I am not to the point of addressing this problem yet but would like to see if anyone has had this problem or point me in a direction for what to look at to solve it. Here is the problem, bucking and or surging when cruising around 1700-2100 rpm reagardless of gear selection. If I let off the throttle is goes away and if I accelerate briskly it smoothes out. When sitting in neutral I can run the motor with no load at this RPM range and have not have a surging or bucking problem. My first thought was maybe the TPS was a little funky at that throttle opening but why would it not surge or buck in neutral? So I somewhat suspect the MAF? Now this problem does not make the car undriveable but is definately a nuisance especially when try light cruise on back roads. On a side note it has been much cooler in the mornings lately and I have noticed the temp gauge is just a hair over the first white line when fully warmed up. I think the bucking, surging has been worse on these cooler mornings.



Any one experience this or have any suggestions. Again I am not actively working to resolve this at the moment, I have an oil pan gasket and motor mounts to change first.



The car is a 1984 euro 5 speed. All stock except for previous owner installed a aftermarket exhaust with not cat.


Thanks for any help

Sam

 

test the temp 2 sensor, and if thats good try another MAF tester any 928 maf will work

 

I had the same bucking or surging problem while driving my '84 Euro. Do a couple seaches on my name and you will find them. After checking and changing quite a bit of stuff, I spoke with the most knowledgable Euro guy around, Dave Roberts from 928 Specialist. He told me that the 84-86 Euro is inherintly lean from the factory and that it does not take much MAF degradation to make it start to buck from the lean condition. Since that car does not have an O2 sensor, the computer cannot adjust for the degrading MAF. His suggestion was to force more fuel into the motor by using an adjustable fuel reg on the passenger side rear (replacing the stock regulator) and also replacing the fuel regulator on the drivers side rear with a fuel damper from the 85-86 US 928. The front center regulator you can leave alone. I did this and jacked up the fuel pressure. It fixed the bucking. I have since had my MAF rebuilt and have dialed the fuel pressure back down, but have kept it higher than stock though. Runs great.

 

The ability of increasing fuel pressure would be a long term solution in addition to a new or rebuilt MAF. I think you could just do the MAF first, and see how long it lasts. This should be the problem. Swapping a MAF from a good running S4 will not always work. I did this out of my '88 that was running great and the Euro was still bucking. It was my opinion and many others opinion that the O2 sensor and computer on the S4 was changing the mixture to cover up the degraded MAF. You will not have that luxury on the Euro unless the federalization clap trapped something in there. I tossed that mess immediately when I got mine.

 

Does the Euro 84 LH computer have the ability to read an O2 sensor but it was just not installed becuase Euro emissions did not require it?

The PO removed the federalization O2 sensor rig I have it but have no idea where the wires connected.

 

The '84 Euro computer will not do an o2 sensor. When I got my Euro, the federalization folks installed a piggy back computer module to handle this. Who knows if it ever worked. I tossed it. I dont think you would want to rely on band-aids like that. Just get the car going as it was from the factory.

As for the MAF, you can get a John Speake rebuild from 928 INTL or somewhere on Rennlist Big Dave had found someplace in Denver that does it for a little cheaper. I thought they had a good reputation. Only John Speake is a Rennlist sponsor. Just do a search for MAF with Big Dave as the username.

 

check and clean the multi pin connector at the right front of the engine bay i chased a surging bucking engine for 2 yrs and it ended up being a poor connection at the multi pin i cleaned recrimped the wires lubed them up reconected and all was great then felt the TT bearings were gone after the motor calmed down oh well thats this winters project

paul with 4 79 928s

 

byrdman you are referring to the thread "'84 Euro running lean" - just brought it up. I would like to know which adjustable fuel pressure regulator you put in. Thanks