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Discussion Starter · #1 ·
Hey there gang,

I bought a run-down CRV for a project, mostly to learn some stuff I'm not familiar with.
So far I've managed to get it running, however, it's bouncing on idle, I'm guessing it from a vacuum leak? Is there any common areas that get vacuum leaks and if so, how can I check for one and how can I fix a vacuum leak??

I think it also smells lean but I can't be sure.

If you think it might be something else please let me know!

Thanks a bunch!
 

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2020 CR-V Hybrid EX
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1,524 Posts
Hey there gang,

I bought a run-down CRV for a project, mostly to learn some stuff I'm not familiar with.
So far I've managed to get it running, however, it's bouncing on idle, I'm guessing it from a vacuum leak? Is there any common areas that get vacuum leaks and if so, how can I check for one and how can I fix a vacuum leak??

I think it also smells lean but I can't be sure.

If you think it might be something else please let me know!

Thanks a bunch!
Some info on the vehicle other than "run-down" would help. Year and trim would be a good start, diesel or petrol would also be good to know (though "smells lean" probably means gas).:)
Lots of smart folks here but they need to know what vehicle they are dealing with.
If you like, you can put your vehicle details in your avatar. Click on your avatar in the upper right for "account details".
 

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2007 CRV
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760 Posts
Youtube has many videos on Honda surging idle issues.
Some are caused by low coolant level
Or Idle Air Control Valve (IAC valve)
Or fast idle control
or ... etc.
Please let us know how the project car goes???

Note: I recently replaced my front right wheel bearing.
Some things did go according to plan which made me feel good
Until, it didn't. Then it was like I wish I could give up and just hand it over to a garage.
But, worked it out hours and hours later. Finished.
 

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Discussion Starter · #4 ·
Some info on the vehicle other than "run-down" would help. Year and trim would be a good start, diesel or petrol would also be good to know (though "smells lean" probably means gas).:)
Lots of smart folks here but they need to know what vehicle they are dealing with.
If you like, you can put your vehicle details in your avatar. Click on your avatar in the upper right for "account details".
Hey!
Good point, it's a 2000 CRV Sport, B20B8 Engine, petrol (sorry I'm Australian, gas means something else here :p)
When I got it there was a misfire on cylinder 3 which I quickly figured to be a cracked exhaust valve, all the valves have been replaced, as well as the head, intake and exhaust manifold gaskets at the same time since I had the cylinder block off.
The timing belt was also replaced when I was putting it all back together.

Hopefully, that's a little more helpful :)

Thanks!
 

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2007 CRV
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760 Posts
If it was a vacuum leak then one can look at live data on a scan tool
and see the short term fuel trim trying to correct the situation
The short term fuel trim should appear to go positive
(trying to add fuel to make up for the vacuum leak or too lean condition)
But remember that as the throttle opens the fuel trim will tend to go back to normal.

Would try cleaning up throttle plate and IAC valve.
Cost a little time and effort (and maybe a little money for cleaner)
 

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Discussion Starter · #6 ·
If it was a vacuum leak then one can look at live data on a scan tool
and see the short term fuel trim trying to correct the situation
The short term fuel trim should appear to go positive
(trying to add fuel to make up for the vacuum leak or too lean condition)
But remember that as the throttle opens the fuel trim will tend to go back to normal.

Would try cleaning up throttle plate and IAC valve.
Cost a little time and effort (and maybe a little money for cleaner)
Hmm that sounds good, I don't have access to a scan tool unfortunately, and from what I gather the gen 1 CRV has a non standard OBD port?
 

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My 1999 ex regular gas. Was doing that with the idle, along with not starting sometimes. It turned out to be the coolant temperature sensor that's in the head below the distributor. Although it did show up as a engine light on the dash and code reader confirmed it w/my OBDII bluetooth adapter.
 

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Discussion Starter · #9 ·
My 1999 ex regular gas. Was doing that with the idle, along with not starting sometimes. It turned out to be the coolant temperature sensor that's in the head below the distributor. Although it did show up as a engine light on the dash and code reader confirmed it w/my OBDII bluetooth adapter.
Now that's super interesting, I just checked and the temp gauge isn't working, and the radiator fans aren't turning on, that might be the culprit!
Do you happen to remember/know the part number for that temp sensor?
 

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Hmm that sounds good, I don't have access to a scan tool unfortunately, and from what I gather the gen 1 CRV has a non standard OBD port?
In the US it has a standard OBD-II port, but I don't know what the CR-V might use around the world.
 

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Hey there gang,

I bought a run-down CRV for a project, mostly to learn some stuff I'm not familiar with.
So far I've managed to get it running, however, it's bouncing on idle, I'm guessing it from a vacuum leak? Is there any common areas that get vacuum leaks and if so, how can I check for one and how can I fix a vacuum leak??

I think it also smells lean but I can't be sure.

If you think it might be something else please let me know!

Thanks a bunch!
I had the same issue, assuming it was all the common items, replaced all of them and in the end it was the valves were too tight.
What confused me was the codes were reporting on all four cylinders, so my logic was something was not working with the intake or all four
cylinders had too tight valves. I thought what are the odds ALL four cylinders had too tight valves. So, after replacing just about every sensor
I finally talked myself in checking the valves (which by the way is a 30,000 mile maintenance item). All 8 exhaust valves were too tight and 3 of the intake
valves were too tight. It was easy to adjust them, took about 20 minutes. My high/low idle issue was immediately gone after fiddling with it for over
a year. I got my 2001 CRV with 80,000 miles on it and it had the high/low idle issue. The past owner had all the maintenance records and none were
a valve adjustment. I think the manual states that a valve adjustment is needed at 100,000 miles but have read that is not correct, it should be every 30,000.
So, if you have over 30,000 miles on your CRV and has not had a recent valve adjustment, do that first before you replace any sensors.
 

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2001 CRV 2wd
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I read somewhere that if the regular valve adjustment is skipped, the valve lash ends up being too tight and it burns out the valve seats. It’s a common problem because dealerships (and most tune-up shops) skip this step. So, now our 20+ y/o vehicles have bad valves and valve seats, idle issues and “vacuum” problems. The idle/vacuum leak diagnosis comes from the bad valves/valve seats, allowing pressure leaks across all the cylinders. Sometimes this leaves unspent fuel to be in the exhaust, resulting in fuel rich exhaust.

The best solution is to replace valves and have the engine head machined/replaced. That’s very time consuming or expensive. It could be an interesting project for motor heads.

A cheaper option is to have the valve lash adjusted. It won’t solve the problem, but it will help.

I bought my ‘01 from my Brother-in-law two years ago for $300 when he moved out of state. It had all sorts of problems and he didn’t want to spend the time to fix it.
 

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2016 CRV Touring AWD
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If its running lean, that will show in the plugs. You've had the head off and repaired, plus timing should all be right. Take a moment to spring clean the engine PCV system, EGR system etc. Check all the hoses, especially where they connect for signs of splitting. Check the electrical system, battery and alternator. Check fuel pump pressure when just started and warm after a bunch of miles.
 

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I read somewhere that if the regular valve adjustment is skipped, the valve lash ends up being too tight and it burns out the valve seats. It’s a common problem because dealerships (and most tune-up shops) skip this step. So, now our 20+ y/o vehicles have bad valves and valve seats, idle issues and “vacuum” problems. The idle/vacuum leak diagnosis comes from the bad valves/valve seats, allowing pressure leaks across all the cylinders. Sometimes this leaves unspent fuel to be in the exhaust, resulting in fuel rich exhaust.

The best solution is to replace valves and have the engine head machined/replaced. That’s very time consuming or expensive. It could be an interesting project for motor heads.

A cheaper option is to have the valve lash adjusted. It won’t solve the problem, but it will help.

I bought my ‘01 from my Brother-in-law two years ago for $300 when he moved out of state. It had all sorts of problems and he didn’t want to spend the time to fix it.
The above is all possible, but what is also possible is just a carbon build up due to the exhaust valves not fully closing. A carbon build-up will burn off a bit after the
valves are adjusted. Before doing the rebuild, I would adjust the valves, drive it for 500 or so miles and then adjust the valves again (they might be too loose (which makes noise)
after any carbon burns off.
 
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