Here is the scenario, the CEL came on and sometimes disappears. When the car is first started and left in IDLE the rpm will drop from 800 to 600/500 and the engine will shake. My mechanic buddy and I investigated and it appears that a misfire happens. If you step on the gas the misfire disappears.
We did a compression check on all of the cylinders and they check out around 175 psi each. Check the plugs and they were not fouled, all white, NGK +4, changed around 3k miles ago.
We checked the Precat O2 sensors and they are both good, even bought new ones to see if they would make a difference and it was the same. The one thing we did notice is that in idle the first precat sensor does not change, stays around .7 unless you step on the gas and hold it around 2500 rpm, then it switches.
Finally we cleaned the injectors out direct from the fuel rail with pro injector cleaner, but nothing.
After investigating everything, we reset the codes and I drove the car around for a week. The CEL came back and here are the codes.
P1477 MFR controlled Aux Emiss Cntrls
P1189 MFR ctrlled fuel and air metering
P1188 MFR ctrlled fuel
P0170 Bank 1 Fuel trim Malf
P0173 Bank 2 Fuel trim Malf
Any suggestions or help would be greatly appreciated. I have access to a mechanic that is a childhood buddy of mine. He works on everything and recently fixed my foghorn crankcase vent valve and hoses. Anyways, before I bring it to the dealership is there anything else we can test to see it might be the cause? Maybe the MAF or the Cam sensors? Or maybe an ECU update issue? Any suggestions would be greatly appreciated. Thank you again everyone.
How do you do that? With the engine running, I'd assume there's too much wind from the fan and belts and things to see the smoke moving from a vaccum leak.
Well we just double checked all the vacuum lines, and their connected. One problem though, he doesnt have a smoke machine, so this will have to be on the list of diagnostics to be attempted if and when I bring the car to the dealership. Is there anything else I can check in the meantime, or look for? thanks again
You put inert smoke into the intake CAR NOT RUNNING with a small pressure and wathc for it to leak out, any small vaccum leak will cause the smoke to escape showing the vaccum leak.
the smoke method sure sounds good and I wish we had access to one. As for the coils. I tried swapping around coils to see if the unaffected cylinders would show up on the fault codes, and nothing happened. The same cylinders are misfiring. Plus coils are pretty darn expensive. Ive been thinking about possibly replacing them though just to see if that is the case, but wanted to gather as much info as I could first. Any other suggestions anyone??!!:thumbsup:
I have told you what you need to do. Check for vaccum leaks reprt back sounds like you have a vaccum leak hence the 02 staying at .07 and then switching when you rev it up
Thanks Seth, the vacuum leak check will be under way this weekend - in the meantime I just wanted to explore all other avenues while I have the time. Thank you to everyone that has responded. I will also check the coils again since their easy to get to.
Okay, well I just got the car back from the independent, and they did a smoke test to see if there were any visible vacuum leaks and the results were - nadda. They said they didnt find any leaks and that there are a number of other things that could be the culprit, but it would take more time and money to diagnose. They charged me $180 for the test and I picked the car up after they asked me if I wanted to move forward with a test and replace as they go diagnoses. I would rather do that part myself. So I am back to the drawing board. Any other ideas mechanics out there?? Please help! thanks
I am kinda scratching my head too right now- keep us posted- I will keep you posted too blossom24! Lets pull the Check engine light and sell these BIOTCHES!!!!
hahaha - if I was not so involved with the passion for fixing this headache, I probably would sell it, but for now I enjoy learning the mechanics involved with the car.
Ill keep you posted if and when I ever find the problem. I recently replaced the crank case control valve and hoses, man was that a B*&%*. I had to undo the manifold and hang it via bungy cords from the hood. Going into it was a mess and scary with all the plugs and hoses and wiring. Putting it back together wasnt too bad though. Plus the valve was **** and full of broken diaphram pieces.
Anyways if anyone has any advice, please do share.. I will be cleaning the MAF today and hoping for the best. How do you test the MAF to see if it is working properly? Is there something I can look at measurement wise on the computer or maybe voltage that I can test? Thanks again everyone
Did this just occur after replacment of the vent vavle? or was this why the valve was replaced?
To test the Maf use a volumetric efficiency read you grams per sec flow from a scan tool you should be 85-90% efficient when you do your calculation if you are not your maf is reading wrong. Here is a link to a free calcualtor http://www.smp-training.com/Pages/ptsframeset.html
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awesome!! Thank you Seth, I will definately look into this! Regarding the issue I am having, it was there before changed out the crank case valve. I was hopeful that after changing the valve that everything would return to normal, but nadda.
I would defiantly check the maf I misread you original post i though all this occurred after replacement of your vents valve, that's why I was so adamant that you had a vacuum leak.
Seth - Well I changed out the MAF with a brand new one and still the same thing. The original MAF is still within spec and good. So back to the store with the new one. Any other ideas? I am running thin on DIY's left to try and troubleshoot. Could it be the evap canister or fuel pump or anything related to that area. I do hear a hissing sound from the back area near the evap canister location when the car is running. Plus all of this did start to occur after the dealership fixed my subframe for free. Any other ideas at all? Thanks again for your time and advice
My car is now having cold start issues, where it will start but not stay on or idle. If I leave the car alone for about 15 minutes after trying to start it a few times, it will start up and stay idle. Could this be a fuel pump or evap issue? All of this started after the Dealership fixed my subframe and removed/reinstalled the evap/fuel lines from under the back of the car. I even noticed that they wiped the black coating off of one of the hoses from the rear of the car to the mid section, exposing the blue color of the original plastic. Why they did this, I dont know. Could this be the culprit? Is there suppose to be a hissing sound coming from the rear passenger side of the car when the car is on? Thanks again for the information.
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