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Lack of backpressure causes stumble?

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Old 03-16-2009 | 12:48 AM
poorboy_616's Avatar
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Default Lack of backpressure causes stumble?

Okay, the wifes 91 Accord just recieved a full tune-up as it had a low speed miss under load, with a stumble @ ~1500RPM.

Now the guy we bought it from just had the intake gasket, and TB gasket replaced. All the hoses are fairly new as well.

The muffler on this car is shot, it's got a large hole up front and pinholes out back. Could the lack of backpressure be causing the stumble? None of my other vehicles have complained about losing some of their backpressure.

Also I have a quick question on the trans-axle and it's shift feel. All the Honda's I have ever driven with Autos have very firm shifts, this one does as well, my wife seems to think that the trans is going because of the firmness of the shift quality. Just to appease her, is this normal?

BTW sport mode is a hair firmer, but WAYYYYYY higher shift points...
 
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Old 03-16-2009 | 10:17 AM
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Sounds like the trans is okay....................the pre-98 trans will shift under positive pressure. It reduces wear on the clutch plates.
2 things you can do to check for EGR problems;
With the engine fully warmed, parking brake on and holding the brakes firmly. Put it in drive and 'power brake' up thru 1500-1700 RPM.
If you feel the lean burn stumble in that RPM range the EGR ports need cleaned.
As well, with the engine fully warmed up and at idle in park, you can reach a finger under the top of the EGR valve and manually lift the plunger, the engine Should stumble severely or die. If not EGR ports need cleaned.
This link might help you;

http://img299.imageshack.us/img299/4005/98074egrep7.gif
 
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Old 03-16-2009 | 03:45 PM
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Thank you, that clarifies a bunch!

It is definately in the lower RPM band just after take-off that we get the stumble. I am going to run out and do the test here in a minute.....
 
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Old 03-16-2009 | 04:10 PM
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Okay, test confirmed!!

The EGR is indeed at fault, now what to do about it? Do I use the TSB and go all out, or Could pull it, clean it and re-install it? Or just replace it all together?

Also, for now, can I run with the vacuum line to the EGR disconnected to get rid of the stumble? Or will do it anyway? Keep in mind, it would be just until I can replace the valve or do the cleaning....

Oh yeah, I discovered some extra wires......

I just about crapped myself......

The guy that had the car before us had put in a nice head unit and very nice speakers. Now that I found the extra wiring, I couldn't resist following them to where they go.....

Too the trunk, of course!

I happen to have a nice sub-box in the back of my jeep (not wired yet), so all I would need is an amp....
 
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Old 03-16-2009 | 04:48 PM
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Originally Posted by poorboy_616
Okay, test confirmed!!
What does that mean? Dude mentioned TWO tests. Which did you do & what exactly was the result?

You may already have the information to determine whether it's plugged EGR passageways vs. bad EGR valve.
 
  #6  
Old 03-17-2009 | 04:37 AM
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Test confirmed, meaning both tests. Sorry I wasn't more clear.

It stumbles under load using the load test, and when you manually work the valve at idle. The idle is also a hair high, which jives with a valve thats stuck partly open.... grrrr.....

Unfortunately, it's right in the range we use while driving thru town, so it gets annoying very, very quickly.
 
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