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Idles But Dies Out When You Give It Gas


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#1 redrocket_ej1

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Posted 07 December 2009 - 02:58 AM

HELP! Girlfriends car 01 toyota corolla, its a ce if it makes a difference.. her cars been running rough latley, i checked and replaced the spark plugs and a coil on #1 cylinder, afterwards i started it up and it idles fine. i put it in gear and go to excellerate and it wants to die out. (it was running before i changed these parts). i dont think its getting fuel, she also has a large vaccum leak at the intake manifold gasket (dont think this is the problem) but its still there.. i pulled the fuel rail with the injectors plugged in and turned the key to the on position and no fuel sprayed, also tried bumping the starter to see if it worked still nothing. so im assuming its not getting fuel. (not sure of the code but it also had a code for cylinder #1 misfire and cylinder #1 lean). im at a loss. this is her daily driver and i need to fix this asap. any help is appreciated. also does the 01 corolla have a fuel filter? i looked along the firewall and under the car but nothing.. could it possibly be in the gas tank? maybe a bad fuel pump? like i said any help is appreciated!!

#2 fishexpo101

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Posted 07 December 2009 - 07:39 AM

Hello and Welcome to the forums.

This Corolla has a fuel filter in the gas tank - part of the fuel tank assembly. But generally does not need to be replaced unless you know there was some contamination poured into the tank (i.e., accidentally filled it with diesel). The system uses a returnless fuel system, so fuel will not spray out as quickly as other fuel injection systems.

Vacuum leak would cause all sorts of problems. Depending on what other leaks are in there - could be causing the off idle stumbling, engine hesitation, as the air/fuel mix will be off. Try resetting the ECM first, clean the IAT and MAF sensors (on the airbox), give the throttle body a good cleaning + fix the vacuum leak, double check that the plug gap is 0.044", PCV is clear and all hoses are running to where they need to go.

When you test it - accelerate with the car in park, see if there is a fuel/spark issue. Then do the same thing and slowly accelerate in gear - see if it cuts out again.

#3 redrocket_ej1

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Posted 07 December 2009 - 09:31 AM

Thanks! I will check all this later on today and get back to you with the results..

#4 redrocket_ej1

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Posted 08 December 2009 - 01:50 PM

ok so i replaced the intake manifold gasket, cleaned the throttle body, cleaned both sensors, and i know the gap on the spark plugs is .044 cause i had to gap them before i put them in.. started the car up and it runs exactly the same. im going to check the fuel pump with an ohm meter today.. is there anything else i should check? going to go work on it in a couple of hours. any help is appreciated!!

#5 fishexpo101

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Posted 08 December 2009 - 06:31 PM

Could be a vacuum leak in any number of those hoses running from the intake manifold. Could even be a leak in the induction or exhaust system of the car causing the stumbling when you get on the gas. You can check the resistance of the punmp, should be around 0.2-3.0 ohms, fairly low resistance. Also check to make sure that there is power getting to the pump, check for broken or shorted wiring.

Does the engine cut out when you try and race the engine in park? Checked to make sure you get good spark on all the igniters?

#6 redrocket_ej1

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Posted 09 December 2009 - 03:34 PM

the fuel pump is getting power and it works fine. the engine will still start but still the stumbling. it STILL has the vacuum leak and for the life of me i cant find out where its coming from. and i would assume its getting spark since i replaced the spark plugs and a bad coil and the car idles fine. just when you give it gas it dies? and yes the engine cuts out if you rev the car in park.. this car is throwing me for a loop as im used to working on hondas which seem considerably easier. please help!!

#7 fishexpo101

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Posted 09 December 2009 - 04:57 PM

If the engine cuts out when rev'd in park or gear - that really points at a possible vacuum leak, throttle body issue (TPS sensor), faulty MAF sensor, leak in induction system, or funky ECM problem. There is a chance that it is related to a fault in the VVTi system (could be trying to run timing too far advanced or retarded). Could also be a weak fuel pump - hard to check, as you'll have to insert a T-fitting before it hits the fuel rail to measure pressure. Dirty injectors can also cause stumbling at higher duty cycles (sticking solenoids or intermittent power). A faulty knock sensor (right by the intake manifold) could also be another possibility - but it would pull timing, but not usually far enough to kill the engine like that.

Anyway you can post a sound clip - just so we can hear how it dies? Have you tried gunning the throttle in park, slowing accelerating in park - to see if it stumbles at a particular RPM or throttle position? Sounds like you will need to throw a data logger to see what the sensors are reporting back to the ECM. Was there any CELs before you starting working on the car, even old ones?

#8 fishexpo101

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Posted 09 December 2009 - 05:02 PM

Forgot to ask - what did the old plugs look like? When you rechecked the new plugs, did they show any signs of oil or fuel fouling (wet plugs)? You can have overly rich or overly lean stumbling - depending on which one it looks like, points are different culprits.

#9 AlaricD

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Posted 09 December 2009 - 05:03 PM

just when you give it gas it dies?


In truth, you're giving it air, not gas, when working the 'gas' pedal. The system is supposed to respond to the additional air with additional fuel, based on what it detects from the MAF sensor and in relation to what the O2 sensors report.

Part of the problem with the vacuum leak is that it's invalidating MAF data in the first place. Opening the throttle then changes the input air from post-MAF sensor to pre-MAF sensor because the throttle plate restriction at idle means that a lot of the air it gets at idle is bypassing the MAF sensor. The system then sees a gigantic change in mass airflow, more than is normal without the post-MAF leak, so it dumps much more fuel.

I would experiment to see if this problem still occurs with the MAF sensor disconnected (just remove the connector from the sensor and leave it physically installed so you don't allow unfiltered air into the system). It may run oddly as it will have no MAF data, but then operating the throttle may give different results. Maybe that will prove nothing, but it might give us some insight.

Note that the CEL should come on with the MAF disconnected. Once reconnected, the light should go out on its own after a couple of driving cycles. I've found on my own '01 LE that I can do similar operations, and after reconnecting the sensor I just need to drive about a mile, then shut off the engine and restart it-- the light goes out as if nothing had ever happened.

Edited by AlaricD, 10 December 2009 - 09:46 AM.