EGR Bypass Question
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EGR Bypass Question
I just dropped in my 351w, I blocked off the EGR but still have the valve in place and connected to vacuum and to the harness connector. My question is this. What is the EGR actually doing at this point? I dont have the tube connected to exhaust, its just there and connected to nothing. Is that causing the computer issues? Do I need to hook it to where it is getting exhaust on the back side of it? The pipe was in pretty bad shape on the exhaust manifold so I had to must crimp it off. I could hook it up if I have to but if it wont hurt anything the way it is I will leave it.
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No you don't need to connect it to the exhaust unless you have sniffer tests to pass of course, then all emissions equipment must be present and working correctly. If you don't have those tests then you can leave the tube off but it's still a good idea to have the EGR valve functional to prevent codes, but you need to prevent fresh air from getting into the intake when the valve opens so you need to install a blockoff plate between the valve and intake. Anything will work here, I have cut a piece of sheet metal roughly the same shape as the EGR flange and sandwiched it between the valve and intake with a couple gaskets.
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Yep its blocked off, have a piece of thin metal in there, just wanted to make sure fresh air on the back side would not make the computer upset. All the gauges are acting crazy the engine shuts off after a couple of minutes. Just eliminating things as a cause. Thanks for the reply.
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Was a 5.0L. I put a Speed Density computer in it with the 5.8L. Its a freshly rebuilt engine, new distributor, and mostly new sensors on the intake. The wiring harness came with the computer and supposedly came from the same truck the computer did but it has a plug I am trying to identify on another thread. The original harness was in very rough shape and caked in oil so I went with the clean harness that at first glance looked the same but has a extra plug that I think we have narrowed down to a AC High Pressure switch near the back of the compressor. My 92 truck was never equipped with this. I got it fired up yesterday and it ran but the tack was high and bouncing around, the volt meter was bouncing around, and it would shut off after a couple of minutes as though you turned off the key. Not a stumble and die, a cut off.
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OH... no.. you didn't. You broke a cardinal rule there.. never never never change any wiring when doing an engine swap, use only the original wiring that was in the truck. 5.0 and 5.8 PCMs are pinned the same so swapping those is no issue, but there is no guarantee harnesses are the same from one year to the next.
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I know.. That is what I am trying to diagnose now and I have already told myself that tomorrow evening I am probably pulling the upper intake loose so I can swap the wiring back. But like I said, the original harness was in VERY poor shape with some splices in it where wires had broke, there is litterly years worth of oil on it which is sad because the blown up engine was put in brand new in 2007 and then some craptastic place in springfield mo rebuilt the top end with one brand new head and rebuilt the other in 2011 and this thing looked like hell under the hood. The harness has been on and off a few times if I had to guess. I will put it back on if I have to but trying to figure out for sure if I really have to. Just not sure why it would be different, its not rocket science, and the truck did start and run and seemed smooth, just sluggish revving and didnt stay running. But yea I will probably stick the old one back on, just to eliminate it as the cause. Just hate to. This harness is clean and all together. lol.. This is why I am too old to be wrenching on this stuff. But I do.
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OK I see why you would want a new harness but it'll probably take a bit more work to make it work.. you will probably have to get into the block connectors and move some wires around after you trace everything and find out where each wire should go.
Try pulling codes with that harness to see what comes up, if you get a hugh list of codes then something major is miswired.. could just be a common signal return wire but it could be a bunch of wires too. You should do the same with the original harness too just to see how good or bad it is electrically, and if everything is at least in the right place then take it off and buzz out each wire so you can build a spreadsheet to use to make the new harness the same.
Try pulling codes with that harness to see what comes up, if you get a hugh list of codes then something major is miswired.. could just be a common signal return wire but it could be a bunch of wires too. You should do the same with the original harness too just to see how good or bad it is electrically, and if everything is at least in the right place then take it off and buzz out each wire so you can build a spreadsheet to use to make the new harness the same.
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I am just going to clean up the harness and move the plastic connectors that are broken from the good harness, Or the 3rd harness I have from the 90 bronco we sourced the 5.8L core from. its a different type of harness with several round connectors instead of one square block, but still has some usable parts I can move over. So hopefully between the three I can fix up the original. I dont have a scanner to pull codes on a vehicle this old. I could probably get a scanner from a newer one. I know Orielly can probably pull them, but It has to drive well enough to get there and right now I have not been able to properly break in the camshaft, need to have it running long enough to do that.
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No actually you don't need a scanner.. you can pull codes with nothing more than a paperclip, but there is a code reader available that isn't very expensive.. the equus 3145 goes for about $25 or so. You don't need to have the engine running to get codes either, the pcm scans the system at key on and will flag serious problems.
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No actually you don't need a scanner.. you can pull codes with nothing more than a paperclip, but there is a code reader available that isn't very expensive.. the equus 3145 goes for about $25 or so. You don't need to have the engine running to get codes either, the pcm scans the system at key on and will flag serious problems.
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Yeah OBD2 is beautiful, just about any scanner will give you real time data and pull or clear codes. I have a system that will do the same on an OBD1 but you have to install a module on the PCM and then plug in a laptop and run some special software.
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That's the bad part. I'm a systems administrator and work with computers servers and networks all day. But when it comes to messing with computer on the car it's all voodoo I just try to stay away from. I honestly like throwing carburetors on muatang and throwing the efi out. But for a daily I like the efi for cold starts and all around drive ability.
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