What engine sensor is this? (pictures attached) - Page 2 - Third Generation F-Body Message Boards

naf · 09-22-2009, 07:53 AM

The bog is likely either your air valve tension or your choke pull off. Your choke pull (the small vac canister, right front of carb) is designed to slightly open the choke blades once the engine is started. It will also prevent (and slightly delay) the air valves from opening until it loses its vacuum signal. Check it by depressing the plunger and holding your finger over the vacuum port on the back of it. The plunger should stay in until you release your finger.

The air valve is the flapper on top of the secondaries. It's controlled by spring tension. If the tension is too lose they open too quickly and will cause a bog. There's a tech article here on how to adjust and a diagram in the carb sticky, top of forum. A good starting point is tighten it until the valves just close then add 7/8 turn. It's a little tricky, you'll have to hold the tension with a small screwdriver while you tighten the set screw.

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Ozz1967 · 09-22-2009, 03:01 PM

Quote:

Originally Posted by naf

The bog is likely either your air valve tension or your choke pull off. Your choke pull (the small vac canister, right front of carb) is designed to slightly open the choke blades once the engine is started. It will also prevent (and slightly delay) the air valves from opening until it loses its vacuum signal. Check it by depressing the plunger and holding your finger over the vacuum port on the back of it. The plunger should stay in until you release your finger.

The air valve is the flapper on top of the secondaries. It's controlled by spring tension. If the tension is too lose they open too quickly and will cause a bog. There's a tech article here on how to adjust and a diagram in the carb sticky, top of forum. A good starting point is tighten it until the valves just close then add 7/8 turn. It's a little tricky, you'll have to hold the tension with a small screwdriver while you tighten the set screw.

I tried adjusting the tensioner on the on the flapper of the secondaries to no effect. It could be that the choke pull is not opening fast enough? Any ideas how fast it's supposed to operate when engaged? I mean, I can sit under the hood and gun the engine using the throttle on the carb and as the car dies, I can see the choke pull slowly move, but the car still dies. How slow or fast is that supposed to be?

naf · 09-22-2009, 09:51 PM

Sounds more like off-idle hesitation now. Your secondaries definitely won't come into play tinkering with it in the driveway. Does it drive ok as long as you baby the throttle?

Is this with the old carb back on, the one that hasn't been rebuilt?

You got it to idle properly at 700 or so rpms?

Check for trouble codes.

Put your timing light to it and verify that the timing is advancing as you open the throttle. It should look to be around 20+ at idle and the advance should increase as you give it throttle.

Tell us what it's doing and I can point you towards some things to check.

Ozz1967 · 09-24-2009, 12:07 AM

Quote:

Originally Posted by naf

Sounds more like off-idle hesitation now. Your secondaries definitely won't come into play tinkering with it in the driveway. Does it drive ok as long as you baby the throttle?

Is this with the old carb back on, the one that hasn't been rebuilt?

You got it to idle properly at 700 or so rpms?

Check for trouble codes.

Put your timing light to it and verify that the timing is advancing as you open the throttle. It should look to be around 20+ at idle and the advance should increase as you give it throttle.

Tell us what it's doing and I can point you towards some things to check.

No trouble codes from the engine, at least nothing that's causing the check engine light to come on. The carb on it now is the original non-rebuilt carb, but it idles well where the re-built carb does not. I have my timing set to 9* advanced with the computer unplugged and I've checked it a few times to make sure it's holding it ok and it does advance as I throttle up. My idle is more like, 900 than 700 but it's smooth, little lumpy but that's from the cam.

If I baby it up, it'll run fine and at higher rpms I can hammer it and it won't stall out, it's only appearing off-idle right now...and badly, evne babying it up can be dicey.

naf · 09-24-2009, 07:45 AM

Classic symptoms that would prompt me to rebuild the carburetor.

You can try a few things before opening it up:

Is the MCS clicking when the key is turned to run? You should hear it click for about a minute, if the engine isn't started it will time off by itself.

You can cap all the vacuum ports on the carb/manifold except the rear one to the vac sensor and see if it runs better and check for leaks. Just don't drive it with the brake booster disconnected.

If you've got, or can acquire, a dwell meter or scanner I can walk you through adjusting the IAB. It may also help with some other diagnoses.

If you want to try to rebuild that one, we can help out.

Remember though that the shop was concerned about a weak distributor. It's probably not causing your off idle issues now but the ignition is the base from which all other adjustments are made. You should probably plan on replacing it at some point.

Ozz1967 · 09-24-2009, 07:51 AM

Quote:

Originally Posted by naf

Classic symptoms that would prompt me to rebuild the carburetor.

You can try a few things before opening it up:

Is the MCS clicking when the key is turned to run? You should hear it click for about a minute, if the engine isn't started it will time off by itself.

You can cap all the vacuum ports on the carb/manifold except the rear one to the vac sensor and see if it runs better and check for leaks. Just don't drive it with the brake booster disconnected.

If you've got, or can acquire, a dwell meter or scanner I can walk you through adjusting the IAB. It may also help with some other diagnoses.

If you want to try to rebuild that one, we can help out.

Remember though that the shop was concerned about a weak distributor. It's probably not causing your off idle issues now but the ignition is the base from which all other adjustments are made. You should probably plan on replacing it at some point.

The MCS is clicking, it's loud enough to hear with the hood closed. On the new carb, it was very, very quiet. I'm not doubting this older carb needs a rebuild, I was just suprised that it seemed to run better than the "new" carb.

Where can I pick up a dwell meter? Autozone?

I will try capping all of those ports to see what happens, at the least it would tell me if the leak is in the intake/engine area or not if I have one.

naf · 09-24-2009, 07:54 AM

You can get a dwell meter at AZ or most any of the others. Runs around $30. I used a dwell meter and a volt meter for years until I finally took the plunge for a scanner at around $250. Of course, with the scanner I can more easily amaze my friends.

Ozz1967 · 09-24-2009, 07:58 AM

Quote:

Originally Posted by naf

You can get a dwell meter at AZ or most any of the others. Runs around $30. I used a dwell meter and a volt meter for years until I finally took the plunge for a scanner at around $250. Of course, with the scanner I can more easily amaze my friends.

To answer your other question, I was going to go with a rebuilt distributor next spring. On my dyno sheet there are lots of slight variations, the power curve isn't smooth, which the shop said was most likely indicitive of worn out bushings in my distributor causing it to waver slightly.

I am tempted to rebuild it, but I want to see if it's something else first. Especially since it idles so well...and until I took it off my 305 when got the "new carb" that didn't work with the 350, it was running very well. Of course this was nearly two years ago now (I got the "new" carb 1 year before the 350 went in and it ran good on the 305).

Ozz1967 · 09-24-2009, 10:04 AM

Quote:

Originally Posted by naf

You can get a dwell meter at AZ or most any of the others. Runs around $30. I used a dwell meter and a volt meter for years until I finally took the plunge for a scanner at around $250. Of course, with the scanner I can more easily amaze my friends.

Ok, got everything put back together and put her on the road this morning...

It idles well, little high at the moment, but idles well. From idle, if I jump on it, it stutters pretty badly before taking off.

Also, I'm having an intermittant "popping" coming from my exhaust, sounds like the right side. Now, I do think that maybe I don't have one of my spark plug wires seated all the way so I'm going to let it cool down before I try and get at it and re-seat it. If this doesn't fix the popping issue, what should I look at?

Lastly, my check engine light came on. Code 41, and 43. Now, I have read in Alldata that code 41 could be a generic code that can be ignored. Code 43 bothers me however...and I dont like it one bit. Could it be caused by having one spark plug boot loose?

I thought for sure I"d have a rich/lean fault 45 or 43 but I didn't. Good old factory set carb lol!

naf · 09-24-2009, 12:16 PM

Code 41 is set by running the engine with the EST wire disconnected, which you do when you set the timing. I've never seen 43 before. I doubt a mis-fire would cause it, as I've run with plenty of mis-fires and never triggered it.

If the cause of your mis-fire is not readily apparent you may want to pull your plugs and check them. Running rich/lean can gunk them up. Next you can check each of your plug wires with an Ohm meter and verify each is reading about the same. Next would be inspecting and maybe replacing the cap and rotor. Have you recently had your coil and ignition module checked?

Could simply be your dist. When you pull the cap and rotor see if there's any side to side play in the shaft. Sometimes you can even see marks on the cap where the rotor has been hitting it. I looked at one a month ago and I still don't see how it was even running, it had so much slop.

Ozz1967 · 09-24-2009, 05:21 PM

Quote:

Originally Posted by naf

Code 41 is set by running the engine with the EST wire disconnected, which you do when you set the timing. I've never seen 43 before. I doubt a mis-fire would cause it, as I've run with plenty of mis-fires and never triggered it.

If the cause of your mis-fire is not readily apparent you may want to pull your plugs and check them. Running rich/lean can gunk them up. Next you can check each of your plug wires with an Ohm meter and verify each is reading about the same. Next would be inspecting and maybe replacing the cap and rotor. Have you recently had your coil and ignition module checked?

Could simply be your dist. When you pull the cap and rotor see if there's any side to side play in the shaft. Sometimes you can even see marks on the cap where the rotor has been hitting it. I looked at one a month ago and I still don't see how it was even running, it had so much slop.

Hmm, it wasn't popping like this two days ago before I started pulling everything apart to get at the valve cover gasket...something's changed.

Pulling the plugs will be a weekend job. The distributor doesn't move enough side-side to rub. The cap, coil, rotor and wires are all less than 1 year old and are MSD (that that MDS matters, I just like throwing that out lol)

Ozz1967 · 09-25-2009, 09:29 PM

Quote:

Originally Posted by naf

Code 41 is set by running the engine with the EST wire disconnected, which you do when you set the timing. I've never seen 43 before. I doubt a mis-fire would cause it, as I've run with plenty of mis-fires and never triggered it.

If the cause of your mis-fire is not readily apparent you may want to pull your plugs and check them. Running rich/lean can gunk them up. Next you can check each of your plug wires with an Ohm meter and verify each is reading about the same. Next would be inspecting and maybe replacing the cap and rotor. Have you recently had your coil and ignition module checked?

Could simply be your dist. When you pull the cap and rotor see if there's any side to side play in the shaft. Sometimes you can even see marks on the cap where the rotor has been hitting it. I looked at one a month ago and I still don't see how it was even running, it had so much slop.

The misfire was caused by the number six plugwire not being seated all the way. so, now i am back to off-idle hesitatiomn issues.