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code 51 bad egr
Topic Started: Sep 12 2008, 08:58 PM (7,493 Views)
metrojoe
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smokin'

my 92 has not been running in over a year and i never got it to start when i got it recently and my dad says the valves or pistons are bad. i see the code thread and thought it would check mine and i found a 5-1 code and my egr is also bad?
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Johnny Mullet
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Fear the Mullet

Code 51 does not mean the EGR is bad. From what I gathered from the info you provided on various threads, the car was probably poorly maintained and the EGR ports are all clogged up. This is probably the cause of your car not starting and your dad saying "it needs pistons or valves".

When the EGR gets all gummed up, then so does all the other components in the head. These deposits build up on the valve and after time, the heat caused the valves to get holes burned into them or pieces break off causing poor or no compression.

Let us know when you are ready to get that car on the road and we can step you through it ;)
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Will
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Victory is mine!!!!

I think you are looking at a total rebuild, or at least the head and EGR. It's not that hard with our motors, and we will all help you through it.
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Sparky
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Ok, I give up. I have a 1994 Geo Metro, 1.0, 2 cylinder, five speed, right at 95,000 miles that had the number 3 cylinder exhaust valve burn a notch in it. Compression on all cylinders was 180, 180, 70. Fine, that's no problem to repair. Three new exhaust valves, a really serious bunch of work with a five angle valve job, some port cleanup, new seals, etc.. It never did give me a code 51 before I did the head work. Upon reassembly I installed a new EGR valve, tested the modulator, and the vacuum solenoid valve, All ok. Now with about 2500 miles on the head job I get a code 51.

In looking at the list of codes I see that code 51 also includes a REGT sensor. It seems that no one on the face of this earth knows what REGT stands for. No results on the internet, I also cannot find it even in the factory shop manual that I have.

You guys are the guru's of the Metro world from what I understand, so what wisdom can you shed on this? I love this car because first, I'm a tightwad and I love 45 to 48 mpg, and secondly, I intend to drive it until it falls over and dies an unnatural death.

Thanks in advance
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Bad Bent
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Facetious Educated Donkey

Welcome to the forum, Sparky! :coffee

REGTS - Recirculated Exhaust Gas Temp. Sensor so REGT is Recirculated Exhaust Gas Temp.

If you pull your EGR and start the engine you will get vacuum and air pressure. If you don't get pressure from the block, and this is likely, the passages through the block and exhaust manifold are blocked with carbon. I pulled the eshaust manifold and cleaned it while it was off the engine. A flex cable attached to a drill has been used with success to roto-rooter the block. IMO. B-)
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mwebb
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FOG

while i am not familiar with early metro EGR
many early EGR systems including the VW ABA engine which i am familiar with
used an
EGR temp sensor
in the line from the EGR to the intake
to confirm that the EGR was flowing exhaust gases into the intake when the EGR was commanded to be on

so it makes sense that
the system may code for the sensor , if the EGR passages are clogged as the value will be outside of what is expected
or it could be open

should be 5 volts supply and maybe 2 or three volts at the signal wire with Key on engine off
and much lower when hot when the EGR is flowing
as measured with a DVOM
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Sparky
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Bad Bent
Feb 14 2010, 08:32 PM
Welcome to the forum, Sparky! :coffee

REGTS - Recirculated Exhaust Gas Temp. Sensor so REGT is Recirculated Exhaust Gas Temp.

If you pull your EGR and start the engine you will get vacuum and air pressure. If you don't get pressure from the block, and this is likely, the passages through the block and exhaust manifold are blocked with carbon. I pulled the eshaust manifold and cleaned it while it was off the engine. A flex cable attached to a drill has been used with success to roto-rooter the block. IMO. B-)
Hey Bad Bent, thanks for your response. I really appreciate it. Here's what I have done so far. When I had the head off to do the work on it, I vatted and cleaned it completely. This included cleaning the passage from the exhaust manifold through the head casting with a small burr, plus running a stainless rotary brush through the passage. It's clean. Today I removed the exhaust manifold and checked the passage from the port to the head casting. It's clean also. (I'm assuming that when you used the term "block" you were referring to the head casting. I don't think the block itself has any passages in it does it? To add, this engine uses a quart of oil about every 5 or 6 hundred miles. It doesn't smoke excessively but #3 spark plug is a bit oily and carbon covered. After about 1500 miles on the head job, and the installation of the new EGR valve, the valve has a little bit of carbon in it. Really more than I like. Compression on all three cylinders, when pumped as high as it will climb, (coil disconnected, throttle open, and about ten seconds of cranking) stands about 205 psi. Good.

Today I also rechecked all the components for the complete EGR system. EGR SV valve, (ok), modulator, (ok) and the new EGR valve itself, (ok). I blew out all the passages (clean) and replaced all the vacuum hoses to each component. I still get a code 51 after about 10 miles of freeway driving.

One thing that I wonder about is that about 5 or 6 days ago I had a code 23 which is the IAT sensor code. I replaced it with a new one and had no more codes until about 2 days ago when I started having the code 51 repeats. Today I also checked the MAP sensor and found the voltages to the connector ok but found the vacuum hose and filter restricted with some red looking liquid. I cleaned it out thinking I had found something that might be connected to the EGR problem. No luck. In fact, the check engine light (code 51) came on even quicker. (2 miles)

I'm throwing a hell of a lot on you aren't I? :(

I said all the above to ask this; do you think that there is another component that can be faulty, not show a code of it's own, and still give me a code 51? If the MAP sensor is not working properly I would think it would give it's own code, but maybe not. What do you think?

Thanks
Sparky
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starscream5000
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Got 70 MPG?

Given your compression numbers. And a recent head job, and the amount of oil that your going through in such a short span of time, I'd say your head job was not done correctly. That or your have another oil leak somewhere. This may or may not be tied into your check engine light issues.
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Bad Bent
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Facetious Educated Donkey

OK, so Johnny Mullet, Will, mwebb and starscream5000 have experience with this, follow their advice. I use 'block' when I meant 'head' like a blockhead. But I can use the boss' D70 and Photoshop. I believe my '91's manual on Code 51 gave us another component, the ECM connections. Take a look and see what the "Authentic Technical Service Information" manual says...

Posted Image Page 1.

Posted Image Page 2.
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chads4dr


Bad Bent, my 1994 Factory Service manual has a different diagram and circuit description, I will try to upload mine tomarrow!

It seems the EGR is tied into the fuel pump relay and fuel injector in our year.

I think code 51 is also a "rationality" code, this is my circuit description direct quote:

The exhaust gas recirculation solenoid vacuum (EGR SV) valve is engine control module (ECM) controlled. System voltage is applied to the EGR SV valve from the FI relay. When the driver in the ECM closes, the EGR SV valve is activated.
DTC 51 will set if the following conditions are met:
*System is operating in "closed loop" operation.
*MAP is less than a calibrated value.
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Bad Bent
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Facetious Educated Donkey

chad8329
Feb 15 2010, 09:16 PM
Bad Bent, my 1994 Factory Service manual has a different diagram and circuit description, I will try to upload mine tomorrow!
Excellent, chad. We upload enough of them eventually we will get it right.

Dare we say, not all Code 51s are the same....
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mwebb
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FOG

...."It seems the EGR is tied into the fuel pump relay and fuel injector in our year."....

they share a common positive supply from the fuel pump relay other than that
they are not tied together .

to see if your EGR plumbing is correct
when the engine is at hot idle
apply a vacuum to the EGR diaphragm , does the engine stall ? or does the idle get rough ?
or choice C
nothing

post your results
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idmetro
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Sparky
Feb 15 2010, 05:38 PM
Bad Bent
Feb 14 2010, 08:32 PM
Welcome to the forum, Sparky! :coffee

Today I also rechecked all the components for the complete EGR system. EGR SV valve, (ok), modulator, (ok) and the new EGR valve itself, (ok). I blew out all the passages (clean) and replaced all the vacuum hoses to each component. I still get a code 51 after about 10 miles of freeway driving.
In my case the EGR passage was clogged tight about an inch back from where it enters the intake manifold under the throttle body (about as far away from the head as you can get), every place else was clear. When you pull the EGR valve can you blow air through both ports?
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Sparky
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chad8329
Feb 15 2010, 09:16 PM
Bad Bent, my 1994 Factory Service manual has a different diagram and circuit description, I will try to upload mine tomarrow!

It seems the EGR is tied into the fuel pump relay and fuel injector in our year.

I think code 51 is also a "rationality" code, this is my circuit description direct quote:

The exhaust gas recirculation solenoid vacuum (EGR SV) valve is engine control module (ECM) controlled. System voltage is applied to the EGR SV valve from the FI relay. When the driver in the ECM closes, the EGR SV valve is activated.
DTC 51 will set if the following conditions are met:
*System is operating in "closed loop" operation.
*MAP is less than a calibrated value.
Thanks for you input. Yes, my factory shop manual shows the same thing. I have, according to all the diagrams, the "enhanced" emissions system. One thing that I am checking out now is the MAP sensor. I recleaned all the passages, including the short passage through the exhaust manifold and the passage leading from the EGR valve port up under the throttle body, reset the check engine light and drove it about 30 or so miles before getting another code. This time it was code 32. (Map high vacuum) OK, I thought. Maybe the map sensor is the culprit. As I stated before, I had checked the vacuum hose leading to it and got some red colored liquid out of it. When I first blew into it, it felt plugged.

After getting the code 32 I rechecked the passages again, drove it about 20 miles and, TA DA♪♫, got another code 51.

I stopped at NAPA to check on a new MAP sensor and ended up crawling out of the place. A new one is available and it's only $395.00 bucks. I'm trying to find a used one. I tried one off a 95 model that I'm not sure it good, nor am I sure that it will work for my 94 anyway. It is a different part number. What do you guys think? Will I need to replace it with the exact part that matches mine?

If you guys see a column of smoke coming from here in Texas you'll know it's a burning Geo. :banghead
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Sparky
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idmetro
Feb 15 2010, 10:10 PM
Sparky
Feb 15 2010, 05:38 PM
Bad Bent
Feb 14 2010, 08:32 PM
Welcome to the forum, Sparky! :coffee

Today I also rechecked all the components for the complete EGR system. EGR SV valve, (ok), modulator, (ok) and the new EGR valve itself, (ok). I blew out all the passages (clean) and replaced all the vacuum hoses to each component. I still get a code 51 after about 10 miles of freeway driving.
In my case the EGR passage was clogged tight about an inch back from where it enters the intake manifold under the throttle body (about as far away from the head as you can get), every place else was clear. When you pull the EGR valve can you blow air through both ports?
Hmmmm, You may be on to something. I remember the first time that I blew air through the two ports covered by the EGR valve, I had good air movement back toward the exhaust manifold but no air movement through the other port opening. Like a dumbass I didn't know that it should have been open. I'll check that out the first thing in the morning. In fact, I think I'll take the throttle body off so I can see it from the other direction. I'm assuming that the passage leads to the area below the TB. Am I correct?

Thanks
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