ANYWHERE you have moderate-to-high humidity and ~40 degree F. weather, you need the heated air intake.
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I logged the engine from a cold start and thing I found a culprit or system The ECM show's the timing advance starting bouncing all over the place as can be seen in blue. Not sure where to head with this.
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I do not have wide band 02 sensor. It is just part of the file in Tuner Pro I'm using. It was a profile that was already made that works with my ECM.
I am very close to seal level. My manual said compression should be 150 but I know that can change with elevation.
Today I ignored the proper procedure of setting timing. I set the timing while watching the vacuum gauge and rolled the distributor until it gave me the highest reading which was 18 -19 inhg. It seemed to run a lot better. Even tonight when I went out and cranked it after it cooled off it didn't stumble as bad. Tomorrow, I am going to verify TDC with a piston stop to be sure. I did not go back and verify with a timing light to see where it ended up. Maybe the mark on the harmonic balancer or timing cover is incorrect. Both were replaced during the rebuild.
Second thing I am chasing is the IAC. It will not reset to closed by jumping A&B on the OBD1 connector. However, it does work to adjust idle speed while the engine is running. I am suspecting the ECM could be failing.
Last thing I want to verify is if the fuel return line or the fuel pressure regulator is a problem. I rebuilt the regulator and throttle body when I rebuilt the engine.
The heated air intake is not connected. I live in Louisiana not sure if it's needed or not.
It starts out with a high idle sounding normal. When it starts to idle down it begins bogging and shaking. Which usually happens within the first minute. The engine was still in open loop when the timing became erratic. When I was troubleshooting adjusting timing by vacuum I ended up at 4 degrees advanced. During this log I was at 0 degrees BTDC. I am trying to figure out if the erratic spark is a cause or a symptom of something else. When I pull the spark plugs when the engine is acting like this they are all soaked in gas from a very rich condition. Once the engine is up to temp the 02 sensor leans the fuel trim out. It goes down near 100 BLM an 100 INT. I am starting to think the fuel pressure regulator may be allowing too much fuel. I rebuilt it with an AC Delco kit. I'm debating on replacing it with a new one or making it adjustable.OK, I just reread the thread, and in this reply you set the timing for max manifold vacuum.
This is a valid troubleshooting step, but I'm curious as to how much spark advance you ended
up with? If it's a bunch, possibly the Knock Sensor circuit is relaying valid info to the ECU, and
it in turn is pulling a few degrees back out (yet hunting/oscillating) in order to keep the combustion
chamber peace despite the advanced base timing?
If you could, please document the timing that you ended up with. (Let's say it's +8 degrees from factory.)
Then, if you could temporarily reset the spark timing to the factory setting, and rerun the graph
that you have above? (ie: Cold start + 4-5 minutes?)
IF on the 2nd run the spark timing graph becomes much less 'noisy' then we have our answer. But if
the graph still has the same look, then we need to investigate the Knock Sensors for being
too sensitive/out of spec? (And if it was me, if the graph was still this noisy on stock timing I'd be tempted
to put the timing back to where the engine runs the best and continue to troubleshoot from there.)
The next step depends upon being able to figure out what the spark advance graph is trying to tell us.
It starts out with a high idle sounding normal. When it starts to idle down it begins bogging and shaking. Which usually happens within the first minute. The engine was still in open loop when the timing became erratic. When I was troubleshooting adjusting timing by vacuum I ended up at 4 degrees advanced. During this log I was at 0 degrees BTDC. I am trying to figure out if the erratic spark is a cause or a symptom of something else. When I pull the spark plugs when the engine is acting like this they are all soaked in gas from a very rich condition. Once the engine is up to temp the 02 sensor leans the fuel trim out. It goes down near 100 BLM an 100 INT. I am starting to think the fuel pressure regulator may be allowing too much fuel. I rebuilt it with an AC Delco kit. I'm debating on replacing it with a new one or making it adjustable.
I show some knock counts at start up but do not show any retards.
I think I'm on the right track. I think it's the new map sensor is reading wrong or a possible wiring issue. While it's running rough and flooding I plugged a mightyvac into the map sensor and dropped it to 20inhg the idle immediately stabilized. The manifold pressure climbed from 16 to 18 inhg. I looked back at some of my old logs. The reading was 55 KPA which converts to about 13.5 inhg.