Trouble with idle at warm temps. I've got a new carb, Edelbrock 1406, all new ignition parts, new wires, plugs included, and am so close, but not there.

Ok, I've set the initial advance at 6* for now. I also adjusted the vac canister for the minimal amount of vac advance possible. I tuned the carbs with a vacuum gauge. I changed out the fouled plugs (again) and the altenator (the old one was going bad).

I hooked the vac advance to a manifold vacuum (supposed to improve low end by giving your full vac advance at idle). Dropped idle down to about 1200 (can't go much lower). Drove the car to the gas station (2 miles). Ran OK, no ping, but no power either. At WOT, the carb makes noise but no ummph (lack of timing advance I assume). Regardless, it never stalled or bogged down to where I had to flutter the throttle.

Filled up, turned around and came back (2 miles again of course). I have a steep drive way, and when the car is suffering from low end death, it's aweful tough to make it up. I get to the top, and the car won't idle, not one bit. I try to start it, it starts eventually, but a very large back fire through the carb this time. I'm glad I still had the air filter on.

Now I'm sure that there has to be an answer for this. I mean, I changed everything, it all works. Starts up, even got hot in the drive way, and cooled down when I turned the fan on. I tuned it in the drive way for about 1 1/2 hours or so, it was plenty warm. Yet when I get back, boom, it dies and won't start right. The distributor was clamped down tight, so the timing didn't wiggle out or anything.

On the way back, it almsot felt as if I had a set of wires crossed, which I of course do not.

I guess I'll try advancing the timing a bit more, and give it some more vac advance through the adjustable can, but I'm baffled now.

I mean, it worked for ever, until I got back home, then it died. I mean I've been working on this since 4 o'clock and it's almsot 7 now and it worked perfect until I got back.

What would cause such a problem?

I'll keep trying. Please help, all suggestions are more than welcome.

 

i'd run the vacuum advance off the carb and not the intake. at idle you don't want any advance, that's where you want the base timing to be at. it sounds to me you have full vacuum advance at idle.

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ICON Motorsports

1st & 3rd

 

I am at full vac advance at idle. It was suggested to me the ODB, in theory it is supposed to help with low end, where I'm definately having trouble.

Besides, if anything, it will idle a little high but should help low end response.


When I get into the mech advance it is ok, but low end definately suffers.

I've tried it both ways, and will try again with the tuned port on the carb, but I have just fried my starter. I tried to be gentle on it, but it gave up the ghost.

I am almost to the point where I wonder if there might be something wrong with a push rod or valve, but the vac guage is pretty steady, which would indicate otherwise.

Please advise further.

 

I agree with EDE....run your vacuum advance off your carb and not your intake! Also, set your TOTAL timing...that'll help alot! Get a timing tape and put it on the balancer!! Unplug the vaccuum advance and have someone rev your car to 3,000 rpms and hold it while you check the timing on the timing tape! This is your TOTAL timing and 36-38 degrees is a good place to put it on most cars like yours!! My friend has his total timing set to about 36 degrees and this makes is initial timing approx. 20 degrees.....see where the performance difference is at now?? Exactly....it's in your timing! My guess is you have it too low!! Once your TOTAL timing is set you can re-adjust the vac canister accordingly to fine tune your performance!!

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1986 Trans AM
305 TPI
200,000+ miles (speedo/odometer non-funtional! Odometer reads 142,000)
4 Wheel Discs
9 bolt Borg Warner Rear (2.77's....oh joy) :P
Completely Stock
Soon to upgrade to a 383 converted from TPI to Carb, Edelbrock 600CFM Carb, Edelbrock Performer RPM Intake, Hedman Shorty Headers, AFR 195's (if I can afford them), XE268 Cam, Moroso HEI ignition kit with external MSD Blaster II Coil and an MSD 6-AL Box!!
Current project: Keeping my 305 running until I get my income tax returns!

 

That cam should pull at least 16-18 inches and idle about 700-800 RPM with a nice lope. I'm just going by the specs as I don't know anyone that has one. My car idles at 900 RPM and pulls 15" in park.

Are you disconnecting the vacuum advance when you set the timing? If not your timing could be way retarded. For now just take Ede's advice and keep it connected to a ported vacuum source on the carb.

If you have a non computer controlled HEI go ahead and set the base timing to 10~12* with the vacuum advance disconnected.

If your engine still has the problems then I would check the float level and then check for a Vacuum leak;

Check out Vaders post here:

https://www.thirdgen.org/messgboard/...ML/006922.html

Good luck, don't give up. You've already put too much in to walk away from and when you get it right WOOHOO!!! hehe...

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91 RS/3.1 - Stock except stereo system, daily driver.

86 IROC - Pep Boys 350 longblock, Performer 750 carb, Performer RPM intake, Comp Cams 280 magnum, Hooker 1 5/8" shorties, Flowmaster Y pipe, 3" pipe to Flowmaster 2 chamber Dual outlet, TH 350 performance rebuild w/shift kit, Daco 2600 Stall, 3.42 Gear Moser 12 bolt w/Eaton posi.

 

You can do as you're doing....running the vacuum advance off the intake, but the problem is, you need a lot more advance...as soon as you hit the throttle under a load, you'll lose the itial timing you have, and actually retard the timing.

You'd be better off diconnecting the vacuum advance, adjusting the intial to 14-16 or so, for the lowend you want....but of course MPG's will suffer.

Sooo, do as the others have mentioned above, run the vacum advance off ported vacuum, if you want to keep running it off theintake vacuum, you'll need to run real light weight springs so that the mechanical kicks in just off idle when you open the throttle.

I think the OBD forgot to mention you need to tune the distributor up some to run it that way. See, otherwise, lets say you have the full vacuum advance at 14* when idling, now put the car in gear, press the accelerator and the vacuum drops...and so does the timing, but the motor start to spin up, and mechanical begins to kick in and begin advancing the timing to full mechnical advance...

I thnk the problem is in the transition you have going from vacuum advance falling out, and mechanical kicking in...this is why I think you need lighter springs to allow the mechanical to work in the transition. You may also need heavier wieghts as well.

 

Racerwannabe,

You're running a similar set up and pulling that much vacuum? I'm not anywhere close to that. Could part of my problem be there also?

 

I just read (and replied) to your other post.

Before you get into your advance, find the cause of the low vacuum.

 

GruveB, yes I am pulling that much vacuum. Don't worry about getting max power or anything else out of your engine yet, first you must get it to a workable range and THEN you can fine tune it.

Here's step by step what you need to do;

~Fix your starter (man that sucks you blew the starter, are you sure it isn't the battery?)
~Disconnect and plug the vacuum advance.
~Turn the idle mixture screws all the way in, don't torque them just seat the screws, then back them out 1.5 full turns.
~Start the car and set your base timing to 10* with the idle speed set as low as you can go. We want to make sure there is no mechanical advance coming in while you set the timing. While you are setting the timing rev the motor with your hand and watch the timing mark advance. Make sure you can rev the motor a little before the timing starts to advance.
~Set the idle speed to about 800 RPM and note your vacuum reading, should be about 10~14". If you are pulling much less than that do the vacuum leak check that I mentioned above.
~If you are pulling the vacuum bump your timing up to 12*, reset the idle back to 800.
~Adjust you idle mixture screws for the smoothest idle, don't worry about getting it dead on, just reliable.
~Leave the vacuum advance disconnected and take another ride to the store.

Is your car better? It should be running a little sluggish but will pull OK if you don't have another engine problem.

Post back the results and I'll help you get it fine tuned so you can spank some 'stangs this weekend.

 

I'm sure it's not the battery, it's fine.

As far as the vac goes, I wonder if I've got a vacuum leak somewhere. I mean, I've used a can of carb cleaner all over the intake and around the carb gasket and what not, and nothing.

I was wonder, what if my intake gasket has some sort of problem, would that steal my power also?

I've had so many problems with this car, that it's been amazing.

I am very close now however, just need to get over the hump.

 

If you've followed my instructions above and still have unusually low vacuum then check for a leak. Once you get this straightened out I'll help you get the vacuum advance and carb tuned. I'ts not hard at all, you just need to go step by step.

I think the following is a great way to check for vacuum leaks. I posted a link to the thread in my first post in this thread but I'll just paste the relevant text here.

You can make the adaptor using a plain valve cover breather grommet. Poke a hole in it to push a short length of vacuum hose through then seal it up with rubber cement.

 

If this doesn't beat all, I have probably changed more starters in my life time than the any person not employeed as a full time mechanic, seriously.

The new starter cranks like hell, but then hits the flywheel!!!! I've tried all combinations of shims, and no luck. The starter was just a little shorter in the back end, but up front looked perfect, bolted in easily, but damn it, I can't get out of my own way on an easy job.

Get this, there are 7 auto parts store here in town, and this was the only start for my car in stock!!!

 

Check this out again:

I took the starter back to autozone, and they still had the old starter. We compared them very, very closely. The gear on the new one stuck out 1/16" further than the original. So we did some more research. There wasn't another new one in the entire town, so we couldn't verify if the new one was assembly incorrectly.

The number on the old starter was worn off, so no luck there. 85, and 86 use the same as my 84. 83 used a different starter, so we pulled one off of the shelf. An exact match. My car is an 84, no doubt about it, but apparently has an '83 engine in it?????

Wierd, wierd, wierd. Like I need more problems anyhow.

 

I told you how to set intial timing.
I don't think you ever answered me about what your fuel pressure is at the carb?
you need to fix the problem that's keeping your needle & seats from sealing first before you go adjusting things.

 

ODB,

I know you told me, and I did it as such. But I hooked up the vac advance can to the manifold, and got some serious detonation at part throttle. I also can't get my car to idle that way under 1500 having the vac hooked up to the manifold, no matter what the initial timing is set at or what the vac can is adjusted to. I've got other issues to fix. Nothing else worked, so I was trying this again with the initial lower than you suggested, since it was the closest thing I had to running. I was hoping against hope that it would work right. My alt has fried, my starter (yes the battery is good---the alt worked fine except under a light load-say 3000 rpm , then it squealed and the voltage dropped--also noticed that it would short out occassionally)and I've had to pick up a new carb, this thing is breaking the bank for me!!!

My daily driver car is for sale, and I'll need this car in about a week or so when that one sells. I am going to check to see if there is perhaps a leak on the underside of the manifold, as there isn't one on top.
Murphy's law is in affect!!!

I am going to experiment with having the vac can hooked up to the manifold again after I trouble shoot this thing a little more.

One of the problems I've been experiencing is that this car has been driven for about 6 months now, but had sat for years. So while everything has relatively low miles, it is all suffereing from lack of use, which is a bad deal on any machine. They're not designed for storage!!!

ODB, no flame, I did as you advised, and I'm sure that it will provide me with great results after I get my problem figured out. Thanks again for your help.

 

man your car does have a lot of problems.

you mentioned that the car sat for years before this. Did you flush out the tank and fuel system before trying to run the engine?
I have a feeling that debris is getting into your carb sticking the needles/seats open and possibly clogging some passeges. If you remove the carb airhorn do you see anything in the bottom of the fuel bowls? dirt, water? anything?
Any kind of debris or water will really screw up the operation of an Edlebrock carb. The needles/seats are very sensitive to dirt.

If you plan to run the vacuum advance (you don't need it), then you're going to need to get an adjustable canister for your distributor. It may be easier for you to just run without the vacuum advance though since you're having trouble tuning with it. You can set your intial and centrifugal advance to work just fine with no vacuum.

if you're still looking for a vacuum leak you may not of thought to plug off the line running to your brake-booster. Sometimes the boosters develop a leak inside that is very hard to track down. Since the car sat for so long I would eliminate that possibility when you can get to it.

It also sounds like you may have a short somewhere since the alternator is squealing.

 

I bought the car about 3 months ago from somebody who purchased the car for his 16 year old daughter. His daughter didn't want the car, she wanted a Ford Ranger???? Just as well, this is a death trap for most teenagers learning to drive.

I have changed all of the fluids, had a dead battery, fuel filter, new hoses and vac lines, and triangle seals and the outter rain seals on the bottom of the window. I've also got a new alt, starter, distributor (HEI vac), comp cams adjustable vac kit, wires, plugs, coil, and ignition module. I still need to have a dent pulled, paint freshened, stereo replaced (doesn't work) and an antenna. So much stuff was brittle and dried it was amazing. No rust, but the Arizona dry heat is death on rubber and plastic parts. I have replaced the valve guide seals (some where complete disentegrated!!) and every gasket except for the head and oil pan.

I do know how to tune a car, as long as I don't run into a serious glitch. I was a deisel mechanic several years, but the only indepth gasoline engine experience I have is on a Volkswagen Bug.....so these cars are very foreign to me. I do know how to turn a wrench and have a little "practical" knowledge that you get from working on vehicles. It's the finer points of tuning and trouble shooting some of the things like carbs and vac leaks that I didn't really have to worry about before.

It is a fun project though. I was into motorcycles for a while, but I can't take my kids or wife with me, so this is more fun...when it works.

 

I FEEL YOUR PAIN BROTHER.I'VE FOLLOWED THIS POST FOR A COUPLE DAYS,AND I'M LEARNING ALOT.THERE ARE ALOT OF KNOWLEDGEABLE PEOPLE OUT THERE.ALOT OF GUYS HAVE EXPLAINED SETTING UP THE TIMING ALOT BETTER THAN I COULD,BUT I THOUGHT I WOULD MENTION SOMETHING THAT NO ONE HAS TOUCHED ON.A BUDDY OF MINE WAS HAVING KIND OF THE SAME PROBLEM WITH HIS 5.7 Z-71 HALFTON,BAD POWER,GAS MILEAGE SUCKED,RAN WORSE WHEN WARM,ETC.HE HAD RESENTLY SWAPPED IN A NEW CRATE MOTOR ALSO (I GOT THE OLD ONE,THANX PAL)AFTER MANY DIAGNOSTIC SESSIONS,THEY FOUND THE DISTRIBUTOR WAS BENT .I ASSUME THEY MEANT THE INNER SHAFT.WHEN IT WARMED UP I GUESS IT EXPANDED SLIGHTLY AND BEGAN DRAGGING WORSE,MAKING IT SEEM LIKE TIMING WAS OFF .HIS COMPUTER WAS HAVING FITS.THERES MY TWO CENTS FOR WHAT ITS WORTH.DON'T GIVE UP.

 

Dude, check that brake booster. I'm having a similar problem to yours with vacuum leaks and that is the only thing I have not tried to block off yet. I will try that today.