Very high negative fuel trim at idle
03-17-2019, 01:11 PM
#51
Turned out to be the valve lash. All valves too tight. Some way too tight. Food for thought. Whoever replied with that suggestion, I wish I had checked that 1st. Fuel trims at idle are right around +/- 0. No bucking, no hesitating, runs strong and hard all the time.
03-17-2019, 05:28 PM
#54
Seems odd to have valve lash way out of whack on newly rebuilt and adjusted head. How much time is on the motor since the rebuild?
03-18-2019, 01:46 AM
#55
Yeah this "IN"vidia exhaust sounds nice and mellow when you're cruising which is what I wanted. At 3500 rpm with top up, if you dip in to the throttle a bit it drones but is easily remedied by just letting off a bit. At 4k rpm ~70 MPH there's almost no drone at all no matter what you do on the pedal. Didn't mention my car has a Berk HFC. But Jesus, right around 5k and up it sounds absolutely fantastic. Loud as all get out too. Then you see a cop and it's a stock exhaust again. ;-)
03-18-2019, 01:47 AM
#56
Glad its sorted! Question is how tight was too tight? Did you take a before and after adjustment measurement?
03-18-2019, 06:27 AM
#57
Moderator
If the mileage is not sufficient to burn the valves due to tight clearance, that leaves one culprit, a “built” head.
Find out the make of the valves.
Theres a reason the OEM head components are going strong after 250k miles, and all those with built heads are broken in less than 10k.
True to 100% of built engines I've seen, the valve adjustment goes to crap in a few thousand miles due to valve face deformation.
Find out the make of the valves.
Theres a reason the OEM head components are going strong after 250k miles, and all those with built heads are broken in less than 10k.
True to 100% of built engines I've seen, the valve adjustment goes to crap in a few thousand miles due to valve face deformation.
Last edited by Billman250; 03-18-2019 at 06:31 AM.
03-23-2019, 06:40 AM
#58
If the mileage is not sufficient to burn the valves due to tight clearance, that leaves one culprit, a “built” head.
Find out the make of the valves.
Theres a reason the OEM head components are going strong after 250k miles, and all those with built heads are broken in less than 10k.
True to 100% of built engines I've seen, the valve adjustment goes to crap in a few thousand miles due to valve face deformation.
Find out the make of the valves.
Theres a reason the OEM head components are going strong after 250k miles, and all those with built heads are broken in less than 10k.
True to 100% of built engines I've seen, the valve adjustment goes to crap in a few thousand miles due to valve face deformation.
There was a lot of carbon buildup on my pistons and valves. This is why I went ahead and had the rebuild done. The engine ran fine before the rebuild. I did notice my fuel mileage getting worse. I was getting 25-26 MPG highway and it dwindled down to 21-22. Now it's sorta everywhere maybe due to my driving who knows. I got 24 one tank and last tank I got 21 mpg. Haven't been vtacing at all. This could also be due to the RPF1's I installed on the car. Although the wheel is lighter, the tire is heavier and there is a larger footprint than the OEM wheels. More rolling resistance? Who knows.
03-24-2019, 04:15 AM
#59
I still say its kinda weird to have valves get tight like that so fast. It makes you wonder if maybe the gaps were set incorrectly during the head rebuild? Were the adjusting nuts loose when you went back in?
I would probably give the valves another look in the not to distant future to be sure they are holding.
But, sounds like you have it sorted out which is good news.
I would probably give the valves another look in the not to distant future to be sure they are holding.
But, sounds like you have it sorted out which is good news.
Last edited by rpg51; 03-24-2019 at 04:19 AM.
Thread
Thread Starter
Forum
Replies
Last Post
Driv300mph
S2000 Under The Hood
1
01-25-2011 06:17 PM