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sebastian manrique
sebastian manrique, Auto Mechanic
Category: BMW
Satisfied Customers: 2524
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: 15 days ago.
Category: BMW
Customer: replied 15 days ago.
Expert:  sebastian manrique replied 15 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 going through this, I know that the repair costs are high but I have to tell you that when these problems occur, the first thing to do is replace the engine completely, there are many damage that we could not even observe. For example, one or another superficial blow to the head of the pistons from 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 a job to the head and 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 blowns happens always told clients that it is best to replace at least the accesories and the head of the engine, which is the head and block assembly because it is very difficult for these engines to be working exactly as they were running before.

On the other hand, if the replacement is not possible, I see it necessary to do several jobs on the injection system, I see that the jobs 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, regarding 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 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 another engine or at least cylinder head and some accesories.

Before finishing, when we have problems at the injection pulse level, that is, when the computer is working without control 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.

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 15 days ago.
Hi, thanks for your comprehensive response. When you say fuel pump do you mean the high pressure fuel pump or the fuel tank pump? Also assuming you mean common fuel rail correct?
Customer: replied 15 days ago.
I do currently have an EGR fault which was not initially present. I am going to replace it, could and EGR cause a misfire like this?
Expert:  sebastian manrique replied 14 days ago.

Dear customer, i mean the intake pump.
The EGR valve recirculate the exhaust gases to the intake system when we have problems in the EGR valve, it can generate various problems in the acceleration system and of course they can cause misfires but it doesn't cause that kinds of blow.

Customer: replied 14 days ago.
I think the original issue that caused the head gasket to blow was to do with over fuelling from a failed injector that’s since been fixed.So to clarify you mean the pump which takes it from the fuel tank, not the high pressure pump on the common fuel rail?
Expert:  sebastian manrique replied 14 days ago.

Yes correct, i meant the fuel tank pump