 F.I. Question - Decelation, It's like shutting off the engine |
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| tracks914 |
 May 17 2010, 08:31 PM
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#1
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Canadian Member  Group: Benefactors Posts: 2,083 Joined: 15-January 03 From: Timmins, Ontario, Canada Member No.: 153 Region Association: None   |
'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 |
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| mtndawg |
May 18 2010, 10:18 AM
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#2
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Member Group: Members Posts: 414 Joined: 26-January 09 From: Granite Bay, Ca Member No.: 9,985 Region Association: None 
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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) 
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| SirAndy |
May 18 2010, 11:38 AM
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#3
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Resident German Group: Admin Posts: 41,641 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(mtndawg @ May 18 2010, 09:18 AM)  Is the deceleration valve connected? It should be near the battery with 3 hoses connected... (IMG:style_emoticons/default/agree.gif) I disconnected the decel valve on my old 1.7L on purpose and the engine behaved exactly as you describe ... (IMG:style_emoticons/default/shades.gif) Andy |
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| Bleyseng |
May 18 2010, 02:40 PM
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#4
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Aircooled Baby! Group: Members Posts: 13,034 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
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.
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| tracks914 |
May 18 2010, 08:31 PM
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#5
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Canadian Member Group: Benefactors Posts: 2,083 Joined: 15-January 03 From: Timmins, Ontario, Canada Member No.: 153 Region Association: None |
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. |
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| Bleyseng |
May 19 2010, 05:27 AM
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#6
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Aircooled Baby! Group: Members Posts: 13,034 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
no, unless you can rewire a circuit board. Change to a 044 ECU and it will go away along with a few mpg.
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| tracks914 |
May 19 2010, 07:50 PM
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#7
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Canadian Member Group: Benefactors Posts: 2,083 Joined: 15-January 03 From: Timmins, Ontario, Canada Member No.: 153 Region Association: None |
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???? (IMG:style_emoticons/default/confused24.gif) |
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| Katmanken |
May 19 2010, 08:52 PM
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#8
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You haven't seen me if anybody asks... Group: Members Posts: 4,738 Joined: 14-June 03 From: USA Member No.: 819 Region Association: Upper MidWest |
A lightened flywheel will have that same symptom.
Got one of those??? |
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| tod914 |
May 19 2010, 10:30 PM
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#9
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Advanced Member Group: Members Posts: 3,755 Joined: 19-January 03 From: Lincoln Park, NJ Member No.: 170 |
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.
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| tracks914 |
May 27 2010, 08:22 PM
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#10
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Canadian Member Group: Benefactors Posts: 2,083 Joined: 15-January 03 From: Timmins, Ontario, Canada Member No.: 153 Region Association: None |
12-14 pounds of pressure or inches of vacuum?
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| tod914 |
May 27 2010, 09:02 PM
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#11
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Advanced Member Group: Members Posts: 3,755 Joined: 19-January 03 From: Lincoln Park, NJ Member No.: 170 |
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?
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