Knocking on hot/humid days?
Thread Starter
Instructor
Joined: Oct 2002
Posts: 181
Likes: 0
From: Windham NH
Knocking on hot/humid days?
On hot/humid days I seem to be getting some knock under 3/4 to full throttle. I don't have any scanning tool but it sounds like knock (marbles in a tin can). 
I have a 2001 with 18K miles on it. I have a Vararam intake as my only performance mod. I use Exxon 93 octane gas.
So... questions...
1) Do you guys think it might be carbon buildup? Do I need to do the engine decarb procedure?
2) Could it be related to the Vararam? Why would it only happen on humid days? I would expect the humid air to be less dense and therefore cause the car to run rich not lean.
3) Other suggestions?
--Bill
I have a 2001 with 18K miles on it. I have a Vararam intake as my only performance mod. I use Exxon 93 octane gas.
So... questions...
1) Do you guys think it might be carbon buildup? Do I need to do the engine decarb procedure?
2) Could it be related to the Vararam? Why would it only happen on humid days? I would expect the humid air to be less dense and therefore cause the car to run rich not lean.
3) Other suggestions?
--Bill
Le Mans Master
Joined: Jul 2002
Posts: 7,076
Likes: 26
From: Nevada and Florida
Re: Knocking on hot/humid days? (bletour2001)
Had that issue with my '01. These engines have a lot of blowby and the PCV system has since been redesigned. Carbon is typical but you will also run leaner with the aftermarket intake. You can decarb but the ping will be back. Another weakness is the stock radiator (too small). You can try going to a 180* t-stat and set your fans lower in 185-190* range to help this condition.
Thread Starter
Instructor
Joined: Oct 2002
Posts: 181
Likes: 0
From: Windham NH
Re: Knocking on hot/humid days? (BHP)
So your telling me I can't "fix" it? I don't hear other people screaming about this much. Maybe I'm deaf 
Basically I need to decarb and do the PVC oil catch mod and lower the temp to try and avoid this?
Man... it don't sound healthy when this happens. I'm surprised more people aren't screaming about it.
Thanks for the feedback
--Bill
Basically I need to decarb and do the PVC oil catch mod and lower the temp to try and avoid this?
Man... it don't sound healthy when this happens. I'm surprised more people aren't screaming about it.
Thanks for the feedback
--Bill
Racer
Joined: Dec 2003
Posts: 411
Likes: 0
From: Jensen Beach Fl
Re: Knocking on hot/humid days? (bletour2001)
Just so you don't feel all alone--my 00 with 58K does the same thing-pings-but not all the time! and its really hot and humid down this way. Dealer said carbon build up and they could fix it for $130-some chemical treatment requiring they have the car over nite-didn't go for it yet--my luck is that this treatment wouldn't work. we'll see (waiting on my C6 anyway) 
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Re: Knocking on hot/humid days? (S1K C5)
Get someone with LS1 edit and a good wide ban O2 sensor figure out if it is knock and if it is caused by the mixture being lean. I would do it soon!!! As mentioned previously the knock is NOT good and the longer it goes on the more DAMAGE is being done.
A few things to check that can cause the hot humid knock problem.:
Timing too high or not responding to load conditions, ( ie bad sensor.)
MAT sensor could be bad.
Intake air temp sensor could be bad.
Knock sensors may not be functioning properly!!
I would get someone to monitor those functions and see if they are responding properly and with in the proper ranges.
I have an 98 Coupe MN6 and a 02 ZO6 and I have never had a problem (that I can hear) with either.
BC
A few things to check that can cause the hot humid knock problem.:
Timing too high or not responding to load conditions, ( ie bad sensor.)
MAT sensor could be bad.
Intake air temp sensor could be bad.
Knock sensors may not be functioning properly!!
I would get someone to monitor those functions and see if they are responding properly and with in the proper ranges.
I have an 98 Coupe MN6 and a 02 ZO6 and I have never had a problem (that I can hear) with either.
BC
Thread Starter
Instructor
Joined: Oct 2002
Posts: 181
Likes: 0
From: Windham NH
Re: Knocking on hot/humid days? (Bill Curlee)
Thanks guys... I will get it checked out ASAP.
I checked if it was throwing any codes and it isn't. I would assume a bad sensor would throw a code wouldn't it?
I did pick up a couple cans of top engine cleaner today to clean her out (I figure that can't hurt), but it sounds like I better get her on the dyno for some testing.
--Bill
I checked if it was throwing any codes and it isn't. I would assume a bad sensor would throw a code wouldn't it?
I did pick up a couple cans of top engine cleaner today to clean her out (I figure that can't hurt), but it sounds like I better get her on the dyno for some testing.
--Bill
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