73 2.0 Hesitates when cold.. Options

[schmidder]

Not a fuel injection expert at all. I have done some research and have read quite a bit, have a specific issue I am having, wondering if folks would point me in the right direction as to what might be the issue with the following symptoms:

1973 Fuel Injected 2.0
Car runs great once the motor is warm
At start up, will hunt for idle, but not always. If it hunts, goes up to 1300 and down to 200. ( live in Nor Cal, so cold means 50 to 75F)
If I don't let the car idle and warm for 5+ minutes, even on a 90F day, when I go to drive, it hesitates badly between 2-3000 RPM and sometimes will just die
Will start back up just fine and once warm, issue goes away
Car will also hesitate if I am in cruising at 3k rpm, take my foot off and then back on, this will happen warm or cold.
Gas mileage is good, otherwise car runs terrific, good power.

I don't mind letting the car warm up and am not looking to just jump in a take off and hammer, just wondering if this is a common issue.

Thanks for your help in advance...

Erik

[JawjaPorsche]

Not expert at all but could be temperature head sensor.

[TravisNeff]

Hunting is most likely from an air intake leak, the hesitation could be from a sticking distributor advance mechanism.

[GregAmy]

As noted above, idle hunting is a symptom of a lean air/fuel mixture. That will be exacerbated when cold and less noticeable when warm. Some possible causes:

- Vacuum leaks
- Head temp sensor
- Bum MPS diaphragm
- Among others...

Vac leaks are the easiest to check for using soap, glass cleaner, judicious use of brake cleaner. You can also measure the resistance of the HT sensor both hot and cold. Here's a link to a discussion regarding the '73 vs 74 sensors:

http://www.914world.com/bbs2/index.php?showtopic=84409#

Bum MPS diaphragm isn't as easy. You can see if it holds a vacuum with a Mity-Vac (or the old suck-and-tongue method) but that's not always a guarantee; mine held a vac fine but it was still cracked and didn't work well.

Start with those, see how far you get.

[JeffBowlsby]

Lets put this myth to bed.

Using your mouth to suck on an MPS does not tell tell you anything unless there is no vacuum at all (meaning the diaphragm is complete useless).

Try sucking on a mityvac and see what the gauge says. You will be surprised at how little vacuum your lungs can create, and at that level of vacuum one cannot perceive if there is a leak at all.

Report back if you find out otherwise.

[GregAmy]

Report back if you find out otherwise.

Was that for me, Jeff? I tried the quick-and-dirty suck-and tongue method; it was "ok". I then put a Mity-Vac on my MPS; it held a vacuum fine for around 20 minutes (about how long it took me to casually finish my beer). Chris Foley said my symptoms pointed right to a mad MPs so I had him pull it apart: the diaphragm was cracked and not functioning properly.

So even a Mity-Vac is not a final answer...

(IMG:style_emoticons/default/beerchug.gif)

- GA