EGR code 33?
09-09-2008, 06:57 PM
#1
Senior Member
Thread Starter
EGR code 33?
My '91 302 is starting to stumble once in awhile - usually when it's going at highway speed and then you try to speed up (not enough to shift to passing gear, but speeding up with the rpm's down).
I pulled the codes, and only came up with 33 - EGR opening not detected?
I pulled the EGR valve off the front of the intake, and it was pretty gummed up with black crap. Per the Chilton book, I scraped some of the gunk loose, and put it back on. Whjle doing this, I disconnected the neg battery cable to reset the PCM.
Took her for a drive, and after 10-15 minutes it stuttered just a bit on the highway. Drove it home, pulled the codes, same thing - code #33.
Do I need to replace the EGR valve? I have vacuum. The tube running from the bottom of it to the top of the engine (under the intake manifold) runs to some other valve, right? Which one am I after? Hopefully the one that's easy to get to...
Thanks for your help!
I pulled the codes, and only came up with 33 - EGR opening not detected?
I pulled the EGR valve off the front of the intake, and it was pretty gummed up with black crap. Per the Chilton book, I scraped some of the gunk loose, and put it back on. Whjle doing this, I disconnected the neg battery cable to reset the PCM.
Took her for a drive, and after 10-15 minutes it stuttered just a bit on the highway. Drove it home, pulled the codes, same thing - code #33.
Do I need to replace the EGR valve? I have vacuum. The tube running from the bottom of it to the top of the engine (under the intake manifold) runs to some other valve, right? Which one am I after? Hopefully the one that's easy to get to...
Thanks for your help!
09-09-2008, 08:56 PM
#2
Senior Member
Assuming there weren't too many changes between model years of yours and mine - there are three main components - the EGR valve itself, the position sensor, and the control solenoid located on the intake manifold toward the driver side rear. Then there's the smaller stuff like integrity of the vacuum hoses, and an unrestricted flow path from the exhaust to the valve.
As the valve is gunked up - perhaps there is a flow restriction in the tubing? Does the valve actually open and hold with vacuum? The position sensor could also be a problem - if you change it, be sure to get the right color, I think grey or white are the options - perhaps the wrong one has been installed in the past?
There's no other valve that I'm aware of in the exhaust gas path.
The EGR typically does not become active until a predetermined temperature or time is reached - thus potentially the reason why you're not seeing problems until the engine has warmed.
Good luck, and keep us posted on the developments.
As the valve is gunked up - perhaps there is a flow restriction in the tubing? Does the valve actually open and hold with vacuum? The position sensor could also be a problem - if you change it, be sure to get the right color, I think grey or white are the options - perhaps the wrong one has been installed in the past?
There's no other valve that I'm aware of in the exhaust gas path.
The EGR typically does not become active until a predetermined temperature or time is reached - thus potentially the reason why you're not seeing problems until the engine has warmed.
Good luck, and keep us posted on the developments.
09-09-2008, 09:20 PM
#3
Senior Member
Thread Starter
As usual, more info might help...
The sensor on my truck is white. The ones listed for that truck at O'Reilly are also white. Not to say it isn't bad, but at least it's the right color...
After looking, I think I was having flashbacks from another car where the sensor and the valve were separate - there is just the valve with sensor on top, the tube, and then the solenoid/vac lines.
It has also been cold the past couple of mornings - it seems to stutter a lot until it gets warmed up, then smooths out. Then it becomes intermittent, like I said it's usually when the engine is under load at low rpm.
Reading on some web sites, some mention that an O2 sensor can cause this code too... any ideas on that?
I hate to mess with the lower tube unless necessary - there's a lot of stuff in the way! Maybe I should replace the solenoid, sensor, and EGR valve one at a time and see if that solves it before moving on to the more time consuming lower tube?
I dunno... I definitely appreciate the knowledge and experience around here, though!
The sensor on my truck is white. The ones listed for that truck at O'Reilly are also white. Not to say it isn't bad, but at least it's the right color...
After looking, I think I was having flashbacks from another car where the sensor and the valve were separate - there is just the valve with sensor on top, the tube, and then the solenoid/vac lines.
It has also been cold the past couple of mornings - it seems to stutter a lot until it gets warmed up, then smooths out. Then it becomes intermittent, like I said it's usually when the engine is under load at low rpm.
Reading on some web sites, some mention that an O2 sensor can cause this code too... any ideas on that?
I hate to mess with the lower tube unless necessary - there's a lot of stuff in the way! Maybe I should replace the solenoid, sensor, and EGR valve one at a time and see if that solves it before moving on to the more time consuming lower tube?
I dunno... I definitely appreciate the knowledge and experience around here, though!
09-09-2008, 10:29 PM
#4
With the EGR having so much crap in it, I would probably replace it, but it isn't cheap. The tube from the bottom of it goes to the exhaust manifold, no valve on that end. The EGR stays closed at idle and wide open throttle, and varies position in between and at cruising speed. Check for vacuum into the solenoid and out. There should be no vacuum out until part throttle. If you can see the underside of the EGR you will see holes in it showing the internal plunger. Rev the throttle and watch for movement or remove the position sensor and watch for movement at the top. Another test is to unplug the IAC and run the engine. You may have to have someone hold the idle steady since the IAC is unplugged. Apply vacuum to the EGR and watch the RPMs. The RPMs should drop if the valve is working. If you don't unplug the IAC it will try to compensate for the idle drop during the test and make it difficult to see the idle drop.
09-09-2008, 11:19 PM
#5
Senior Member
Thread Starter
Ok - so let me make sure I'm looking for the right thing at the right time here...
I'm checking vacuum out of the solenoid to see if it's the culprit?
Then I'm checking movement on the EGR to see if it's working?
If both check out it's probably the sensor?
Either way, the crusty old EGR is probably due for a $130 update anyway...
What do you think about the O2 sensor theory? Ever heard of that causing an EGR code or this sort of stuttering? I bought the truck used, so I have no idea when it was last changed if ever.
This old truck is like a house of cards! One thing leads to another... and another... but hey - at least it's not leaking oil!
I'm checking vacuum out of the solenoid to see if it's the culprit?
Then I'm checking movement on the EGR to see if it's working?
If both check out it's probably the sensor?
Either way, the crusty old EGR is probably due for a $130 update anyway...
What do you think about the O2 sensor theory? Ever heard of that causing an EGR code or this sort of stuttering? I bought the truck used, so I have no idea when it was last changed if ever.
This old truck is like a house of cards! One thing leads to another... and another... but hey - at least it's not leaking oil!
09-09-2008, 11:38 PM
#6
Senior Member
Thread Starter
A little bit of thinking later, I have some more info that might help confuse the situation or maybe narrow down the problem.
Let's consider a normal cold start/drive to work - it does the normal high idle, then drops down to about 1000rpm in park. Drop it into gear and it drops to around 700rpm.
If it's acting up, it'll chug and stutter at 55mph after coasting and starting up a hill (putting load on the engine, but not enough to down shift). After getting totally warmed up, this seems to settle down.
Coming back home, it's warmer air temp, but starts the same. Once again, if it's acting up, it'll chug under load (but not at higher rpm's).
At this point, at a complete stop it will try to die. Get it into neutral or park soon enough, and it'll recover.
Finally get home, feeling lucky that I haven't walked 10 miles... pull into the driveway and put in park, it'll idle up to about 1400rpm. I can flutter the gas pedal, but it still settles back to high idle.
I'll see tomorrow if cleaning out the EGR helps at all. I took a short drive after cleaning the valve, but tomorrow's trip to/from work will tell the tale for sure. Once I get back home I'll test the solenoid and valve as recommended and see what happens.
Let's consider a normal cold start/drive to work - it does the normal high idle, then drops down to about 1000rpm in park. Drop it into gear and it drops to around 700rpm.
If it's acting up, it'll chug and stutter at 55mph after coasting and starting up a hill (putting load on the engine, but not enough to down shift). After getting totally warmed up, this seems to settle down.
Coming back home, it's warmer air temp, but starts the same. Once again, if it's acting up, it'll chug under load (but not at higher rpm's).
At this point, at a complete stop it will try to die. Get it into neutral or park soon enough, and it'll recover.
Finally get home, feeling lucky that I haven't walked 10 miles... pull into the driveway and put in park, it'll idle up to about 1400rpm. I can flutter the gas pedal, but it still settles back to high idle.
I'll see tomorrow if cleaning out the EGR helps at all. I took a short drive after cleaning the valve, but tomorrow's trip to/from work will tell the tale for sure. Once I get back home I'll test the solenoid and valve as recommended and see what happens.
09-10-2008, 12:13 AM
#7
Yes.
Yes.
If it's acting up, it'll chug and stutter at 55mph after coasting and starting up a hill (putting load on the engine, but not enough to down shift). After getting totally warmed up, this seems to settle down.
Coming back home, it's warmer air temp, but starts the same. Once again, if it's acting up, it'll chug under load (but not at higher rpm's).
Coming back home, it's warmer air temp, but starts the same. Once again, if it's acting up, it'll chug under load (but not at higher rpm's).
At this point, at a complete stop it will try to die. Get it into neutral or park soon enough, and it'll recover.
Finally get home, feeling lucky that I haven't walked 10 miles... pull into the driveway and put in park, it'll idle up to about 1400rpm. I can flutter the gas pedal, but it still settles back to high idle.
Finally get home, feeling lucky that I haven't walked 10 miles... pull into the driveway and put in park, it'll idle up to about 1400rpm. I can flutter the gas pedal, but it still settles back to high idle.
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09-10-2008, 04:45 PM
#8
Senior Member
Thread Starter
I haven't played with the EGR yet, but I will later this afternoon. In the meantime, here's how today's driving went...
On the way to work - it was smooth as silk ...until I got about 1/4 mile away, then it started chugging again. Bad enough that it died as I pulled into a parking space.
I had to run an errand mid-day, and on the way there, it chugged all the way. Shut it off, did my thing, then it was super smooth all the way back to work.
On the way home, it stuttered a bit early in the trip, but smoothed out nicely the rest of the way home.
I pulled in the driveway and pulled codes. This time, no EGR code, but a 173 - HEGO too rich (or something like that). Is that the O2 sensor?
I also thought about the IAC. Is that something that can be cleaned, or is it a replacement only? More importantly, where the heck is it?
Thanks again for the guidance - you should start charging for tech support! I'll post my findings on the EGR later (hopefully my cleaning cured that, and the lack of a code 33 gives me hope, but we'll see).
On the way to work - it was smooth as silk ...until I got about 1/4 mile away, then it started chugging again. Bad enough that it died as I pulled into a parking space.
I had to run an errand mid-day, and on the way there, it chugged all the way. Shut it off, did my thing, then it was super smooth all the way back to work.
On the way home, it stuttered a bit early in the trip, but smoothed out nicely the rest of the way home.
I pulled in the driveway and pulled codes. This time, no EGR code, but a 173 - HEGO too rich (or something like that). Is that the O2 sensor?
I also thought about the IAC. Is that something that can be cleaned, or is it a replacement only? More importantly, where the heck is it?
Thanks again for the guidance - you should start charging for tech support! I'll post my findings on the EGR later (hopefully my cleaning cured that, and the lack of a code 33 gives me hope, but we'll see).
09-10-2008, 05:03 PM
#9
Senior Member
Thread Starter
I just tested the EGR components:
At the solenoid, I have low vacuum even at idle - revving the throttle doesn't increase vacuum. Probably bad.
With the EGR vacuum line connected, revving the throttle doesn't move the valve, but that could be due to the solenoid.
So... should I begin this journey with a $35 EGR solenoid and a $50 O2 sensor?
At the solenoid, I have low vacuum even at idle - revving the throttle doesn't increase vacuum. Probably bad.
With the EGR vacuum line connected, revving the throttle doesn't move the valve, but that could be due to the solenoid.
So... should I begin this journey with a $35 EGR solenoid and a $50 O2 sensor?
09-10-2008, 10:11 PM
#10
First off, HEGO is heated exhaust gas oxygen sensor. Don't change it, it's working. It's telling you that the air/fuel mixture isn't correct. It might be bad but probably isn't, you will see after you fix the other problems.
Code 173, my book is showing 3 digit codes for '92 and up. '91 and before use 2 digit codes. Check the codes again to be sure, but your truck may use the '92 computer.
People have cleaned the IAC, so you can try. It should be on the intake manifold near the throttle body. If it's not working properly, which I think it isn't, it can cause the truck to run rich.
Before changing the solenoid, make sure the EGR is working. Take a vacuum pump, hook it to the EGR and apply vacuum. See if it moves. If you don't have or don't want to buy a vacuum pump, just hook a vacuum hose to the EGR and suck on the end.
Code 173, my book is showing 3 digit codes for '92 and up. '91 and before use 2 digit codes. Check the codes again to be sure, but your truck may use the '92 computer.
People have cleaned the IAC, so you can try. It should be on the intake manifold near the throttle body. If it's not working properly, which I think it isn't, it can cause the truck to run rich.
Before changing the solenoid, make sure the EGR is working. Take a vacuum pump, hook it to the EGR and apply vacuum. See if it moves. If you don't have or don't want to buy a vacuum pump, just hook a vacuum hose to the EGR and suck on the end.