I have blocked off the EGR tube and removed the valve and solenoid, partly because i couldnt afford to fix it all up, and partly because well I just dont want the clutter in the engine bay and at the end of the day its not really needed (or so im told).
Reading through various threads on here opinion is divided upon wether removing the EGR system is a good or bad thing. My car certaily is running better without it although it is somewhat lean now.
In any case what i need to know is two things.
1) What should I do with the electrical connection from the solenoid, should I short any of the wires or just leave it disconected ?
2) Do I need a reprogrammed prom to cure the lean burn, and if so where can i get one ?
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09:01 PM
PFF
System Bot
Apr 9th, 2010
Rafe Zetter Member
Posts: 277 From: Staffordshire, Great Britain Registered: Dec 2008
Bump, could really use some input here, does anyone know if i need a new prom to solve the lean burn ?
It's not going to be lean. The ECM will adjust for the lack of extra fuel for the EGR being off. If you disconnect the solenoid you will likely get a code 32. You could leave the solenoid connected and the vac line to EGR plugged and be done with it. If you need to remove the solenoid, you will need a chip with the EGR logic turned off.
As far as needing it, it reduces NOX emissions with little to no impact to mileage and certainly none to performance. Need? No, preferred? Yes.
If you know someone over there with a some 2732 proms, a burner and/or eraser to reprogram yours, I can send you a binary with it disabled. Otherwise, wait from someone on here that can send you a prom already changed for the missing EGR.
What is the year and trans? Auto? Manual? 4 spd? 5spd? I assume it's a V6.
[This message has been edited by TK (edited 04-09-2010).]
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06:49 PM
Rafe Zetter Member
Posts: 277 From: Staffordshire, Great Britain Registered: Dec 2008
its an 86 V6, I certainly have noticed that it runs better since I removed the EGR, but the ECU shows a lean condition which is what i was expecting after reading PFF threads...
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07:35 PM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
As TK said (and you really should be listening to him) it should NOT be running lean. If it is, you have another problem. As far as needing a new prom, again, you really shouldn't just for removing the EGR system. Heck, we ran our race car on the stock prom for two years. If you want the SEL to go off, there is a way to jumper around so that the PCM thinks it's working without burning/buying a new chip.
John Stricker
quote
Originally posted by Rafe Zetter:
its an 86 V6, I certainly have noticed that it runs better since I removed the EGR, but the ECU shows a lean condition which is what i was expecting after reading PFF threads...
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08:44 PM
BL3200 Member
Posts: 131 From: Harze, Liege, Belgium Registered: Oct 2009
I've already melt a piston due to defect EGR valve (the membrane had craks so the valve did not work). It happened during a high speed long distance drive on german high way (no speed limit).
EGR is lowering your combustion temperature by injecting exhaust gas (thus CO2) in the intake manifold. If you switch it off, you will have more oxygen and your combustion temperature will increase. So in a long drive, it might be armfull (melt piston). I don't need to describe the feeling you have when you see an enormous blue cloud in your back mirror....
------------------ Bernard Fiero V6 GT 1987 (Manual)
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09:03 PM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
You do know that the EGR system is only active at very specific manifold vacuums and conditions, right? Those conditions are low power cruising conditions. If you melted a piston from a defective EGR it was because it was stuck OPEN and not closed, which if you remove the EGR would be a constant state.
John Stricker
quote
Originally posted by BL3200:
I've already melt a piston due to defect EGR valve (the membrane had craks so the valve did not work). It happened during a high speed long distance drive on german high way (no speed limit).
EGR is lowering your combustion temperature by injecting exhaust gas (thus CO2) in the intake manifold. If you switch it off, you will have more oxygen and your combustion temperature will increase. So in a long drive, it might be armfull (melt piston). I don't need to describe the feeling you have when you see an enormous blue cloud in your back mirror....
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09:27 PM
Apr 10th, 2010
BL3200 Member
Posts: 131 From: Harze, Liege, Belgium Registered: Oct 2009
I totally disagree with what you say My EGR was perfectly close and I did melt a piston, beleive me. When the EGR is stucked open, the car runs very bad at idle. Just make a test by yourself when the car is at idle speed: if you raise the EGR membrane by yourself, the idle speed will change and the car almos stops!
After replacing my EGR, I did the same test drive (same speed, same temperature condition) and it never happened again. EGR WAS THE REASON!
------------------ Bernard Fiero V6 GT 1987 (Manual)
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05:18 AM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
You may disagree all you like, that's certainly your right.
However, you did NOT melt a piston because your EGR was closed, that simply defies logic on how the system works. The EGR is only supposed to be open at high manifold vacuum cruise conditions. Whatever melted your piston was not the result of a stuck closed EGR. Your test of lifting the EGR at idle is meaningless. In fact, the reason it runs poorly at idle when you lift it is because it is leaning the mixture so if it's stuck closed, pray tell how the mixture is leaned?
Plug a scanner in and watch the a/f ratio when you make your test and you'll find I'm correct.
Our race car ran for two years with no piston melting and no EGR fitted running a stock ECM. When we had the 3.4 in the Finale the EGR was blocked off for 2 years with no issues. There are dozens of members of the forum that are running with blocked EGR's with no pistons being melted. If I remember when I get over to the sop in a few hours I'll look in the shop manual and post exactly what conditions command the EGR valve to open and I'd wager that it wasn't even supposed to be open when you melted your piston.
John Stricker
John Stricker
quote
Originally posted by BL3200:
I totally disagree with what you say My EGR was perfectly close and I did melt a piston, beleive me. When the EGR is stucked open, the car runs very bad at idle. Just make a test by yourself when the car is at idle speed: if you raise the EGR membrane by yourself, the idle speed will change and the car almos stops!
After replacing my EGR, I did the same test drive (same speed, same temperature condition) and it never happened again. EGR WAS THE REASON!
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05:41 AM
BL3200 Member
Posts: 131 From: Harze, Liege, Belgium Registered: Oct 2009
High vaccum happens when you are at high RPM and as you say, it is under that condition that the EGR is supposed to work TO LOW DOWN THE COMBUSTION TEMPERATURE AS IT IS CLEARLY DESCRIBED IN THE SERVICE MANUAL!
Another thing I forgot to mentioned in my story: when I first melt a piston, I changed the engine (I had a spare one) and the same thing happen with the second engine (melt piston). I replaced the piston to the second engine and did not drive untill I found the problem. So, logically thinking, the reason of the melting piston was the same for both engines. These two engines had in comon the EGR valve that, as I mentioned, had a broken membrane. I bought a new one, replace it and did the same test drive several time and piston never melted anymore.
By the way, racing condition means variation in RPM (acceleration, deceleration) while in my case I was driving more than 1 hour between 160 and 180km/h
After replacing the EGR, the problem was solved and some GM mechanics did agree on my analysis.
------------------ Bernard Fiero V6 GT 1987 (Manual)
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06:56 AM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
Take a MAP reading at WOT high rpm and see how much vacuum you have. Nearly none, that's how much. Almost Atmospheric pressure. Now it CAN be high vacuum if you close the throttle at high rpm, but it doesn't have to be.
I wasn't aware I said what kind of racing I was doing. The Bonnevile Salt Flats has very little variation in throttle or acceleration. Neither does open road racing which has 7-10 miles of straights.
John Stricker
quote
Originally posted by BL3200:
High vaccum happens when you are at high RPM and as you say, it is under that condition that the EGR is supposed to work TO LOW DOWN THE COMBUSTION TEMPERATURE AS IT IS CLEARLY DESCRIBED IN THE SERVICE MANUAL!
Another thing I forgot to mentioned in my story: when I first melt a piston, I changed the engine (I had a spare one) and the same thing happen with the second engine (melt piston). I replaced the piston to the second engine and did not drive untill I found the problem. So, logically thinking, the reason of the melting piston was the same for both engines. These two engines had in comon the EGR valve that, as I mentioned, had a broken membrane. I bought a new one, replace it and did the same test drive several time and piston never melted anymore.
By the way, racing condition means variation in RPM (acceleration, deceleration) while in my case I was driving more than 1 hour between 160 and 180km/h
After replacing the EGR, the problem was solved and some GM mechanics did agree on my analysis.
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10:05 AM
PFF
System Bot
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
"The EGR vacuum control uses an ECM controlled EGR valve. The valve is normally closed and the vacuum source is a ported signal. The ECM will turn the EGR "ON" and "OFF" (Duty Cycle) by grunding the CKT 901. The duty cycle is calculated by the ECM based on information from the coolant and MAP sensor and engine RPM. The duty cycle should be o% (no EGR) when the TPS input below a specified value, or TPS indicating WOT."
So, when does the ECM command the EGR "ON"?
Notice that below about 50kPA the duty cycle of the EGR is small. IOW, it was commanding it closed above 2800 rpm. Since you said you were driving for 1 hr at speeds between 160 and 180 kph (100 and 115 mph) in a V6 Fiero I can pretty much guarantee you that you were running at or near WOT and therefore not seeing MAP of above 50 kPA.
Now add to the above that once your TPS shows over 70%, the EGR is disabled. In addition, once your coolant temp gets to a little above the temperature your thermostat opens, the O2 sensor is hot enough to be sending the ECM varying voltages telling it that it's reading, and the onboard timer has gone past a programmed time since start-up, the system goes into closed loop mode that actively adds fuel when the O2 reads a lean condition. If you're WOT, then it will go back to closed loop (sort of, on the Fiero) but then we're back to very low MAP readings that have the EGR disabled again.
Believe me when I tell you there are many, many street driven cars on this forum and many race cars with the EGR's either removed or disabled that are NOT melting pistons. The amount of exhaust gas that's permitted to go through the system is small and is used for one thing and one thing only, to reduce NOX emissions. If not for that, it wouldn't be on the engine because to be blunt, it reduces fuel efficiency every time it's opened.
An engine, any engine, wants two things to run and run well. Air and Fuel. Anything else is going to reduce fuel efficiency. Dense air has more oxygen in it by volume, that's why engines run better close to sea level and more poorly at higher elevations. Running an engine at low elevations is similar to boosting it as compared to "normal" performance at altitude, that's why aircraft that are turbocharged can maintain at or near 100% power ratings at high altitudes (talking piston engines here, not turbines). ANYTHING, let me say that again, ANYTHING, that is in that mix that is NOT air and NOT fuel is going to reduce efficiency. Exhaust gas is a by-product of combustion. If it increased overall efficiency it would be wonderful because we could just pipe it back in and have a perpetual motion machine, each cycle making the engine more and more efficient, but it doesn't work that way.
The only reason EGR is on there is to reduce NOX emissions. That's it, no other reason. If the engineers can develop an engine that doesn't need EGR to lower the NOX they would (and have, there are a few, but the Fiero engine isn't one of them) because THEY know that every time that valve opens they're going to reduce the efficiency of that engine by adding contaminants to the air charge.
John Stricker
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11:26 AM
Rafe Zetter Member
Posts: 277 From: Staffordshire, Great Britain Registered: Dec 2008
On an '86 you should connect the DK GRN and BLK/WHT wires together. They go into the connector that plugs into the EGR Solenoid and are terminals "C" and "D".
John Stricker
quote
Originally posted by Rafe Zetter:
Well it does make me feel a lot better hearing a couple of guys that know what they're talking about saying that the EGR removal will do no harm.
Can anyone tell me how to jumper the connector to avoid the code 32 ?
Ah were you on Holiday while in Germany and pullling a caravan?
A bit OT, but there was a guy selling a Fiero on ebay UK recently and the pictures showed him towing a caravan with his fiero. It was a small caravan tho one of the mini things....
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05:27 PM
Rafe Zetter Member
Posts: 277 From: Staffordshire, Great Britain Registered: Dec 2008
On an '86 you should connect the DK GRN and BLK/WHT wires together. They go into the connector that plugs into the EGR Solenoid and are terminals "C" and "D".
Thanks John, I going connect my engine up tomorrow (bolted the cradle back in earlier today) and i'll try that. From memory aren't there four wires on that connector, what is the best thing to do with the others ?
[This message has been edited by Rafe Zetter (edited 04-10-2010).]
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05:30 PM
phonedawgz Member
Posts: 17091 From: Green Bay, WI USA Registered: Dec 2009
Yes, there are four wires in the connector, the other two activate the EGR solenoid on command from the ECM. Just ignore them, they won't bother you.
John Stricker
quote
Originally posted by Rafe Zetter:
Thanks John, I going connect my engine up tomorrow (bolted the cradle back in earlier today) and i'll try that. From memory aren't there four wires on that connector, what is the best thing to do with the others ?
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05:37 PM
PFF
System Bot
Apr 11th, 2010
BL3200 Member
Posts: 131 From: Harze, Liege, Belgium Registered: Oct 2009
Just want to let the uncultivated person know that it is in Holland (supposed you know where it is ) that we pull caravan. In Belgium we carry suitacases, we eat French Fries (or freedom fries as some of you call it ) and drink beer
For the rest it's up to you beleive in what you like. I only reported hard facts, nothing else.
------------------ Bernard Fiero V6 GT 1987 (Manual)
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06:26 AM
phonedawgz Member
Posts: 17091 From: Green Bay, WI USA Registered: Dec 2009
Well if you make it to Green Bay, stop by, I'll buy you a beer.
I have hosted 4 German exchange students, and they all tried telling me stories about Belgiums on holiday pulling their caravans on the German highways.
[This message has been edited by phonedawgz (edited 04-11-2010).]
I've already melt a piston due to defect EGR valve (the membrane had craks so the valve did not work). It happened during a high speed long distance drive on german high way (no speed limit).
On my old GT, I had an exhaust gas temp gauge and while traveling a particular stretch of road, the exhaust temp would climb to around 1400 degrees- the extreme end of the scale. I could give it a little more throttle and the ecm would go into 'power enrichment' mode and the temps would come down to under 1200. I suspect that your high speed adventure was on the edge of the programming for normal air/fuel ratios and since the ecm was staying in the normal fueling side of the program, the extended amount of time at such elevated temperatures found the weak link. But what do I know.
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10:04 AM
La fiera Member
Posts: 2207 From: Mooresville, NC Registered: Jun 2008
I believe what the brother from Belgium is trying to say is that you can have hi vacuum at high rpm and at light or part throttle, which he achieved at high speed cruising and I do agree with him. If this is the case there is substantial amount of negative pressure that can meet the conditions to activate the EGR as the other fellow member is trying to explain, which he is also right. Cruising at about 75-80mph part throttle and looking at my live data in my scanner I recorded from 39 to 45% EGR steady activation. This means that with the EGR and selenoid removed the criteria is met for the ECM to do its calculations and fine tune the AFR at those specific conditions. The only criteria missing is the change in manifold pressure when the exhaust gas is introduced by the EGR, which is disabled in my car. So, knowing that the engineers at GM thought about that specific scenario they must've put a table of calculations for the ECM to follow and compensate for the lack of manifold pressure change or any other way to make-up for the missing change in manifold pressure. Now, if the Belgium brother criteria surpassed those make-up calculations then the ECM has nothing to go by and damaged is prone to happen, which it did. You are both right, but since the brother from belgium didn't have a "black box" we will never know exactly what happened.
R.Moloon
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10:41 AM
Apr 12th, 2010
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
All well, good, and reasonable but for one thing. He wasn't driving 75-80, he was driving 100-110. There is a significant difference in throttle opening at that speed and I'd be most anything it is well past the 70% mark where the EGR is disabled.
A faulty EGR system can cause engine damage, no doubt, but a properly permanently blocked system will not.
John Stricker
quote
Originally posted by La fiera:
I believe what the brother from Belgium is trying to say is that you can have hi vacuum at high rpm and at light or part throttle, which he achieved at high speed cruising and I do agree with him. If this is the case there is substantial amount of negative pressure that can meet the conditions to activate the EGR as the other fellow member is trying to explain, which he is also right. Cruising at about 75-80mph part throttle and looking at my live data in my scanner I recorded from 39 to 45% EGR steady activation. This means that with the EGR and selenoid removed the criteria is met for the ECM to do its calculations and fine tune the AFR at those specific conditions. The only criteria missing is the change in manifold pressure when the exhaust gas is introduced by the EGR, which is disabled in my car. So, knowing that the engineers at GM thought about that specific scenario they must've put a table of calculations for the ECM to follow and compensate for the lack of manifold pressure change or any other way to make-up for the missing change in manifold pressure. Now, if the Belgium brother criteria surpassed those make-up calculations then the ECM has nothing to go by and damaged is prone to happen, which it did. You are both right, but since the brother from belgium didn't have a "black box" we will never know exactly what happened.
R.Moloon
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06:48 PM
La fiera Member
Posts: 2207 From: Mooresville, NC Registered: Jun 2008
Good logical thinking jstricker. But I don't want to find out like Jackie Ickx did in Belgium. I noticed my AFR bars on my meter dissapeared longer than normal while cruising with the EGR blocked and disabled, and this phenomenon never happened while the EGR was hooked up and working. I don't know what the criteria is for the EGR to activate but I've noticed that the only times that it didn't activate in my car was at idle, decel and WOT, anything in between there was some percentage of activation regardless of the load or speed I was going. I'm waiting for my chip with the EGR disabled then, off to the road course. Hope this thread helped somebody.
quote
Originally posted by jstricker:
All well, good, and reasonable but for one thing. He wasn't driving 75-80, he was driving 100-110. There is a significant difference in throttle opening at that speed and I'd be most anything it is well past the 70% mark where the EGR is disabled.
A faulty EGR system can cause engine damage, no doubt, but a properly permanently blocked system will not.
John Stricker
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08:34 PM
Apr 13th, 2010
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
I did the same thing. blocked off the EGR port on the intake, and removed & capped the mushroom on the exhaust y-pipe. left the solenoid in place, and connected to the harness. I drove like this for 2 seasons, with zero issues. I did eventually get a chip made.
and now, many years later - I am looking at putting a EGR back on. I have since done a 7730 swap, and have a brand new digital EGR to install. I hope to get a MPG or 2 back......
I have heard the melting cyls due to no EGR - and I have to think there is a 2nd or even a 3rd issue causing this. the O2 sensor reads the exhaust and adjusts the mix accordingly. yes, during EGR time, it does allow for a slightly leaner mix & advances the timing. but nothing to a damaging level - and it knows due to O2 readings.
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09:49 AM
Apr 14th, 2010
La fiera Member
Posts: 2207 From: Mooresville, NC Registered: Jun 2008
Just got my chip with EGR deleted and custom for my upper plenum ugrade. It pulls steady until valve float or rev limiter (6500rpm)? I though I didn't want rev limiting. It feels like it has an electric motor for an engine. Thanks Mr darthfiero. Idles nice, accelerate beautifully, throttle response is very snappy and it even sounds different. Will datalog live AFR with a wideband and see how is the mix, it feels alright right now. Thanks again Rick!
) that we pull caravan. 
