Does the EFI 5.0 need the egr spacer?

[Mercracer]

I can tell you that I drove my LX through 2 WI winters (my only daily driver at the time) with no coolant going to my EGR spacer which had no EGR gasses going through it. No icing issues.

[Crownvicman289]

well, you're both possibly right, and let me tell you why.

if the egr valve is opening and feeding a signal to the ECM that it opened, but it does not in fact have any flow, the engine runs lean and with more timing. if the EGR valve does not open, or it has an eliminator plug or something that feeds an always-closed signal, then the motor runs richer and with less timing. Thats not to say it runs richer than it needs to, but it runs richer than it would if the EGR system was working. This is part of why later EGR systems use a flow sensor and not simply a valve position sensor. With the position sensor, the valve can open, but the ports can be clogged (or blocked) and the ECM has no way of knowing it. It simply assumes all is cool as long as it sees that valve in the open position. With a flow sensor, the ECM can tell if there is actually exhaust gas moving through the valve and will adjust itself accordingly.

What vehicles actually have an EGR flow sensor? If it opens and there's no flow, you're lean/detonating. If you fake the EEC into thinking it's closed, it won't run richer, it'll just run stoich with normal fuel/timing values. The only way for it to run fat is if the EGR is open but the EEC sees it as closed. Valve open or closed, it'll still run at stoich, so ideally the AFR's never change, just the amount of fuel injected. Where it becomes a wash is on a heavy, unaerodynamic vehicle (like a truck) where it makes slightly less power with EGR open so your foot goes down slightly farther and in the end you burn the same amount of fuel. This seems to vary from one car to the next, one owner to the next.

what I posted is a quote from Corral.net... it was part of a tech info thread made by a retired Ford engineer, who happens to be one of the top EEC-IV tuners in the country and also helped design the EEC-IV system.

Well somewhere there's a disconnect, because I'm sure he knows what he's talking about, but that reads bass ackwards. I don't post these things unless I know I'm right and I think I did a decent job explaining myself.

[cld783]

What vehicles actually have an EGR flow sensor?

anything with obd ii usually including the 4.6 crown vics.. it's called a dfpe sensor.

[86VickyLX]

anything with obd ii usually including the 4.6 crown vics.. it's called a dfpe sensor.

DPFE, Delta Pressure Feedback something with an 'e' The earlier 4.6s use a PFE sensor, with is basically the same, except it only senses one change in pressure. Where as the DPFE monitors two pressures. They do the same job.

[gadget73]

The coolant is there to cool the EGR spacer. Exhaust gasses are hot. It has zero to do with your throttle shaft.....

I did some testing on that, and I'm not sure its much of a cooler. I ran my car 20 miles down the highway with the coolant hoses hooked up and the EGR working, and checked the voltage at the ACT. I unhooked the coolant lines and drove home, EGR still working. The ACT indicated that the intake air charge was about 15 degrees cooler with the coolant lines unhooked. Would need more testing for the results to be conclusive but thats what my quick and unscientific test had to say about it. All that said, I don't run the coolant lines, and I do have working EGR on the car. The throttle has never iced, and the cooler isn't melting through or anything like that.

[gadget73]

What vehicles actually have an EGR flow sensor?

4.6 motors have them, 4.0 and 5.0 Explorers and late 90s 4.0 Rangers at least have them. I'm sure others have them too. Some of them are really cutely designed. Silicon rubber hose feeding hot exhaust gas through a plastic pressure sensor. yes, that really does work out about as well as you might figure it does.

[1990LTD]

4.6 motors have them, 4.0 and 5.0 Explorers and late 90s 4.0 Rangers at least have them. I'm sure others have them too. Some of them are really cutely designed. Silicon rubber hose feeding hot exhaust gas through a plastic pressure sensor. yes, that really does work out about as well as you might figure it does.

So it works as well as anything else Ford designed in the 1990s?



I can attest to the fact that your car will run rich with the EGR in place but disconnected. No block off plate, etc, just vacuum disconnected from the valve (closed position.)

Over time the front part of the plenum where the EGR is routed actually started to discolor from heat. That's when I figured that EGR is probably supposed to be functioning for a reason, and hooked the shit back up.


Run EGR - They put it there for a reason!!

Anyone wanna buy a lower-to-upper plenum EGR blockoff spacer?

[gadget73]

well, it worked, but if things clogged up it would tend to melt the hose and/or the sensor. Some were metal, and just the hose would bake but I remember replacing a plastic one from a 99 Ranger that was all melted. I think we used a metal 96 Explorer part to make it go. The idiot light went off. Don't know if the truck ran much different, but not having irritating lights is an improvement.

[Crownvicman289]

Re-read your post, it'll cause you to run LEAN if you block the EGR and don't tell the EEC. It'll also advance the timing, so if you've already advanced it past stock you might encounter pinging.

OK, so I re-re-read because I know 88GM isn't a dumbass and it appears I am a dumbass. We were both right. That last line is what threw me. What the article is saying is that when it sees that lean condition that I was screaming about from my soap box, it adds fuel to the long and short term fuel trims, which are then added to the open loop fueling, so now the only time the car runs right is in closed loop and anywhere else is rich. I remember my 1988 Chevy with 350 TBI engine had a way of detecting EGR flow without an EGR sensor: it anticipated a fluctuation from the MAP sensor when the PCM commanded the EGR valve open.

[BigT]

I have a 1986 GM with LoPo Speed Density. I plugged off the vacuum line and kept the position sensor connected. I have a couple of days of minor problems while the computer is “learning” the configuration. After that, it every thing is fine. I get 19-20 MPG (which is great for a car that big and old), and is what I got with the EGR working.

The oxygen sensors working with the computer should end any over riching of the fuel. The EGR does not function all the time and should not affect the fuel mileage that much. If the computer receives high fuel signals from the O2 sensors it will compensate for it and bring it back down to the proper level. Fuel rich/lean should be constantly adjusted by the computer with or without the EGR.

BTW, the minor problem I had: When I went from Drive to Reverse to back into my driveway, the engine would die. After a couple of days it’s good to go. But anytime the battery is disconnected, the computer has to go through the learning process again.

[Crownvicman289]

The computer won't look to the O2's until a certain temperature is reached. It also ignores them during high load situations and possibly during transient (pedal is moving) situations. During any of these conditions, the learning that your EEC just did richened up up the maps in any area that the O2's provided feedback on.

[gadget73]

the O2 sensors aren't always that useful for serious fuel trim issues either. A number of people, myself included, have had problems with non-stock motors that ran extremely lean, yet didn't set any ECM codes about it. The ECM didn't fatten up the mix enough for the engine to be happy, but it didn't seem aware or concerned about the problem either. Basically I think the bottom line for everything to be as right as possible is to keep the engine configuration as close to what the ECM expects as you can, unless the ECM is tuned to expect something different.

[86VickyLX]

The fuel trim adjustments on these cars, and the mustangs fucking suck. They'll compensate for slight variances, and I mean slight. Anything more it will throw a light and the computer won't do shit with it. The ones that would have the best adaptability (besides OBD-II) would be the '94/95 Mustang. Since they were OBD-II prep, but still EEC-IV.

[Crownvicman289]

Has anyone ran a wideband at the same time though? I'd expect the learning ability of the car to be quite limited. If you don't know how far off you are to begin with, then there's a good chance that the factory put a bullshit tune on there to begin with and was already leaning heavily on the O2's to clean everything else up. My '98 GMC ran 13.XX's open loop at operating temperature with massive hills, valleys, and spikes in the STOCK VE table. I couldn't believe my eyes. I re-wrote the VE table and it's within tenths now of stoich everywhere. . . at a certain temperature and altitude, but that's a totally different discussion. Point being, stock tune on a stock car is capable of sucking total balls, and if it's wrong in the right way, mods can actually help to a certain extent. For instance, increasing VE where my truck ran rich, be it by fitting a bigger cam or better flowing intake/heads, it would run closer to stoich open loop and the O2's would do less correcting to get the AFR's where they need to be. If someone were to run a wideband on a stock car in open loop and could datalog that to a spreadsheet, that would be very educational. One could then follow up running the same scenario with the O2's plugged back in to see how effective they truly are. When I do the Exploder engine, I plan to set the AFPR with a wideband. I imagine it'll be a compromise getting the cruise and WOT to play nice.

[gadget73]

Most factory tunes tend to be on the rich side of stoich, particularly in open loop. Its safer.

I think there are ways to program the eec4 to accept input from a wideband o2 sensor, and then you could datalog the whole thing. That would be real nice to have for a tuning aid, an actual rpm vs load vs A/F graph to figure out exactly what to screw with to get the proper results.