Valve lash throwing off tune?
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Honda-Tech Member
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Valve lash throwing off tune?
Hey guys,
I have an internally stock b18c1 gsr motor with bolt-ons (header, cat, exhaust, intake, throttle body, intake manifold, IMG). The car was tuned last year by Xenocron on ECtune and made 170whp and felt awesome. This past week, I got maintence performed by a trusted Honda mechanic and got a new oem timing belt kit installed and the valve lash adjusted because my valvetrain was very noisy.
When the valve lash was adjusted it was EXTREMELY loose and basically every valve was adjusted and tightened to spec. After this the car would barely start because the idle was much lower (under 500) and when I would give it gas in order to start it the idle was shaky. I drove home and adjusted the idle at the throttle body and it is now able to hold a better idle but the car is definitely LACKING POWER. The mechanic explained that my tuned ECU will not learn like a stock ECU, and the fact that the valves were so out of spec that now being adjusted is throwing off the tune causing it to act this way.
Is it SAFE to be driving this car this way until I can get a re-tune, and can adjusting the valves really throw the tune off this much to change the drivablility and idle? Thanks
I have an internally stock b18c1 gsr motor with bolt-ons (header, cat, exhaust, intake, throttle body, intake manifold, IMG). The car was tuned last year by Xenocron on ECtune and made 170whp and felt awesome. This past week, I got maintence performed by a trusted Honda mechanic and got a new oem timing belt kit installed and the valve lash adjusted because my valvetrain was very noisy.
When the valve lash was adjusted it was EXTREMELY loose and basically every valve was adjusted and tightened to spec. After this the car would barely start because the idle was much lower (under 500) and when I would give it gas in order to start it the idle was shaky. I drove home and adjusted the idle at the throttle body and it is now able to hold a better idle but the car is definitely LACKING POWER. The mechanic explained that my tuned ECU will not learn like a stock ECU, and the fact that the valves were so out of spec that now being adjusted is throwing off the tune causing it to act this way.
Is it SAFE to be driving this car this way until I can get a re-tune, and can adjusting the valves really throw the tune off this much to change the drivablility and idle? Thanks
Honda-Tech Member
Joined: Jul 2006
Posts: 2,817
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From: Kansas
Re: Valve lash throwing off tune?
Please define "way out of spec" with a number, this is important.
Was the valve adjustment done at the cam to rocker gap or the valve to rocker gap? Very important.
In my experience a valve adjustment affects the idle quality enough to require some type of manual adjustment (or throttle cleaning) 3/10 times, and it depends a lot on the car. Honda's I generally have few issues with, although the LMA assemblies can make noise.
I would suggest not driving it until you verify your engine timing is correct, and the valve lash is correct.
Was the valve adjustment done at the cam to rocker gap or the valve to rocker gap? Very important.
In my experience a valve adjustment affects the idle quality enough to require some type of manual adjustment (or throttle cleaning) 3/10 times, and it depends a lot on the car. Honda's I generally have few issues with, although the LMA assemblies can make noise.
I would suggest not driving it until you verify your engine timing is correct, and the valve lash is correct.
Honda-Tech Member
Joined: Feb 2005
Posts: 4,235
Likes: 127
From: Mustard Belt
Re: Valve lash throwing off tune?
Please define "way out of spec" with a number, this is important.
Was the valve adjustment done at the cam to rocker gap or the valve to rocker gap? Very important.
In my experience a valve adjustment affects the idle quality enough to require some type of manual adjustment (or throttle cleaning) 3/10 times, and it depends a lot on the car. Honda's I generally have few issues with, although the LMA assemblies can make noise.
I would suggest not driving it until you verify your engine timing is correct, and the valve lash is correct.
Was the valve adjustment done at the cam to rocker gap or the valve to rocker gap? Very important.
In my experience a valve adjustment affects the idle quality enough to require some type of manual adjustment (or throttle cleaning) 3/10 times, and it depends a lot on the car. Honda's I generally have few issues with, although the LMA assemblies can make noise.
I would suggest not driving it until you verify your engine timing is correct, and the valve lash is correct.
I will add that being loose before (whatever the measured number is) and in spec now would mean that now the valves are opening slightly sooner and reaching a slightly higher peak lift. I am more familiar with the single cam adjustments but I'm having a hard time believing that this small amount of change in the valve action in the positive direction is making the car run worse. whether your ECU "learns" or not, it should be able to cope with the small increase in flow from a valve adjustment.
just my hunch, but it sounds more like a timing issue.
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