8.1 idling 10 rpm too high

boatrboy said:
? Also see posts 32 and 37 - thoughts?
Click to expand...
The MAP at idle is still a bit high it appears. It should be closer to 5.8 PSIA which is about 18 In Hg. Maybe someone else can comment on the idle vacuum for these engines. Assuming the new data is accurate then still there appears to be a bit of a vacuum leak somewhere or the throttle body needs adjusting. At least the IAC seems to be modulating at idle now. However, it is hard to say because the data at idle isn't the same as we looked at which was key on, engine not running, and fault list. The TPS at 0.12% is curious - you might want to visit setting up the throttle body then the TPS.
 
ttmott said:
The MAP at idle is still a bit high it appears. It should be closer to 5.8 PSIA which is about 18 In Hg. Maybe someone else can comment on the idle vacuum for these engines. Assuming the new data is accurate then still there appears to be a bit of a vacuum leak somewhere or the throttle body needs adjusting. At least the IAC seems to be modulating at idle now. However, it is hard to say because the data at idle isn't the same as we looked at which was key on, engine not running, and fault list. The TPS at 0.12% is curious - you might want to visit setting up the throttle body then the TPS.
Click to expand...

I don't think that a vacuum leak would manifest itself as you suggest. The MAP sensor should be reading the air pressure and it doesn't care if the air coming in would be from the IAC motor, the parked throttle blade or a vacuum leak. To me the TPS not at zero is not unusual, still below were the "idle mode logic" would be set which kicks off the IAC and spark idle logit to try to control to target RPM.

The fact that MAP is higher on this run vs someone else (or a later run) could be explained by the idle spark. Idle is control by the dance of spark and the IAC motor, spark moving fast (cyl even to event) and the iac motor moving slower. Once the desired idle is achieved the system doesn't care is map is slightly higher... it just pulls back spark to remove extra tq.

Anyway, I'm just speculating at this point, it's hard to diagnose anything remotely, and with just single snapshots and not graphs, etc.
 
Ericinmich said:
I don't think that a vacuum leak would manifest itself as you suggest. The MAP sensor should be reading the air pressure and it doesn't care if the air coming in would be from the IAC motor, the parked throttle blade or a vacuum leak. To me the TPS not at zero is not unusual, still below were the "idle mode logic" would be set which kicks off the IAC and spark idle logit to try to control to target RPM.

The fact that MAP is higher on this run vs someone else (or a later run) could be explained by the idle spark. Idle is control by the dance of spark and the IAC motor, spark moving fast (cyl even to event) and the iac motor moving slower. Once the desired idle is achieved the system doesn't care is map is slightly higher... it just pulls back spark to remove extra tq.

Anyway, I'm just speculating at this point, it's hard to diagnose anything remotely, and with just single snapshots and not graphs, etc.
Click to expand...
Wow - Eric - did you write the 555 program? :) Did Tt help??
I will try to capture a graph as I go though an rpm rise. All of my runs on the port motor show an idle of 650 and the map is pretty consistent in the 6.3 range. This is similar to the data supplied by tri in post 27.
I can’t wait to drive my boat and see what it runs like. It always runs good, just idled a little high until now. I purchased new plugs and wires, even though the plugs are only 1 yr old. and will install them to start my season. I’ve been out of commission with foot surgery so I haven’t taken boat out since launch….
And thanks for the information - I’m getting quite an education here.
 
boatrboy said:
Wow - Eric - did you write the 555 program? :) Did Tt help??
I will try to capture a graph as I go though an rpm rise. All of my runs on the port motor show an idle of 650 and the map is pretty consistent in the 6.3 range. This is similar to the data supplied by tri in post 27.
I can’t wait to drive my boat and see what it runs like. It always runs good, just idled a little high until now. I purchased new plugs and wires, even though the plugs are only 1 yr old. and will install them to start my season. I’ve been out of commission with foot surgery so I haven’t taken boat out since launch….
And thanks for the information - I’m getting quite an education here.
Click to expand...

The short answer is no, not directly. But I started as a co-op doing the SW on some early-80s TBI programs then worked on a bunch of others until mid-90s, mostly V8 cars (vette/F-body), LT5 Lotus, Ilmor Indy engine, etc., then some HW, back to SW on 4 cyl, HW on marine for short time, then hybrid trans. Those were the days when the SW was one or two folks so you kind of had to do it all. But even as things got more compicated the base controls were very much the same, but a lot more diagnostics. Along the way when on package would improve in an area (for example IAC getting lost, new init logic), others would pick it up as well. By early-mid 2000 when I move on the controls team were dozens to a 100 folks doing defined small slices of the SW and the number of engineers that understand the whole picture is small. The marine controls started with a version of SW and HW that I had worked with, but it never had to do the full emissions controls until after I wasn't involved.
 
Latest update -
For the first time in weeks I was able to take the boat for a ride.
The boat started and both engines idled at 650 on the nose. Ran the boat for about an hour on Long Island Sound and it ran like a dream. Tested WOT on the way back and back at the dock she idled perfect. I did not rescan after this run today, but at this point I’m happy with the performance.
Once I get around to changing the plugs and wires, I’ll rescan again and compare data.

Thanks to all who were helpful.
 
You must log in or register to reply here.

Forum statistics

Threads
113,224
Messages
1,428,898
Members
61,116
Latest member
Gardnersf
Back
Top