MicroSquirt-Engine starts, impossible to maintain idle

BugsOli

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Jul 1, 2013
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Ok guys, I'm stumped and it might probably be a stupid error on my part but... long story short: tried to redo the timing on my MicroSquirt equipped 302 after changing the head gaskets and removing my EGR.

I've set my engine to TDC, stabbed in the distributor, made sure that the pointer was set to the #1 spark plug cable and set my timing in TS to Fixed 20°, exactly like the first time I did it 1 year ago.

The engine cranks and idles for 10 seconds but then it dies, so I've turned the dizzy clockwise and tried that multiple times... until it hits the fuel rail on the driver side :bang:
I tried multiple fixed timing in TS (10, 15, 20...), tried using the Trigger Wizard per the recommendations but as soon as I update the value in TW, the engine dies.

I'm lost... should I restab the dizzy at another angle to give me more "room" to turn it and try to get as close as possible to the 20° (and use the TW) or is there something else that I should look into?

The Spark Output is set to Going Low, I've reset my TPS, the Cranking RPM was set to 500 (I'm going to try 350), the Idle Control Algorithm is set to Open-loop, the Required Fuel has not changed since 1 year (24 lbs injectors, standard 302).

Don't know, I might be missing something, I've enclosed my MSQ (nearly the same one I've sent you @a91what )

Thanks for all the help you can give me mates!
 

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a91what

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Apr 6, 2011
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you may want to force the idle valve to a high position in the testmodes [top right select box] this will hopefully allow you to hold the rpm high enough to get the timing set.
just so im sure, your leaving the spout plugged in correct?
 

BugsOli

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Jul 1, 2013
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So, some news from Europe.... your tip did the trick to set the timing @a91what ! thanks a lot mate! I've checked that my dizzy pointer was correctly pointing to the #1 cylinder by rotating the engine to TDC once again, then restabbed the dizzy a little bit further clockwise to allow for more "rotating room".

But............... (there is always a but with our cars right?): after setting the cranking RPM to 350 (instead of 500) and setting the timing to 20 degrees (matches with the damper), I put it back to Use Table and it idles a couple of seconds more than before but still dies and I can hear a hissing noise when it dies.... so I'm thinking VACUUM LEAK!!!! crap, I feel like it's coming from the back of the GT40 lower intake, I hope the gasket there has not moved but I'm not too sure :eek: only way to find out is to remove everything again right?
 

a91what

SendMeUrDataLog
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Apr 6, 2011
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So, some news from Europe.... your tip did the trick to set the timing @a91what ! thanks a lot mate! I've checked that my dizzy pointer was correctly pointing to the #1 cylinder by rotating the engine to TDC once again, then restabbed the dizzy a little bit further clockwise to allow for more "rotating room".

But............... (there is always a but with our cars right?): after setting the cranking RPM to 350 (instead of 500) and setting the timing to 20 degrees (matches with the damper), I put it back to Use Table and it idles a couple of seconds more than before but still dies and I can hear a hissing noise when it dies.... so I'm thinking VACUUM LEAK!!!! crap, I feel like it's coming from the back of the GT40 lower intake, I hope the gasket there has not moved but I'm not too sure :eek: only way to find out is to remove everything again right?
can you get me a datalog of the car running and dieing out
 

96pushrod

I think they're a little easier to get off
May 15, 2018
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So, some news from Europe.... your tip did the trick to set the timing @a91what ! thanks a lot mate! I've checked that my dizzy pointer was correctly pointing to the #1 cylinder by rotating the engine to TDC once again, then restabbed the dizzy a little bit further clockwise to allow for more "rotating room".

But............... (there is always a but with our cars right?): after setting the cranking RPM to 350 (instead of 500) and setting the timing to 20 degrees (matches with the damper), I put it back to Use Table and it idles a couple of seconds more than before but still dies and I can hear a hissing noise when it dies.... so I'm thinking VACUUM LEAK!!!! crap, I feel like it's coming from the back of the GT40 lower intake, I hope the gasket there has not moved but I'm not too sure :eek: only way to find out is to remove everything again right?
If you can hear a hiss from the lower intake, and it’s for sure not coming from something like a vacuum port then it’ll probably have to come apart. Double check you don’t have any ports left uncovered on the upper intake, or cracked lines before ripping everything apart.

If you can have someone give it throttle time stay running you can probably do some more checking to confirm the vacuum leak.
 
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BugsOli

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Jul 1, 2013
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Sorry for the late reply, I'm not always home.

I was wondering if I could try something "redneck-style": put sealant around the back of the intake and see if that helps? If not then I take it apart...
Or, I can hook up a boost gauge that I have laying around, to one of the vacuum port on the upper intake (one is capped off) and see how much vacuum I get? What do you guys think?

I'll do a data log today, hopefully it will show something relevant
 

BugsOli

Member
Jul 1, 2013
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Amazing, started the car, it shooted way up in the RPM but stayed idling for almost 1 minute.... maybe it's because it's a cold start after almost 2 weeks with the negative terminal out of the battery?
Anyhow, here is my data log and my current tune, I've been abled to take picture of the seal under the lower intake, looks like it's correctly positioned and I couldn't hear the hissing noise when the engine died this time.

PS: I have a video as well where we can hear the horrible exhaust leak that I have, don't know if my headers are cooked (they have at least 30 years) or if it is the flange between the headers and the OEM H-pipe, I'll need to address that at one point
 

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96pushrod

I think they're a little easier to get off
May 15, 2018
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Interesting :chin
How can I check if my sensor is still good (it's brand new)? I'll check on the forum because I think I remember seeing a post on how to check sensors and stuff
You can run a resistance check based on ambient temp. If it changes with temp you’re probably alright. I believe there’s a write up on here, just google it and it should show up.

I’d check to make sure it’s scaled correctly in ts