Idle Problems - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
LinkBack Thread Tools Display Modes
post #1 of 11 (permalink) Old Apr 10th, 02, 09:57 PM Thread Starter
Tech Team
 
Join Date: Jul 2001
Location: CO, USA
Posts: 38
I ran a search but couldn't come up with any ideas so here goes.

The car is a 1967 camaro, 350, automatic. I don't know anything about the internals of the motor because I just bought it a few months ago. The car will run rough at idle but fine at part throttle or WOT. When it is in gear (auto) it won't idle below about 700 RPMs and even there the tach fluctuates about 100 RPMs. In addition, when it is put in gear the RPMs drop about 500 RPMs. I know it will drop a some but doesn't this seem like a bit much?

Here are the things I have done to try to fix the rough idle:
-set and reset the timing. I have tried
everything from 4 BTDC to about 20 BTDC
-put on a new edelbrock 600 or 650 (can't
remember which). I also tried adjusting the float levels down about a 1/4 inch
-replaced the manifold gasket
-replaced all the vacumn lines and checked for vacumn leaks with carb cleaner. I couldn't find a leak anywhere
-replaced the points with an HEI distributor along with all new components except for the shaft itself and the pickup coil. While doing this I replaced the wires, and plugs
-header gaskets

I'm not sure if this has anything to do with it but my tranny shifts real early even at WOT (about 3500 RPMs for the first shift and 3000 RPMs for the second). Also the air fuel mixture screws don't seem to make much difference when adjusted (some but not much). I have hooked a vacumn gauge up to manifold vacumn and the gauge seems to bounce around. Is it possible that the motor has a bigger than stock cam in it and it will have to run lumpy at idle? Is there any way to tell?

Sorry for being so long winded but I wanted to get all the details in there. If anyone has any suggestions they would be greatly appreciated since I have just about exhausted my ideas.
Richard

[This message has been edited by ratchet (edited 04-11-2002).]
ratchet is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old Apr 11th, 02, 12:45 AM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 31,656
Garage
It is possible there is a lumpy camshaft installed.

With vacuum gauge hooked up, come off curb idle, vacuum gauge should smooth out at 15-20 inches and be steady reading.

One thing you might try, insert X amount of feeler gauge shims in the back (secondary) barrels to barely open them. Start hot engine, now you should be able to turn down curb idle screw, which closes primary plates and idle mixture screws should have more effect. The more shims added, the less the primary plate opening, the more effect the idle mixture screws will have.

Once a good steady idle is obtained, typically 900-1100 rpm, inspect carb to see if Edelbrock has a secondary stop screw and adjust secondaries to this shim thickness.

Reset base timing, 10-14 BTDC?, and readjust carb. You will typically lose 200 rpm when trans is in gear, manifold vacuum should be steady, may have to kick up curb idle alittle.

Readjust trans throttle cable, shut engine off, hold gas pedal to the floor, unlock cable clamp at carb bracket, push back on cable housing. You will feel a little resistance for the last 3/8 inch of travel, push through this resistance, and lock the housing. Release carb.

Above all, be sure carb returns to idle from WOT, for your safety as well as others. This is most important. If it doesn't, fix it now.

Don't mean to sound like your father, just giving some good sound advice.

Others here will have some good info to help you, These I've given, I hope, will help.

------------------
Everett 68/350/PG/11.90/115mph
Everett#2390 is offline  
post #3 of 11 (permalink) Old Apr 11th, 02, 04:42 AM
Senior Tech
Call me Funk
 
Join Date: Dec 2001
Location: Powder Springs, GA
Posts: 3,405
Send a message via AIM to CFunK
<BLOCKQUOTE>quote:</font><HR>Originally posted by Everett#2390:
It is possible there is a lumpy camshaft installed.

manifold vacuum should be steady, may have to kick up curb idle alittle.
<HR></BLOCKQUOTE>

If it is a big cam, the vacuum would fluctuate a bit, wouldn't it? Not a lot, say 1-1.5".

Is it dropping 500 RPMS, down to 200 in gear or is it dropping from 700 down to 500 in gear.

I am battleing the same problem right now. Little 327 in my 67 is exhibiting the same "problem" you have. We have boiled it down to a large cam 272-290 and a tight convertor.

Sucks buying a car and not knowing at least what cam is in it.

-Funk
CFunK is offline  
 
post #4 of 11 (permalink) Old Apr 11th, 02, 09:58 AM Thread Starter
Tech Team
 
Join Date: Jul 2001
Location: CO, USA
Posts: 38
Everett- What do you mean by the trans throttle cable? Are you talking about adjusting the throttle linkage so the throttle opens up all the way? I am unable to work on the car during the week but will definately try the secondary shims and check the off curb idle vacumn this weekend.

Funk- It is dropping from about 1200 in park to about 700 (or even 600) in gear. What do you do about a tight torque converter? Is there any adjustment or do you have to change it? How did you narrow down what cam you have?

Thank you both for your replies and keep them coming.
Richard
ratchet is offline  
post #5 of 11 (permalink) Old Apr 11th, 02, 10:58 AM
Senior Tech
Call me Funk
 
Join Date: Dec 2001
Location: Powder Springs, GA
Posts: 3,405
Send a message via AIM to CFunK
Mines dropping from about 1000 to 650-700 in gear. I have had a couple of people "in the know" suggest the cam was pretty big due to the lope at idle.

The only way to losen the torque convertor is to replace it with one that has a higher stall. The convertor I have now is around 1900. Should be using one around 2400 - 2600. One question have never really gotten a definitive answer on is will a tight convertor affect idle quality?

-Funk

[This message has been edited by CFunK (edited 04-11-2002).]
CFunK is offline  
post #6 of 11 (permalink) Old Apr 11th, 02, 04:38 PM
Senior Tech
 
Join Date: May 2001
Location: Ashby,MN, USA
Posts: 8,305
a stock converter will affect idle quality on an engine that isn't built for low end grunt. the stock converters are designed to make the tranny work real smooth and invisible to the driver- so they are damn near locked up at idle. when you throw in a big cam made for mid-range and topend power, the torque at idle speeds will be low and allow the converter to drag it down more when it is put in gear.
before i switched from a TH350 to a stick, my HOT cammed 355 idled at 1200 in park, and got dragged down to about 700 or so in gear. the first engine i ever built was a stock rebuild with a mild "RV" cam (whatever that is), and the idle speed was at 600 whether it was in gear or not- it just didn't affect that engine at all, due to the torque output being right up there at idle.

------------------
1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
see pics here http://community.webshots.com/user/novaderrik
novaderrik is offline  
post #7 of 11 (permalink) Old Apr 12th, 02, 12:42 AM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 31,656
Garage
Yes, unfortunately, a lumpier cam will need a looser torque convertor for better idling when in gear.

Cfunk & novederrick are right, stock convertors are too tight for a larger than stock cam, put too much load on the engine and bog it down, i.e., 1200 rpm neutral, 700 rpm drive. There is no outside adjustment, replacement is the only solution, along with an external air-to-liquid auxiliary trans oil cooler on the return line, top line from radiator. Smaller t/q convertors generate alot more heat due to higher liquid shearing inside.

The trans throttle cable connects to the throttle linkage lever on the carb and snakes to rear of the engine and disappears underneath on the pass side. Looking from the floor up, cable goes into the trans case on pass side close to the fill tube and connects inside to the throttle valve assembly. This controls somewhat WOT performance, along with the governor out back in the trans extension housing.

This cable needs to be hooked up and adjusted to the instructions I gave earlier. This should allow 5200-5500 rpm shift points.

Curb idle will be a trade-off between the stock convertor and lumpy cam, one will need to adjust by using trial and error method.

Everett
Everett#2390 is offline  
post #8 of 11 (permalink) Old Apr 14th, 02, 08:22 PM Thread Starter
Tech Team
 
Join Date: Jul 2001
Location: CO, USA
Posts: 38
This weekend I hooked up a vacumn gauge to my motor. It would move between 10 and 11 @ idle in park. Does this sound about right? When I brought the motor off of curb idle the vacumn was very steady and didn't jump around. Since it didn't jump around does that mean I don't have a vacumn leak?

I looked for a trans throttle cable but didn't see any linkage other than throttle hooked up to the carb. I bought a universal detent cable and crawled under the car to try to hook it up but couldn't find anywhere to hook it up to on either side of the tranny. The tranny is a TH400, does this type of tranny use a different type of kick down regulator?

I tried opening the secondaries a little but it didn't seem to make any difference. Actually with the secondaries open I could turn the A/F mixture screws all the way in but the motor didn't die.

I got it emmissions tested this weekend. It passed but the guy said it was running rich. Maybe I'll get a calibration kit and play around with that.

I went cruising around and noticed when I punch it it will puff light grey smoke. Does this help clue anybody in about what the problem might be?

Thanks for the replies and any other ideas would be great.

Ratchet
ratchet is offline  
post #9 of 11 (permalink) Old Apr 15th, 02, 12:44 AM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 31,656
Garage
First off, let me apologize for not asking which trans you have installed. TH400's don't use a cable, they use an electric switch down behind the gas pedal to downshift to lower gear.

Ten-11 inches of vacuum is good, as long as it is steady, that's fine. Yours looks good.

Usually, when secondaries are opened up, primaries can be closed alittle more to maintain the same rpm's. Thus, with primaries alittle more closed, idle mixture circuit works alot better.

No, with this little vacuum, reads like you have a lumpy cam, idle is what you make of it, tune for the best.

Alittle gray smoke at accelleration usually means some oil is being sucked into the combustion chamber from the valve guides. Either worn guides, worn valve stems, or may be leaky valve stem seals. You might pull a valve cover and see if the umbrellas are still on the springs. If not, did they put aftermarket stem seals or cups over the guide to prevent oil from seeping through?

Another possibility might even be leaky intake manifold gasket(s). The manifold does cover the lifter valley.

Well, give you some food for thought, you seem to be going in the right direction. Maybe others here will have some good suggestions...

Everett
Everett#2390 is offline  
post #10 of 11 (permalink) Old Apr 15th, 02, 04:37 AM
Senior Tech
Call me Funk
 
Join Date: Dec 2001
Location: Powder Springs, GA
Posts: 3,405
Send a message via AIM to CFunK
I did a bunch of TNT this weekend trying to solve a very similar problem as yours.

This is what I had to do to get mine to idle at 1100 in park and 700-800 in gear. It still idles rough but the more I work on it the more I am resolving myself to the fact it's just the nature of the cam.

Idle mixture screws out 2 turns, both sides. Blue stepup spring, base timing set to 17*. I had to fiddle with the idle stop screw a bit to get it just right. It idles well, still lumpy, but I think this is as good as it's going to get with this unknown cam.

I am actually quite pleased. The only remaining issue is a what feels like a "miss" when leaving a stoplight, light throttle, after sitting for 45+ seconds. General stop sign to stop sign driving this "miss" isn't present. It was "missing" badly before dropping down the step up spring.

Next on the list is a torque convertor upgrade.

After piddling with this thing for over a month I have learned to think out of the box. That is, yes there are certain guidelines to follow when tuning the engine but some combos need to work outside "the box". I feel this is the case in my situation and is probably the same with yours. Especially since the internals are unknown.

Bend the rules a bit, and don't be afraid to try something outside the box.

-Funk
CFunK is offline  
post #11 of 11 (permalink) Old Apr 15th, 02, 08:28 AM Thread Starter
Tech Team
 
Join Date: Jul 2001
Location: CO, USA
Posts: 38
Everett-No problem about the tranny ID, I probably should have mentioned it. I will try to find a kickdown switch for it this weekend. As far as the oil consumption I'm not sure what they did with the valve guide seals so I'll probably just live with it for now. I don't think its a manifod gasket as I just changed it and was pretty careful but I may be changing it again soon. Once again thanks for the help and I'll just keep fiddling with it.

Funk- Just got your email this morning. We should definitely stay in touch so maybe between the two of us maybe we can get it figured out. Please let me know how your torque converter swaps affects it.
ratchet is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome