 D-jet idle and lean issues. |
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| Literati914 |
 Jun 27 2025, 09:41 AM
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Senior Member  Group: Members Posts: 1,983 Joined: 16-November 06 From: Dallas, TX Member No.: 7,222 Region Association: Southwest Region  |
1.7 w/ original D-jet.
I have the idle screw on the TB cranked all the way down/closed (which doesn't seem right tbh) and the car's idleing around 900rpm - which is within the recommended 850+/- , and the idle does not really "surge" too much but is not necessarily rock steady either. I'm also getting a steady 16.5 A/F on my gauge during idle and warm driving. So too lean. BTW, the CHT gauge has never gotten over 300 so it's not trying to over heat. I'll be spraying the vacuum connections to see if I can find leaks - but other than that, what would be the most obvious culprit(s)? My theory is that the idle screw needing to be closed (for a reasonable idle) is just combating say, a bad AAR or something. Sound logical? What tests can I do to the AAR or other items to look at first? |
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| Ishley |
Jun 27 2025, 04:09 PM
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Member Group: Members Posts: 219 Joined: 4-October 21 From: Clarendon Hills Il Member No.: 25,957 Region Association: Upper MidWest 
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My ‘72 has the idle mixture knob on the ECU.
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| emerygt350 |
Jun 27 2025, 04:14 PM
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Advanced Member Group: Members Posts: 2,979 Joined: 20-July 21 From: Upstate, NY Member No.: 25,740 Region Association: North East States |
QUOTE(Ishley @ Jun 27 2025, 04:09 PM)  My ‘72 has the idle mixture knob on the ECU. Well, you could richen it with that. I suspect as the engine ages it probably has different requirements from when it left the factory. Have you tried some PEA fuel system cleaner? Like the 10$ gumout stuff? Maybe your injectors are getting gummy. A lean mix is gonna play havoc with idle, could be as simple as a bad tank of gas.... |
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Posts in this topic
Literati914 D-jet idle and lean issues. Jun 27 2025, 09:41 AM
ctc911ctc I vote:
Vacuum leak throttle body and Plenum
Go... Jun 27 2025, 12:58 PM rjames You may have a vacuum leak, but it sounds like you... Jun 27 2025, 01:56 PM emerygt350 Mixture is unaffected by leaks. Idle rpm is. I a... Jun 27 2025, 02:29 PM Literati914
My ‘72 has the idle mixture knob on the ECU.
... Jun 27 2025, 05:38 PM Literati914 You guys asked if this condition just started - we... Jun 27 2025, 05:54 PM
rjames
You guys asked if this condition just started - w... Jun 27 2025, 06:17 PM Ishley My 72 ECU knob does nothing. I have an Air fuel ga... Jun 27 2025, 05:58 PM JeffBowlsby A reminder that the ECU idle mixture knob is only ... Jun 27 2025, 06:40 PM Literati914
Did restoring it include a motor rebuild or a new... Jun 27 2025, 08:02 PM emerygt350 What Jeff said. That is a good sign that your TPS ... Jun 27 2025, 08:06 PM Literati914
A reminder that the ECU idle mixture knob is only... Jun 27 2025, 08:18 PM Literati914
A reminder that the ECU idle mixture knob is only... Jun 27 2025, 08:20 PM brant 16.5 at all conditions seems wrong
Idle mixture d... Jun 27 2025, 08:21 PM emerygt350 Did you set the TPS according to the instructions?... Jun 28 2025, 05:26 AM JeffBowlsby That TPS board is worn out, should be replaced. Jun 28 2025, 08:13 AM Ishley You might want to try a new O2 sensor. I’ve have... Jun 28 2025, 10:45 AM emerygt350 I have been using disposable Amazon o2 sensors. 29... Jun 28 2025, 02:07 PM Literati914 Yes the MPS still has original rivets and opeque p... Jun 28 2025, 08:00 PM JeffBowlsby TPS calibration method 1.7L if you don’t have it... Jun 28 2025, 08:58 PM emerygt350 These cars will do fine without the TPS so it can ... Jun 29 2025, 04:02 AM Literati914 Yea I think I actually have two separate issues go... Jun 29 2025, 11:49 AM |
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