# Knocking noise when accelerating hard



## SleepyJoe (Nov 1, 2002)

For the past month, I have noticed that when I accelerate hard, between 2500 and 4000 rpm, there is a strange knocking noise. Regardless of if my engine is warm or not. I haven`t noticed any difference in power, its just that I am worried this could be a prelude to something very bad. Also, I remeber my engine beeing smooth (as smooth as a 2.0 can sound...) but know it`s obvious that something is different
I installed a chip and the sound is more prenounced now and threw a wider rpm range. Beside a Neuspeed Chip and an Air Intake, I haven`t modded my engine. Oil is changed every 3000km (3000/1.6 = 1875 miles)
Seriously guys, I really don`t know what this is...Help!


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## RaceJetta (Oct 18, 2002)

*Re: Knocking noise when accelerating hard (SleepyJoe)*

I would guess rod bearings, or maybe too much ignition advance. Marbles in a sack noise - ignition, more like a hammer on the block, I'd think rod/crank bearings. Either way, get it diagnosed before it breaks something...


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## SleepyJoe (Nov 1, 2002)

*Re: Knocking noise when accelerating hard (RaceJetta)*

Thanks for the reply!
Ok I think this noise would be more of a marbles in a sac noise. So when you say the ignition, I have to change the ignition? Or do I have to change also the plug wires? 
Anyhow, I will bring it to a vw specialized shop to ask them about thoses two possibilities you mentionned


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## bigteal (Sep 11, 2002)

*Re: Knocking noise when accelerating hard (SleepyJoe)*

marbles in a sac noise after chip install? maybe a bad batch of gas, preignition or detonation maybe? rod noise would surely get louder with more RPM, at least from what i have seen in the past ( but i guess v8's and kia engines don't apply here huh?)


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## Glenn J (Feb 16, 1999)

*Re: Knocking noise when accelerating hard (bigteal)*

Agreed...sounds like a fuel issue. Try a tankful of hightest and run some Techron fuel system cleaner through there while you're at it.


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## VDUBLUVENTO (Jul 20, 2001)

*Re: Knocking noise when accelerating hard (SleepyJoe)*

i am also having the same problem i was told i could have a bad injector 
i still need to get it checked out. Do you guys think a bad injector would cause a noise like this ?


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## SleepyJoe (Nov 1, 2002)

I have been runing premium (91) fuel for the past month. When I got the chip, I still had a half tank of regular fuel (87) and the sound was a lot more prominent. When I switched to premium fuel it became less loud, but its still there... 
I should also mention that before chipping, the marbles in sac sound happened once in a while and was barely auditable. Now, it a lot more prominent. 
What is wierd is that sometimes I notice it a lot more. It seems to be a bit intermitent... 
Do you guys think that if I got my ECU scanned, it would have saved the codes dexcribing my condition? Is OBD2 monitoring sensitive enough to notice this type of problem?


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## RaceJetta (Oct 18, 2002)

*Re: Knocking noise when accelerating hard (SleepyJoe)*

You certainly have a detonation issue.
If the OBD2 ECU would notice something worth reporting, you'd have your CEL on.
I think you may want to reduce your base timing. You have detonation issues. If you had the sound before, and it is more prominent now, then back off your base timing. The chip will certainly set your timing more agressively. Get this fixed soon. Prolonged detonation can ruin your motor in a big way. Worst case scenarios would be a damaged piston ring land, cracked ring, and other internal damage... not fun... There are no codes for detonation that I know of, it tries to control it, but it doesn't work that well. Detonation is controlled best by the computer up to about 4000 rpm, then above that rpm, 4 cylinder engine 'sounds' look very much like detonation to the knock sensor, and it becomes challenging for the computer to completly eliminate it. Also, there is only so much retard available to the ignition system too... Get your timing checked with a good timing light...


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## ylwGTI (Jan 18, 2002)

*Re: Knocking noise when accelerating hard (RaceJetta)*

i might be wrong , but how about the knock sensor???


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## A3Infidel (Nov 29, 2000)

*Re: Knocking noise when accelerating hard (RaceJetta)*

I experienced the same thing right after my cam / chip install, a lot of people told me it's normal. It's most pronounced when the car is cold, I'm thinking it's a timing advance issue also. I've lived with it for around 40K miles with no problems.


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## SleepyJoe (Nov 1, 2002)

*Re: Knocking noise when accelerating hard (RaceJetta)*

Hmmm...not good news. Ok, so essentially I must go to a mechanic and ask them to check my base timing. Tell me if I`m right: base timing is the timing before any modifications such as chipping. So essentially, my base timing is bad, and on top of that, it is worsened by my chip setting the ignition even more agressively. Is the base timing ajusted manually, or must it be reconfigured threw the ecu?


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## Clean97GTi (Nov 28, 2001)

*Re: Knocking noise when accelerating hard (SleepyJoe)*

Make sure your chip isn't made for 93 octane (if all you've got is 91) If you've got one that is, send it back for reprogramming/exchange. The chip will advance the timing too much for 91 octane.
However, if the knoicking noise was prominent before the chip, I'd suspect bad timing or possibly some lifter noise.


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## SleepyJoe (Nov 1, 2002)

*Re: Knocking noise when accelerating hard (Clean97GTi)*

Does anyone know what fuel grade a Neuspeed chip designed for a VW Carbrio 8V, Golf/Jetta 8V III 1996-1999 uses? (I have a removable chip, don`t have to solder in or out).
I have access to 91 octane and 94 octane fuel (which cost SO much).
Like posted before, I use 91 octane fuel. But I tried 94 octane fuel and still got the infamous marble in a sac sound.


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## bigteal (Sep 11, 2002)

*Re: Knocking noise when accelerating hard (VDUBLUVENTO)*

quote:[HR][/HR]i am also having the same problem i was told i could have a bad injector 
i still need to get it checked out. Do you guys think a bad injector would cause a noise like this ?[HR][/HR]​maybe. when injectors go bad, there usually is a dead cylinder involved too. if it's not missing, than you probably don't have an injector problem. but sometimes when a bad or clogged injector tries to fire, it sounds like a shorted plug wire, makes a fast tapping sound.


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## bigteal (Sep 11, 2002)

*Re: Knocking noise when accelerating hard (SleepyJoe)*

quote:[HR][/HR]Hmmm...not good news. Ok, so essentially I must go to a mechanic and ask them to check my base timing. Tell me if I`m right: base timing is the timing before any modifications such as chipping. So essentially, my base timing is bad, and on top of that, it is worsened by my chip setting the ignition even more agressively. Is the base timing ajusted manually, or must it be reconfigured threw the ecu?[HR][/HR]​ base timing is factory timing. 2.0l motors are not a DIS system ( distributor less ignition), so i would imagine it's probably manually adjusted, but please correct me if i'm wrong.


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## SleepyJoe (Nov 1, 2002)

*Re: Knocking noise when accelerating hard (bigteal)*

bump, can anyone confirm this? Someone with a Bentley?


[Modified by SleepyJoe, 6:48 PM 12-19-2002]


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## Glenn J (Feb 16, 1999)

*Re: Knocking noise when accelerating hard (SleepyJoe)*

Before you start playing with the timing, run a tankful of 94 through your system. Get the current tank as close to empty as you feel comfortable driving with, then fill it up with 94. If that solves your problem, it's the octane rating. You can either have the chip reprogrammed, get rid of it, or pay for the 94 octane gas. Let us know what happens.


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## SleepyJoe (Nov 1, 2002)

*Re: Knocking noise when accelerating hard (Glenn J)*

Sorry, it`s been a long time since I have last posted on this thread, but to answer your question, I've tried 94 Gas with no reduction whatsoever of the rattling noise while accelerating. Some listened to my engine and reved it with the throttle body while listening. He says that he thinks there is nothing wrong with the engine itself being that the rattling does not occur in neutral, just in gear. So he told me that i might have some sort of part thats loose in the engine bay. Just can'T see what it could be. This problem is SO nagging.


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## FighterJet (Jul 13, 2001)

*Re: Knocking noise when accelerating hard (SleepyJoe)*

I've had rattling in my car for quite a long time. Check the heatshield if it rattles only with load. If not...It may be your lifters...I've had the same type of noise. I couldn't hear it while in neutral either. But that's because I was reving the throttle too hard when diagnosing the problem. Try reving lighter (or how you would normally driving) while in neutral. You might hear the rattle then....Good Luck


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## Pushrods (May 14, 2001)

*Re: Knocking noise when accelerating hard (SleepyJoe)*

quote:[HR][/HR]Some listened to my engine and reved it with the throttle body while listening. He says that he thinks there is nothing wrong with the engine itself being that the rattling does not occur in neutral, just in gear.[HR][/HR]​I wouldn't call that a fair diagnosis... Just revving it in neutral doesn't apply a load to the engine. Detonation pretty much only occurs when the engine is under load AFAIK...


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## VDUBJ (Mar 22, 2003)

*Re: Knocking noise when accelerating hard (SleepyJoe)*

The NS P-Chip for the 2.0L 8V OBDI is 91 minimal.


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