91 civic stall on hot engine

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  #1  
Old 04-06-10, 05:58 PM
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91 civic stall on hot engine

howdy
91 civic dpfi engine. 1.5l
starts and drives fine.
on hot engine, will start and stall; give it 10 seconds, will start and run fine.
here's the thing though:
new main relay and new distributor. thus, ignitor is new. main relay clicks just fine, the way it is supposed to.
the rest of it is, pretty much, new either. wires, plugs, etc. idle is nice and stable. idle air valve cleaned few mths ago. coolant level good.
last job done - injectors pulled out and cleaned overnight in cleaner. were not even that dirty.
slight pressure on gas pedal, for hot starts, takes care of this stalling perfectly. engine starts right away and runs fine.
any ideas? by the book, it's either relay or ignitor - except they are new.
no warning lights, CEL, or such. drives fine. no smokes, slight oil sipping (190 000 miles) from engine head gasket, planned to be replaced in may.
 
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Old 04-06-10, 07:41 PM
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sounds like might be a case of vapor lock, what does the fuel pressure do when this occurs,

a lot of the new formulations for fuel are prone to vapor lock again even with a pressurized fuel system,

murphy was an optimist,
 
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Old 04-06-10, 08:42 PM
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donno what fuel pressure does, too complicated for me to check. it's not a big deal, as far as i have gas pedal pressed, it starts fine.
feels like it wants just a ted bit more of throttle opened while on hot engine start. pumping pedal several times and starting just from the key does not help, i tried that. K&N air filter, so air is going through fine.
maybe it is vapor lock. with engine cool or cold - none of this issue. fuel system is clean, i ran about dozen of STP gas treatments through it when i was resurrecting her. was female student car for a while.
 
  #4  
Old 04-07-10, 09:09 AM
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I've seen vehicles which have been modified like with a different air filter or whatever and this causes problems.

So the question is: Was the air filter modified a long time ago and has it been running fine for a long time with that? (A full year of hot and cold weather driving conditions.)

The air flow is an exact thing measured by the engine computer. If you change the air flow, the engine computer air sensors (MAF, air temp) could be getting wrong information.

Then other than that, the thing to do would be to "catch it in the act". This will be difficult because the problem does not hang around long.

If you have an old timing light, you could place the pickup on a spark plug wire (if you have spark plug wires) and during those 10 seconds of it not starting, see if it is getting spark or not.

Another thing is if it was running fine, then new parts were installed and the problem started. Try replacing those parts again or reinstalling the old parts and see if the problem goes away. Do this one part at a time so you can see which part is causing the problem.
 
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Old 04-07-10, 06:39 PM
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i think i have it figured.
rule of the thumb is - look at the last job done. injectors were cleaned. of course, i did not replace O-rings, as the "looked fine".
well, when she was "not starting" today, she did it plain as a flooded engine does.
which got me thinking.
got that feeling, i have O-rings not quite tight now, with somewhat leaky seal. thus, on a hot engine, slight fuel leak into the intake causes "flooded" condition or, maybe, that vapor lock. piece of cake, will have rings replaced saturday.
and no, air filter/flow was not modified. it is regular high air flow k&n in stock box. she's been running on it well for over a year.
problem coincides exactly with injectors cleaning. right after.
thanks to all for input.
 
  #6  
Old 04-07-10, 07:13 PM
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pumping pedal does nothing on a fuel injected car, no accelerator pump to move. if the key is on, pumping the pedal might actually cause a lean start because on some it signals the computer the engine is flooded.

why is it called the fast lane if we're not supposed to speed?
 
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