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99 Civic won't idle


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On my way home from work a few days ago, I came to a stop sign (luckily right in front of my house), put the clutch in, and the car died. Started right back up, and died. It runs with my foot on the gas, but it just immediately dies when not on the throttle.

 

I thought at the time that it was probably an Idle Air Control Valve problem that is common in this gen civic, so I took it out, cleaned it and put it back with no change. After doing that, I started it and kept it running for 15 seconds or so (by revving the engine) and notice that the crack in my exhaust manifold (that has always been there) had gas spewing out of it. Like, a pretty good amount of gas.

 

So, my new theory would be that for some reason a ton of gas is dumping in, and the engine can't idle. But when I am revving, it lets enough air in to keep the engine running (albeit very rich).

 

Things I've checked...

- No CE code being thrown

- TPS signal is good and isn't stuck at WOT

- Pulling the MAP connector doesn't change anything

 

I thought about a stuck injector... but it seems like that would just cause 1 cylinder to miss, and not kill the entire engine. If the fuel is coming from the injectors, it is all 4 injectors going crazy at once. And wouldn't that throw a CE code?

 

Another theory was that the Fuel Pressure Regulator diaphragm has failed and is pushing gas through the vacuum tube, into the intake manifold, and into the cylinders. That would seem to make a lot of sense, why the ECU doesn't know that it's happening... but I pulled that vac hose and can't find any traces of fuel.

 

So... I am at a loss. Any other ideas? If I can't diagnose anything by tomorrow, I guess I'll just start throwing parts at it... probably starting with a new FPR and going from there...

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There is some good info here:

 

http://www.justanswer.com/honda/702ro-honda-civic-ex-1999-civic-d16y8-fuel.html

 

It won't throw a code because I believe the ECU is seeing normal readings that require a ton of fuel to be sent to the engine. Could be your TPS; check to see it's reading 0.5V at idle (it'll read 5V at WOT).

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Woah, tons of info in there. I'm sorting through it all now.

 

To answer your question about TPS - I haven't put a multimeter on it, but I do have an OBDII scan tool. It read ~9% throttle with the key in IG ON position (engine off), and when I pressed the throttle, it moved up accordingly. So, I think its signal is OK.

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Quick update...

 

I turned IG ON and multi-metered each injector harness. All 4 had 12v on one pin and ~0v on the other. So, no strange signals from ECU to injector.

 

Pulled the vac line off of the FPR and started it... still had fuel dumping out of the exhaust mani and no fuel coming out of the FPR... so it's not a FPR problem.

 

THEN, I started pulling the injector harnesses one by one. For 3 of them, the engine suddenly ran with a huge miss. But one of them (the far left when facing the engine, whichever cylinder that is), made no difference whether the harness was hooked up or not. I only have a basic knowledge of how injectors work, but it seems to me that it is stuck completely open, and is just dumping fuel regardless of voltage telling it to open or close.

 

I have a new (reman) injector coming tomorrow, so we'll see if that fixes it or not.

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The computer provides a ground to complete the circuit for the injector. In other words the injector driver does not provide 12v pulsed, it provides ground to open and close the injector. I would get a noid light and test to see if you have the ground provided from the PCM.

 

If you get a scope, you can pin out the injector and check the function of the injector driver.

 

Also check the continuity from the injector harness to to the PCM.

 

 

http://0.tqn.com/d/autorepair/1/0/g/6/83237644.gif

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Forgot to update this thread yesterday...

 

Threw the new injector in, and it started and ran smoothly with nothing coming out of the crack in the exhaust mani. Yay! Shut it down right away and changed the oil (great minds think alike, Dorito). Started it back up and let it get warm. Woah, lots of smoke out of the exhaust from all the fuel dumping out before. Had the hose and a fire extinguisher at the ready, but luckily did not need it. Smoke lessened as it warmed up, then went away eventually.

 

Took it for a quick spin around the block and logged some data, everything looked good. Drove it more today and everything is still seemingly OK. My 35 mile drive to work tomorrow should be a good final test :)

 

Thanks for the helpful tips everyone.

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  • 4 weeks later...

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