Fixed My rough idle and hard start problem

[LELeach]

To "81" and "Cam7" I fixed my rough idle and difficult hot start problems.
The hard start issue was cured by a new fuel pressure regulator. I checked the fuel pressure and found that it would bleed down to "0" after shutting off the ignition. $ 60 at Auto Zone. The rough idle issue was carbon build up in the compustion chambers and possible some in the injector tips. I discovered this by checking the compression and finding every cylinder had higher compression than new engine specs. I removed the intake air hose from the throttle body, reved the engine to about 2500 rpms and slowly poured about 8 ounces of a 12-ounce can of Marvel Mystery Oil into the throttle body. I poured the last four ounces in rapidly and let the engine die. I let it sit for about 10 minutes and restarted the engine. DO NOT TRY THIS IN YOUR GARAGE OR DRIVEWAY IN A POPULATED AREA!!!!!! Once the engine started you could not see the vehicle for about 30 seconds due to the massive amout of white smoke from the tail pipe. The engine smoothed out in a couple of minutes and it now idles smooth as silk. I learned the Marvel Mystery Oil decarbonizing trick from my high school hot rodding days back in the early 1960s. Thanks very much to everyone who responded and helped me with this problem. LELeach

[Stoeger]

Yep, this is called the HOT SOAK, a trick used by the BMW guys. Pretty much any valve/injector cleaner can be used, the most popular ones are Chevron Techron Concentrate, or the SeaFoam product. I injected the Techron into my 89 325i and it helped a ton!

[Stoeger]

Just curious, exactly what intake air hose did you use?