Going to an Explorer 302

[1980c10]

Take off your valve cover and rotate the engine the TDC both the valves on the #1 cyl will be closed. Stick a checker in the plug hole to verify your at TDC. Then look at the timing pointer and see if It is at TDC. If it is proceed to set your timing to 10* BTDC with the spout out. Then you can verify its not a timing issue.

+3 on unplugging the o2's. Its easy, its free, and its fast, and you might find something out.

[gadget73]

that kind of doesn't make sense. If it shows that there is too much air, that means there is not enough fuel. Its a ratio thing, and since you can't really reduce the amount of air, then you have to make up for it with more fuel. I really wonder if its something with the combustion chamber design affecting the exhaust temperature in such a way that the O2 sensor gives bogus readings, or maybe its the bump in compression with the P heads that makes the fuel and timing maps not work well. Something just doesn't add up here. There have been plenty of more modified engines run on speed density without these issues. I also know of a couple of SD P head motors that run fine, yet both of the ones I've personally seen ran badly in the same kind of way.

[86VickyLX]

that kind of doesn't make sense. If it shows that there is too much air, that means there is not enough fuel. Its a ratio thing, and since you can't really reduce the amount of air, then you have to make up for it with more fuel. I really wonder if its something with the combustion chamber design affecting the exhaust temperature in such a way that the O2 sensor gives bogus readings, or maybe its the bump in compression with the P heads that makes the fuel and timing maps not work well. Something just doesn't add up here. There have been plenty of more modified engines run on speed density without these issues. I also know of a couple of SD P head motors that run fine, yet both of the ones I've personally seen ran badly in the same kind of way.

My engine performance teacher is thinking of an EGR problem. Which would kinda make sense. EGR opens, Vacuum decreases, O2 sensors think it's rich, ECM pulls fuel. Pop pop pop, the cycle continues. If I let the car idle, let it go through the weird idling, and let it smooth out, it doesn't pop at all. No popping.

[gadget73]

I seem to remember Tom's car did that too. Have you tried driving with the EGR vac line unhooked ? How about plumbing in a vacuum gauge to see if you can match the popping to the EGR valve opening?

The funky idle I also don't really get. EGR doesn't work at idle. I could believe its screwing you up at cruise speed, but I'd like to know what that wierd open loop idle crap is about. It shoudn't be that obvious when it switches to closed loop.

[86VickyLX]

I seem to remember Tom's car did that too. Have you tried driving with the EGR vac line unhooked ? How about plumbing in a vacuum gauge to see if you can match the popping to the EGR valve opening?

The funky idle I also don't really get. EGR doesn't work at idle. I could believe its screwing you up at cruise speed, but I'd like to know what that wierd open loop idle crap is about. It shoudn't be that obvious when it switches to closed loop.

Right, the EGR doesn't work at idle, but that doesn't mean that it can't. I will run a vacuum gauge into the car and look at the reading while its popping. I forced the egr to open at idle, and how the engine sounded and acted was pretty close to how it would during the weird idle.

[88grandmarq]

First thing I would do is check for obvious vaccum leaks.... make sure the throttle body and EGR spacer are sealed correctly to each other and to the intake plenum.
Also, I would pulling the EGR valve off and test it with a vaccum pump, make sure it doesn't stick.

make sure the all of the vaccum lines are routed correctly and you have the line/hose on a working vaccum port. also make sure the fuel pressure regulator has its own/dedicated line, dont split it or T it off with something else.

make sure the Red hard plastic supply line to the EVR solenoid is hooked up and the GReen plastic line should go from the EVR to the EGR valve. check both lines and make sure they dont leak or are kinked/crimped somehow.