Stalling when in gear and lurching.

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Kihlian

Kihlian

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Hi all,

First post here, I'm hoping I can get some answers on about my new ride, and get it back on the road asap with you guys help. I did my best to use the search function to find my problems but just couldn't seem to find anyone with my exact problems.

Here's some back ground, I bought this beautiful red 74 Duster, no rust, nice interior about 3 weeks ago. Apparently rebuilt 318, with no receipts. Only thing was that first and third gear slipped pretty bad in the old 727. So I bought a new 727 from a fella down in San Jose who was a Chrysler transmission tech for 30 years, converter and all. I had my mechanics put the transmission in and ever since I've had this problem.

When the car first starts cold it sounds great, idles great, drives great, flies no problems. In gear and out it idles as it should.

But after a while of driving (about an hour or two of warming up), when I come to a stop at a red light after about 30 seconds, it will idle low, and stall if left alone, and ever so often it'll lurch forward just a bit, foot on the break. If I switch it to neutral it will run fine. I put it into drive and go.

If I let it cool down over night, it runs great in the morning, until it gets warm warm.

I brought it to my mechanics today and they turned up the idle and said try driving it now, although it helped, it ran great until it fully warmed up, then same stuff.

My mechanics also mentioned that my break vacuum booster isn't functioning properly and may be causing this issue as vacuum is escaping when I break, thus the transmission issues. I don't know much about how vacuum works or the inter workings of this car, I have't had time to work on projects much lately.

As a side note, I checked the trans fluid, it's a little high, but no discoloration, no burned smell.

I hope this all makes sense, I've tried to be as clear as possible. Just looking for any advice, avenues to take.

Thanks so much for your time guys.
 
They may be right on the booster; if it leaks it will allow air into the intake manifold under the carb. But it would seem unusual to see the brake booster leak only after 30 minutes of operation. But if you can put it into neutral with the brakes on and it will idle OK warm, that says that the booster is probaly not it.

You can check this booster theory by buying a vacuum gauge and connecting it to the intake manifold via routing some vacuum line from the inake manifold into the passenger compartment where you can see the vacuum gauge, and checking the vacuum level at stop and idling, first when cold and then when hot. You should normally get about the same vacuum readings cold and warm. If the guage reading drops and stays low when you apply the brakes, then you have a booster leak. (If the booster is good, it can drop momentarily when you first apply the brakes but return to the same vacuum reading after a moment.)
 
A leaking booster could cause this, but timing and tuning could cause it also.
After it's warmed up and doing this, what happens if you pull the e brake, put it in gear and idle with your foot off the brakes?

Normal seeming?

Probably the booster.
 
Just had the timing checked the other day, all is well there. Carb could probably use a tuning.

I'll try plugging the pvc valve hose. Might as well.

My fear is that it has something to do with the transmission, or the torque converter. When it gets warm like that, and starts to do it, it feels like there's a lot more shaking from the front of the car. When it lurches, it feels like somethings catching. I don't really know how to explain it. When cold the trans runs great, shifts hard, feels fine.

Thanks for the advice guys, I've ordered a new booster, so only time will tell.

If it isn't the booster/vacuum leak, what could it be?

Thanks guys.
 
You need to do checks with a vacuum gauge while you do things like the PCV check and other tests. If not, you are missing important info that will be needed to help troubleshoot this. The problem has several different possible sources (vacumm leaks in multiple places like booster, manifold, etc., fuel pressure, ignition, carb tuning, trannie and so on), and you need to do testing and get info to share, not just throw parts at it. Otherwise, all we can do is guess.

While you are at this, consider calling the place where you got the trannie and ask what they think.
 
so you're saying the shift quality degrades when the engine gets warm?
 
my Duster used to feel like the 727 was locking up and stalling the car while sitting at red lights-felt like slowly letting the clutch out on a standard while keeping the brake planted. Put it in neutral and it was fine. Turned out to be the EI control module (so as you can imagine it took a while to troubleshoot it).
 
nm9stheham,

You're totally right, I'll go grab one today, drive and see what happens. I wouldn't be surprised if there are other vacuum leaks, already had to fix a valve cover leak. I'm just worried somethings breaking the more I drive on it.

FredS,

Shift quality feels about the same as far as I can tell, it doesn't seem to shift any different when it's doing this lurching thing.

95teetee,

That is EXACTLY how it feels, I have to put it in neutral if I don't want it to die on the street. By EI control module you mean the electronic ignition control module, right? I have the chrome box in my rig right now, I've heard mixed experiences with the chrome boxes.
I could probably mention have been having some strange problems with voltage, driving it stays at around 15-16v, then dips down back to 13-14 when idling, seems to go away/stop the more the car is warmed up. Maybe that could have something to do with this.

I'm going to check the vacuum and come back with what I find. Then we can go from there.

Thanks for the help guys.
 
Update,

Finally got around to checking the vacuum, and checking for any vacuum leaks. And, after the engine is warmed up, a leak starts to appear on the intake manifold, bad one too. Engine vibrates pretty bad, starts to stumble and miss, and dies. Only thanks to a buddy was I able to figure this all out, so thank you buddy.

Also replaced the brake buster, breaks much smoother now, and initially idles great.

Anyway, could that this is what was causing the lurching? I hope. I'll update as I go.
 
Sounds to me like the carb is flooding or the fuel is getting hot. It could also be fuel starvation. I would say it is a carb/fuel problem
 
Timing is all well??? If you set it by the book, it's MILES off from where it will run best.

Where is it set at idle?

A vacuum leak will make it run poorly as well.
 
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