Hi All,

I seem to have an intermittent problem with fuel delivery. It only affects the left side and seems to be getting worse. I noticed three weeks ago some shudder and hesitation at low rpm. I had low O2 readings on the left side at idle and cruising but seemed normal under acceleration. I had both O2 replaced and still saw low numbers on the left at idle and low rpm although sometimes especially when cold O2 numbers looked normal. Now I see increasing knock counts and this seems to coincide with the low O2 readings and the rough running. I wonder if this is more likely mechanical problem somehow or electrical. It seems more likely electrical to me. Any suggestions would be appreciated. These injectors are new as of this spring and seemed fine for several months.

 

I didn't notice, do you still have an EGR system or did you remove it? Also what is your vacuum level lately?

 

Yes, I still have EGR. I looked through my logs and see it has happened since 6-25. If I put both O2's on my Datamaster graph the drop on the left side is obvious. It seems to last only for 5-30 seconds 2 or 3 times on a 20 minute drive. It seems to happen only once the engine is hot. It may be getting worse because the last few days I am seeing big knock counts, too. It really seems related to outside air temp and voltage drop from the charging system as the engine temp goes up. I see voltages as low as 12 in Datamaster log. Usually voltage is 12.6 to 13.0 and that seems a little low to me. The low O2 counts seem to occur even when 12.7 or 12.8 shows in logs though.

 

What's the condition of the sensors like IAT, MAP and TPS? Have you checked vacuum level yet? Try disconnecting the MAF sensor and see what happens. By the way the voltage level can also screw with sensor readings. Check the battery voltage while the engine is cranking and see also if the voltage level rises once the car is running.

Look at the EGR to see if it's stuck or leaking.

 

I have not looked hard at things like that because it only happens on the left side. It does not look like a single weak or lazy injector. It seems to be the whole bank on the left side. This would seem to eliminate fuel delivery and pressure, most electrical problems, and sensor malfunctions. The low O2 readings at cruise are linked to the rough engine feel and the increasing knock counts so I think it is really lean and not just a bad O2, which is new, or exhaust leaks letting in fresh air to the sensor.

 

Move all of your left bank injectors to the right and see if the problem follows them.

 

Thanks,
I actually had not thought of that. I don't see how a whole bank could do this. I don't know exactly how the fuel rail works though and have not looked at a schematic of the wiring for the injectors either. If nothing else maybe if I touch them all the problem will disappear at that.