.

Although I have a flashlube kit installed to prevent valve seat recession, I tend to keep an eye on the valves in a regular basis, so if there is a problem, I will detect it soon.

I really cant tell the timing advance via obd(don't have the socket), so not quite sure what happens in that rev range.
Click to expand...

Sounds like it is pinking (AKA pre-detonating) to me, especially if it is doing it under load. If an engine had a genuine knock from either the bottom end, cylinder head or both, you would hear it even when just revving the engine, with the knock getting faster as the RPM's climb.

My advice would be to put in some fresh fuel and take the car for a drive using just petrol, and see if it get's any better after giving it a mile or so to start drawing in the fresh petrol. You could even try using a higher octane fuel, or even an octane booster additive to see if it is an issue with the AFR. Make sure to let us know if it helps (providing you do try it of course!) and then we can go from there, as an issue like this is not easy to solve when the car is not here to look at, and you could end up changing lots of parts that weren't needed.

Best start with simple stuff first! :)
 
Yes, I can only ear it on load. While freely revving, everything is ok.

Yesterday I put 10 liters of 98 RON petrol and a Bardahl Injector Cleaner, the only decent injector cleaner I found on a Sunday morning.

By now, after a few KMs, the noise is almost(or completely) gone.
I will now run on petrol util I the reserve light comes on. Then I might give it a try with 95 RON, and see how it goes.
 
have you tried turn of flashlube? I don't like how engine is working with it on petrol too.Finally after 3 years of using flashlube i deistalled it completely, as I think it is total nonsense to lure peoples money.

I have checked spark plugs and oxygen sensor before and after deinstalling system. Oxygen sensor became clear(was a little black with lube system), and spark plugs became bright brown/clear too
 
I have the electronic flashlube, it only works when running on LPG, so yes, its "turned off".

About the sparkplugs, I use ZFR6FIX-11, the iridium ones, and the last time I checked, they were in pretty good shape:



About the oxygen sensor, don't know about it. I have replaced it a couple of years ago, but don't remeber how it looked.
 
After getting to the reserve light, the knocking/pinging, the Bardahl seems to have done some effects.
I put on it more 10€ of 95 RON. The noise is not as loud as it was before and not so frequent.
It occasionally happens between 2500-3000rpm on 2nd gear, not always, and depends on the load.

While running on LPG, there is no noise, but as it was already said, LPG has a higher octane ratting, being much harder to detonate.

Today I tried to monitor the KnockSensor(KS). I connected a digital multimiter to the knock sensor pin on the ECU, and measured the voltage agains the ground.
I had to put the multimeter in the 200mV scale to get some values while running on petrol in the rpm range that made the noise, and still, I got very low values.
I think the highest value that I got was about 50mv, which seems very low.

Although knock sensors do produce its own voltage, and it's a very low voltage, don't know if this is a normal value or if it's too low. Also, the multimeter is not the best way to monitor the Knock Sensor, since the signal pulses, instead of having a fixed value.

I am tempted to try another KnockSensor, but a new Honda sensor is way too expensive to buy it with out knowing if its the culprit.
I have found a few cheap ones on ebay, but don't really know if they work or not. Might give it a try, after all, they are quite inexpensive.

http://www.ebay.co.uk/itm/310668239841?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
http://www.ebay.co.uk/itm/221134131395?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

The correct part number is: 30530-P5M-013

I have looked for them on other(more reputable) online shops for the KS, but no luck...

Does anyone have a spare(used) Knock Sensor? That would be great for testing :)
 
It is possible to take knock sensor from any honda what has 1pin conector.
I had rover swaped h22a. used sensor from CRV 2.0L(european crv was most current car than jdm prelude :) ). worked perfectly. I believe it would work for this engine too.If there is any scrapyard it is worth to try to search for it.
 
It's not easy to find Hondas in junkyards in Portugal, at least in the area where I live :(
 
I wonder if this would work in the accord :unsure:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=251368244218&ssPageName=ADME:X:RTQ:GB:1123
 
I have just cleaned the EGR as well as the EGR distributer plate. It was not very bad, all holes were free and nothing was clogged.

Since I had to remove the fuel injectors, I give them a light clean with an injector cleaner product. To clean them properly, I would have to force the cleaner product through them, which means that I would have to pressurize the cleaning agent in some way, and power on/off the injectors. At the moment I don't have the proper material to do that, so I just give them a few "sprays" on the inlet and outlet.

After re-***embling everything, I let the engine to warm up, and went to a drive. Although the noise is still there in some rev range under load, I thing it has decreased a little more.
This leads me to believe that either the injectors could need a proper cleanup or some injector is not working properly...

Either way, I am still looking for knock sensor. Been looking for breakers at ebay, but still got no luck.
I guess my best chance would be to go for a used one from another model, probably something like this:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=251368244218&ssPageName=ADME:X:RTQ:GB:1123

Not sure if it would work or not :unsure:
 
have you checked how many wires has your knock sensor? quantity of wires are the same like in ebay picture? if yes, than it is worth to try :)

But i don't think that it is knock sensor problem. if knock sensor were bad than you ignition timing should be late at max.i would suggest to check your ignition timing (with ignition timing lighthttp://www.ebay.co.uk/bhp/ignition-strobe-light )somewhere i think, it should be 12 degrees on idle . if it is good than there is no need to buy a new one.

For injector cleaning i would suggest only ultrasonic cleaning bath. if there is one somewhere around you.
 
Linas said:
have you checked how many wires has your knock sensor? quantity of wires are the same like in ebay picture? if yes, than it is worth to try :)

But i don't think that it is knock sensor problem. if knock sensor were bad than you ignition timing should be late at max.i would suggest to check your ignition timing (with ignition timing lighthttp://www.ebay.co.uk/bhp/ignition-strobe-light )somewhere i think, it should be 12 degrees on idle . if it is good than there is no need to buy a new one.

For injector cleaning i would suggest only ultrasonic cleaning bath. if there is one somewhere around you.
Click to expand...

The knock sensor also has one wire.
I had already checked the ignition timing with a ignition timing light while shorting the SCC, and the timing is correct.

About the injectors, can't find anywhere around to do an ultra-sonic clean. Also, I can't be with the car stopped for a couple of days...
 
when you short scc timing always will be 12. even if anything is wrong.try to check without shorting
 
Linas said:
when you short scc timing always will be 12. even if anything is wrong.try to check without shorting
Click to expand...

Humm... haven't thought about that, but that makes sense...
Will try it again in the weekend.
 
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