914World.com [Powered by Invision Power Board]

Posted by: tracks914 May 17 2010, 08:31 PM

'75 2.0 mostly original, new injectors, runs good except on deceleration. If I take my foot off the gas it's like putting on the brakes.
Back when I used to race I liked a car that would engine brake for me but driving (cruising) around town I would like something a little mellower. Is there anything I can do to smooth out the deceleration?
Tx
Doug

Posted by: mtndawg May 18 2010, 10:18 AM

Is the deceleration valve connected? It should be near the battery with 3 hoses connected...
http://members.rennlist.com/pbanders/decel.jpg

Attached image(s)

Posted by: SirAndy May 18 2010, 11:38 AM

QUOTE(mtndawg @ May 18 2010, 09:18 AM)

Is the deceleration valve connected? It should be near the battery with 3 hoses connected...

I disconnected the decel valve on my old 1.7L on purpose and the engine behaved exactly as you describe ...

Andy

Posted by: Bleyseng May 18 2010, 02:40 PM

On a 75 the ECU has the fuel shutoff when you life the throttle until 1500 rpms when it kicks the gas on again...you can get good mpg with this setup. As noted have the decel valve hooked up to smooth out the transision.

Posted by: tracks914 May 18 2010, 08:31 PM

QUOTE(Bleyseng @ May 18 2010, 12:40 PM)

On a 75 the ECU has the fuel shutoff when you life the throttle until 1500 rpms when it kicks the gas on again...you can get good mpg with this setup. As noted have the decel valve hooked up to smooth out the transision.

When decelerating the car does burp a burst of gas when I hit about 1800 rpm. Can I override this feature?
The decel valve is hooked up but it might not be working right.

Posted by: Bleyseng May 19 2010, 05:27 AM

no, unless you can rewire a circuit board. Change to a 044 ECU and it will go away along with a few mpg.

Posted by: tracks914 May 19 2010, 07:50 PM

QUOTE(Bleyseng @ May 19 2010, 03:27 AM)

no, unless you can rewire a circuit board. Change to a 044 ECU and it will go away along with a few mpg.

044 ECU - what does that come off of? I have a couple of 1.7 ECU's????

Posted by: kwales May 19 2010, 08:52 PM

A lightened flywheel will have that same symptom.

Got one of those???

Posted by: tod914 May 19 2010, 10:30 PM

You can adjust your decel valve too. I played around with it for a while and the car seems to like it best when its set around 12-14 pounds of pressure. You can set the pressure value with a mitivac. You loosen the nut on the small end so you can adjust the pressure as to where it releases. Attach the mitivac to the center post i believe (been a while), pump it and you'll see where the diaphram opens and the pressure releases. Adjust the small end till you get it where you want it.

Posted by: tracks914 May 27 2010, 08:22 PM

12-14 pounds of pressure or inches of vacuum?

Posted by: tod914 May 27 2010, 09:02 PM

12-14 lbs. on the meter reading of the gauge. You don't have to have a gauge to adjust it, just helps set a base line. I believe screwing the small outlet - out decreases the pressure. Inversly screwing it in will increase. Try turning yours inward a few full turns and see if that makes any difference. Can always back it out. I take it your dwell and timing is good?

Printable Version of Topic

Click here to view this topic in its original format

914World.com _ 914World Garage _ F.I. Question - Decelation