Author Topic: How to obtain the smoothest idle?  (Read 4233 times)

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Offline SuperSix

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How to obtain the smoothest idle?
« on: June 13 2009, 08:19:58 AM »
Seems like all the TR's I have had had very lopey idles, is this inherent to the engine design?

What can be done to these to get the smoothest idle?
'87 GN, 60lb, TA49, THDP, FTP cam, T+ lots o' shit - SOLD
'07 Ford F150 Lariat 2WD, 5.4L 3v - 255k
'20 Kubota BX2380. FEL, 60" deck
'78 IH/Case 184 Lo-Boy
'99 Kawasaki Bayou 400 4x4

Offline ULYCYC

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Re: How to obtain the smoothest idle?
« Reply #1 on: June 13 2009, 09:03:52 AM »
Stock V6's are balanced to allow the vibration to exit at the soft motor mount. When you build a fresh motor and have it rebalanced most shops use a formula (50%) that sets a vertical imbalance instead of the stock 36.6 horizontal. Not much you can do about this since you are trading off on up and down or side by side engine imbalance. The short answer is make the fueling a little richer at idle and open the plug gap. :rolleyes:   Also check the basics like a vacuum leak, bad plug wires, worn plugs, bad maf and the other usual issues
ED BAKER
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Offline Steve Wood

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Re: How to obtain the smoothest idle?
« Reply #2 on: June 13 2009, 10:07:45 AM »
I guess I have been driving them too long with too many different combinations because I don't seem to notice it anymore once the car is warmed up. :)

Modern chips from Turbotweak or Bob Bailey seem to have improved the idle as far as my experience goes.  They run open loop, or quasi open loop, at idle and this allows a richer air/fuel which makes a big difference if everything else is in good order.

One thing that often happens on cars with older injectors is that they may get some deposits on the tips, or gum build up, and they don't spray correctly, or uniformly.  Given the very small duration of the pulsewidths at idle, this can be very noticeable at idle, but, not so much during normal driving.  Removing and cleaning the injectors will usually make a difference, but, on a very old injector, it is probably better longer term to buy new injectors.

Our cars control the idle air with a solenoid (IAC) that is pulsed by the ecm.  The lower the iac counts, the less input the ecm has on the process.  Sometimes, reducing this number will smooth an idle somewhat as the engine is not reacting as much to perceived load.

If you are not familar with the process, you might read the tps and iac adjustment sections of this page on my site  and see what happens

http://www.vortexbuicks-etc.com/tuning.htm

And as Ed stated...all the basics, leaks, etc.... :)
Steve Wood

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A lot of broken parts does not make you a racer; it makes you a slow learner.

Offline SuperSix

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Re: How to obtain the smoothest idle?
« Reply #3 on: June 13 2009, 10:12:03 AM »
Nice - thanks. Seems like the usual culprits.

Is it a given that the #3 cam lobe will wipe eventually? My TR has 130k on it.
'87 GN, 60lb, TA49, THDP, FTP cam, T+ lots o' shit - SOLD
'07 Ford F150 Lariat 2WD, 5.4L 3v - 255k
'20 Kubota BX2380. FEL, 60" deck
'78 IH/Case 184 Lo-Boy
'99 Kawasaki Bayou 400 4x4

Offline Steve Wood

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Re: How to obtain the smoothest idle?
« Reply #4 on: June 13 2009, 10:17:02 AM »
I had one with 210,000 miles on it for a short time...it had not failed at that time.

My experience is that if they are installed correctly, they don't fail.
Steve Wood

http://www.vortexbuicks-etc.com

A lot of broken parts does not make you a racer; it makes you a slow learner.

Offline Recklessrob

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Re: How to obtain the smoothest idle?
« Reply #5 on: July 08 2009, 05:29:22 AM »
The cam in my 170k engine is still good as well. I don't belive the
stock cam had that problem. I think that was only the early flat tappet aftermarket cams.
Rob

Offline SuperSix

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How to obtain the smoothest idle?
« Reply #6 on: July 08 2009, 09:02:10 PM »
Is it worth getting a measuring tool and checking the lift?
'87 GN, 60lb, TA49, THDP, FTP cam, T+ lots o' shit - SOLD
'07 Ford F150 Lariat 2WD, 5.4L 3v - 255k
'20 Kubota BX2380. FEL, 60" deck
'78 IH/Case 184 Lo-Boy
'99 Kawasaki Bayou 400 4x4

Offline Steve Wood

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How to obtain the smoothest idle?
« Reply #7 on: July 08 2009, 09:19:29 PM »
no...look at the base of each lifter...if none are scrubbed off, there is no significant damage to the lobe

Lifters are convex to begin with....it will be obvious if anything has been eaten away
Steve Wood

http://www.vortexbuicks-etc.com

A lot of broken parts does not make you a racer; it makes you a slow learner.

 

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