subject nearly says it all.

I am getting detonation and I just installed LT headers. I am thinking it leaned it out too much. what are your opinions?
btw I am also using TR55's

what should I do to fix the problem?

colder plugs? bigger injectors? dyno tune? all of the above?

and just to let you know the engine is stock. my only mods are a K&N FIPK, Hooker LT's and 3" exhaust

 

Did you install the O2 sensors? Did you damage any of the O2 sensors? Your car should compensate for any increased airflow. That's what the oxygen sensors and MAF are there for. To give feedback on the Air/fuel ratio.

 

Have you checked for any exhaust leaks? Run a Seafoam cleanse or pour about 5 tablespoons of ATF in the intake on a warm engine... same thing... it creates smoke. The smoke should only come out of the tailpipe. Any other leaks will become very apparant.

 

Are you saying you have detonation because you can hear it? More likely its exhaust leaks. In the extremely unlikely event you managed to lean things out, the PCM should be able to pull enough timing through knock retard to eliminate the knock before you hear it. Get it on a scanner and check for knock retard, O2 mV levels, and any other things that will cause knock.... e.g. -excessive coolant temps. Also check for elevated long term fuel corrections (BLM's) on one or both sides - a sign of exhaust leaks, and misfires due to burned plug wires.

 

yes I can hear the detonation. the only time I can hear it is when the car is under load i.e in sixth gear and low rpms and then accelerate. I know I dont have any exhaust leaks because I had one and that has been fixed. when I had the leak you could hear that at ide. you can not hear what I am hearing at idle. also it has an intermitent low rpm stumble sometimes it feels like I am starting out in third, when reality I am starting out in first, when other times it is just fine.

and to answer the other question I did install new O2 sensors

finally, I let a friend of mine who has a lot more experience with these cars drive it around for a while, and he says that it even feels to him like it is pulling the timing, even sometimes when we cant hear anything.

 

You'll never know what it is doing with the timing until you scan it.

Can I assume you deleted the EGR with the LT install? One of the incidental benefits of EGR is reduction of knock when you lug the engine under low rpm/low load. But it just should never knock so bad you can hear it. That would mean its pulling 12-15deg and its still not enough.

 

Just a thought... Injuneer, suppose the knock sensor got damaged or disconnected during the header install. He says he gets the detonation under load... so if it can't retard knock because it can't detect knock, wouldn't that permit knock?

 

no I do not have the EGR anymore. I know that part of its function is to keep the combustion temperatures lower, are you suggesting that the knock could be caused by the higher temperatures in the combustion chamber?

I am planning on getting it scanned tomorrow morning so we will have more info to work with then.

if this is caused by the higher combustion temps. what else could I do to stop it. perhaps add more fuel? I know that cams that have less overlap create the same effect as the EGR - so does this mean that I need a cam now?

 

first go to a gm dealer and order a knock module for a stock lt4 corvette, (96, i think). next take off the spark plug wire boot heat shields, if those dont fix it change your plugs and wires only use ac delco. ps, knock module is in the computer.

 

Maybe Lt4 knock sensor would help?

 

the knock SENSOR is the same, the module is different.

 

sorry chevy didnt see you already posted that!

 

thanks for the suggestion but I already have an LT4 knock module -- that dosent stop knock anyway it only interprets it, and ideally eliminates timing retard due to false knock "noises"

 

Hey guys,

He did put some taylor OVC wires on it... and each wire has some "heat socks".

The car *is* definitely detonating at lower RPM's under load, and it's so bad you can hear it. I know he put some Bosch O2 sensors on it <- could this be the cause?? The car does feel like timing is getting pulled out of it. You can almost feel the car stop wanting to accelerate.

I thought it might've been some bad gas but Ryan said his car has been doing this since we put the headers on 2-3 weeks ago.

 

well I went to the shop today and they said that I am pulling 2-3 degrees of retard under normal or hard accleration, and 9,12, and 13 degrees when I really lug it such as in 6th gear and around 2K rpm and then try to accelerate, and also if I do a "skip shift" and such. also they said that the coolant temp. was fine, injectors were working perfect, O2 sensors were perfect, no codes, no midfires or anything like that. it is definately nothing obvious so any other suggestions would be appreciated.