[Yam_440i]

I recently undertook the job of changing injectors on my car as I was getting regular rough warm starts. My idea was that I had leaky injectors, therefore fuel on plugs made warm starts bad. Cold starts were generally fine.

So I bought brand new index 12 injectors, fitted them and coded with Protools Android app.

Checked all lines, connectors etc, everything looked good.

Straight after fitting them, my engine would crank but would not start. It just kept dying soon as it cranked. I reflashed to stock map, and thankfully it started again, however with very rough idle. I then mapped stage 2 again, reset throttle map (via pedals not MHD) and things got better. Took it for a long hard drive and found that I was misfiring in cylinder 2+3, with some O2 sensor codes, aswell as running super rich (exhaust popping like MHD burble setting on "hard")

Next day, I changed to new coils, and reset lambda and fuel rail adaptions via MHD, and boom things were good again, no more rough idle, no misfire codes, and car felt pretty great.

However, after going for a hard drive to test it, stopped over, turned it back on and it started shaking hard on idle. MHD monitor shows fuel rail pressure jumping to 1800+ on start up, and gradually going down to 700. Soon as it would reach 700, it would go lower to 600-500 the car would begin stumble. To save the car from stalling, I guess the ECU would make the rpm idle rise to 800rpm, by then fuel rail pressure stabilizing around 750.

I have no idea what is going on at the moment, but so far I have changed fuel injectors and coil packs. I am due to change spark plugs soon regardless.

Without throwing parts/money on this thing any further, can you please help me diagnose what the issue could be?

[TheMidnightNarwhal]

What is you lpfp PSI.

Also, does it stricly missfire in cylinders 2 and 3? If so swap coils around other cylinders to see if coils is issue.

[Yam_440i]

Originally Posted by TheMidnightNarwhal

What is you lpfp PSI.

Also, does it stricly missfire in cylinders 2 and 3? If so swap coils around other cylinders to see if coils is issue.

LPFP hold stable pressure at 72.5psi.

The misfire codes only appeared once, which was one cylinders 2 and 3. After resetting adaptations on MHD and putting in new coils, the misfire codes have not appeared. But it still idles rough and fuel rail pressure drops, until the idle raises by itself and stabilizes at around 850rpm to stop the engine cutting off.

I also have had a O2 sensor code pop up too 2C2D (oxygen sensor before catalytic converter, coasting mode check). Again, since clearing the code, it has not come back.

Just a bit lost at how this is all happening after 6x index 12 injector change.

[dpaul]

Originally Posted by Yam_335i

I recently undertook the job of changing injectors on my car as I was getting regular rough warm starts. My idea was that I had leaky injectors, therefore fuel on plugs made warm starts bad. Cold starts were generally fine.

What you describe is not a "classic" leaky injector scenario. More typically, you have rough cold starts because it takes a while for the fuel to leak out. Not rough warm starts. In fact, it is hard to understand how a leaky injector would produce rough warm starts but not also rough cold ones.

1) Did you ever actually look at the spark plugs to see of they were wet with fuel?

2) You don't indicate what modifications you have installed. That's important to know. Since you said you loaded the MHD stage 2 map, I assume you have made some changes so tell us what they are.

3) Since you have an indication that your rail pressure may be abnormal, perform a WOT log to look at the fuel pressures under load. To do that, first, put your car back on the stock map. Then, get to about 2500rpm in 3rd gear then put the pedal all the way down until 6500. Make sure traction control is completely off.

[Yam_440i]

Originally Posted by dpaul

What you describe is not a "classic" leaky injector scenario. More typically, you have rough cold starts because it takes a while for the fuel to leak out. Not rough warm starts. In fact, it is hard to understand how a leaky injector would produce rough warm starts but not also rough cold ones.

1) Did you ever actually look at the spark plugs to see of they were wet with fuel?

2) You don't indicate what modifications you have installed. That's important to know. Since you said you loaded the MHD stage 2 map, I assume you have made some changes so tell us what they are.

3) Since you have an indication that your rail pressure may be abnormal, perform a WOT log to look at the fuel pressures under load. To do that, first, put your car back on the stock map. Then, get to about 2500rpm in 3rd gear then put the pedal all the way down until 6500. Make sure traction control is completely off.

I appreciate your advice.

1) here is a photo of my spark plugs which I took out today. They looked a bit wet with oil, but there was no strong smell of fuel. How do they look to you?

They are ordered by cylinder number.



2) I am FBO, running MHD Stage 2. Specifically - Downpipes, FMIC, DCI, upgraded chargepipe and BOV.

3) I will do that asap and report back with a link to the log.

I fitted 6 new OEM Bosche spark plugs, overall it seemed to improve. However, once again, after a warm start, the rpm fluctuated at idle and stabilised around 800rpm. Can still feel small hiccups on idle too.

[dpaul]

My point was that you should have looked at the spark plugs before you decided to replace the injectors. Since you now have "brand new" injectors, it would be very unlikely for any of them to leak. And, in fact, there is no sign of leakage.

Are these the "new" plugs you fitted or the originals?

The "wet with oil" you comment on is only the threads, possibly from a past or present leaking valve cover gasket or just oil spilled during oil changes or top-offs.

There is something different about the second plug from the left but I can't see it well enough to make a guess about it.