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sebastian manrique
sebastian manrique, Auto Mechanic
Category: BMW
Satisfied Customers: 2504
Experience:  Director Ejecutivo at Multiservicios Cruz de las Mercedes
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Brought an E91 2008 318i with a misfire and potential

Customer Question

brought an E91 2008 318i with a misfire and potential injector issues.Replaced and coded the injector and it ran fine however after a week started running rough on cold. I was getting round to looking at it however a week later the head gasket blew! I ripped the engine out and rebuilt it and guess what? Still misfired.Ripped the engine out again, rebuilt it however got the head resurfaced as it was warped this time and had the block and head pressure tested. All good, however, guess what? Still misfires. Below is everything I’ve done.- Replaced all 4 injectors and coded
- Replaced all coils
- Replaced all spark plugs
- Replaced rocker cover and ccv
- Replaced head gasket
- Head resurfaced
- Block and head pressure tested (all clear)
- Replaced MAF
- Replaced O2 sensors
- ECU tested (all clear)
- Smoke tested (all clear)
- Replaced all engine block seals and gasketsNow when you start it cold it has a slight rough running that turns into a bad misfire and limp mode once hot. I’m at a total loss!
Submitted: 9 days ago.
Category: BMW
Expert:  CarDoc replied 9 days ago.

Hi, How are you?
I'm Shabaz, one of the automotive experts, I'm sorry you're experiencing problems with your car, I will do my best to help you today.

Is the misfire on a single cylinder?

Customer: replied 9 days ago.
Hello, No not specifically.
Expert:  CarDoc replied 9 days ago.

Has the car been scanned for faults or logs of misfires? This information is available on diagnostic machines and it will also tell you which cylinder is misfiring.

If you do the unplugging test with the injectors or spark plugs, you will know which cylinder is misfiring because there will be no change in engine behaviour when the injector or coil is unplugged.

Customer: replied 9 days ago.
It isn’t cylinder dependant. When running diagnostics it does show an EGR fault that was no presenting initially. When running further diagnostics on the egr it shows the attempted value was 90% open however the actual value was only 60%
Expert:  CarDoc replied 9 days ago.

Have you removed and checked the EGR? Did you try to re-learn it?

If the EGR is sticking, it will most likely fail the re-learn procedure. If the misfires are happening on all cylinders, I wouldn't rule out a timing issue, I would double check the timing.

Customer: replied 9 days ago.
Double checked the timing and it’s definitely correct.I haven’t yet tested the egr, do you know how I could test the egr on this particular car as it’s electronic and not vacuum. Could the egr cause this misfire?
Expert:  CarDoc replied 9 days ago.

Electronic EGR is tested with a diagnostic tool. Have you tested the vanos solenoid? it should be around 11 ohms on a multimeter and you can also remove and put 12v to the solenoid to test its operation. Other sensors that can cause misfiring is the crankshaft+camshaft position sensors but I would recommend fixing the EGR issue first because you have replaced a lot of parts as it is.

Customer: replied 8 days ago.
I have tested the solenoid, they open and close with 12v. Would you recommend I still test the resistance?
Expert:  CarDoc replied 8 days ago.

Yes you should test the resistance, even if they open and close, it could still be faulty. 11 ohms is what you're looking for.

Customer: replied 8 days ago.
I have just tested them and they both came back at 10.8. How would I test the camshaft position sensor?
Expert:  CarDoc replied 8 days ago.

Was it a stable reading at 10.8?

Camshaft and crankshaft position sensors are tested with an oscilloscope because the signal is a waveform not a specific voltage. If it's a 3-wire sensor then you can only check for power+ground (hall effect sensor). A 2-wire sensor has a ground and signal wire (it produces its own voltage- inductive sensor) so, you can only check the ground on this type of sensor.

Customer: replied 8 days ago.
good news I have an oscilloscope! Ok so I’ll check out how many pins the camshaft has as that’s easy to get to, if memory serves correct I think it’s two pins however I will check. Any head what I’m looking for on it?By the way thanks for your continued support. Very knowledgeable!
Expert:  CarDoc replied 8 days ago.

It's my pleasure. You're looking for a continuous waveform that doesn't change. Have a look at the picoscope WEBSITE, it's got brilliant training guides which explains a lot about oscilloscope waveforms and what you should be looking for in camshaft and crankshaft waveform correalation.

Customer: replied 8 days ago.
Funny enough my oscilloscope is pico! I’ll have a look tonight and test it on the weekend and report back on my findings! I’ve removed the EGR today and replacing that tonight/morning.
Expert:  CarDoc replied 8 days ago.

That's even better. Pico have a lot of support and training, you can learn a lot from their guides. All the best and let me know how you get on. Thank you

Customer: replied 8 days ago.
I got the EGR removed. It’s an electronic one, it was stuck open by about 70%. It seems it will not go back to closed by just the force of the spring itself and needs physical intervention to close it. The replacement seems to close on its own if I open it. So it’s obviously faulty and is stuck open. I guess that’s more than likely my issue?It makes sense as the misfire isn’t really bad until the car gets hot. I guess once the exhaust gas gets really hot it just kills the engine. What’s your thoughts?
Expert:  CarDoc replied 8 days ago.

It's possible because metal expands with heat and therefore all the clearances between components change and if there is any existing problem, it can cause an issue. The valve inside the EGR is basically the same thing as the valves in the engine head, instead it is controlled with a cam on a motor spindle. Misfiring due to the EGR is not common but it can happen if airflow is being restricted (air:fuel ratio and all that sciencey stuff), if the EGR was gunked up, make sure to check and clean all the pipework associated with it.

Customer: replied 8 days ago.
If the EGR is stuck open like mine I guess it would ruin the ratios by throwing in way to much carbon dioxide and not enough oxygen.I’m going to attempt to get it back together with the new EGR tomorrow, by the way removing it is not a fun job on the N43!! Right at the back of the engine! So I’ll let you know how it goes. Fingers crossed as I’ve been fighting getting this working for a long long time!!
Expert:  CarDoc replied 8 days ago.

I know, BMW love making things unnecessarily difficult. I don't think it can measure CO2, just sees it as hot air to be honest, it's just that the 14.7:1 air:fuel ratio gets thrown off and possibly air temperature which alters the density of the air therefore affecting the volume of air entering the cylinders, I think even that is digging to deep but it's likely to be something along those lines if the EGR is causing the misfire.

Hopefully, all this graft will pay off. All the best!

Customer: replied 7 days ago.
Hello, replace egr and car runs smooth as anything when cold. After 15 minutes of running and it’s hot it runs rubbish, engine management light comes on and goes into limp mode. Getting two errors, misfire on cylinder 3 and maf sensor.I’ve already replace every injector, spark plug and coil. I did double check and swap the coil and plugs with cylinder 1 and the issue remained on 4.When checking the smoothness values 1,2,4 all are between 0 and +503 however sits around -200 and -800 when in complete limp mode and dyes then you push on the accelerator.
Customer: replied 7 days ago.
This is when cold and it’s running well
Customer: replied 7 days ago.
This is when it’s hot and misfiring
Customer: replied 7 days ago.
Low pressure fuel pump at idle
Customer: replied 7 days ago.
High pressure fuel pump at idle
Expert:  CarDoc replied 6 days ago.

The smoothness value shows that there is a misfire on cylinder 3. Did you check for spark with the spark plug removed? also check the injector pulse with a 12v test lamp.

Customer: replied 6 days ago.
I haven’t I will test the spark plug tomorrow, I guess this would rule out an issue with the wiring to the spark plug?How would i test the injector? I don’t know what the test lamp is. Is there a way I can do this by back probing it to just a normal 12v light to flash when it pulses?
Expert:  CarDoc replied 6 days ago.

Yes, you should see a good spark at the plug (not a faint spark, also check the condition of the plug and see if it's not wet with fuel) and yes you back probe the ground wire at the injector connector with a 12v test lamp, a test lamp is basically a 12v bulb inside a probe with a wire for ground and the tip of the probe is used to find 12v power, you can search on google to see what it is.

Customer: replied 6 days ago.
Is this the right thing? I guess I’d connect the ground to the chassis and the end to the live on the injector?https://www.halfords.com/tools/hand-tools/all-hand-tools/circuit-tester-6-24-volt-708434.html?
Customer: replied 6 days ago.
Again thank you for your great Adobe and support!
Customer: replied 6 days ago.
Advice**
Customer: replied 6 days ago.
I’ve just checked YouTube how to test with a light probe so I will try that with the spark plug in the morning and report back!
Expert:  CarDoc replied 6 days ago.

My pleasure and yes that's the right tool.

Customer: replied 6 days ago.
tested the coils and sparks today all came back ok. Also tested the cam sensors and they’re ok. Results attached
Customer: replied 6 days ago.
Exhaust attached. Intake was the same.
Customer: replied 6 days ago.
I tested the injectors and they are all the same except injector one. Results below.
Customer: replied 6 days ago.
Injector 4
Customer: replied 6 days ago.
Injector 1
Expert:  CarDoc replied 6 days ago.

There's definitely a difference, it's good to do the same with all injectors for comparison so you know which one is the odd one out.

Customer: replied 6 days ago.
It’s definitely 1. I’ve only sent injector 4 as an example however they’re all the same as injector 4 (picture one), except injector one. I tested the resistance of all the injectors and they were all 199-200ohms
Customer: replied 6 days ago.
Would this mean the ecu is sending bad data to the injector or could it still be the injector regardless of the resistance being the same as the others?
Expert:  CarDoc replied 6 days ago.

Did you test it unplugged or plugged in? test it unplugged if you haven't already.

Customer: replied 6 days ago.
I tested them plugged in and backprobed. So unplug them all and rerun the test? If the values returns to the same as the others then it’s probably injector, if it stays the same then it’s the signal to the injector?
Expert:  CarDoc replied 6 days ago.

Yes that's exactly right for both questions.

Customer: replied 6 days ago.
You’re a cleaver man! Simple process of elimination right! Thanks mate, I’ll try this tomorrow!!
Expert:  CarDoc replied 6 days ago.

Thanks mate :) it's the best course of action in this situation.

Customer: replied 5 days ago.
Hello so I retested them today. Seems I didn’t have a good connection on the backprobe, all came back clear when testing unplugged and retested with back probing and all came back ok. I did a resistance test on each line as well for every injector and they all came back the same. So unfortunately it back to square one.The car misfire a little when first started until warm, once warm it’s dreadful and goes into limp mode. It has a lag until 2000rpm regardless of if it’s hot or cold and a medium amount white smoke from the back. Doesn’t smell of anything.
Customer: replied 5 days ago.
These are the values when it’s hot and the misfires really bad
Customer: replied 5 days ago.
Customer: replied 5 days ago.
Customer: replied 5 days ago.
Customer: replied 5 days ago.
Customer: replied 5 days ago.
It is to note when I changed the egr a couple days ago it ran smooth as butter until it got hot after about 15 mins then it misfires on as normal.Now it always misfires even when cold but worse when hot.
Expert:  CarDoc replied 5 days ago.

White smoke is a sign of water, could just be condensation. It's difficult to understand over a computer screen but it highly likely to be a timing issue because it's misfiring across all cylinders. I will opt-out and see if there is a BMW expert available to help.

Expert:  sebastian manrique replied 4 days ago.

Hi, my name is***** your mechanic automotive expert, and I will be happy to assist you today. In some cases, I may need more information to assist better. I apologize for any delay.

Dear customer, I am sorry for what you are presenting, I know that the repair costs had to be high but I have to tell you that when these kindof problems occur, the first thing to do is replace the engine completely, there are many damages that we could not even observe For example, onesuperficial blow to the head of the pistons casuing deformations at the level of the cylinders, problems in the fittings or in the rest of the hidden chamber on the block, even until the injector rests suffer defects, then all these deffects accumulate and when we believe that the replacements of the moving parts of the cylinder head would solve the problem but it is not like that. That is why I personally when there this type of explosions always told clients that it is best to replace at least the head and the accesories of the engine, which is the chamber and block assembly because it is very difficult for these engines to be working exactly as they were running before.

On the other hand, not only in your case i would replace the engine, but I see it necessary to do several jobs on the injection system.
I see that the jobs you have done here have been on the spark plug coil and injectors, but I see it necessary to replace the rail and the pump, because in the rail there may be problems regarding the regulation and fuel return. If the injection regulator is working incorrectly, there is too much fuel in the cylinders, as well as if the return is sealed or does not allow the correct passage of fuel, either for some defect dirt or blows on the return rail, this also creates excess fuel.

Now with respect to the fault that you present in terms of the engine, it is very difficult to tell you that with the repair that you carried out the vehicle will be working correctly due to the factors that I mentioned, in the beginning but as in the same way due to the future of the failure, I am going to recommend you do the replacement of the rail and the fuel pump first and if this does not correct the problem you will have to locate athe head and its accesories.

Before finishing the answer to your query, when we have problems at the injection pulse level, that is, when the computer is working uncontrollably and there is no regulation in the fuel injection pressure system, there is an excessive injection pulse that we can take as normal but the computer may be the cause of these problems as well.

My goal is to give you the best advice i can based on your description, I hope to be helpful, if you have any doubt please do not hesitate to reply back.
Kind regards, Sebastian.

Customer: replied 4 days ago.
Surly that’s just throwing money at a wall and hoping it sticks? The heads been resurfaced, completely reconditioned and pressure tested. I don’t see why replacing it would be beneficial at all?In regards ***** ***** fuel rail and pump. Both have been tested as previously mentioned and have been proven to work fine. They both have the correct pressures.
Expert:  sebastian manrique replied 4 days ago.

Dear customer, how i did indicate, these engines when they suffer this kind of blows, they are never good to rebuild, these kind of problems mostly even though there are no compression problems, even though the cylinder head has been very well resurfaced, remember that not only pressure can affect the cylinder head but also the cylinders and pistons, but I know about the high repair costs, but to indicate that there is a failure in another area such as at the electrical level computer, I do not see it feasible, the most I could recommend is that you do a study of the injection pulse, also, check how the pulse is , i.e the regulation with the injectors are working, to see if there is an excessive increase that has caused the problems, but anyway, ats the rail was already verified, return problems should not affect.

I can only tell you to check the status of the injection pulse and to think or evaluate the replacement of the engine unfortunately.