Suggestions for passing emissions
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Suggestions for passing emissions
Hoping to get some help getting my truck to pass DEQ. I have a 78 F250 2wd standard cab with 400/C6. I rebuilt the engine last year and it now has 3000 miles on it. It has Tim’s pistons, Comp cams DEH 265, a Holley steet dominator with EGR, rebuilt Edelbrock 1406, headers and dual exhaust. New plugs, wires, cap and rotor, 195 deg thermostat, PCV valve, and the distributor was rebuilt.
I have to pass DEQ in OR with HC <= 300 and CO <=2.5 and my truck is at 345 for HC and 5.4 for CO out of both pipes. The plugs are gapped correctly and are good for color. Compression is ~165 on all eight. Timing is set at 10 deg, 34 deg with centrifugal weights, and another 10 vacuum advance. The shop that rebuilt my distributor had me run the vac advance on manifold vac for better throttle response which puts the idle timing at ~17 deg. Vacuum at idle is ~17” with manifold vac on distributor and ~15” without. The vacuum slowly moves around; up to 17.5 and as low as 16 and is erratic. I have tried blocking off all of the hoses one at a time for possible leaks and they are all new. If I plug off the PCV the idle and vacuum drop, but the vacuum gauge is still not steady. Idle mixture screws are both set to achieve best vacuum.
It is acting like a miss, but one that seems to affect all cylinders. I can pull a vacuum on the EGR valve to open it up and the engine starts running really ruff, but I guess there could be a small leak across the seat. The engine has always acted this way and I am pretty sure it is causing the failing readings. I tried a different ignition module with no change. Thought about the coil, but it seems like it would me more of a at speed issue that rough idle. I also noticed when I pulled the air cleaner off that the air intake for the PCV system does not seem to have any flow through it even though the PCV valve is pulling strong. I don’t have a lot of experience troubleshooting issues like this and would like to get some advice before I start throwing parts at it. Would also like to what others with a similar setup get for idle vacuum and how smooth the idle is. Sorry about the long post, just wanted to get as much info in as possible.
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Thanks,
Jeff
I have to pass DEQ in OR with HC <= 300 and CO <=2.5 and my truck is at 345 for HC and 5.4 for CO out of both pipes. The plugs are gapped correctly and are good for color. Compression is ~165 on all eight. Timing is set at 10 deg, 34 deg with centrifugal weights, and another 10 vacuum advance. The shop that rebuilt my distributor had me run the vac advance on manifold vac for better throttle response which puts the idle timing at ~17 deg. Vacuum at idle is ~17” with manifold vac on distributor and ~15” without. The vacuum slowly moves around; up to 17.5 and as low as 16 and is erratic. I have tried blocking off all of the hoses one at a time for possible leaks and they are all new. If I plug off the PCV the idle and vacuum drop, but the vacuum gauge is still not steady. Idle mixture screws are both set to achieve best vacuum.
It is acting like a miss, but one that seems to affect all cylinders. I can pull a vacuum on the EGR valve to open it up and the engine starts running really ruff, but I guess there could be a small leak across the seat. The engine has always acted this way and I am pretty sure it is causing the failing readings. I tried a different ignition module with no change. Thought about the coil, but it seems like it would me more of a at speed issue that rough idle. I also noticed when I pulled the air cleaner off that the air intake for the PCV system does not seem to have any flow through it even though the PCV valve is pulling strong. I don’t have a lot of experience troubleshooting issues like this and would like to get some advice before I start throwing parts at it. Would also like to what others with a similar setup get for idle vacuum and how smooth the idle is. Sorry about the long post, just wanted to get as much info in as possible.
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com
fficeffice" /><o></o>Thanks,
Jeff
