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Arench, Master Technician
Category: Honda
Satisfied Customers: 1490
Experience:  30-years experience auto and truck repair.
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1993 Honda Accord: Le..the vacuum line off the stalled

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I am working on a 1993 Honda Accord Le. The car passes all sections of the emissions test accept the NOx portion. I was tinkering with the egr, took the vacuum line off the egr and created vacuum at the egr and the car stalled out. Therefor assuming that the egr works. When I put a vacuum gauge on the vacuum line leading to the egr I get a reading of 6 and only when I punch the throttle and then the vacuum disappears to 0. Slowly accelerating the engine I do not get a reading at all. What part on the car determines the vacuum pressure and when vacuum is applied to the egr. Note also that the car was at warm operating temp. when I tested the vacuum

Greetings from Arench.


Sounds like the egr is working to me. The ECU determines how much and when to open the EGR. The fact that you do get a vacuum signal makes me think your troubles lie elsewhere.


Since I do have a smog shop we are intimately familiar with the NOX problem on Accords.


Most often what we find is in three areas.


First is ignition timing set too high.

Second is clogged EGR passage in the intake.

Third is timing belt off 1 tooth.


Even though the egr open stalls the engine you could still have a cogged intake passage. From the EGR to the engine the passages branch off into 4 separate passages. What happens is EGR flows on two of the passages and two are clogged.


We try the timing thing first, then we move on to EGR port cleaning.


Here is a video showing the EGR clean out process on 91 Accord, yours is similar.






Arench and 3 other Honda Specialists are ready to help you
Customer: replied 7 years ago.

I was hoping for a simpler solution but with 340,000km on the motor I am sure that you are correct. My only other question is: would blocked passages cause the vacuum solenoid to click on then off after a few seconds at high idle.(would the computer do this?)



This is normal operation because the egr only opens under certain load conditions, its not constant or predictable. To see it working continuously the car would have to be driving down the road or running on a dyno.


Try knocking the timing back first before going through this messy process. With late timing you will have low power. Loosen the distributor bolts and turn the distributor counter-clockwise to retard the timing.





Customer: replied 7 years ago.
Sorry to be a pain but I was curious if the egr system on a Honda is very different from a 1991 gmc pickup. My pick up has a continuous vacuum of about 16-19 at 2000-2500rpm but the honda has only 6 and only when I punch the throttle. I cant help but think that the vacuum should be consistent and the egr opens when necessary other than at idle

yes its completely different, the Honda is more complex and has an egr lift sensor, the gmc has no sensor and its a very "dumbed down" type of system.


Your Honda vacuum control system is functioning normally. If you want to see the valve open all the time you will have to tee in a vacuum gauge to the line and drive it.


8 inches of vacuum if full lift of the valve on the Honda.







Customer: replied 7 years ago.

In your opinion and experience allowable ppm of NO in ontario is 467 and my reading is 614. Do you think that adjusting the timing will compensate enough for a pass. I am cheap and this will be my fifth etest. Also if I get this thing to pass can I still give you a tip payment?



You can add a bonus any time and yes retarding the timing will get it to pass.


Going on a cooler day will help also. Going first thing in the morning when they open will also help. Going on a rainy day will help even more.


The whole thing about NOX is the combustion chamber temperature, the lower the better.



Customer: replied 7 years ago.
Thanks so much. I was told to take the thermostat out and return it after the test to keep the engine cooler and drive the snot out of it to heat up the converter, add gas line antifreeze to the tank. What are you thoughts?

Skip all that, by making the engine run cold you will only waste fuel and then fail for a CO instead of NOX.


Forget the alcohol, thats is just plain dumb.


Driving the snots out of it is not needed because the converter only takes 2 minutes of normal driving to reach maximum temp, it will be hot when you get there.





Customer: replied 7 years ago.
Thanks, XXXXX XXXXX try it and let you know how I make out. P.S. Sounds like good advice since all other readings ie. CO an HC are very low now.

Good luck.


Follow your question link in email back here and let me know how it went.


You will want to crank the timing back up after the test or she will run like a dog.





Customer: replied 7 years ago.

I will be going for the etest on saturday. How much should I retard the timing or do you go as much as possible such that it still runs.



I like to go for it all. But they can't test the car if it won't move. Play with it so you get the most retard possible and still be able to take off from a light. Go in the morning.





Customer: replied 7 years ago.
tks, will do
Customer: replied 7 years ago.
Had the etest done today and it failed worse nox came in at 730

NOX can't go up when retarding the timing unless the car is overheating or you didn't connect everything back on the EGR.


Did the car feel like it had less power?


Perhaps you need to find someone to tweak the car for you and verify prior to testing. Do you have a regular mechanic shop you deal with?





Customer: replied 7 years ago.
I retarded the timing as far as it would go(which isnt very far) but the engine still ran great

Thats a sign that the timing belt off. When you turn it to the limit counterclockwise it should be a dog—I mean really a dog.


You should line up the belt and see if its off one tooth.





Customer: replied 7 years ago.

Sorry how do you line up the belt? Is it a difficult task?



It requires removal of the belts, crankshaft pulley and timing covers. Then you turn the engine by hand until the number one piston is at the top and the bottom mark is aligned on the crankshaft. The you observe the parks on the camshaft gear to see if they are inline with the edges of the cylinder head. If the alignment off not correct the timing belt must be removed and reinstalled to put the engine back in proper time.


Its not difficult but a lot of things can go wrong if you are not familiar with this type of job.



You said the dist. didn't move very much, you are aware there are 3 bolts holding this down. It should move a good 15mm.