I have a 1993 BMW 325i that has developed a sever sputter on acceleration. When the car is cool it seems to be fine but as soon as it reaches Operating Temp the sputter begins. Seems to level off and almost disappear when I hit cruising speed. The condition started off very slight a couple of months ago but recently here in AZ when the outside temp started hitting 100+ degrees it has become severe. Any ideas out there
Country: United StatesMake: BMWModel: 325iYear: 1993Engine: 2.5 L DOHC
Fuel pump is l year old. Tried changing the spark plugs and found 2 of the spark plug wells full of oil so I changed out the valve cover gasket and that solved that problem. Did a compression check and all cylinders are at apout 220 PSI except 2 of the cylinders are at about 190.
HelloThis could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak. Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engineMight also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.if the engine condition is the same then chances are the meter or the connection to it is faultyAir leaks are very temperature dependent as gaps can open or close up as things expand with heat, so the weather and engine temperature can effect them.This leads them to be quite intermittent in the case of mild leaksits also worth cleaning the airflow meter by removing it from the car and spraying the exposed sensor wires inside the tube with a brake or switch cleaner - ensure that the cleaner is one of the old fashioned, non Eco type that does not leave a residue On no account touch the sensor wires with anything physical as they are extremely fragilethe low compression on 2 cylinders isn't ideal but the car should otherwise run without sputtering
Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing