Only Cylinder #3 not firing? Why?

[LittleRedRocket03]

I have an 03 Cooper S. During initial start up all four cylinders fire and the engine revs to 1500 RPM before climbing back down to about 1000 RPM. When it reaches 1000 RPM it then goes into steady idle mode which is when cylinder #3 stops firing and the engine idles roughly at 600 RPM. I took out plug wire #3 during initial start up to confirm this. When I removed it during initial start up while it was climbing to 1500 RPM, I could audibly hear cylinder #3 not firing, and when I put the plug wire back in, engine firing sound went back to normal. When I put it back in, I let it climb down to 1000 RPM and the engine was still firing normally. When it entered steady idle mode, the engine firing sound changed and idle dropped to about 600 RPM. While it steadily idled at 600 RPM(but idling pretty roughly), pulling plug wire #3 had no affect on the sound, pulling every other plug wire had an effect, confirming that cylinder #3 wasn't firing. Note that plug wire #3 was always sparking but the cylinder stopped firing after entering steady idle mode at 600 RPM. When I give it gas after it enters steady idle at 600 RPM the engine RPM doesn't climb above 1200 RPM. If I give it gas during initial start up the engine will actually rev to about 3000-4000 RPM but no higher. I have no idea why and I was hoping someone could shed some light on it.

[marque]

Hi Ya

I don't know what you have tried so far, but there is a problem with the coil pack on the no3 position, if you pull off the lead and see if it is corroded on the terminal at the coil end, if it is see if you can borrow one to try, but if it's corroded on the outside it will be on the inside its a known fault and it may be the problem I think MSD or screaming demon coil is the best option if you have to replace it DO NOT be tempted to fit a plasma booster
You can also try pulling out your spark plus checking the gaps and putting no3 in no1 cylinder try it if it's the same swap a lead with no3 try it again Incase you have a bad lead or spark plug. It might produce a spark but under load and compression it wil fail

Hope this helps

[LittleRedRocket03]

it also threw two codes P1688 and P1106

[marque]

Hi ya

p1106 is TMAP sensor fault
P1688 is Low mass air flow, electronic throttle actuator fault
Remove the plugs look for corrosion and give them a squirt with wd40 also it might be worth pulling the ones on the DME as well give them a squirt to

Have a look at this link, wieght for the counter to count down on the right and down load fill its a mini service manual in PDF might be of help to you :-)
http://megaupload.com/?d=NXE0568I
Hope this helps

[stead34]

Start with the basics, like compression test, then you can start swapping things around from one cylinder to the next.Ask yourself is the plug wet with fuel when its removed, as if its getting no spark, or is the plug dry like a faulty injector, can you feel the injector working. Don't run it to long if you suspect its fueling as you can damage the CAT...

[LittleRedRocket03]

Performed a compression test. I got 130 psi on all cylinders and note I'm at 7200ft. of elevation. I swapped the spark plug wire and spark plug with cylinder 4 and the results were the same, cylinder 3 stops firing. So the only thing that makes sense to me is a problem with fuel injector 3 or a computer malfunction.

[marque]

Hi ya

Ok have you tried another coil pack yet.

Also If you suspect the injector have a look at this link shows you how to clean them, but I would recomend if they are bad get them cleaned properly or replace them. but this will give you an idea what condition there in
You could remove injector 3 and swap with another injector see if the fault moves with the injector

Check out this video on YouTube:

Fuel injector cleaning - YouTube

[LittleRedRocket03]

The coil is new and I also ohmed it out with a DMM and the readings were normal. I am going to take the fuel rail off and was wondering how you detach the hose that goes into the regulator on the rail.

PS that guy needs to take a XANAX the next time he makes a video and put double sided tape on his fingers. Neat way to clean injectors that I didn't know about. Thank you

[marque]

Hi

Yer I think he needs velcro gloves or double sided like you say :-))))
The fuel feed pipe unplugs, when you have got the intercooler off you see the fuel feed pipe and as you look at it, it has a black plastic ring on the right hand end of it. if you hold the feed pipe and push it to the right slightly and push back in the plastic ring then pull the feed pipe to the left it should pull off.
When you get the rail off to unclip the injectors there is a clip it just pulls out. Just remember there are two groves in the injector just be carefull that when you put it back together that there in the right grove.

[LittleRedRocket03]

Here is a summary of the situation so far. My car starts up fine and runs on 4 cylinders briefly before going into idle mode where cylinder 3 cuts out. I think the engine also goes into some kind of limp mode because the engine won't rev above above 1100 rpm after cylinder 3 cuts out. The DME is throwing two codes:

P1106 Manifold Air Pressure Sensor Too Low at Engine Stop
P1688 Electronic Throttle Control Monitor Level 2/3 Air Mass Flow Calculation Error

As far as trouble shooting goes I have taken these steps:

-Ohmed out the Coil Pack. Readings are normal so the coil pack is ok
-Switched spark plugs and plug wires between cylinders 3 and 4. Same condition resulted meaning the spark plug and plug wires are ok.
-Cleaned the injectors. Same condition resulted
-Switched injector 3 with injector 4. Same condition resulted meaning the injector 3 is ok.
Reset the DME multiple times. Same condition was still there.

I've read p1688 can come up from different things namely the BPV, the MAP, or the harmonic balance. I am going to check all of these tomorrow. As far as causes for p1106 goes, I have no idea where to start. I've read that it could be cause by a vacuum leak. Someone with a cracked expansion tank had the same code thrown so I might fill the car with coolant and see if that helps maybe idk.

Maybe someone has encountered a similar problem but I am still dumbfounded as to why cylinder 3 cuts out unless that is part of a normal limp mode.

[LittleRedRocket03]

Sorry I forgot to mention in the summary I ran a compression test and got 130 psi across the board. Note I am at 7200 feet of elevation.

[LittleRedRocket03]

I am thinking it is the computer. I fried my old DME, got a new one then had it realigned with my immobilizer and my key by RPM Motorsport. Is it possible this new DME is bad and is causing the problem? Trying to figure out the source of cylinder 3 not firing and the codes being thrown.

[LittleRedRocket03]

I tested the wires to the number 3 injector. Both show no resistance. I got freeze frame data and I got 11.2 in Hg at 0rpm and ~7.2 in Hg at 1400rpm. Are those pressure readings normal. Granted I am at 7200ft of elevation but shouldnt it be around 23 in Hg? PLEASE HELP!!