1994 5.7 TBI/ Vortec/ Intake/ EGR Question - Hot Rod Forum : Hotrodders Bulletin Board
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Old 11-03-2012, 11:17 AM
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1994 5.7 TBI/ Vortec/ Intake/ EGR Question

Ok Guys got a few questions for you. Ive been reading a lot about this topic online and I have seen way to many people saying different things. First of all I have a 1994 c1500 5.7 TBI. Ok I have posted before about my vortec heads (906) and I want to put them on my 94 Truck. I have a intake for these heads, an aftermarket jegs intake. (non egr). So with that in mind my plan was to put all this on my truck and do away with the egr. Currently I have a cam in the truck already that was designed for Low end torque since I haul lots of wood I wanted a good setup. Not that the stock was bad but I like a little more performance. So here are my questions.

1. Will my computer work fine with this setup??

2. Can I do away with the egr as the intake I have is a non egr application??

Anything else you all have on this let me know as Im sure Im forgettin something.

Here are the cam and intake I have.

JEGS Performance Products 200102 JEGS Performance Hydraulic Flat Tappet Camshafts

JEGS Performance Products 513002 JEGS Champion Series 331 Performance Dual Plane Aluminum Intake Manifolds

Thanks Guys

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Old 11-03-2012, 01:55 PM
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I believe you'll have to have the ECM reprogrammed to "turn off" the EGR.
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Old 11-03-2012, 02:35 PM
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Do you have any idea how that is done?? Can I do it myself??
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Old 11-03-2012, 03:07 PM
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94 still uses an OBD I computer, which has limited computing power. The computer will likely not be able to compensate for the cam without burning a new PROM. Similarly, the fuel and ignition maps in these PROMs are take advantage of the fact that the EGR lowers combustion temps, so they tend to run a more aggressive advance curve in the midrange. The EGR control from the computer is actually the least of your problems, since the computer simply sends a 12V signal to a solenoid. If the solenoid is not hooked up, nothing happens so long as the connector is taped up and can't short out.

Bottom line is that you need a custom PROM.
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Old 11-03-2012, 03:18 PM
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What about emmison test I don't think your truck will pass.
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Old 11-03-2012, 06:28 PM
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We dont have emmisions testing in Kentucky. I have had this cam in my truck for some time now and has been running strong. As far as the solenoid plug, where would that be located. If its on the passenger side by the throttle body it is unhooked. If thats not it I dont know where that plug goes and I have searched up and down for something to plug it into. I also can not find an egr valve on this truck. Im used to the space ship looking ones on the early model vehicles that bolt on the intake manifold on the passenger back corner.
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Old 11-03-2012, 09:48 PM
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If I remember correctly the solenoid is mounted to the same bracket that the MAP sensor is mounted to, and that mounts to the intake on the passenger side by the throttle body. There will be a nipple on it and the plug is green if I remember right.

It may run fine now but I doubt it will once you get the heads on there. You should have a chip burned for it but that takes time and money if you are going to do it yourself, and money if you have someone else do it. I had a similar setup but with other variables that made the mail order tunes not work for me. You may be able to get something that works going through Brian at www.tbichips.com. I would at least visit the website and check it out to see if that is something that you want to do. The other option is to find someone locally that does it, but it's usually about $1K because of the time involved.
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Old 11-04-2012, 07:42 AM
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Im wondering if the guy who had the truck before me already did all that. The green plug on my truck is the one thats been unplugged since I have owned this thing. When I got it It got bad fuel mileage. I tore it down put that cam in it adjusted the timing a little bit cause it was out when I got it and it runs very strong now. I think Im going to throw the heads and intake on and see how it is. If it doesnt run right ill take it back off. I dont see why it would run bad. I will def. get a chip for it tho. They make them for my truck.
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Old 11-04-2012, 09:59 AM
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If it's unplugged and you are not getting a check engine light, I would say either it has been turned off already as long as he didn't just pull the bulb in the cluster.

It may run ok, who knows. The heads are a major factor in determining what the fuel table should look like. The ECM will adjust it some using the O2 sensor, but the older O2 sensors are not very good (especially the one wire sensors) and the ECM can only adjust it so much anyway.

The heads are also a major factor in the timing table and will require a few degrees less total timing than the old swirl port heads you are taking off. If you end up getting it together and it knocks at WOT, you can disconnect the timing connector and retard the timing a couple of degrees, then reconnect it and that will take 2 degrees out of the entire curve. It's not right, but it should work as a bandaid.
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Old 11-04-2012, 10:08 AM
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the o2 sensor is a two wire and it is unplugged also. The guy said he put alot of money in this truck and said he changed the engine and it was beefed up but when I tore it down everything was stock and the block number said it was a 89 to 95 2 bolt chevy so i dont think he changed it. The engine light bulb is still in. It does not stay on tho. o2 sensor is a two wire but thats been unhooked the hole time. If I put a carb on this I would have to change nothing would I??? what about the sensor that plugs into the side of my throttle body??? I thinks its my TPS. My mechanic said I could hook a carb right up and it would ber fine. What do you think???? This TBI setup is just like a carb setup but with a computer, If i put a carb on i wouldnt need the computer right????

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Old 11-04-2012, 10:50 AM
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I thought all of the truck blocks were 4-bolts. My '91 C1500 had a 4-bolt 350 in it when I took it out.

I'm not sure what the hell that guy did. If you have the computer controlling everything, the O2 sensor needs to be connected. That is the only way the ECM will do any kind of adjustment to the fueling. I have a feeling that he did all of this stuff to it, connected everything up and it didn't run right. If he disconnected the O2 sensor, the engine will always run in open loop and it will always run rich. I bet your fuel mileage is horrible. It the cam is not computer friendly, that also messes with the ECM because of the huge swings the MAP sensor will report to the ECM. Forcing it into open loop would take care of that.

The two wire sensors are also not too desirable because they have to be hot for them to work. At idle, they cool down and if they cool down too much, they won't report the correct readings then either.

You've got some decisions to make and some more investigating to do. I have a feeling the O2 sensor is unplugged because the cam is not computer friendly. That is just a guess because I have no idea what the cam specs are, but it sounds like the most logical reason to need to disconnect the O2 sensor. If that is the case, you won't be able to run it any better than it is now (and it may even run worse once the new heads are on) unless you have the chip burned again. The EGR isn't there an you don't have a check engine light, so it's likley that the chip has been adjusted. The O2 sensor is just for adjustment, so if the chip was altered, maybe it was altered in a way that does not require the use of the O2 just so it would run. Come to think of it, you don't have a check engine light for the O2 not being connected either, so that may be the case.

The heads are worth maybe 20hp, so you have to decide how much that 20hp is worth to you. Maybe you won't want to change them. Maybe you will change them and it runs good, maybe it runs worse and now you're stuck finding someone to custom burn you a chip for $$$. You might want to pull the ECM and see if they put a sticker on it or something. That could be helpful if you wanted to have the chip adjusted. TBIChips puts on right on the chip. The ECM is behind the glovebox.

I spent big bucks doing all of this myself and hundreds of hours of reading, learning, and doing, and in the end threw in the towel and went to a carb. Mine came down to not being able to get my TBI setup to pass emissions though, partly because I didn't know enough about what I was doing to cheat it through, where the carb makes that a lot easier. Out of the box it ran better than the TBI system I had ever did, though it's still a carb and still has cold start challenges that TBI doesn't have. I also don't have very good MPG's but I didn't build it for MPG's, I built it to haul *** and I beat it every time I leave the garage with it.
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Old 11-04-2012, 01:15 PM
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A check engine light will set for the EGR under these conditions

Closed loop operation
Continuous Road speed of XX miles an hour or more for more than X minutes

Not certain of exact time verses road speed, but it is necessary.

When driving, the ECM checks the EGR by closing the valve and measuring the change across the MAP sensor vacuum value.
It checks it after closed loop is achieved, and road speed is over a certain speed- and time elapsed value.Reason being it is assumed after X amount of minutes that the trip will be an extended one, long enough to sustain conditions for testing.
I would bet if you drove it down the highway at 35-55, steady cruise, for 10-15 minutes, the EGR code would set.
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Old 11-04-2012, 05:41 PM
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Ok let me explain to you about the truck when I got it. I bought the truck cauese it had 150000 mile on it and got it for cheap. Figured it would be a good work/farm truck since I haul lots of fire wood. When I got it the fuel milage did suck very bad. I filled the tank up and got 70 miles. Ya crazy right. I had a brand new cam I bought in Feb. that was for low end torque so I decide to use this cam in this truck. I put the cam in put the engine back together and it still sucked the gas down. Come to find out the timing was off so once I got that corrected I get 300 miles per full tank of gas. Thats fine with me, its a truck. The guy who had it before the guy I got it from had headers on the truck. The guy I bought it from had factory exhaust put back on it. The exhaust he had put on it had an o2 sensor in it but it doesnt have the right plug to plug in to the truck so the connecotr is just hangin there. The correct o2 sensor was plugged into the truck and just hanging there. I took the correct one and stuck it in the glove box. The one that is in the exhaust (the one with the wrong connector) is welded on the exhaust. (stupid right). So I was going to cut both connectors off both o2 sensors and put the correct connector on the sensor thats stuck in my exhaust right now so it would be functioning. But I havent because the truck runs great right now. As I said in my last post I would like to switch to carb. I might even get better fuel milage, maybe not but besides I know I would get some power thats being held back. As far as I know I would have to change The distributor but other than that I dont know. Know I guess If I could get by with the TBI I would but a carb does sound like a better route. As far as what you guys are tellin me it doesnt make sense cause I know I have no egr and no o2 sensor but my truck runs like a charm. I have had my glove box out before but never paid attention to any stickers on it. I just thought it all looked normal. This is kinda strange. But what did u have to do to put a carb on your tbi setup.
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Old 11-04-2012, 05:57 PM
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It's not crazy because lots of people do it. I did it. You need a carb, distributor, an intake manifold, and need to do a little bit of wiring. It really isn't a big deal. I went through and disassembled the wire harness and removed the wires to sensors/actuators/injectors that I wouldn't need anymore to clean things up. Outside of removing wiring and connectors, you have to wire the fuel pump relay different and will need to wire the distributor different, but the wires are already there. You will also need to wire the choke if you have a carb with an electric choke. It needs to be an ignition wire, but NOT the ignition wire to the distributor. I ran a separate relay for the choke.

The ECM is behind the glove box and the chip would be behind the access panel that should have two screws holding in on. I believe it sits on top of the HVAC box.

If the O2 sensor is welded to the exhaust it is junk. If you were going to use it, take it to an exhaust shop and have them cut it out and weld a bung in so you can use your new sensor. It shouldn't cost much. With O2 sensors, you cannot cut the wires because they won't work right afterwards.

It's probably running like a champ because the chip was tuned to run in open loop. If you change the heads it probably won't run that good anymore, expecially with no O2 sensor to provide feedback for fuel trim.
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Old 11-04-2012, 06:04 PM
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Ok so if I make this a carb setup will I still be using the computer. I have the intake and a disributor but no carb yet. And that would be an HEI distributor like the old style right.

Man I appreciate your help.
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