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Author Topic: stalling at idle  (Read 493 times)

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Offline chriss

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stalling at idle
« on: July 14, 2021, 10:08:31 PM »
I have a '71  2000cc automatic.  I had the engine rebuilt a few years ago and then about 2 years ago I had the carburetor rebuilt. After I had the engine rebuilt, the installer thought the lifters or followers were a little noisy, so I had them adjust the valves and they were to specs. after a 300 mile round trip to a car show two years ago i noticed that when coming to a stop sign, the car would die. a friend of mine checked it out, the timing marks and so on, but still came up with a stall at idle. the points, plugs , fuel pump were all new when the engine was rebuilt, he did find the decelaration valve had a tear, so I replaced that. so the same car show trip 300 mile round trip  last weekend, when I left it still won't idle at a stop sign, but runs down the road ok. by the time I get it back it can barely run, it feels like a sticking choke, but they are open. also the car had pretty much no power, I know the 4 cyl is not like a modern 4 cyl. but it should have a little more power than it has. has  anyone have any ideas?
1971 Pinto sedan 2000cc      1969 Plymouth Satellite 4dr slant 6  69k miles      1980 Olds 442  1 of 886.     1992  Mustang LX 5.0 convertible, 1987 Camaro convertible 1 of 263. 1995 Z28 convertible 21k original owner . 2008 Silverado. 2016  Camry  s/e

Offline PintoTim2

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Re: stalling at idle
« Reply #1 on: July 15, 2021, 09:05:00 AM »
The 2.0L OHC is not underpowered.  You've got 122hp stock which is pretty darn good for an older non-turbo.  The C3 auto will diminish your acceleration, but shouldn't matter at idle.    Can you determine if it's rich or lean at idle?   When it stalls, does it restart without pumping the gas (ie- it stalled rich) or does it need more fuel to light off (ie pumping the pedal to get the accelerator pump to add fuel - that'd be lean).  Too little timing at idle would give you a very low idle RPM as would a throttle stop that is too low.  What is the engine idling at?  If you shift into neutral, does that help (ie- the trans is adding drag to the engine).    Back in the day - 1980ish (showing my age...) my Dad's '72 2.0L had a carb float that saturated with fuel & ran it very rich (lousy fuel economy too).   It had a composite float.  A switch to a brass float cured that. 

Offline Wittsend

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Re: stalling at idle
« Reply #2 on: July 15, 2021, 11:35:07 AM »
Start with a tach and vacuum gage and see what it is reading. To me it seems you have an air leak somewhere or the idle is adjusted too low. As PintoTim2 stated above it can be many things (and more than his list).

1. Make sure the timing is correct.

2. Feel/listen around vacuum lines, gaskets etc., anywhere air can leak. If there are leaks they must be fixed before the idle can be set.

3. Set idle - ensuring the car is up to operating temperature and ensure the choke has pulled all the way off.

I don't know much about the Decel valve other than people often removed it as it was a problem.

Engine valves that are adjusted too tight will lower compression/power and have the potential to burn valves because they do not seat properly and heat is not removed. When I got my '73 with the 2.0 some of the valves had zero clearance. Simply adjusting them brought compression on some cylinders up from 60 PSI to over 100 PSI.  The goal of proper valve adjustment is to ensure the valve fully closes which requires a gap between the rocker arm and the cam lobe. But the gap needs to be small enough that the lobe doesn't "slap" the rocker arm and make excessive noise. I mention this because as worded you seem to have experienced the idle problem after the valve adjustment and the 300 mile trip.

Lastly, my '73 had the C-4 automatic. Compared to a modern economy car it was pretty gutless. The 2.0 was 122 cubic inches, - not horsepower.  The factory rating was about 100 gross HP but that was the old version of rating horsepower. By the standard that has existed since 1972 (net rating) the factory rated the 2.0 at 86 horsepower. More importantly the HP was higher up in the RPM range. Thus down in the lower RPM the torque was less.