[JamesM3M5]

I put 6 brand new injectors and decoupler elements on last Friday thinking it would cure the light load, under 2000RPM misfire or "bump" feeling. The problem is much better now, but still does it to a lesser extent. Cost me $700, but I was hoping for a better result. The seal on #1 was a bit whipped, but all the others looked great. All 6 new injectors had much larger flow numbers (210-250 versus 150-190) than the old ones.

I've already cleaned the intake ports and changed plugs. The engine runs super strong with Procede on Map 4 with PWM meth, but at light load and also at idle, the engine has what I can only think is a random misfire. No codes at all, and no misfire counter available on the Autologic diagnostics.

So I dunno. I was hoping for a home run.

[RnmEvo9]

Coils?

[jpsimon]

I assume you changed the plugs too?

[TurboBimmer]

I would change the coils.

[konok99]

Same problem here. I just replaced all injectors and spark plugs. It seems much better than before but still have slight bump feeling at low rpm.

[tcw]

I thought the partial throttle low rpm hesitation/"bump" was cured with an intake cleaning.

[2jzn54]

clean your map sensor, check/change coils/plugs.. regarding intake valve cleaning i would clean your map sensor and see if it does it for ya.

[2jzn54]

also reset adaptations!

[themyst]

Originally Posted by tcw

I thought the partial throttle low rpm hesitation/"bump" was cured with an intake cleaning.

This is what i was thinking.

[themyst]

my injector coding is rated 227-249, within that range. the first 3 digits are 569-580.

[blisstik]

All of that helps and an oil free intercooler.

[GeorgiaTech335coupe]

Fuel pump?

[hemi to e90]

You pulling any codes?

[chili36]

Coded properly?

[Joshboody]

Eh, live with it. Mine has always had very slight hesitation at idle "sometimes". Its the n54. I think it has to do with pcv.

Do you seafoam... Could give it a double can treatment next oil change.

[Tzu]

Did you ever take the tune out?

[JamesM3M5]

1) Intake cleaned by me to clean, bare metal in October 2011. 8k miles since then. Problem has been present since I bought the car 10k miles ago. Plugs were done at the same time.

2) Injectors coded with Autologic

3) No misfire codes, no codes at all, CAN clear OFF. No problems at high pressure (>50bar), problems are all at low pressure (<50 bar at idle and low load under 2k cruise)

4) Running in Map 0 still has the problem. Physical removal of the Procede has not been done.

5) Problem is about 80% gone since the new injectors.

6) Coils - maybe, but no misfires under heavy load or high RPM, only idle and light load under 2k. Leads me to believe that coils are not the problem unless the ECU is deliberately firing the coils lighter under those conditions. I do know that the MSD80 and many other earlier ECUs will fire the plug up to 5 times at idle, and it can detect bad coils under all driving conditions. But I have no codes.

[Tzu]

These annoying problems are the worst to diagnose. I feel for you.

Any time I had any issues while running the procede, first thought is to reset all adaptations. I beleive the procede resets only short term adaptations. It may take a week or so for long-term to learn enoguh, just a guess here. INPA can display and reset your LTAs, but it will take the same amount of time for them to relearn. What maps are you running? FWIW, part throttle driving with the procede was never amazing IMO.

Nothing wrong with cleaning your MAP sensor either. Worth a try.

Lastly, have you logged on map 0? Check fuel pressure. If you say it's fine on WOT, check for oscillation during part throttle conditions.

[BADS335]

Without codes it is difficult to chase. I had a similar issue but managed to get codes. Turned out I had a bad plug. Only had about 2k miles on it too. I tried EVERYTHING too. If you really do have a problem, you should get a code eventually. Then it will be easier to dermine. You could also try cleaning and swapping (from one location to another) VANOS solenoids. Easy job.

Good luck!

[JamesM3M5]

Coils and plugs might be worth a try. Unfortunately you cannot log in Map 0, no CAN intercept in Map 0 on the Procede. Cleaning the MAP sensors is free, so I'll try that first. I also have a pair of VANOS soleniods with low miles I can try, too.

I've found the Procede to drive exceptionally well at part throttle, no complaints about throttle tip-in, cruise, or overrun other than the engine makes so much low end torque that a small change in throttle can upset passengers (watching their heads bob).

[Jeff@TopGearSolutions]

You have an OCC yet? Stock intercooler?

[Tzu]

Shiv said you can trigger a procede fault (eg. methanol overflow) and log in map 0. I personally have not tried it, but I think Ilma did successfully.

Yea if you're going to clean your MAP, may as well clean or swap your VANOS too.