Anyone else notice rich at idle with EFI engines?

[Miljack]

Hi all,
given the current state of the cost of gas, I noticed that when idling our PAN/Python smells "rich" at idle. I'm just wondering if any of you with the later model EFI engines also notice this at idle. The boat runs great at all other engine speeds, and reading the plugs really doesn't tell me anything because I haven't done a high speed "cut" to know what the plugs look like at operating engine speeds.
Are the EFI controllers "adjustable?" What ECM does PCM use on their engines, is it proprietary to them?

thanks,
Jack

[Mikeski]

RE: Anyone else notice rich at idle with EFI engines?

the systems run open loop because the o2 sensor would get fouled with water. under certain operating conditions (cold air) not all the fuel will be burned at an idle. the systems are described fairly well in the older PCM manuals.

[DavidF]

RE: Anyone else notice rich at idle with EFI engines?

Yep, my '95 TBI EFI engine runs rich at idle. PCM says this is normal but suggest I lower the fuel pressure about 2psi. It helped a bit. My engine has a 950 cfm throttle body, so it can burn some fuel, but man does it scoot.

[SGY]

RE: Anyone else notice rich at idle with EFI engines?

DavidF. I've heard that TBI boats are the fastest Nautiques on the water. Even faster than today's new boats.

[DavidF]

RE: Anyone else notice rich at idle with EFI engines?

Maybe, but I think there are two versions of the TBI engines...Pro Boss and Pro Ski. I have heard that the Pro Boss TBI is indeed rated higher than the GT-40's. I have the Pro Ski and it is fast enough for sure. Information on the TBI engines in scarce, so I am not sure of the above.

[nms1991]

RE: Anyone else notice rich at idle with EFI engines?

Miljack make sure your engine is running at 140 to 160 degrees so hte computer gets out of warmup mode (richer running to speed up the warmup). Only way to get in and change the perameters in the ecm is to have the program that pcm used to program it with. The ecm is made by delphi for the marine industry but it is programed by each marinizer for particular applications.

[Miljack]

nms,
thanks for the reply. Yes our water temp is 160 (indicated), any advantage to running these marine engines hotter? I know there is fiberglass downstream in the exhaust, how much water temp in the engine before you begin running into other system(s) problems?

thanks,
Jack

[DavidF]

The coolant sensor as used by the EFI ECM is simply a swith (open or closed). If the coolant temperature satisfies the switch then the ECM switches to normal mode (i.e. NOT warm-up mode). So, increasing coolant temperatue will really accomplish nothing as related to rich idle.

Measure the continuity of the coolant temperature switch (not to be confused with the coolant temperature sender) both cold and warm. You should have continuity or open circuit then vise versa.

Some engine have three coolant temperature "probes" (like my '95 TBI EFI engine): 1: Coolant temperature sending unit for temperature gauge. 2: Coolant low temperature switch for cold starts. 3: Coolant high temperature switch for over temp limp mode/warning light.

[nms1991]

Actually DavidF the ect is a variable thermal resistor in the efi systems so the computers can adjust the richness of the system requirements at certain temps. But miljack no there is not a advantage because the system is calibrated to run richer if the system gets over a set temp. But you may want to have a person or service center that has access to a computer with a diagnostic program to see what the computer is saying.