tunedbylorange.com

Hey guys,

This one seems to defy all text book knowledge.

I have a 2000 Civic DX auto that goes lean when the throttle is pressed

as you can see in the vid when you give it gas it goes lean
if you try taking off from a light or a stop sign it goes lean and stalls out
http://www.youtube.com/watch?v=HtPP-N_R5u8


so far here is what has been done

catalytic converter has been replaced...old one had a crack (like they always do)
fuel filter has been replaced...fuel pressure rises when gassed
intake manifold gasket has been replaced
throttle body has been removed & cleaned gasket looks good
map sensor o-ring has been replaced
checked intake manifold, all vac lines & hoses with carb cleaner for vac leaks...none found

We have tried:
2 different throttle postion sensors (TPS)
2 different map sensors,

We have tested:
-coolant temp sensor
-02 sensor
-ECU
all test o.k.

Anyone have any experience with this one?
I am open to any sugestions

Thanks in advance,
Rob

newtron63h

id do a compression test just to give you a bit more information.......probably wont show you anything but its easy enough that its worth it. and along that same idea, valve clearance is a good idea to check too........again probly wont show anything but it might and its easy.

clogged injectors could do this......you say FP rises when you give it some throttle(so clogged injectors could flow enough to idle but when you give it some throttle they cant flow enough fuel and therefore it goes lean to the point of dying). check the fuel pump flow rate......should be about a liter per minute i believe.

tunedbylorange.com

thought about possible injectors

more info on the condition:
when driving it only goes lean & wants to stall when the gas is pressed suddenly...
if gas is applied gradually it runs ok

may try replacing them..it's about the only thing that has not been replaced
them & the fuel pump

newtron63h

ok so when u press the pedal gradually does it pull normally up to redline?

Former User

Is the mechanical timing off by a tooth?

Any CEL codes?

tunedbylorange.com

checked the timing marks...they are dead on

no CEL

changed the fuel pump... to no avail

tried changing the intake air temp sensor... to no avail

next I'm going to try a set of good D16Y7 injectors that a friend has

any more ideas anyone?

Former User

Is the ignition timing also dead on?




Is this how the mechanical timing looked:




Also, what are the fuel pressures with and without the FPR vacuum hose connected?

tunedbylorange.com

yup the mechanical timing is the same as the pic above

checking the ignition timing right now

fuel pressure is good
- 43 psi without vac. hose to regulator
- 33 psi with vac. hose to regulator

92civlude

Maybe fuel. you might have some **** gas in the tank.

tunedbylorange.com

ignition timing is good as well

has new fuel in tank....symptoms occurred on previous tank of fuel

Schister66

Well...i thought this was going to be an easy fix, but you've nearly exhausted all efforts. My only thoughts at this point would be that something is disrupting the flow of fuel...be that a clogged injector(s), something in the fuel lines/fuel rail or maybe its simply a dirty in-tank filter on the pump. Something isn't able to supply fuel to the engine when demand arises. Have you logged fuel pressure from idle to when the car is moving?

I'm trying to work through this in my head while typing...

Just know i'm thinking about the problem and will stop back periodically to check progress or if something crosses my mind. I love a good problem

tunedbylorange.com

tried removing fuel pump filter

Former User

A few other thoughts:

-Crank sensor in the distributor. It controls both spark and fuel. Maybe it's malfunctioning. Test for resistance and a short.

-Does disconnecting the O2, MAP, or TPS sensor prevent the problem?

-Test the O2, MAP, and TPS sensor wires that run to the ECU for a short and for resistance.

-Test whether the MAP and TPS sensors receive the proper reference voltage (5V) from the ECU.

-You really can't directly test the ECU. Have you tried swapping in a known good ECU?

tunedbylorange.com

have swapped with another good ecu...to no avail

The problem is also intermittent doesn't always go lean when throttle is pressed,
primarily when it is stabbed

will try the above suggestions along with the injectors

I was thinking it could be the crank sensor in the distributor as well
it appears the distributor been replaced before

Former User

This is the most difficult type of problem to solve. All testing must be done before, during, and after the problem occurs if you hope to reveal the cause.

tunedbylorange.com

I agree.....
the good thing is, it does it more often than not

fleabag

You say that you've changed it out with two TPS sensors.. what if you have a bad/weak ground or damaged wiring? That would explain the intermittent issue.. Try shaking the wires going to the TPS sensor and see if that changes anything.

newtron63h

i agree with Schister66, im leaning towards you having some kinda blockage in the fuel system so that if you slowly give it gas, it can keep up.....but if you stab it, it runs out of fuel sometimes to the point of dying. when you slowly give it the gas does it pull normally up to redline? i would suspect that a fuel restriction would cause a leaner reading the higher the rpms go. if this is NOT the case, then id pretty much rule out a fuel restriction and go to work making sure you have proper reference V, signal V, and grounds on all sensors that might affect this.

tunedbylorange.com

Looks like the civic is fixed!

A good friend let me borrow his distributor off of his 97 EK hatch
(which is super clean BTW)

I had to make a jumper harness because the 99 distributor plug is different than the 97

But as soon as I put it on the car it ran great
.....looks like the distributor was bad after all

the funny thing is we usually have a good dist. laying around for the purpose of troubleshooting...didn't have one for this car.

need to put some miles on it to confirm the fix
I'll get back to you guys

newtron63h

makes sense, snap throttle puts alot of load on the ignition system......good enough to run, but you snap the throttle and it cant handle it.

fleabag

but why would it go lean?

tunedbylorange.com

I believe the crank sensor in the dist. controls fuel & spark

tunedbylorange.com

it was the distributor