has any one resolved an issue with knocking sound on their vq30de? (sounds like rod knock) it happens when the car is completely warmed up , when it is first started up it wont start knocking un til it reaches operating temp, then after awhile it goes away? while in park it idles rough (shakes) i ve gotten p0300 done fuel trims tests in bank one i get -7-9% ect. short term guess the ecu is reducing fuel for a rich condition its running in open loop all the time. check all the sensors coils ect which are new plugs ect still cant find the problem , please give me an idea

 

Please separate your questions instead of lumping your issue into one big clusterf*ck. Thanks...

 

eeekkk... my first guess is a heavy spark knock ..with some sort of retarted timing .but you seem to have pretty good knowledge of how to trouble shoot. What kind of oil and gas are you running?

how bads the knock...like a hammer on your valve cover?

 

first thing the 20 year old need not to post go some where else with your childish remarks the question is clear and simple , now for the the person that responed maturely i ive been using 93 octane since the life of the car knocking is coming from the rear valve or center of the block dosent sounds like valve tapping more like rod knocking from th crank, i use redline 10 w 30 and mobile 1 10 w30, i scanned the fuel trims i noticed bank one fuel trims are not normal for long term 20 percent is the max but it gets no where near 20 percent its most 7-9 percent dont know would a o2 sensor thats dying cause knocking, in the nissan service manual it shows a low possibility, being that the o2 sensor control the air to fuel ratio and injector pulse could it be possible. strange thing i dont get an o2 sensor code

 

Even if the O2 sensor went bad the ECU would go into safe mode, basically running open-loop the whole time. Since it would run extra rich the combustion temperatures would go down so knocking/ping is unlikely.

BTW, WTF does my age have to do with anything?

 

your first post

 

even though its a maxima Id check compression to make sure my internal are ok..and rule it out

 

sound like a good idea , strange thing it goes away after awhile

 

ive had several jetskis and other small engines that had marginally low compression and ran fine just has some top end noise. if it comes back lower than you expect you can still drive it while you deicde what you wanna do..ive never seen a vq with low compression ..hopefully your not the first

 

open loop is a program that built is into the ecu at one setting instead of constantly adjusting safe mode is more for ignition system to where the kncok sensor has failed, but i understand your response but combustion temp dosent go down tempeture is changes all the time depending on the throttle applied you answer helps thanks

 

i hope im not the first

 

it runs good but some time sliggish

 

What i meant is that when the a/f mixture is rich, combustion temps go down. Of course at higher loads the temps would go up, but if the ECU was in open-loop the whole time as is the case with a failing o2 the combustion would be stable and knocking/ping would be unlikely.

 

yes your correct but remember the o2 sensor controls the injector pulse i was leaning towards the o2 sensor in the nissan service manual on the trouble shooting charts it has it as a low posibility some times the things the seem to not be the cause often is the cause , but ive always taken care of the engine never abused its just a strange case

 

i would figue if it was mechanical it would happen all the time , my sister had a doge stratus and it was knocking even when she was driving the knocking would get louder you knw how those american engines are i remember back in 1987 when i use hear the american car knock brand new and the japanese run forever

 

If you hear the knock at idle then it's got nothing to do with a/f, it's most likely mechanical. When the car is cold the oil is thick and masks small problems such as rod knock. As the engine gets up to operating temp and the oil gets hot it thins out slightly. Thats when you'll hear noises such as rod bearings or the wrist pin. A small knock heard at idle says you have something wrong with the bottom end of the motor. Either a wrist pin has worn out or a bearing spun. You can drop the oil pan and take the bearing caps off each rod and look for damage or feel for excessive play on any of the connecting rods. Also look closely at whats in the bottom of the oil pan. If you find excsssive amounts of metalic sludge, start looking for a used or rebuilt motor.

 

sorry for the newbiness......can someone explain open loop for me?

o by the way....nismology....u live off of 160th rite>?