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914World.com _ 914World Garage _ Which way to turn

Posted by: KaptKaos Apr 9 2005, 03:11 PM

Stock 73, 1.7 with FI. Seems to be running a little lean. Which way do I turn the knob on the brain to make it run a little richer? I certainly do not want to over do this, just a slight adjustment, so how far should I turn it?

Thanks,
Joe

Posted by: scott thacher Apr 9 2005, 03:22 PM

the ecu knob only does idle, if you want it richer across the whole range put a 100 ohm resistor in line with the cht

Posted by: anthony Apr 9 2005, 04:42 PM

How are you determining that it is running lean?

Posted by: Bleyseng Apr 9 2005, 05:02 PM

I am wondering too???

This I wanna hear..

Posted by: mike_the_man Apr 9 2005, 05:13 PM

Right is richer, left is leaner. But listen to all the other guys first. How do you know it's lean, and know that turning the knob on the ECU only adjusts idle mixture.

Posted by: Aaron Cox Apr 9 2005, 06:51 PM

im sure he has a wide band O2 sensor right joe?

Posted by: KaptKaos Apr 9 2005, 07:03 PM

QUOTE (Aaron Cox @ Apr 9 2005, 04:51 PM)
im sure he has a wide band O2 sensor right joe?

/whap

No Aaron, I don't have an O2 sensor. I'll tell you what you can stick in my tail pipe.... ah, nevermind.

Anyway, getting a little backfiring when cold. Cold start injector is not connected, so its not surprising. Just starting to a very infrequent hesitation at speed. Went to go pull the plugs today to look for signs there, but the kids got into the way.

FYI - I generally do not go off half-cocked and start playing with stuff. My general process is to gather as much info as I can. This way I am fully cocked before I screw it up.

Posted by: anthony Apr 9 2005, 08:31 PM

QUOTE
Just starting to a very infrequent hesitation at speed.

Around 3,000 rpms when crusing? Most likely culprit is the TPS if it hasn't been swapped out in a million years.

Posted by: vsg914 Apr 9 2005, 08:39 PM

QUOTE (anthony @ Apr 9 2005, 08:31 PM)

QUOTE
Just starting to a very infrequent hesitation at speed.

Around 3,000 rpms when crusing? Most likely culprit is the TPS if it hasn't been swapped out in a million years.

What he said. Worn Tps cuts off the fuel for a split second. Brad Anders says that is the only thing that will cause "bucking" at cruising speeds. My limited experience agrees with him. Unplug it and see if it goes away. It won't idle very well, and it won't accelerate very well, but it will cruise perfectly.

Posted by: KaptKaos Apr 9 2005, 09:27 PM

Doh!

Forgot one more symptom. After running for a while, if I come to a stop, the car will really bog down in first. Almost like it is going to stall. Once it gets about 1800-1900 RPM it goes just fine. Still the throttle switch?

Posted by: trekkor Apr 9 2005, 09:46 PM

Check fuel pressure.

Increase to enrichen.

KT

Posted by: double-a Apr 9 2005, 11:10 PM

my car is doing this, 1.8 liter l-jet engine, does the same random "hesitation" or "bucking" at speed. it's been driving me nuts.

what's a tps???

~a

Posted by: vsg914 Apr 10 2005, 08:37 AM

Tps= throttle positioning switch. I know nothing about the L jet, so don't know if you have one or not.

Posted by: double-a Apr 10 2005, 10:33 PM

yup, got a tps. i pulled it and cleaned it, car still stutters a little.

~a

Posted by: swood Apr 10 2005, 10:51 PM

Small Vacuum leak? That'll cause a lot of problems too.

Do you have all the L-Jet manuals? There are numerous ones available.

Posted by: scott thacher Apr 10 2005, 11:18 PM

on a l jet a stutter can be 2 things, one the dizzy is not adavncing right or its sticking. i would pull it clean it and make sure you set the timing right. the second thing is the flapper has a varible resistor in it. you should pull it and hook up an ohm meter to it and push it through its range to see if it has a worn spot.

while you are in there you should check the fuel pressure, on a l jet it changes with vacumn. it could be the fuel pressure not doing what it should.

Posted by: Cap'n Krusty Apr 10 2005, 11:31 PM

QUOTE (KaptKaos @ Apr 9 2005, 05:03 PM)

Anyway, getting a little backfiring when cold. Cold start injector is not connected, so its not surprising.

You misunderstand the function and operation of the cold start valve. It has to be REALLY cold, and it ONLY operates when the starter is engaged. You're NOT gonna get backfiring because of the CSV. The Cap'n