I am having trouble getting my new 2056 with a 9590 cam to idle. When I start it is idles around 500rpm or lower and I can't speed it up with the by pass screw.
I am running L-jet injection
I hear a hissing sound when the engine is idling but I cannot find a vacuum leak, plenum couplers are new and all other hoses are in good shape.
I can't find the hissing with a mechanics stethoscope so I was going to try to find a leak with propane but it has been too cold to work on it lately.
The idle does seem to get a little better after it has warmed up a bit I think, it has been several weeks since I have had it out.
One question I had is does the new cam require any change to the mixture? if so how do I go about adjusting the mixture?
Thanks in advance for any input
Yes
One question though, when I set the timing I set it to 900 rpm after the vacuum advance lines are removed and plugged correct or set it while they are connected and then remove?
with thee lines plugged should the idle change as the distributor is rotated? If so rotate it till it is 7.5 degrees BTDC and then lower the idle with the idle adjustment screw?
What are the rest of the engine specs?
You may find drilling a 1/8" hole in the throttle plate will help. There are times when the engine moves more air at idle than the stock idle bypass screw will allow for.
2.0 Heads were done by Len Hoffman
CR 8.56:1
Full Raby valve train kit
Stock L-jet throttle body, air cleaner, and intake runners
stock 2.0 heat exchangers
pertronix ignition
Anything else that I am not listing?
Sounds like you are doing the timing properly.
With L-jet, the idle speed lowers if there is a vacuum leak, and the car will not start at all if there is a leak to large.
With D-jet, the idle speed will increase with an air leak, same as with carbs.
Before you go and modify things, check everywhere for leaks, again.
It amazes me how I miss leaks the first five times I look for them....
Typically I find all the leaks the last time I look for them.
If its that lean, there has to be a leak...if you add a hole, that will just add air...is your idle stop screw set right?
Valve adjustment will make a big impact to the idle...ask me how I know...
What is the right setting for the idle screw? Is I back it out all the way it doesn't really change the idle much.
I took an extra TB and drilled an 1/8" hole and had noticeable improvement. I could actually get the idle to change a little with the screw, particularly after it was warmed up.
I guess I can always go back and check the valve adjustment just to see if it makes a difference.
on the other hand, if it works.......
Have you read up on how to tune L-jet?
Are you familiar with the bypass screw on the air flow meter?
Have you tried adjusting it?
Its doubtful that drilling a hole in the throttle plate will improve the function of your system.
The idle is so low because there isn't enough fuel for the amount of air getting in the engine.
hmmm.. this would explain why I have to use the throttle stop to get the idle I want...the bypass screws don't do much if anything.
I don't pull a very large vacuum at idle..but can get a pretty decent 800 rpm..
got it! thanks!
I read the article online about tuning L-jet which has been very helpful.
I richened the mixture up all the way and the engine still would not idle. So I tried the hole in the throttle plate and I am much closer to getting numbers that are more in line with where the mixture should be.
The article stated to move the static mixture till you got idle close I couldn't even get close. the mixture screw on the meter is only supposed to be used to fine to mixture at idle
right now my numbers are:
Accel - 12.4-13.7
WOT - 12.1-12.7
Cruise - 12.6-13 Too rich I know
Idle 12-14 I am still having some fluctuation in the idle and it not coming down after driving
So do I lean it out more to bring the cruise mixture down and then richen up the dynamic to keep the other numbers where they are?
Jake,
I have the timing set at 7.5 BTDC@800rpm now
you mentioned timing in your last post, Is there more I need to do with this?
I have a 9550 cam, with Ljet. Whereabouts might this hole get drilled? I'm chasing my last (hopefully) vacuum leak this evening, and depending on how that affects things, I may need to try the drill my idle still hunts at temp.
I drilled mine in the center just to one side of the shaft. not sure if that was the best location or not.
I drilled mine in the center just to one side of the shaft. not sure if that was the best location or not.
Thanks Jake
would full advance be around 3500 rpm?
Ok I went back and set the timing at full advance 28 degrees BTDC
I am still fighting the idle.
When first started it idles low
As it warms up it rises to 800 rpm
Once it is reved it idles at 1800 rpm
If I turn the bypass screw in I can lower it but as soon as I rev the engine it climbs back to 1800 rpm
If I try to pull it down by placing a load on the engine it will drop but as soon as the load is gone it climbs right back up.
Acts as if the vacuum retard isn't working. I checked the diaphragm and it was good.
Idle mixture @ 800 rpm is 19.6 - 20.7
when it idles at 1800 rpm mixture is 13.1-14
any more ideas of what to look for?
Yes I drilled the throttle plate and it is much better but now the idle behaves as mentioned in the last post. What is making it keep going to 1800 rpm?
My mixture numbers are running like this:
Idle 1800 rpm 13.1 - 14
Idle 800 rpm 19.6 - 20.7
Accel. 13.1 - 13.7
WOT 12.3 - 12.7
Cruise 13.1 - 13.8
From what I have read the accel. and WOT are pretty close to the correct range, Cruise is way too rich
Any suggestions (Richen the Static and lean out the Dynamic?)
Can you get a an adjustable fuel pressure regulator for L-Jet? Can one form D-jet with the adjustable screw be used?
It is now climbing to 1800 RPM because the additional air leaned out the idle. Lean engines idle high and won't settle when you toss them a rev.
An AFR meter is fairly worthless at idle, because the exhaust pulses are too slow and because of reversion in the exhaust system. Make the engine happy at idle, give it what it wants- it probably wants to be a lot fatter than it is now.
ok so I finally had a chance to get back to working on the car.
I richened the L-jet by moving the static mixture adjustment 1 tooth richer and leaned out the dynamic mixture by 3 teeth.
The idle is starting to come down but everything else is too rich so i tried 3 more teeth leaner on the dynamic. I believe this is inducing another problem by relieving spring tension on the barn door it is allowing the wiper to swing past the potentiometer and then the engine cuts out till it comes back onto the potentiometer.
Also the accel. and WOT numbers are still too rich.
So I seem to be stuck by not being able to get the idle mixture rich enough without making all the mixture too rich. The idle mixture screw on the meter does help a little but not enough to get it where ti needs to be.
Is there something else I can do?
Will changing the advance on the timing have an effect on mixture? particularly at WOT and accel.?
Is there any benefit at looking into changing fuel pressure and or adding a resistor to the CHT circuit(or is that only applicable on D-jet)? to change the mixture
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