F4i Intake Backfire!!!

[hockdane]

We have just finished wiring up the same f4i that we have used in a previous years car, and went to start it up, and all it did was pop and backfire in the intake. Just to rule out anything we did I hooked up the stock ECU and the same thing happened. This would make me to believe that there is a sensor problem or something like that. If anyone has any info or has experienced this problem could you give me some help? Thanks.

[hockdane]

We have just finished wiring up the same f4i that we have used in a previous years car, and went to start it up, and all it did was pop and backfire in the intake. Just to rule out anything we did I hooked up the stock ECU and the same thing happened. This would make me to believe that there is a sensor problem or something like that. If anyone has any info or has experienced this problem could you give me some help? Thanks.

[exFSAE]

Make sure the injectors and plugs are in the right cylinders with the right firing order.

[mike86z28]

Remember, firing order is 1-2-4-3 for the F4i

We experienced many intake backfires last year, check your injectors, you may have a leaky one. Also verify your timing.

[hockdane]

the injectors and there wiring look fine as per honda service manual. is that firing order for the plug/coil locations as well?(with the exhaust side facing you do the coils go 1-2-4-3? or 1-2-3-4

[exFSAE]

The injection and firing order on the F4i is 1-2-4-3.

However, if you have a stock harness or what have you and the wires are labeled for what cylinder they go to.. they obviously plug in 1-2-3-4.

Make sure you have 1 going to 1.. 2 to 2, 3 to 3.. ie you dont have the whole harness backwards.

[hockdane]

we have all of the wiring in the stock location. it seams as if the ignition timing is off, but i can not understand how or why that could happen. it is the same setup we used last year and it worked well. we also made sure all of the sensors are working properly as well.

[exFSAE]

Have you checked for gremlins? They are real.

[hockdane]

we are finding that out first hand!!

[Poe]

Cylinder 1 is on the stator side of the engine, not the cam chain drive side, just in case. Have you taken anything apart inside the engine? The stock wiring is labeled with the cylinder numbers, not the firing sequence, best I can remember.

[Michael Hart]

Definitely check your ignition timing and also that your cams are indicated correctly. Last year, one of our engine guys put the cams in 180 deg. out of alignment causing a lot of frontfires like you describe.

The other thing to double check is your fuel pressure. Low fuel pressure can cause frontfires sometimes too

[JaredC]

Double check your VR ref/sync sensors. We had our ref VR sensor wires switched around which made our car run "retarded".

[Grant Mahler]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JaredC:
Double check your VR ref/sync sensors. We had our ref VR sensor wires switched around which made our car run "retarded". </div></BLOCKQUOTE>

I have had the same issue - but don't understand why? A VR sensor is a coil surrounding 2 elements - a magnet and a ferrous bar. When another ferrous material passes by, the field changes, the magnet lead goes high, and thus a voltage differential is created. If you switched the wires, it would simply be the inverse yea? Why does this work, but work poorly? For example, I have had it be off by ~2* at idle, ~10* at 6000rpm on a v8? What doesn't work when you switch the wires?

[JaredC]

If you switch the wires, the voltage will be the negative of what you want. The sensor will still pick up the correct frequency but the phase will be all out of whack. It'll have the right number of spikes, but the signal will be zigging when it should be zagging.

You'll still have air, fuel and spark all at the right frequency (ie fuel and spark once per 4 stroke cycle, ignoring wasted spark and batch injection considerations), but the timing within the cycle will be out. Depending on the sensor, tooth configuration, the ecu config, the engine (and cams), whether you run sequential or batch injection, whether you run wasted or individual spark, how much ignition advance you run, the phase of the moon, and the colour of your shirt, it may still run, just poorly. Other times it may turn your internal combustion engine into an external combustion one.

[The Bunker]

Do you know if you coil harness is wired in series or parallel? That can sometimes cause the described symptoms.

[hockdane]

we found out that one of the guys put the #4 coil in #1 cylinder and same deal for the rest of the cylinders as well. we switched everything around and it fired right up. thanks for all of your help!!