Alberta04SS Posted December 25, 2011 Report Share Posted December 25, 2011 I have a 2004 Lq4 in by truck and I have 170 000 kms on it. Since I have owned the truck it has had no issues up until a few mouths ago and has been a lot of fun. Last summer the truck started lacking power top end and I ended up doing an intake system cleaning and replaced the fuel pump, sender unit and fuel filter, while I had the truck in i picked up new push rods, LS6 springs and new 1.82 rockers. I drove the rest of the summer like this and had no issues, about one week before I parked the truck for the winter (I live in calgary) I noticed it felt really soft on the top end at WOT or close too it and would fluctuate and pulse on highway hill climbs and at WOT. The air fuel ratio would be all over the place. MY mods to this point: Volant CAI B&B exhaust Long tube headers with custom mid pipes and no cats. comp cam valve springs crane cams 1.82 alu rockers crane cams push rods E fans wide band air fuel installed diablo sport tuner and cats tuned out at the shop. I have been planning on fabricating a twin turbo set up, LS6 heads and a possible re build but I really need to make sure the engine and tranny are ready for more power and running strong first and since its parked i figured now would be as good of a time as any. Info as to where my diagnosis should start and common problems would be great. cheers Quote Link to comment Share on other sites More sharing options...
detjoe Posted January 2, 2012 Report Share Posted January 2, 2012 I would guess the lifters are beat. the rockers are putting more pressure/leverage on them so I could see them losing pressure at higher rpm's. does it tick after starting it up after sitting for a few days??? Quote Link to comment Share on other sites More sharing options...
Cramer Posted January 3, 2012 Report Share Posted January 3, 2012 (edited) Lifters maybe, but it sounds like maybe a broken valve spring to me. Especially with the 1.8 rockers. The spring (s) are probably just broke but still around the valve. There fore you still have resistance at lower rpm's to keep the valve seated, but it's floating around in upper rpm's or under a load. Pull the valve covers off and do a visual on the springs. If something doesn't look totally right, take a mallet and tap on the rockers. You should hear a thud sound. If you hear a ringing sound there is a broken section in there. Edited January 3, 2012 by sinr98 (see edit history) Quote Link to comment Share on other sites More sharing options...
Alberta04SS Posted January 5, 2012 Author Report Share Posted January 5, 2012 Lifters maybe, but it sounds like maybe a broken valve spring to me. Especially with the 1.8 rockers. The spring (s) are probably just broke but still around the valve. There fore you still have resistance at lower rpm's to keep the valve seated, but it's floating around in upper rpm's or under a load. Pull the valve covers off and do a visual on the springs. If something doesn't look totally right, take a mallet and tap on the rockers. You should hear a thud sound. If you hear a ringing sound there is a broken section in there. Thanks for the advice! They are upgraded springs. Yesterday was warm so I started it up and there was a noticeable ticking under the passengers side (sounds like a ford) when I get a chance ill pull the cover off, all the work was done less then a year ago at a performance shop would this be something they would cover if it was improperly seated to begin with? Quote Link to comment Share on other sites More sharing options...
Alberta04SS Posted January 6, 2012 Author Report Share Posted January 6, 2012 Thanks for the advice! They are upgraded springs. Yesterday was warm so I started it up and there was a noticeable ticking under the passengers side (sounds like a ford) when I get a chance ill pull the cover off, all the work was done less then a year ago at a performance shop would this be something they would cover if it was improperly seated to begin with? I just removed the passengers valve cover and the most forward rocker seemed to make the most ticking when i tapped it. how much side to side play is preferable? some seemed quite sloppy. Quote Link to comment Share on other sites More sharing options...
detjoe Posted January 7, 2012 Report Share Posted January 7, 2012 oe rockers can take a shit too, take it off and see if the bearing are still there if they are broken then you just need to make sure you fine the pieces...then pull your drain plug and see if there is any crap on the oil pan maganet glad you have it located to the valve train. Quote Link to comment Share on other sites More sharing options...
Alberta04SS Posted January 9, 2012 Author Report Share Posted January 9, 2012 Well i pulled the culprit off and its all okay. I changed the oil and checked the plug and it was all clean. Yesterday I replaced the spark plugs and put some new MSD wires on plus a new air filter and took the truck for a drive and again at low RPM and everything seems tight with lots of torque but as soon as i get into the power band at 75 to 100% throttle same problem, no power and uneven power with fluctuating RPM. No codes were thrown and the A/F raitio was all over the place, mostly rich. Quote Link to comment Share on other sites More sharing options...
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