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Registered User
Join Date: May 1999
Location: Signal Mtn., TN
Posts: 43
Question Rough and missing on cold morning start!?

It's a '74 2.0 D Jet. On two separate runs (+ or - 200 miles each way), one last fall and then again this week, I have experienced rough running and cutting out. This happened immediately after startup in the morning. It smoothed out in about four or five minutes, but was unsettling as I was 150 miles from home. As it stays in the garage thru the winter, these are the only times I can remember starting it up after it stayed outside in the cold (around freezing). What's going on here? Is there any history of this. Help?!
Old 10-29-2001, 06:26 PM
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Registered User
Join Date: Jun 2001
Location: Ellicott City, MD, USA
Posts: 99

When I got my car, most of the hoses were off and lying in the engine bay, so I learned a lot from this web forum and have experienced some similar problems. So, here's my $0.02...

1. There is an auxuiliary air valve (AAV) on the drivers side of the engine bay, below the airbox and near the oil filler. The inlet hose runs from the airbox, to the AAV and then through another hose into the air distribution box (drivers side) and into/around the cold start valve (cold start injector). The cold start injector will generally only work for one blast when the engine is below 30 degrees or so. The AAV is electrically heated and it rotates to close a pass-through hole as the engine warms. Typical heat and close times are @ 5 minutes from cold.

a. Is it wired up and working. Try a voltage test with a Digital Multimeter (DMM)on the wire connection when started.

b. Is it working -- Remove the AAV and apply 12V from two jumper wires. The unit should heat and the internal valve should turn after several minutes.


Start the engine and put your finger over the airbox hose end. You should feel suction. If no suction, then is it electrical or is the valve stuck or is the hose off or is the hose leaking air? These valves are NLA, so you will need to pry your open or find a working used unit if it is frozen closed. If you let the engine and AAV warm-up, the suction will decrease and then stop (again @ 5 minutes from cold).

2. Engine Tin Flaps may be stuck in the open position from a broken engine tin cable from the thermostat. These flaps are spring loaded in the open position, which would slow warming on a cold day. See recent posts for the excellent feedback from this board on that subject.

3. My tune-up work and vacuum leaks waere all done with new parts, but I fixed it too well. After getting the injectors and vacuum lines renewed, my car had a terrible warm-up stumble. The problem turned out to be the expensive and sometimes tweaked Manifold Pressure Sensor (MPS). My MPS was tweaked by the PO and it is the wrong part number, so I was able to turn the screw where the MPS plug should be. A simple 1/4 turn richer and I was fine. But if your MPS is the correct number and not tweaked, then look elsewhere...

a. Does the MPS hold vacuum pressure
b. Does the MPS have the correct OHM readings from the electrical plugs

4. Do you have any vacuum leaks? Try some starter fluid sprayed on the manifolds, the air intake gaskets, the throttle body, the AAV, etc. If it speeds up, you've got a leak.

5. Finally, check out Paul Anders AWESOME D-Jet page at

Good Luck,
Old 10-30-2001, 08:24 AM
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Registered User
Join Date: May 1999
Location: Signal Mtn., TN
Posts: 43

Thanks retro 74.
That's what I thought, too.


PS...No, really that was about as complete an answer as I have ever heard on any subjet. Many thanks. I now have a place to start. I was the guy who asked about the broken thermostat. I think I'll fix that first and go from there (though maybe a quick and thorough look at the hoses would be a great idea.) Thanks again retro 74.
Old 11-02-2001, 05:15 AM
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