Engine idles rough in "Drive" but fine in neutral or park...

[Twilight Fenrir]

I drove my '66 to a car show in Grand rapids, MN today... and every time I came to a stoplight, the engine started sputtering and coughing, and nearly died. I got into the habit of throwing it into neutral, and that seemed to work fine, untill I had to go again. It also idles nicely in park.

Once I get up above 40-ish mph, all hesitation goes out the window and it runs smooth as silk. I know the last time I drove it, it did not have this issue... but that was over a month ago now. The only thing I've changed, is attatching the carburetor rod, and dropping/repairing the gas tank. There was a slight fuel leak, but I fixed that.

Not sure if it's related, but when the engine has been running recently, in order to start it, I usually have to do so in WOT. But I know I don't have my choke honed in quite yet...

I tried looking it up online, but there are soooo many different answers for what could be causing this... most of them don't apply to my Toronado. (Sensors and such)

Any help would be appreciated.

[Twilight Fenrir]

Oh, I also changed the oil.

Checked all fluid levels in trans, and engine, all green. Trans has brand new fluid in it. I had them on hand, so between the previous post and this one, I changed the distributor cap and rotor to no effect...

Also, I may have exaggerated when I said the car ran fine in neutral Once it's all the way hot, it idles smooth... you pretty much have to have your foot on the gas when just starting it up to keep it going... So... maybe I've just got a air/fuel issue... But, I haven't tinkered with the carburetor since it was running last time... it is notably warmer out though...

[Twilight Fenrir]

While continuing to poke about... I notice that the visible metal on three of the passenger-side spark plugs has turned white. I understand this means one of two things, either I am running lean, or I am burning coolant.

Many months ago, I had a very slight coolant leak. I put a quarter of a bottle of BarsLeak in the coolant system and it went away. I didn't change, or look at the plugs at that point, never occurred to me. So maybe they've been that way since then, but I don't remember them being white when I changed my spark-plug wires. (After fixing the coolant) Again, didn't pay much attention at the time.

Running lean, and fouled spark plugs sound like a good combination to cause trouble under load to me. But I'll keep poking about.

[Twilight Fenrir]

Day 2 in the effort...

Started easy, replacing spark plugs, and fuel filter... Car seems to idle in park more stable, but in drive it still dies... Also... I think I stripped the threads on the carb inlet... It just wouldn't stop dripping, and it was one more 10th of a turn at a time T.T

While fighting with the dripping fuel, I removed the vacuum line from right above the fuel inlet, and the engine promptly died. Removing a hose like that should affect the RPM's, but it shouldn't kill the engine should it?

I had replaced the short vacuum lines under the hood. PCV, Distributor, transmission... but I didn't touch the brake booster, or the accessory line. That accessory line will be a nightmare if that's the issue... Headlights, trunk, the lines for climate control.

Pretty sure I got plenty of fuel. After turning off the engine, I removed the fuel line and it shot out all over the place. So I've got good fuel flow and pressure. With fuel, and spark out of the way, that should leave air... and the dreaded vacuum lines....

[xgecko]

Vacuum is your first variable to eliminate. Try blocking any non-essential vacuum ports including the power brake booster and the transmission and get a vacuum gauge. Verify what your vacuum reading is before going any further; either you have a vacuum issue or you do not. If you do then you need to fix it before proceeding further. You should see more than 15 Inches Hg; I barely make that much which is why I am completing a conversion to Hydroboost later today...

Carb tuning is, in my eyes, a nightmare. I hate carbs with a passion now. I have to tune mine as it was originally intended for a Big Block Chevy and appears to be jetted too rich which means I will have to take it apart to change the jets. I mention this because I had some of your symptoms and have managed to adjust them away for the most part.

When I first started my new engine I had significant choke problems. I ended up determining that the vacuum pull-off was not working - this feature opens the choke slightly once the engine is running. I also had to adjust the fast-idle. Not sure that any of this applies to you, but it is worth checking since you have choke issues.

Once the car is running you need to verify the idle mixture. Unlike me you probably have the correct jets in the carb so you can perform the standard adjustment procedure; turn them all the way in then out 2 full turns. With the vacuum advance off the car should run, but barely, when fully warmed up. You now want to turn them out or in a half turn at a time until you get the peak vacuum/rpm value.

Hmm... you need to get some more data if that fails to resolve the problem.

[Twilight Fenrir]

Well, the needle on my vacuum gauge wiggles very rapidly between 10, and 15 in/hg, no matter what lines I block off. I've definitely gotten the in-park idle a bit smoother, but when I throw it in D it still dies.

haven't had time to fiddle with idle screws, I'll check that out tomorrow.

[xgecko]

Check out Scenarios #5 - #8 in the link below. It suggests you might have a valve issue...


http://www.secondchancegarage.com/public/186.cfm

[Twilight Fenrir]

Check out Scenarios #5 - #8 in the link below. It suggests you might have a valve issue...


http://www.secondchancegarage.com/public/186.cfm

Hey, that's a pretty nifty link, thank you. It looks more like it might be 5. It's very, very rapid. 8 seems to be more gradual. I know I had a lifter clicking, maybe it's causing issues. I'll pock up a compression tester and see weather I need to rebuild my heads... Or possibly reconsider getting those ludicrously expensive, but totally awesome eddelbrock aluminum heads

[xgecko]

The heads are wonderful. However... if you are going to go with the heads why not complete the deal with the Rockwell Aluminum intake? I am very happy with it indeed and probably will go with both heads and intake for my 68 when I get to it...

I am presently having my driver's side exhaust manifold machined as I write this. I have been totally unsuccessful at getting a good seal and I suspect the slight pitting and corrosion has been the cause...

[Twilight Fenrir]

The heads are wonderful. However... if you are going to go with the heads why not complete the deal with the Rockwell Aluminum intake? I am very happy with it indeed and probably will go with both heads and intake for my 68 when I get to it...

I am presently having my driver's side exhaust manifold machined as I write this. I have been totally unsuccessful at getting a good seal and I suspect the slight pitting and corrosion has been the cause...

Because that would cost a fortune If I upgrade the intake, i'll need a different carb. I have the money, but I don't want to spend it I can't even begin to justify spending $1600 for cyl heads, unless I pretty much need them. I can't see spendong that much again for slightly better airflow, as I understand, the stock ones flow pretty good.