Slight surging under load. Should I worry?

windseye

Member
I have a 2003 158 SHC with 300k. It has new rebuilt injectors and EGR valve and generally starts and runs well. I notice that while under load at freeway speeds there is a slight, rhythmic surging, about 4 cycles per second. This usually occurs when on cruise control going up a grade at freeway speeds. What should I be looking for? Does the EGR need cleaning? is there some slippage in the transmission? Is there a problem developing with the turbo?

When I bought the van the EGR was dead and there was severe rumble strip noise. Replaced EGR , new ATF and cleaning of the transmission sump and solenoids per Doktor A's procedure fixed the problem.

Any suggestions what to check?
 

jmoller99

Own a DAD ODB2 Unit.
I had a similar issue on my 2002 - it was air in the fuel lines (not very many, but once I stopped, I could see a few air bubbles in the fuel line going up to the high pressure fuel pump. I replaced my fuel filter with one that did not have the water sensor in it (this is a common place for fuel air leaks, especially very tiny leaks). The 2002's and 2003's have the fuel pump on the engine (2004 and later have a high pressure pump in the fuel tank), so they suck the fuel thru the filter from the engine side - very easy to get fuel flow/air leak issues.

You might want to find someone with a DAD unit and check your injector fuel pressure while you drive - its also possible that your HP fuel pump needs to get rebuilt.
 

randol35

New member
I have a 2003 158 SHC with 300k. It has new rebuilt injectors and EGR valve and generally starts and runs well. I notice that while under load at freeway speeds there is a slight, rhythmic surging, about 4 cycles per second. This usually occurs when on cruise control going up a grade at freeway speeds. What should I be looking for? Does the EGR need cleaning? is there some slippage in the transmission? Is there a problem developing with the turbo?

When I bought the van the EGR was dead and there was severe rumble strip noise. Replaced EGR , new ATF and cleaning of the transmission sump and solenoids per Doktor A's procedure fixed the problem.

Any suggestions what to check?
Did you ever fix this? I have the same surging problem under load between 40-65 mph. No check engine lights, and the van runs perfect otherwise.
 

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