My bird has a stalling problem that I cannot figure out. It idles smooth when cold, but once warmed up the idle is sort of rough, like it's missing. It loves to stall at stop lights, just before the light turns green, after sitting for 30 seconds or more. Putting the car in neutral helps a lot, but what a pain! When idling, if I turn the heater motor to high or hit the high beams it will sometimes cause a hickup bad enough to stall the engine. Voltage regulator maybe? It also bogs when shifting (TH350), like it's not getting enough fuel, or maybe the air valve is too loose (quadrajet).

It even stalled today when I was coasting in drive at 20mph.

I think the cam is a performer plus 204/214, so it should idle smooth at pontiac specs? The performer cam spec numbers are similar to an 067.

What should my idle speed be in drive with that cam???

So far I've done the following:
-tried timing settings 9, and 12 degrees initial.
-set the idle at different speeds. Increasing idle does help, but it will only let the car idle longer before the inevitable stall. I would like an idle speed of 500 to 600rpm in drive, I've tried as high as 750rpm, and it helps, but I don't think it should be that high.
-checked for vacuum leaks to the best of my ability. Tightened the intake bolts and carb bolts. They were loose. it didn't help. Maybe I need to pull them and install new gaskets.
-changed the spark plug wires, rotor and cap. No points, I'm running Pertronics.
-cleaned the plugs. They are not old so i didn't replace. Narrowed the gap from .045 to .035.
-checked the wiring. found several issues. Loose positive at alternator. Installed new terminal, cleaned up post. Did not help.
-voltage regulator was loose on firewall. Replaced screws and remounted. verified good ground.
-made sure engine was grounded to firewall. did a resistance check. it's all good.
-added a ground wire from the distributor to the firewall. did not help.
-inspected the mechanical advance. it was a little rusty, so i sprayed the hinges with WD40 and worked them. dried them off. The springs seem to be weak, but the mechanism moves smoothly.
-inspected coil wiring. looks fine. nothing loose. coil is only 2 years old. MSD blaster.
-hooked up a vacuum gage to the carb and adjusted the idle screws for maximum vacuum.

Maybe it's actually two problems. One is electrical and the other carburation. The electrical is causing the stalling, and the carb is causing the major bogging during shifting. But it is a big bog...almost like it's loosing spark. Maybe I need to look at the power wire for the coil a little closer.

What I plan on trying next:
-checking float level
-changing fuel filter (it's not that old)
-checking fuel pressure
-checking to see if my float bowl leaks, since it's a q-jet and i've read it's a problem. This is a Edelbrock Performer RPM Q-jet and it's maybe 3 years old.

I'm also a little skeptical of the Pertronics. When i first installed it a few years back, I was experimenting with plug gap and at .060 I noticed the same stalling problem, so I backed it off to .045. That's also why I recently re-gapped to .035, figuring the stock gap would be best. I just wasn't driving the car much back then, but since I had it painted I'm driving it a lot.

Does anybody have ideas? Or, is this post so long you didn't get to the end and just gave up? lol

Thanks,
Dave

try a new coil and do a balance test on the cylinders.even though the plugs look good,one may still be bad.

Also check for a vacuum leak, either a cracked hose or grommet at the brake booster or PCV valve, or loose carb bolts.

Had a HUGE cam in a 400 with a Torker II and an 850 Q-Jet. Had a 4.5" vacuum signal at the rear carb port. Had same symptoms as you describe.

You must have a weak vacuum signal somewhere, leaking power brake booster, bad brake booster valve, vacuum leak at the base plate, carb to intake or bad float level adj.

With it becoming worse after it gets warm, metal and gasket material expands somewhat. Isuspect a leak at, near or within the booster/valve if equipped. As well, cars will idle higher when cold (choke) usually around 500 rpm's. If you have a leak, the higher RPM's when cold will offset the leak. RPM's induce vacuum. I suspect that your 500 RPM drop after warm is causing the problem. Try, just for [censored]'s and giggles, after car is warm, adjust idle to 1500 and drive it around. You will not stall or sputter.....Also higher RPM's increase voltage output. if low at idle, maybe you are getting a poor signal to that electronic distributor. Remove alternator and battery..take to Autozone or Murrays for a free load test. Check your battery charge at alternator and at battery..Mine reads 16.4 at alternator and 14 at battery..you will get a voltage drop with accessories. lower voltage at battery, under 12 is a sign that the regulator, lights, starter, distributor or heater fan (could be) poorly grounded or causing excessive draw.

Placing the car in neutral increases engine RPM which, in turn produces extra vacuum signal to replace the leak where ever or to supply sufficient neutral balance to the leak as to zero out the leak loss. You should be at 900-1000 RPM idle with that cam and an auto trans. 6-700 with a manual trans

Plug a vacuum gage in the rear port of carb. read in neutral and in drive after warms up. Post results. The main port in rear is the port for the vacuum to brake booster if power brake equipped. If power brake equipped, and signal is 15-17" you are good. If in drive, it dives, you don't have a booster or booster check valve issue. If not power brake equipped, you may have a leak somewhere if signal is below 15" with that cam. I have never checked a vacuum signal with that 067 grind, so maybe someone can check theirs and relate.

Also check the coil resistance (ohms) Maybe buy a stock $10 coil?

With this being cold/warm related, I suspect vacuum...or voltage at alternator not sending out proper output when warm and rpm's drop.

JMSFUO.

My guess to, a vac leak somewhere.



My friend Pat had put a Pertronics on his '67 400. He was lucky to be carrying the point set he took out, for it broke down coming back from the lake. Start with the simple stuff and work your way up.

When was the last time it ran good? Did it ever run good with the set up you have now? How often do you run it? Without any background your symptoms are almost meaningless. The answer could be as simple as changing your fouled spark plugs or as complicated as bad compression. There is no way to tell without a little history. Give us the 'course of events'.

Check, the vacuum. Had almost the same problem but it was when I hooked the vacuum line to the heater controls. A/c cars are vaccum operated and have lots of places where they can leak. Also check the modulating valve on the tranny, If you pull the vaccum line off that and its wet the diaphram could be shot. My two cents. Let us know what is was when you fix it so I can add it to my what to try list. Merry X-Mass Ron Hein

thanks for the ideas. i'll be testing more today...

Has it ran bad since this cam was installed?not to belittle you but you but if it started since the cam install.Did you pay attention to the marks on your timing set? if the cam is installed in the wrong position it could cause the enginet o run poorly or not at all and could really screw with your vacuum since the valves are opening ate the wrong time.just a thought.


Jeremy Wyborney
http://firstgenfirebird.org/show/closeup.mv?CarID=790

I was thinking along the lines of a timing issue too, but I'm not a mechanic like some here are

Youve checked your right foot???

The thing about timing is that it usually stays the same. That's why we need to know if and when it ran good. How long it sat, ect....... The first thing I do when I troubleshoot a machine at work is get some history from the operator. No history = a bad/wrong diagnosis.

could be bad gas

From your Christmas dinner

Adjusted the float. It was too low. Seems to have fixed the bog. Need the roads to dry out to be sure.

I'm almost sure now the idle problem is vacuum related. plugging the vacuum advance and disconnecting the transmission shift modulator seemed to help. I need a vacuum tester or a long road test on a dry day to confirm. It's been raining cats and dogs here. I try not to drive Betsy in the rain.

dave

Sorry we couldn't help Dave. Seems like you have it all figured out yourself.

Thanks for all the input. I'll be trying all of you suggestions and posting results when the weather is better. We received 2 inches of snow last night.

Well, I did a bunch of vacuum and voltage checks as you all suggested and here are the results.\

vacuum 18 @ 750rpm in neutral
15.5 @ 550rpm in drive

The vacuum level does not change if transmission and vacuum advance are disconnected and plugged, so i guess they are ok. The only other thing is the PCV, and the diaphram on the carb (q-jet) and they are ok. Tonight I drove the car with the vacuum advance disconnected and reconnected. It kind of accelerates irratically when it's connected. It could be bad, but it doesn't leak at idle because it's hooked to ported, and is not drawing any vacuum with the throttle shut off.

I did some voltage checks also.

Voltage 15 Vdc @ 750rpm in neutral at the battery and alternator
9 Vdc @ 750rpm on hot side of coil
2.8 Vdc @ 750rpm across coil

in drive @ 550rpm the voltage drops about a tenth.

Do those voltage levels sound ok???

I think in the process of doing all of this I uncovered the electrical problem. The edelbrock q-jet has an electric choke, and needs to be wired a source that is hot only when the ignition is on. I had it hooked to the hot side of the coil. On hind site this was a bonehead idea. When it's hooked to the hot side of the coil, the voltage on the coil drops 1 volt to 8 volts. So, I found a new voltage source for the choke. Now the engine doesn't quit when I turn the heater motor on at idle, or hit the hight beams.

Anyways, after all of this I went for a long drive and the car didn't stall once!!! The problem may be solved! I still think the idle is a little choppy, but hey it didn't stall at least. Please God I hope it's fixed!

Dave

Most likely. It sounded to me like a weak spark, so your fix goes along with my thinking. Now you need to get your distributor sorted out!