iintermittent randomlean

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iintermittent randomlean

Postby Gralen » Sat Aug 05, 2017 9:04 am

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New to megasqirt second post

Running factory built MS2Extra 3.4.3 with Ford 302 TFI in 38 Ford wide band O2 sensor engine is not new

Have been working my way through the process of tuning using the auto-tune function and things seem to be dialed in pretty close as far as having my AFR being where I want them however i have thus continuing problem of intermittent blips of lean. The O2 gauge shows it and the engine bucks. It happens at all throttle settings and loads and can be quite violent. Under light acceleration if it starts it will stop if I go to full throttle but then will start up again under that condition.

I have replace the injectors, new distributor, new TFI unit, new coil. completely took the harness apart and checked all connections when I installed the megasquirt. Fuel pressure is 30-40psi

To be honest it was doing this a bit before installing the megasquirt with the OEM ECU that's why Ii replaced distributor and TFI unit before I started. I was think spark misfire but because I can stop it with harder acceleration I assumed ignition was good. Check compression

I have smoke checked the intake system for any leaks and found none. I have attached a short data capture this shows the events two modes one just at idle the other in drive(automatic transmission)

Any help would be greatly appreciated
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Last edited by Gralen on Sun Aug 06, 2017 1:21 pm, edited 5 times in total.
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Re: iintermittent randomlean

Postby billr » Sat Aug 05, 2017 9:43 am

I see no files attached. Try again to post the MSL and MSQ.
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Re: iintermittent randomlean

Postby Matt Cramer » Wed Aug 09, 2017 12:59 pm

This could be an ignition miss. What's it running for ignition?
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Re: iintermittent randomlean

Postby Gralen » Wed Aug 09, 2017 1:24 pm

The megasquirt is utilizing the ford TFI unit input to the Megasquirt
The distributor, coil, anf TFI unit have all been replaced.

Its that is smooths out with hard acceleration for a few seconds then the miss starts up again and its random, this what confuses me about it being spark related.
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Re: iintermittent randomlean

Postby kaeman » Sat Aug 12, 2017 6:26 pm

One place you may want to check is the spark plugs and wires, I had a randomly occurring miss and found that one of my new spark plugs was defective. I have also had plug wires go bad and give the random miss also. check your plug gap, you may need to close it up a bit depending on the fuel and compression you have. Good luck.
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Re: iintermittent randomlean

Postby Gralen » Sun Aug 27, 2017 10:39 am

thank for the support
I got new MSD replacement performance coil.
installed and tried to start engine would barely start as ignition was to far to advanced.
Checked timing and had to retard distributor almost 20 degrees. reset base timing to 10 degrees engine runs perfect tuner studio results look like what i expected.
Very important lesson learned I suspected ignition from start and replace coil with what i thought was a good coil.
Hard to believe that the coil was throwing of the timing that much.
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