Hello all. So here's the situation:
Car is tuned and running fine most times. Lately, whenever I start the car after its been sitting, it takes 2 cranks to fire and then runs like crap. The car will backfire and stumble until I give it enough gas to clear it out. After that, it runs fine.

It seems like the startup process is fouling out the plugs. It also seems to only be the front plugs that are fouling. I've burned through multiple sets of plugs but the problem goes away temporarily with new plugs.

Car has new plug wires (crap auto zone brand, though)
Ignition coils tested to be good.
6 month old id1000 injectors

Could the plug wires be the culprit? I've tested the compression numerous times and it's fine.

My AFR'S seem to be fine throughout the fuel map, including idle.

 

You haven't mentioned the most pertinent information; what ECU is in the car and who tuned it? If the answer ends up as you tuned it, you've probably got a poor startup map.

 

E6x and tuned by a tuning shop. As mentioned, it runs fine with new plugs but the front rotor plugs don't seem to get a clean burn. Rear rotor plugs always look fine.

 

sounds like a bad injector on the front..
It will leak,cause bad start then clear when you put the nuts to it...then run fine as you said.

 

Ugg. I wonder if that's the case. The injectors are pretty new. I'll probably get them tested. There seems to be a difference in egts between rotors too. The exhaust exiting the front rotor seems cooler than the rear rotor. I don't have a guage but I can feel the temperature difference by hand at the back of the exhaust.

As mentioned, compression still checks out. Could a leaky injector be putting too much fuel in and reducing combustion temps?

Edit: I'm going to swap the suspected injector to the rear rotor to see if the problem moves to the rear rotor.

 

I'd also say Ohm out the Autozone wires while your at it, for ***** and giggles. Auto parts store crap is just that, crap.

 

Will do. I just swapped the injectors around and so far the exhaust temp difference is still there. To me, this indicates the front rotor isn't burning the fuel mixture completely. This is baffling as compression is still spot on.

 

are you familiar with the mapping of your ECU or did you get someone to tune it and hand you back the car saying it's good to go?
Not saying it's a bad thing,I know squat about the Ecu and mapping too,But I would check with your tuner as to what the front rotor is getting Fuel wise especially in the start up phase.
My old tune was a total snot bag and the car would not even consider Boost for a half hour..until it was "really warm" and then it Said" ya,I am ready..let's play"

By the way they have those infrared thermal readers ..real cheap now..(see them for about 30 bucks.).If you suspect a difference in temp then that temp reader can tell you there is a difference..just point and shoot.

 

Yeah, I'm familiar with the mapping and ecu. I've tweaked a few parts of the current tune as it was initially very rich for an NA. I suppose I should clarify, car is an NA S4 with ITBS. The tuner noticed the temperature difference between rotors and made me aware of it. The car was still running fine so we proceeded with the tuning.

Checked the resistance on the spark plug wires and they came out to 8.9k ohms. I also checked the resistance on the leading coil in the car, and a spare leading coil. This came out to 15k ohms and 14k ohms, respectively. I tested the resistance by putting the multimeter leads in the plug wire holes in the the coil. Do these values seem good? I've also tested the coils per the FSM and the resistance was in spec. So.. I'm still lost lol.

 

Another observation. Fuel pressure drops to zero immediately after I turn the key off. I have an adjustable fpr/gauge and by the time I turn the car off and get to the engine, the pressure is zero. Could this be another definite symptom of a leaky injector? Or just an issue with the FPR?


Edit:

So I didn't have time to pull the fuel rail and test for leaks tonight. However, I took another look at my ignition maps. I bumped up my idle ignition angle 1 degree and idle smoothed out a ton. I also cleaned the spark plugs. I guess we'll find out if the car floods again tomorrow morning.

Does anyone feel like taking a look at my ignition maps to see if the problem could be in there? Mods feel free to move this thread if you deem it necessary.

 

I, for whatever, can't make heads or tales of those maps you posted, However...

You want the starting timing to be retarded, then when the engine is running at idle have it go back up. Ignition retard at start helps a lot.

 

Lol. I can post the text version later. I also forgot to post the ignition crank map.

 

Come on that is Easy JJ...
if MARIO eats the Triangle you get 2000 bonus points!

(sorry DJ.,I had to man..lol!)

 

So once again, I delayed the inevitable and didn't pull my intake manifold. However, I got some images of my timing maps. For some reason, the E6X doesn't allow a text view of the trailing coil, so that map is as posted as above.


Text view of leading ignition. I bumped up the timing 1 degree in 2 more areas and the car purrs like a kitten now. No more lumpy idle with the accessories turned on. I'm not sure how to read the text version but I've NEVER seen my ignition to be 38.00 degrees. The 2D bar graph shows this.



Cranking map. It's currently set to 10 degrees.



It also seems that my TPS sensor isn't being read by the E6X. My text engine data and gauge page says 0% no matter what amount of throttle is being input. I've re calibrated it within the ECU several times with no luck. I think its time for a new TPS.

 

djsl, can you do me a favor and ohm out the secondary of your coil in relation to ground, but reverse the leads (negative on coil tower, positive on chassis). I bet there is a diode in there because 14kohms sounds excessive.

 

I'm not quite sure what you want me to do based off your description. Maybe the words aren't translating to me. Do you mean ohm out leading 2 with the negative lead in the plug connector and positive lead on the chassis?

Also, I pulled everything to test for leaking injectors and no dice. The rail receives pressure but the injectors hold just fine with no leaks. However, my fpr indicates that fuel pressure is immediately back to zero within milliseconds. I have no fuel leaks anywhere.

I'm starting to think my fpr is shot and every time I crank the car, 45 psi of fuel is being sprayed into the housings. If everytime the key is cranked the pump primes again, this, in turn, is flooding the car.

Is this possible? Could this be the issue? I feel like the fpr used to hold pressure longer and it no longer does. I should also add the car has a brand new t2 fuel pump. Maybe Banzai-Racing or j9fd3s may have some insight on this, as I've seen some threads related to it.

 

the car doesn't lose coolant does it? bad coolant seal can foul the plug on the chamber that is leaking water on startup

 

Car hasn't lost any coolant. Doesn't smell like it either. Coolant level hasn't dropped at all and buzzer hasn't gone off since I flushed the radiator. I'm probably going to pressure test it just to make sure.

I did notice there was a bunch of oil residue in the lower intake runners. It wasn't pooled up but it was definitely full of residue.

 

Problem solved! It was the stupid tps sensor. Somehow, I must have recalibrated the throttle incorrectly as it was reading 0 at full input. I recalibrated it again and now the ecu is reading the full throttle sweep. Cranked the car and it started on the first try!

My guess is the ecu was running the car off the map sensor alone and with inconsistent vacuum during cranking, the injectors were just spraying fuel in and flooding it.