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Discussion Starter #1
I've got a really bad hesitation off idle, bad enough that the car will die or backfire through the carb unless I accelerate real lightly, and the car is idling very poorly, but only when in gear. It will idle okay for a few seconds then start cutting out like it's going to die, then pick back up and idle for a couple seconds, rinse and repeat. Once the engine is at cruising speed, it runs great and pulls hard if you drop the hammer on it, it's just at idle and right off idle that I'm having problems.

The problem with the car cutting out at idle didn't start until I swapped out the distributor. I dropped in a Pertronix with a flamethrower 3 ignition module, and a new flamethrower coil. I also wired in a 12v relay since the Pertronix requires the full 12v. I've checked the voltages and I'm getting 12v across the relay and at the coil.

The hesitation has been there since I got the car, but it's much worse since i replaced the distributor. Since I've owned the car, in the last three months I've replaced the intake and carb, re-wired the entire engine compartment with new wiring harnesses, replaced the solenoid, voltage reg, and replaced the intake manifold gaskets twice, as well as replacing the distributor, coil,plugs and wires. I've checked the timing, and tried tuning the carburetor. I also tried pulling off the distributor hold down and cleaned it and the block real good where it makes contact, to make sure it was getting
good contact. I've checked the firing order and made sure the wires are in the correct order as well.

I suspect I have a vacuum leak, but I can't find it if I do. I've tried spraying carb cleaner everywhere, but that hasn't turned up anything. I don't know if there is something wrong with the new distributor, or if i installed it wrong, or if I just exacerbated the already existing problem.

If anyone has an suggestions, I'd appreciate it. I hate to take it to a shop, but I've about run out if ideas.
 

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Well, I offer a few suggestions but certainly not THE definitive list. First how old is the fuel? I have seen some old gas create real issues. Assuming this is not the issue I would then check to see the float level in the carbs followed immediately by checking the fuel pump. Having a bad fuel pump will cause the fuel in the float chambers to be low. Maybe enough to start but not much more than that.
It goes without saying having test gauges would be helpful at this point. Measure your fuel pressure from the pump then have a line discharge into a can to check on volume. Realize a plugged fuel line or intake will often show pressure until open flow is allowed. Also see what your vacuum reading is. Is there any chance you are using a riser piece under the carb? Those can create issues frequently.
You said you checked timing. Be sure TDC on the pulley is actually that. Typically popping back through a carb points to some timing issue. Not meaning to be insultive but also make sure you are using the right firing order and correctly identify which cylinders are which number. I have seen confusion on occassion when folks get the firing order of a 302 and 351 mixed up.
I wouldn't give up just yet. It sounds like you've just missed something.
Sometimes it's best to step back and recheck those things you're positive are fine. Go down a punch list.
Realize if the engine is running like crap, trying to locate a vacuum leak with a combustable spray may not work as well as it would with a smooth idle.
Best of luck. I'm sure others will offer direction here.
Russ
 

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I just reread what you wrote. Another thought. There are different circuits in the carb. You could have one of the idle jets plugged while the mains are clear. Only the idle jets would then cause the problem. When you kick it in the slats, you're up on the primaries and the idle jets/ports don't do much at all. Maybe get some gas torch cleaning wires and go through the carb.
It's easier being on site but that's not possible here.......
I run a Pertronics I in the race car and it is clean up to 8K, and yes it does need 12v. I don't think that is the problem.
I think you're close on the above !
Russ
 

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Discussion Starter #4
Thanks Russ. I have actually checked all the things you listed there, except for the fuel pressure. The carb is brand new and I had the same symptoms with the old factory one as well, so I had ruled that out as the culprit. The firing order is correct, or at least it is now. I originally hooked up the wires for a 351 firing order when I put the dist. in, but turns out the PO swapped the cam and I have a 302 firing order. It wouldn't even run with the 351 firing order. Manifold vacuum is good and steady, no erratic reading on the gauge.

The car actually idles perfect until I put it in gear, which is really throwing me off. I'll try checking the fuel pressure too and see where I'm at there. I'm not sure if I'm dealing with one issue, or two separate ones here. The hesitation has always been there, even before I started replacing anything, and has never gone away but only gotten worse since I replaced the distributor. The miss while idling in gear started happening immediately after installing the new distributor, which was the last thing I did.
 

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Double check the firing order, you may have a couple wires crossed. Be very careful and follow each wire to the plug to be sure.

Second, what is your initial timing set at, it could be too retarded. However, it does sound like a crossed pair of plug wires to me
 

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Discussion Starter #6
That was my initial thought too, but I've checked and rechecked the wires several times and they're correct. Well at least for a 302, 1-5-4-2-6-3-7-8. I went out and rechecked them again, just to be sure. Initial timing is at 10 btdc. I tried retarding it to 6 deg, and advancing it to around 14 deg with no difference.
 

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I've got a really bad hesitation off idle, bad enough that the car will die or backfire through the carb unless I accelerate real lightly, and the car is idling very poorly, but only when in gear. It will idle okay for a few seconds then start cutting out like it's going to die, then pick back up and idle for a couple seconds, rinse and repeat. Once the engine is at cruising speed, it runs great and pulls hard if you drop the hammer on it, it's just at idle and right off idle that I'm having problems.

The problem with the car cutting out at idle didn't start until I swapped out the distributor. I dropped in a Pertronix with a flamethrower 3 ignition module, and a new flamethrower coil. I also wired in a 12v relay since the Pertronix requires the full 12v. I've checked the voltages and I'm getting 12v across the relay and at the coil.

The hesitation has been there since I got the car, but it's much worse since i replaced the distributor. Since I've owned the car, in the last three months I've replaced the intake and carb, re-wired the entire engine compartment with new wiring harnesses, replaced the solenoid, voltage reg, and replaced the intake manifold gaskets twice, as well as replacing the distributor, coil,plugs and wires. I've checked the timing, and tried tuning the carburetor. I also tried pulling off the distributor hold down and cleaned it and the block real good where it makes contact, to make sure it was getting
good contact. I've checked the firing order and made sure the wires are in the correct order as well.

I suspect I have a vacuum leak, but I can't find it if I do. I've tried spraying carb cleaner everywhere, but that hasn't turned up anything. I don't know if there is something wrong with the new distributor, or if i installed it wrong, or if I just exacerbated the already existing problem.

If anyone has an suggestions, I'd appreciate it. I hate to take it to a shop, but I've about run out if ideas.
Hi,
Have you check the engine vac at idle? When you say idling poorly when you place it in gear, this must be a C4? Could it be you have the curb idle set to low for an auto? I don't think this to be the "cure all", but, it is often not set correctly. You don't mention your engine or carb type and size. Have tuned the carb, using a vac gauge?
 

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Discussion Starter #8
It's the car in my sig, I'm running a 351w with an fmx tranny. The carb is a holley street avenger 670cfm. I've put a vacuum gauge on it and it's pulling good steady vacuum and I've tuned the a/f mixtures. I thought about the idle too, and if jack it way up, it actually fixes the problem. However, it's obviously way too high, to the point where it's hard to stop the car and you can't shut it off without it dieseling for a long time.
 

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It's the car in my sig, I'm running a 351w with an fmx tranny. The carb is a holley street avenger 670cfm. I've put a vacuum gauge on it and it's pulling good steady vacuum and I've tuned the a/f mixtures. I thought about the idle too, and if jack it way up, it actually fixes the problem. However, it's obviously way too high, to the point where it's hard to stop the car and you can't shut it off without it dieseling for a long time.
What are you running for initial timing and w/ or w/o vac advance?
 

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Discussion Starter #10
I ended up taking the car to the shop to get it aligned, and had them check this out while it was there. They looked at it, and pretty much told me they have no idea what's wrong. However, they did find out something interesting. No matter how far they advanced the timing, it would never start pinging. The guy said he had it all the way up to 45 deg, and it never pinged once.

So, I got it home and said what the hell, and cranked the initial timing all the way up to around 25-30 degrees. That got rid of the cutting out when idling in gear, and made a huge improvement with the hesitation, though it's still there. At 10 deg. initial advance, it's practically undriveable though. Now obviously something is wrong, but I don't have a clue what, and I don't want to leave it running that far advanced. The shop said maybe the cam timing was off, could that be the problem? Could installing the distributor off a tooth on the cam cause this? Any help would be greatly appreciated, thanks!
 

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I ended up taking the car to the shop to get it aligned, and had them check this out while it was there. They looked at it, and pretty much told me they have no idea what's wrong. However, they did find out something interesting. No matter how far they advanced the timing, it would never start pinging. The guy said he had it all the way up to 45 deg, and it never pinged once.

So, I got it home and said what the hell, and cranked the initial timing all the way up to around 25-30 degrees. That got rid of the cutting out when idling in gear, and made a huge improvement with the hesitation, though it's still there. At 10 deg. initial advance, it's practically undriveable though. Now obviously something is wrong, but I don't have a clue what, and I don't want to leave it running that far advanced. The shop said maybe the cam timing was off, could that be the problem? Could installing the distributor off a tooth on the cam cause this? Any help would be greatly appreciated, thanks!
Hi
OK, this is very unusual, to say the least. Forgive me if I'm regressing here, but, I'm trying to get my mind around where "normal" should be here.
Where is the vac canister pointing? With 289/302s, it should be pointing to about 6:30- 6:35. This would be the normal starting point, to which, adjust for 10-12 degs. initial advance.
Have you verified, when the balancer is set at TDC on the compression stroke, the dizzy rotor is pointing to about the 1:00 position (#1 plug) and both valves are completely closed and verified with having just a little play in each?
When you set it at 25-30 degs. is the dizzy vac plugged?

To answer your question, 1 tooth off is not going to make this type of difference. It just means, your vac is s little closer to the rad hose, and you have little less "swing or arc" room when checking and adjusting your timing.
For example, I run 14-16 initial and my vac points to about 7:30, or so. In fact, it almost touches the rad hose, when I'm at 16 deg.

I think, if you haven't already, go through the TDC, rotor, and valve verification process. In my mind, if those valves aren't closed, as verified by the procedure, and don't have that slack (play) in the rockers, then, the cam's got to be checked.
Do you know anything about the cam?
What do you know about the distributor? Yr, any mods etc.

When I see something like this, I return to basic checks. Again sorry, if regressing.
 

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and I don't want to leave it running that far advanced. thanks!
It may not be that far advanced. The outer part of the balancer may be slipping around and tdc as shown is really not. As Ken mentioned, you'll have to verify tdc, not using the balancer marks, and based on your results, take it from there.
 

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It may not be that far advanced. The outer part of the balancer may be slipping around and tdc as shown is really not. As Ken mentioned, you'll have to verify tdc, not using the balancer marks, and based on your results, take it from there.

Good Point Greg!
Not know the age and condition of the balancer, that is a very real possibility. I had a HIPO unit fail like that, from age and torque. In fact I kept it as a "show and tail" piece.
 

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+1 on verify TDC is actually TDC. You can drop the distributor in any slot you want in theory, the canister will just point in a different direction. You could also put the number 1 wire on any spot on the distributor (beside the center one for any smartazzes out there!) as long as you keep the firing order correct.

If you don't know where your TDC is you don't know what timing your running. It should run fine at 10 degrees intial timing though.

Nate
 

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Discussion Starter #15
Thanks for the advice guys. The distributor is in roughly the 6:35 position and I'm just guessing it's around 25 - 30 deg advance right now, without the vac advance hooked up. I can't actually read the marks on this balancer past around the 15 deg. mark, because they're completely worn off. When I swapped the distributor, I cranked the motor to TDC based on the markings on the balancer, and made sure it was on a compression stroke. The rotor was pointing at the number one spot on the distributor when I pulled off the old cap, and it was pointing there when I put the distributor in as well. However, I didn't verify the valves were closed, I just went off the timing marks.

Judging by how old this balancer appears to be, your theory of the timing marks being off is totally possible. I have no idea what has been done to this motor, or what's in it, other than the fact that it has a 302 cam. It's obviously pretty old though, judging by the overall condition. The only things I have done to it is replaced the intake and carb, and swapped out the distributor for a pertronix unit.

Sounds like I need to pull off the valve covers and make sure this thing is really at TDC. If everything matches up there, does that mean the cam timing is off? If it is off, would I be okay running it like this for a while? I'm planning on having a 408 built in the next year, once I get everything else up to par, so I really don't want to go dumping any more time and money into this tired old motor. Thanks again for your help!
 

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You don't need to pull off a valve cover. You can do it through the #1 spark plug hole. Bring #1 up on compression, put some sort of feeler in the hole ( I use a straw or something else soft). Using a wrench on the crank bolt, I move it back and forth to see where the piston just starts to drop. It spends a few degrees at top, so I watch for the drops and split the difference. For me, It's easier and cleaner than pulling a valve cover.
 
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