View Full Version : Engine Knock - what causes it?
Sorry if this is a newbie question, but I've recently developed what I believe is engine knock.
New plugs, fuel pump and MAP sensor have recently been fitted. Any idea what other areas should be checked for causing this?
Is it a 'Ping' or a 'Knock'
Dude:flame Dev
I'd describe it as a ping. Similar in nature to the high pitched "pinking" A series mini engines suffered from when pullling away in high gears at low speed...
Have you upped the boost !!!!
Try going and filling up with Optimax from a diff petrol station
Dude:flame Dev
Running optimax, from a number of different stations.
Boost about 0.9, so not that upped!
If you are really not sure get someone who knows to have a listen to your car , i suppose its a poss that one of the knock detectors on the car has gone down , it should not det at .9 bar on optimax !!!
Dude:flame Dev
why have u got a new MAP? is it a stock one? stock ECU?
Originally posted by eyefi
why have u got a new MAP? is it a stock one? stock ECU?
The plastic connection on the one that was on the car was hanging off! It is Stock, as is the ECU.
Originally posted by eyefi
when does it occur?
Virtually all the time. The car is nearly unusable.
The more throttle the more there is. Boost is a total no no!
has this happend exactly since u put the new MAP in? how does it idle? it sounds like its the wrong item or knackered causing an incorrect fuel mixture. could u put the old one back in to test?
it could also b a fubar fuel pump. any changes to the pumps wiring?
wrong grade plugs in the extreme could maybe cause something like this, but i doubt it. which plugs have gone in?
id look at everything u have changed when it started to happen. who did the work?
The knock started on the way to Paul Whiffin's to install the plugs etc. The broken MAP was spotted and changed out, but didn't improve the situation at all.
The plugs are NGK cold ones, can't remember the part number but recommended by Foodfreak.
Brand new Walbro (spelt wrong I think) went on yesterday, still the knocking persists!
Ahhhhhh!
Chris Wilson
20-08-04, 09:34
This sounds just about the nastiest fault I have heard on a JZA80, there is no way a low compression engine like the TT should pig off boost unless timing is wildly out. It could be the MAF or MAP sensor, it could be all sorts of things. But if it IS pinging I wouldn't run it another yard unecessarily! Are you sure it's not a mechanical knock, maybe someting like the front pulley come loose? I had a MKIV with an aftermarket flywheel in the other day, the clowns who fitted it hadn't tightened it up and it was just about falling off..........
Originally posted by Chris Wilson
This sounds just about the nastiest fault I have heard on a JZA80, there is no way a low compression engine like the TT should pig off boost unless timing is wildly out. It could be the MAF or MAP sensor, it could be all sorts of things. But if it IS pinging I wouldn't run it another yard unecessarily! Are you sure it's not a mechanical knock, maybe someting like the front pulley come loose? I had a MKIV with an aftermarket flywheel in the other day, the clowns who fitted it hadn't tightened it up and it was just about falling off..........
This is causing me some concern too, and has left Paul and I scratching our heads at this point!
Car is hardly being used. Biggest problem is living 40 miles from Paul!
There is no noise from the engine at idle, or at very very low speeds, or when at a constant speed. Just under acceleration. Hope this info helps.
Originally posted by Chris Wilson
I had a MKIV with an aftermarket flywheel in the other day, the clowns who fitted it hadn't tightened it up and it was just about falling off..........
had'nt tightend the flywheel? :eek: :eek:
Originally posted by nigelc
The knock started on the way to Paul Whiffin's to install the plugs etc. The broken MAP was spotted and changed out, but didn't improve the situation at all.
ahh, right. sorry i thought u meant the things had been changed and the problem had started, not that the parts had been changed to try and cure the problem.
No mate. It was there for a week or two, just a little bit, then on the way to Paul's it just got worst. Figured that new plugs and pump would probably sort out any fuelling issues. How wrong was I!
Have you checked for engine diagnostic codes?
-Ian
got any errors in stored in the ecu? have a look on mkiv.com for how to check this.
ecu earths?
FPR and associated vac hoses?
slipped timing belt?
slipped adjustable cam gears?
sounds like u need an expert to look at it :(
Chris Wilson
20-08-04, 10:08
Has it lost power, feels gutless? A wild shot, check with a torch up the exhaust, the stuffing hasn't come out and blocked up the system has it? That would cause big power loss and pinging...
Originally posted by Chris Wilson
Has it lost power, feels gutless? A wild shot, check with a torch up the exhaust, the stuffing hasn't come out and blocked up the system has it? That would cause big power loss and pinging...
What about a dead CAT? They can fall apart and block the exhaust system as well...
-Ian
Off to mkiv.com to look up the engine diagnostic codes for tonight.
Exhaust is new on the car, lower CAT is out. Upper CAT still in.
Car only done 39k, but I guess CAT could of failed...
:(
geoffvalenti
20-08-04, 10:42
Unfortunately, AIUI you can't just short out E1 + TE1 you'll need an OBD II scan tool to get the codes for a VVT-i :(
Unless anyone knows a way :)
Chris Wilson
20-08-04, 11:02
Metal matrix cats, they don't break up, not like the ceramic ones in MR2's. Won't be that.
One less thing, phew!
Could the BOV be causing any problems, and is it worth putting stock back on?
geoffvalenti
20-08-04, 12:11
Originally posted by nigelc
Could the BOV be causing any problems, and is it worth putting stock back on?
Well I suppose if its leaking badly/fcuked and drawing in lots of air after the metering, in theory you'd run very lean and cause it to ping. BUT if its leaking that much, the car would run awfully all the time, I doubt that it would idle well/at all and it would be generally running bad.
If you've still got the old one it's probably worth swapping back to the OEM one, just to eliminate it, as its not a difficult job but I think my money would be elsewhere :)
Originally posted by geoffvalenti
Well I suppose if its leaking badly/fcuked and drawing in lots of air after the metering, in theory you'd run very lean and cause it to ping. BUT if its leaking that much, the car would run awfully all the time, I doubt that it would idle well/at all and it would be generally running bad.
If you've still got the old one it's probably worth swapping back to the OEM one, just to eliminate it, as its not a difficult job but I think my money would be elsewhere :)
Think I'll do it to eliminate it. I didn't think it would be relalated, but at the point of trying anything at the moment.
SirCharlesworth
20-08-04, 13:59
I know this sounds odd.... but it is deffinately knock/pinking/pre-ignition/det you are experiencing? and not some kind of bearing failure on the bottom end? You could always get the car dyno'd to make sure it isnt running lean anyway, but i wouldn't know how to check the timing :confused:
geoffvalenti
20-08-04, 14:28
Just a thought.
Have you checked the ignition timing? You should be able to get an inductive timing light to work on No. 1 cylinder lead and shine it onto the crankshaft pulley. Timing should be 10 deg BTDC. Theres not a lot you can do to alter it but at least it eliminates something else.
Whilst you've got the plug cover off, check the cam timing. Turn the crankshaft pulley until the marks line up at TDC, then look at the camshafts to ensure that their marks align. If you cant see any marks turn the crankshaft through 360 deg and look again.
Another long shot, but any port in a storm :)
richardharmon
20-08-04, 17:56
Can you get timing lamps that work off the 12V feed to the plug-top coil packs then? I often wondered how one would check the timing on the TT?
Soonto"HAS"soop
20-08-04, 18:09
Going back to basics, with all the mods you've done, have you reset the ECU?
Ben..
geoffvalenti
20-08-04, 20:22
Originally posted by richardharmon
Can you get timing lamps that work off the 12V feed to the plug-top coil packs then? I often wondered how one would check the timing on the TT?
No, but if I remember correctly No1 plug is on a lead rather than connected directly to a coil pack. You can connect your timing light's inductive pickup to that.
Either way just connect the light to the coil pack HT lead that involves No 1 cylinder
richardharmon
20-08-04, 20:52
Originally posted by geoffvalenti
No, but if I remember correctly No1 plug is on a lead rather than connected directly to a coil pack. You can connect your timing light's inductive pickup to that.
Either way just connect the light to the coil pack HT lead that involves No 1 cylinder
There's no HT lead for any cylinder, all the coils are plug-top. I suspect the only way to do it is to get some sort of HT lead with a spark plug top on one end and a plug socket on the other, take out coil pack No 1 and use said HT lead to connect the spark plug to the coil pack. Anyone else done this another way?
geoffvalenti
20-08-04, 21:00
Originally posted by richardharmon
There's no HT lead for any cylinder, all the coils are plug-top.
Yes there is! The coil packs connect directly to one plug and have a lead coming from them which go to another plug. Its a wasted spark system so both plugs fire but only one is at the correct moment IYSWIM :)
Originally posted by richardharmon
There's no HT lead for any cylinder, all the coils are plug-top. I suspect the only way to do it is to get some sort of HT lead with a spark plug top on one end and a plug socket on the other, take out coil pack No 1 and use said HT lead to connect the spark plug to the coil pack. Anyone else done this another way?
You dont need a lead evn on a non vvti you can use a timing light ;)
Dude:flame Dev
Originally posted by geoffvalenti
Yes there is! The coil packs connect directly to one plug and have a lead coming from them which go to another plug.
this is true for VVTI but not for standard engine
geoffvalenti
21-08-04, 00:12
Originally posted by eyefi
this is true for VVTI but not for standard engine
Yeah, agreed, but in this particular thread, we're talking about a VVT-i, aren't we?
This is definately a VVTi thread! I'll try reseting the ECU, see if it helps and post the results, probably be tomorrow now.
richardharmon
22-08-04, 01:44
Okay, my mistake, I didn't know the VVTi system used a wasted spark system, the standard engine has a coil for each plug. Seems like a step backwards to me!
Okay, so now that's cleared up, how do you use a timing light on a non VVT-i engine, put the inductive pick-up round the 12V feed? Sorry to hijack the thread, I just wanted to know :stupid:
Update!
Well, the car is sorted. Big thanks Paul Whiffin and the boys at Thor.
Turns out the knock was on the car probably due to a combination of the following:
broken MAP sensor
standard fuel pump
dodgy fuel filter
Those were the problems before the tuning started (but unknown at that point).
Tuning involved:
Lower decat
Megan Racing exhaust
FCD
Cold Plugs
After the tune up, the knock got worst, and the parts above were change for new or uprated parts. Knock remained...
Ended up with Thor for a rather long session, and net result was:
The HKS FCD was causing the knock.
An unexpected culprit to say the least!
My advice to all is if you are trying to find a fault, don't forget to check your new parts even if they were added after the fault, as sods law says it's there staring you in your face!
Once again, big thanks to Paul.:cool: :cool:
The HKS FCD scales the MAP signal to avoid hitting fuel cut, so it effectively leans off your entire airflow range :eek: Bargepole time.
Er, hope you weren't gonna try and sell it :D
-Ian
Originally posted by Ian C
Er, hope you weren't gonna try and sell it :D
No chance! Got a new one to replace it as it was brand new and fooked! Phew!
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