Today’s Symptoms:

On some MB vehicles, intermittent surging MB E320 engines might be difficult to fix. The surging or sudden high idle might not be noticeable at first and the vehicle might run as if it is normal. A lot of times, the surging occurred in split second and it is hard to detect. The same situation happened to me when a customer complained his 2004 MB E320. The engine was a 3.2L and has a 5 speed automatic transmission. No codes were found when my scanner was connected.

Diagnosis on intermittent surging MB E320:

I was swamped with a lot of jobs when this intermittent surging MB E320 came and my instincts pointed me in replacing the cam and crank sensors after no codes were found. To prevent unwanted parts, both sensors were checked with my labscope tester and the readings seems to be normal. I pulled out all the spark plugs to check for correct gaps and they were all fine. I also read the model’s service bulletin and beside having one ecm (computer) reprogramming (reflash), there is no mentioned of any intermittent surging MB E320 problems. I called up some of my garage friends and they are not aware of any engine problems like this. I also checked the other troubleshooting basics like testing the engine vacuum leak, fuel pressure and all wiring connections were found to be within specifications.

Fix of intermittent surging MB E320:

This intermittent surging MB E320 was becoming a nightmare after all my attempts to fix the problem failed. Then the next day, I got a call from my buddy who worked in a transmission shop. He told me this problem is common which is caused by radiator failure with coolant leaking to the tranny. When this happens, it causes the tranny torque converter to perform erratically which can be mistaken for an engine surge. In most cases, if the problem is caught early, you can fix it by replacing the radiator, otherwise, you have to replace the transmission and torque converter too. When I informed my customer about this, he immediately called up his extended warranty provider who promised to fix the problem for him for free. I am just glad to have this out of my hands but from now on, I will be careful when dealing with this intermittent surging MB E320 engine problem.

Thanks!

Richard