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No spark?

kevin camps
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kevin camps Enthusiast

kevin camps

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21 hours ago, richard wysong said:

How you making out?

SOLVED:

ended up pulling out the parts cannon and threw a new coil in it even though the old coil tested good, sure enough that’s what it was, the spark must have been just weak enough to not be able to gap the rotor to the points,

 

truck runs and drives now but still falls flat on its face if I’m idling at a stop light for more than 10 seconds, idles fine and there no cam timing codes, fuel pressure tested at 50 psi at idle, I’ll probably do new plugs because it’s been 50k since my last change and go from there, I’m living in the city during the week for school so I’ll live with it until the weekend

 

i should add that if I’m stopped and hold the break/gas so it stays around 1000rpm it won’t stumble, when the truck stumbles it’s so bad it seems it might stall right in the middle of the road

richard wysong Senior Enthusiast

richard wysong

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That could be the TPS or possibly a vacuum leak , if you have a scanner that does live data it will help with the diagnosis

kevin camps Enthusiast

kevin camps

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Just now, richard wysong said:

That could be the TPS or possibly a vacuum leak , if you have a scanner that does live data it will help with the diagnosis

I had the scanner hooked up yesterday, tps readout seems good, bank 1&2 long term fuel trims we’re high while cruising. I didn’t check what it did when it was having the issue

richard wysong Senior Enthusiast

richard wysong

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That would indicate that it,s running lean so maybe a vacuum leak? Pull the PCV and the breather  from the valve covers and see if there's vacuum in the crankcase, maybe an intake gasket slipped out of place

kevin camps Enthusiast

kevin camps

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2 minutes ago, richard wysong said:

That would indicate that it,s running lean so maybe a vacuum leak? Pull the PCV and the breather  from the valve covers and see if there's vacuum in the crankcase, maybe an intake gasket slipped out of place

Thats what Im beginning to think aswell. Sucks that all my tools are at home, I’ll try to get home tomorrow and do some digging. I’ll let you know what the results are

kevin camps Enthusiast

kevin camps

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5 hours ago, kevin camps said:

Thats what Im beginning to think aswell. Sucks that all my tools are at home, I’ll try to get home tomorrow and do some digging. I’ll let you know what the results are

I managed to run home quick to run some tests, testing vacuum from the manifold it’s a steady 17inHg, increasing when i apply throttle, fuel trims slowly creep up after snapping the throttle, cleaned the mag sensors then all fuel trims are in spec, truck doesn’t stutter or bog when the maf is unplugged..

richard wysong Senior Enthusiast

richard wysong

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Posted (edited)

check for a leak between the MAF and the throttle body. There was a post a while ago of similar symptoms and the OP determined the cat was partialy clogged causing the stumble. That may not be your case where the vacuum increases with throttle though , You could remove an upstream 02 sensor to check the back pressure

Edited by richard wysong
kevin camps Enthusiast

kevin camps

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5 minutes ago, richard wysong said:

check for a leak between the MAF and the throttle body. There was a post a while ago of similar symptoms and the OP determined the cat was partialy clogged causing the stumble. That may not be your case where the vacuum increases with throttle though , You could remove an upstream 02 sensor to check the back pressure

I will check for leaks Tomorrow, truck has headers and a full exhaust with no cats so it’s not a flow problem 

kevin camps Enthusiast

kevin camps

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20 hours ago, kevin camps said:

I will check for leaks Tomorrow, truck has headers and a full exhaust with no cats so it’s not a flow problem 

Checked for vacuum leaks today, sprayed some ether by all the gaskets. Looks to be a tiny leak by the egr valve and next to the throttle body, I spent a hour getting all sorts of fuel trim readings so here’s the list

 

maf unplugged at idle fuel trims good

 

mag plugged back in, truck still running, fuel trims good maf reads 4.24g/second at idle

 

as long as the truck stays running since the maf was plugged back in the fuel trims stay good when driving
 

truck shut off and restarted with maf plugged in, fuel trims good, maf reading 9.05 at idle

 

drove around the block, maf plugged in, fuel trims very high, maf reading 4.62 at idle

 

I will get some gaskets on order and do new plenum, egr, and throttle body gaskets, plenum gaskets have been removed and reinstalled a fair few times so it could be leaking in the middle by the injectors aswell

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