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      07-29-2020, 03:57 PM   #1
drocket77
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P0300-P0306

As the title states I am getting those codes, except for P0301. #1 has never had a misfire, with the exception of removing the intake pipe while running. Here is the things I have done so far.

1. Replaced spark plugs.
2. Switched the coil packs around, and all will eventually have a misfire except #1.
3. Made a smoke machine and have checked while warm, and cold, no leaks.
4. Dangerously sprayed starting fluid around vacuum tubing, and no change in rpm digital bi scanner was hooked up, and idle stayed at 745-765.
5.New oil cap(holds pressure when I did smoke test, and rpm will change if I take it off while car is running.)

I have reset then went on a drive from a cold start and it throws the code exactly 3 miles into drive. Tried it after it warmed up, and exactly 3 miles into drive. It doesn't matter if I was stopped at a light, did 70mph on the longer stretch or 35 mph.... 3 miles in it ALWAYS throws the first code.
I think this may have something to do with the O2 sensors, as ALL of them are pre cat, and the lambda is the same for bank1 and 2. Previous owner didn't even have a cat on it.

The only other thing I am thinking is maybe a random stuck lifter, but its happening on all but #1..... Any other suggestions?

I have also reset adaptations about 200 miles ago, and wondering if it is still in a learning state. And the reason I reset adaptations is that I got new exhaust, new IAC, and new MAF sensor(previous owner didn't even have one).
Does anyone have any advice?

Last edited by drocket77; 07-29-2020 at 04:02 PM.. Reason: forgot to add #5
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      07-30-2020, 11:42 AM   #2
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Is the engine actually misfiring or is the computer misinterpreting it as such?
You will know if you have random misfires, the engine will not be running smoothly.
If your engine is running smoothly, consider the possibility of a crankshaft position sensor issue, or wiring issue:

https://www.newtis.info/tisv2/a/en/e...rs-1-6/Xayhvs6
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      07-30-2020, 06:40 PM   #3
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Engine runs fine, and no stuttering, nothing seems out of the ordinary. I replaced the camshaft position sensor connector for the exhaust side, cause the connector plastic broke, but was doing it before this. I thought it may be this sensor, or a cam sensor, but seeing as those are electronic, you would think they would throw a code. That is unless, it is completely random and not totally dead.
I Will just buy one and install. I know its near the starter, and will prob be a pain.

Thanks for the help.
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      07-30-2020, 07:46 PM   #4
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Sure, by the way I'm an armchair mechanic so I'd get a second opinion on whatever I say I would also try to do some data logging of the crankshaft position sensor to get qualitative information about the irregularity.
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      08-03-2020, 07:01 PM   #5
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That wasn't it. I installed new one, and car wouldn't start. I was at a loss. I took the new one off, and saw it had 2 o-rings.. I noticed when I took the old one off there wasnt one. I just chalked it up to maybe it didn't have one. But took the extra one off and reinstalled started right up.

My next thing to do is replace the whole intake tubing with whats supposed to be there. There are no vacuum leaks downstream of the throttle body. The tubing is a mishmash that kinda works. Previous owner had CAI with the wrong MAF sensor. I put the correct maf and the tubing is to small, so I bought some connectors from Pepboys, but still need one that fits the CAI to the maf. the OD on the CAI is "3-5/8. Once this storm passes I will work more on Wednesday.


Nothing has worked so far, and I am putting my bets it is a voltage issue to one of the coil packs. I tested the ohms a few weeks ago on the coil packs, and they all were really close to each other... forget what the # was but remember I looked it up and was within spec. I do not know anyone with a scope, so I will most likely have to take it to a shop and have them confirm or tell me its something else. If it is something else, my next point of interest will be the fuel system. ie... fuel pressure, or injectors.

Last edited by drocket77; 08-07-2020 at 11:33 AM..
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      08-10-2020, 02:19 PM   #6
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So far the things I have installed havent fixed it, but, hey at least I have new parts on it. I Just installed new coil packs on all of the cylinders., and it still has the random misfire. It did feel a bit more responsive, but that could just be placebo, or I may also need to reset adaptations again...

Below is the freeze frame on #5. I have also put 93 octane this time, and made sure I ran it pretty low before refill(had 91 last time)




My next step is to test the fuel system. I think the easiest to start with would be pressure testing it, and then get reading off of fuel sender and check filter. I don't wanna mess with the injectors just yet, as this is probably going to be a PIA and the most expensive thing compared to the other parts.

I really an leaning more towards Fuel/Air issue, and may even have to purchase the OEM airbox and intake tubing. (CAI is on it now)
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      08-10-2020, 11:24 PM   #7
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i doubt it, just remove your injectors and take them to someone who is proficient and has the equipment for cleaning them, and refurbing them, seals and such.

Shouldent be more than a couple hundred bucks. I had mine done last year for 200US, locally, although one of the seals needed to be redone after i got them back.

just inspect before re-installment.
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      08-11-2020, 12:08 PM   #8
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I just did some pressure testing on the fuel system. Fuel rail after starting the car for 10 seconds was 52psi. I waited 10 minutes and checked again, and it dropped to 46.

I was waiting for my new ram to come, cause my laptop is stuggling to do anything these days. 2gb on W10, and takes 2 minutes just to open INPA, let alone trying to open ISTA. I know with ISTA, I will get a better view of what actually going on.


If in fact if it is the injectors, I am just gonna buy new ones, good luck to get into any reputable shop within 25 miles. They are booked 3 weeks out. After I install them, wont I have to use INPA to input the new values.

I am reading different vehicle BB's, and most are saying it should hold steady for at least an hour. And then its should start gradually decreasing pressure. I think now the easiest to start with is FPR, then to the tank and sending unit and filter. I think my scanner has a section I can do a ventilation check, so I will do that one also.

Last edited by drocket77; 08-11-2020 at 12:18 PM..
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      09-17-2020, 04:54 PM   #9
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Still no luck. So far new injectors,coils,plugs, intake boot,MAF, crank sensor, IAC valve.My next things were to check on fuel delivery. It was a bit weird that I could control the tank ventilation solenoid, but not communicate with the EKPS.

So what I have found so far is that I have no comms to my EKPS. I assume that the EKPS is pulse width modulated, and will always keep the pump at a a certain %. This percentage is enough to keep a decent amount of fuel pressure even at significant load. What boggles me if I am getting no comms, shouldn't that have thrown a code? I am not good at wiring diagrams, and don't really know all the symbols or lingo. But from what I gather the Comm is connected with D-Can H, D-Can L, and Can Com to K-BUS. I am assuming I need to check each one of those connections. What should I be looking for...ie..voltage?


And is the module on the passengers side rear trunk, near the wheel well?

https://www.newtis.info/tisv2/a/en/e...supply/qJ5aaO8

I don't know if this would fix my issue, but at least I will have piece of mind if I fix the no comm issue and also tick off what isn't causing my issue.
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      09-17-2020, 11:05 PM   #10
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How did you come to the conclusion that "you have no comms to the EKPS" and what do you mean by that exactly.

You said your engine is running fine but you're getting misfire codes, right? Or are there symptoms?
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      09-18-2020, 04:11 AM   #11
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Bi directional scanner.I can read/reset/test most modules..ie...ABS,chassis,program keys.... for just about any car.

The only time I can predict symptoms is at startup, I do notice it misfire , but clears up in under 5 seconds. It then it wont throw a code until it is driven 3 miles at which time it throws a code for cylinder2 and 5, then about 1 minute later for 3-4-6, maybe 1 out of 10 times it will throw p0301 . Before I replaced my injectors, I could feel the misfire, but I don't feel any misfires except at startup. So there may have been and still are multiple causes. The earliest any Euro mechanic in my area has for appt. is mid Oct...
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      09-18-2020, 09:17 AM   #12
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Interesting. if it's driving normal after startup I think it should be ok to drive without worry. during some steady state driving, log and share your fuel trims (both long and short term) and o2 sensor readings (primary/b1s1,b2s1/pre cat). you want to make sure the car is not running rich fuel trims and seeing lean at the o2 sensor because that may foul your o2 sensors
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      09-18-2020, 06:22 PM   #13
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I am not worried about damage, or anything. I just need it fixed so I can pass inspection. I took the trunk completely apart today, and made the mistake of not undoing my battery before taking my amps out. Well, the 12v hit the outside of the amp when I unscrewed the positive off the amp. Luckily it was just my sub amp, and I still have tunes, just out $300 as it won't come out of protection mode. There is only 1 module in that trunk and it is the telemetrics module. Is the EKPS module somewhere else?

I also unhooked the MAF sensor, and went for a few rides. No codes other than MAF hot film, and temp... no misfire codes. Which is really making me think there is a prob with the EKPS module, or wiring. With the MAF removed the ECU is does not know how much air is coming in and is I do not know if theres a MAP
sensor. So I think the ECU just sets it to maximum fuel. When I purchased this, there was no MAF, and the oil smelled of gas.

Can someone confirm location of EKPS module? Everywhere I look it is saying the trunk, but like I said, its not there, not even in the battery box...Is it actually connected to the gas tank?, or is that just the pump itself?
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      09-18-2020, 11:17 PM   #14
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this is the information source I trust on Z4M fuel system. That said, do you have an older non-M? if you scroll all the way down to the comments it is mentioned that some models do not have a module, just a relay.

https://www.pelicanparts.com/techart...eplacement.htm
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      09-19-2020, 01:19 AM   #15
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I am gonna look for a relay. I noticed that it is controlled through A41, which should be behind the glove box near the fuse panel.
https://www.newtis.info/tisv2/a/en/e...si-roa/RZoY1Uu

I also looked at this.

https://www.newtis.info/tisv2/a/en/e...supply/XhflKCR

With that diagram, I should be able to follow the wires on the pump, and see where they lead. I was under the car 2 days ago, and didn't notice any loose or frayed wires. But it should be nice out the next few days, so thats better than the last month of 85 deg without shade.
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      09-21-2020, 01:36 AM   #16
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After digging through the interwebs.... I found the location for the relay. Behind the fusebox. But while searching I found my EWS module and saw a few wire near there unplugged. I could not for the life of me find where they go, One is a 4 prong plug with only 2 wires the other is a 2 prong with 2 wires.... This car sure does have some gremlins. Oh, and the trunk there was another 2 prong wire near the telemtrics unit that aren't hooked up...

I really need to find another Z4 and just have a day to go over it and take some pics of areas that are wrong with mine.
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      09-30-2020, 01:06 PM   #17
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If you can take a pic of what you are looking at. That be helpful. Thanks
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      10-08-2020, 10:43 PM   #18
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any update?
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      10-09-2020, 04:50 AM   #19
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What's this telemtrics unit? The only unit that does anything not related to stereo crap is the abs unit in the rear, all the other modules are radio/TV/amp/GPS etc.
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      10-10-2020, 01:45 PM   #20
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Sorry, no update yet. Been busy doing other peoples cars/trucks. Did ball joints, electrical, coil packs.... on a few cars for acquaintances.. I went on a drive for about 10 min with the MAF unplugged and no misfire codes... Once I get some extra funds, I will purchase the "correct" MAF sensor. But being out of work right now sucks , and my car is closer to the bottom of the list of things we need right now.

The telemetrics unit is for the radio--nav stuff, that I do not use. I have aftermarket google touch screen.
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      10-23-2020, 01:08 AM   #21
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Gee, sorry to hear, hope you get things sorted out
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      01-10-2021, 12:09 PM   #22
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OK, I just received a used MAF sensor and air box. Installed them and new AGM battery. Drove the car for about 45 min and no codes. I am so happy. Before I would get codes after 3 miles, so I am crossing my fingers this will get me past inspection now. The only thing that is a must for now, is adjusting the emergency brake.
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