Misfire cylinders 4 and 7.

ANSWER : You need to check the PCV tube that goes behind the intake and connects into the back side. The hose can get a leak in it, causing a vacuum leak on the back side. This will create lean conditions that may be worse for cylinders 4 and 7 specifically on this engine.

If the hose is good then try and have the injectors replaced or cleaned for these two cylinders. You could swap them with different cylinders to see if the problem moves along to the other cylinder, doing so will help pinpoint the issue.

If you decide to get the car looked at, consider YourMechanic, as a certified technician can come to your location and diagnose your car’s misfire. An accurate repair can then be made once the problem has been pinpointed.

ANSWER : Driving for an extended period with a misfiring cylinder can certainly do damage. That cylinder will run hotter because of the misfire and piston and/or valve damage can occur. If you need help having this repaired, a certified professional from YourMechanic can inspect the misfiring situation and have this addressed properly.

ANSWER : Without checking the ignition coils and spark plugs myself for proper spark output I would say the engine is misfiring and may be the coils and plugs. It is also common for the valve cover gasket to leak oil into the spark plug tubes shorting the coil and spark plug out so it cannot fire. The check engine light is flashing due to the misfire is active and additional catalyst damage can happen if you keep driving with the misfire and raw fuel dumping into the catalyst. I would recommend having a mobile mechanic like one from YourMechanic come and do a through diagnosis to see if the valve gasket is leaking into the spark plugs and caused damage to the coils and spark plugs. If it is leaking then the valve cover gasket should be replaced with the spark plugs and contaminated ignition coils replaced then computer codes an be cleared and the vehicle road tested for any other problems from driving the vehicle with the engine misfiring.

ANSWER : This may be a problem with the exhaust catalyst partly clogged causing excessive back pressure. There is a test where the O2 sensor is removed and the back pressure tester is put in the hole to see if the catalyst is clogged.

The computer should be scanned to see if you are running lean from bad O2 sensors or for some other reason. The coil may also be weak and not putting out enough spark energy. Have the system checked by a mechanic since this truck engine may have exhaust problems, engine carbon build up, cracked valve seats, O2 sensor problems, coil problems, camshaft and distributor cam gear worn problems. The list goes on and will require a qualified mechanic time to diagnose this complaint for you. If a shop or mechanic cannot figure it out then it may take a factory trained mechanic to be able to diagnose the problem down to one of the listed issues. The best thing to recommend is to replace all the tune up items first so these can be eliminated. This means coils, plugs, wires, fuel filter and air filter, and PCV valve.

ANSWER : A misfire to cylinder 1 may be a fuel pressure regulator sensor problem but it is most likely due to a clogged injector on number one. You will need to scan and view data to see if fuel pressure sensor is needing replacement first. Then have the injectors cleansed to see if the codes go away.

I’d suggest you get this looked at by a qualified technician who can perform these checks to diagnose your Check Engine Light and make the appropriate repairs to your vehicle.

ANSWER : Hi there. The Exhaust Gas Recirculation (EGR) valve may be not designed for the emissions requirements for U.S. standards. If the EGR is pulling from cylinder number 4 and after replacing the EGR and the computer detects a misfire, then the EGR is malfunctioning and not responding. When you close off the tube to the EGR and the EGR light comes on and the misfire light goes out, then the EGR is not responding to your emissions system. I recommend replacing the EGR with the OEM specified part for the engine and all of the issues should go away. If you need further assistance with your misfire and EGR, then seek out a professional, such as one from Your Mechanic, to help you.

ANSWER : Hello. It sounds like you may have the wrong parts installed on the car. Due to the fact that multiple people have worked on it you may have some parts that do not meet specifications. From what it sounds like to me though you either do not have an ECM in the vehicle with the correct programming or you have a connection issue. If all of the grounds are not clean and tight then that will cause this. if they are then the computer needs to be programmed to your vehicle at the dealer and that may take care of it.

ANSWER : Hello there, thank you for asking about your BMW 760Li. I don’t know what year your BMW is, but there was a technical service bulletin (TSB) on some models regarding the fuel injectors. Although I can’t seem to locate the TSB, the fix was to replace all of the injectors. This problem was so common that BMW issued an extended warranty on the injectors to 10 years/120,000 miles. This may be the problem with your vehicle. Of course, there are many other potential causes as well. My advice is to have your vehicle diagnosed by a professional, such as one from YourMechanic, to inspect your rough idle and misfires or replace a faulty fuel injector.