BoostinJaxG

So i a thread over on g35 driver but its not getting much response....so i'm going to try here.


Here is the car:

2003 g35 coupe
70k miles
turbonetics kit, 10psi 388whp, maybe 30k miles on it over 4-5 years.

The problem: About a year ago, maybe more....the car started having issues right when boost would start building where it would hesitate and buck and not make power. It was very inconsistant...sometimes it would work just fine, somtimes i couldnt even merge on to the highway without it hesitating....but ONLY when it started to transition into boost and above.

So i continued to drive the car back and forth to work...and the issue gradually got worse and more often until one day i noticed it stumbling at idle at a red light. The next morning i cranked the car up and it started really rough, but once i pulled out on to the street it cleared up (still not working in boost). Leaving work that day, same thing....really rough idle after start and really choppy loud exhaust until about a mile or 2 down the road then it again it cleared up. At this point the car is showing a random misfire code on the dash. Long story short, next morning....car ran really rough and choppy when i was heading to work...so bad i had to turn around a park it.



So now i was faced with a choice, is it spark or fuel? first thing i did is replace spark plugs, didnt help, regapped them, didnt help, regapped again, didnt help.

My buddy came by with a live scan tool and hooked it up, showed that it was trying to add 20% fuel at idle, it was obviously fuel starved.

Next thing i did was order a new fuel pump....thinking the pressure was falling and was causing the misfires and lean issues. Walbro 255 to replace the walbro 255 that was in there. When i go to remove the old walbro pump, the grommet that sits on top of fuel pump when it slides into the housing came out shreded, i search and find multiple issues exactly like my own.



So i thought this was the problem...but the bigger problem is....NO ONE knows the part number for this grommet and infiniti/nissan both act like it doesnt exist...so one brilliant fellow had the same problem...and found a mitsubishi part that he thought would fit and work...he tried it out and claims it's been working fine ever since. here is the part



So i ordered one and popped it on, stuck the new fuel pump in there...and sure enough....running exactly like it was before...really choppy and rough.

What else could be my problem here? I dont want to have to buy the 60-100 dollar adapter just to test fuel pressure at the fuel rail...but i know it's a fueling issue. What else could be my problem here?! i want my car back!!!!

Spike100

Have you pulled any codes?

I realize why you focus on the turbo addition, but the problem might drill down to stock parts that are old and worn.

You are describing problems that happen with faulty camshaft sensors and crankshaft sensors. I suggest getting codes even though you have modified the engine.

--Spike

BoostinJaxG

Only code it popped was the code for random misfire. I think it is p0300.

myfirstzcar

Is that 10 psi on a stock bottom end?
Your engine doesn't seem to be recognizing the extra air, for whatever reason. I have to think maybe there's an issue with the MAP sensor, and maybe the ecu doesn't understand what your upgraded sensor is supposed to be capable of, which is why you don't have a code for a map sensor problem.....or maybe I'm just pissing in the wind on that one. Your multiple misfires are clearly from detonation.

Either way, I think your ecu isn't responding to the extra air. Keep in mind, when your ecu sees a problem, especially a lean problem, it's going to start dumping fuel at any rpm.....but only in a default kind of manner. I think that's why you have hard starting and a rough idle for a few minutes. The problem going into boost is screaming MAP, not fuel pressure.

BoostinJaxG

Yes, 10psi on stock block. It's not only at boost now, its running rough and misfiring at idle too. There isnt any extra air at idle is there? doesnt the ecu run things at idle, not the map? It's tuned with a UTEC, your suggestion is try to replace the map sensor?

BoostinJaxG

Anyone think this could be related to a boost leak?

myfirstzcar

It could very well be a boost leak, yes. The problem is that it should be pretty loud and easy to notice.
Your idle is probably from the ecu telling the engine to go rich so it can try to survive. That's what usually happens when there's a problem. It's not going to just stop running rich every time you idle the car. Don't forget you have larger injectors now.....that still doesn't mean it's running rich enough under boost though, look for a boost leak first.

BoostinJaxG

Very good info there, thank you...I think I'll buy a boost leak tester. It must be a pretty bad leak but the car idles pretty loud anyway...so it's hard to tell with it running. What size is the inlet pipe on turbonetics? 2.5 or 3in....Anyone know?

myfirstzcar

I don't know the pipe sizes, but a boost leak can usually be heard.

BoostinJaxG

I just got done hooking it up to another live data scan tool and fuel trims were 9 and 3 percent....which i was told is fine. Also let the car run for a while and unbolted the fuel line at the damper and it squirted pretty good....which leads me to think pressure is fine, at least up until that point.

I just tried an ECU reset but the misfire is still there at idle and while driving. really quite rough. I also tried cleaning the MAF again.

The code reader also showed 2 more codes that were stored...one was p0113(intake air sensor 1) and p0183(fuel temp sensor a)

Any idea if these codes are related to the p0300 and misfires im getting?

I was hoping to be able to read live misfires to narrow down which cyl is the most and how often but the reader wasnt able to.

BoostinJaxG

compression showed between 180-165 psi all around.
Plugs replaced
Fuel pump replaced
Long term fuel trims looked acceptable (3 and 9 percent)
Cleaned MAF
Retightend all intake piping clamps(100 times)
Sprayed for vacuum leaks...nothing noticeable.

Car still misfires idle and drives like crap. SES light blinks intermittently when driving it up to speed.

What am i missing here?

myfirstzcar

It must be going rich for some reason.

BoostinJaxG

a vacuum leak or intake manifold leak would cause the car to run lean, since its sucking in unaccounted for air correct?

So what causes it to go rich? even at idle. (if that is what is happening)

It doesn't spit any black smoke at all, doesn't overly smell like gas or anything.

padilla03z

iTrader: (2)

Ses light blink is a sign that ur coil packs goin out. Idk why u got random misfire and not a certain cylinder but that happen to me too before I boosted.

BoostinJaxG

when your coil packs went out...did all 6 go out at once? and when you checked your codes...did it show a specific cylinder(p0301-6) or just a random misfire code(p0300)?

padilla03z

iTrader: (2)

At first my car ran normal but at highway speeds the check engine light would blink. Then I started noticing a misfire but it was on and off and red a p0300. Then finally 3 days later when I had the coil Pack in hand (only 1 went out) it started to read p0302 which was the second cylinder. But thats basicly the whole process

BoostinJaxG

So your car idled normal and everything? Sounds pretty different then my issue but similar in some cases... I wish it did show a specific cylinder though...but it hasn't...makes me think it's a more vast reaching issue that effects all cylinders, like fuel pressure or boost/vacuum leaks. Something that could effect all 6 cyl

padilla03z

iTrader: (2)

No no it idled rough just not till it was ****ed. Once it got ****ed it had a crap idle and crap when it was running. Same as urs. I wanted to assume it was something that controlled everything because of the random misfire but I set my knowledge and pride aside and it fixed it....

BoostinJaxG

well, your car did give you a specific cyl to look at...mine hasn't, so I wouldn't even know where to start. I don't think it would be worth buying 6 and replacing them all...do you?

padilla03z

iTrader: (2)

Hell no they are $100 a piece. U can try this. Unplug em one cylinder at a time while its misfiring. If the misfire sounds the same it means ur coil pack was already bad but if u unplug it and it sounds worse (like two cylinders misfiring) that means that one was good so plug it back in. Understand what I'm saying?