Engine Dies When Braking

This has been happening for a while now but it seems to happen more often now that it's cold in the mornings. When I crank up and take off in the mornings, sometimes the truck acts like it wants to stall, but only when I hit the brakes and come to a stop. And it seems like the harder I hit the brakes it more it wants to stall. Once the truck warms up and I drive for a while it doesn't happen again. And it only seems to happen after it has been sitting overnight. When I leave work, it doesn't happen. Any thoughts?

I suppose I should tell you some of the things I've done to try to resolve this. Over the past several months I have changes my plugs, replaced the PCV valve, cleaned the throttle body, tested the TPS sensor with my voltmeter. Also there are no codes.

Hows the vac lines going to the brake booster look?

The lines look fine. And if it was a vac leak wouldn't it happen all of the time instead of just after the truck has been sitting for 12+ hours?

I did all of the steps in the Operating Check and Airtightness Check sections of my Haynes manual. Basically the steps are:

1. Depress the brake pedal several times with the engine off and make sure that there is no change in pedal reserve distance. CHECK!
2. Depress the pedal and start the engine. If the pedal goes down slightly, operation is normal. CHECK!
3. Start the engine and turn it off after 1 or 2 minutes. Depress the brake pedal several times slowly. If the pedal goes down farther the first time but gradually rises after the second or third depression, the booster is air tight. CHECK!
4. Depress the brake pedal while the engine is running then stop the engine with the pedal depressed. If there is no change in the pedal reserve travel after holding the pedal for 30 seconds the booster is air tight. CHECK...kinda?

On that last one after longer than 30 seconds it did feel like the pedal slowly depressed a little bit further.

I'm wondering if it might not be the braking that causes it. I could just be that that's when I notice it. This morning I'll try testing it out and see if I cost slowly to a stop if I can still get it to stumble.

So yesterday morning I coasted to a stop to see what would happen and it still stalled. I have noticed that it only seems to do it when it's in gear. If I shift to neutral it doesn't happen.

Sounds like your TC isn't unlocking like it's supposed to.

Is there anyway to test the TC or service it? I can't seem to find too much about it.

You sould probaly check you map sensor readings and the iac count. The map sould be around 29. If nothing is found there check the cam and crank sinc state. They may go in and out of sinc and not cause a dtc to set.

Could you say all of that again in English and using only small words?

MoparWild said:

You sould probaly check you map sensor readings and the iac count. The map sould be around 29. If nothing is found there check the cam and crank sinc state. They may go in and out of sinc and not cause a dtc to set.

Click to expand...

Deviate said:

Could you say all of that again in English and using only small words?

Click to expand...

MAP sensor = Manifold Air Pressure
IAC = Idle Air Control
Cam and Crank sensors must be in sync, its a check for the computer, if it gets inconsistent readings it will know and let you know (usually).

You need something capable of datatlogging/accessing the PIDS (inputs). SC 3865 and maybe DSP (dunno?) are capable fo doing this.

Ah I see. So can I find out all of this info without a tuner or do I need tell my wife that I just have to buy a new "tool" to fix my truck?

Here's another little tidbit. So this morning when it happened as I was coming to a stop I hear a vibration sound coming from under the truck and then it did it's stumble-try-to-stall deal. Now, I have heard a similar vibration sound like that for nearly as long as I have owned the truck but it was never followed up by this stalling thing until the last 9-10 months.

Not sure if it might be related, but when I'm driving at highway speeds and I stomp the accelerator, sometimes the engine revs like I'm hitting passing gear without actually going any faster and then finally accelerates. Does that all sound like a TC issue?

check for codes? Could be the speed sensor. Mine did that for a while, cruise control also didn't work. Did a brake job and cleaned everything up and it fixed the problem.

No codes at all. That's probably the most frustrating part. If it would throw a code at least I would have a starting place.

How worn are your brakes?

I replaced the front pads within the last 6 months. I didn't do anything with the rear brakes though.

My truck just started doing the same thing wile my wife drives it to work, but I haven't had a chance to address it yet. It has been well below zero day, and night, here.

From your description, I would say check your transmission fluid level. When the level gets low, the transmission hangs up while trying to downshift as you stop or slow down. The sudden load on the engine can cause it to stall and die, especially when you add the turning of a power steering pump, and the fan on high/brake lights pulling from the alternator all at the same time.

Something else you might try, if the level is fine, is put your truck in neutral (with the parking brake set) while warming it up, so the trans fluid is circulating the whole time, causing it to warm up while it's parked.

Last week, when my overdrive wouldn't work, I discovered that our trucks will not allow overdrive below a certain temperature, due to the trans fluid being capable of freezing.

I had to cover my trans cooler with cardboard and warm the truck up in neutral to get the fluid to a temp high enough to allow overdrive. Depending on how cold it is where you are, the thickness/temp of your trans fluid may be causing the same hang-up in the trans that low fluid would, which is why you only see the problem on your way to work, and not on your way home (after the temp has warmed up).

Before I covered my trans cooler and after driving several miles without my overdrive working, I tried to put the trans in neutral as I pulled over. The trans hung up so bad coming out of drive and into neutral, that it jarred the truck and killed the engine immediately. I went home, covered the cooler and let it run in neutral for a few minutes. It stopped hanging up immediately and overdrive worked right away too.

I will be doing the same things, as well as cleaning the battery terminals to assure a solid ground to the battery. If you follow along, I bet your problem will stop. I will keep you posted on my progress as well.

I just noticed you are in FL. I wouldn't think it would get cold enough there for the temp of your fluid to be the whole issue. By the way, I believe your overdrive is controlled by ambient temperature, whereas mine is controlled by fluid temperature, in case you ever run into that issue too.

Your transmission is obviously hanging up, which is why when it is in neutral and you stop it doesn't stall out. The question is, what else may be butting extra load on your engine to cause the trans to be the final straw, which is why I would clean your battery terminals thoroughly. A combination of your alternator working extra hard, with your trans hanging up could be it as well.

I would consider a trans service if the level is good, and try running it in neutral for a few minutes before leaving the house in the meantime.

UPDATE! When my wife got home, I checked the trans fluid level and it was good. She said the truck was still stalling and dying when she would slow down to stop or turn, but it would start right back up and idle fine after that.

I had her take it back out, since I was on duty, after approximately four minutes of idling in neutral to warm up the trans fluid, and problem solved! She has left the house two more times since then and, as long as she leaves it in neutral for a minute or two before leaving, there is no stalling at all.

I should also point out that my transmission fluid and filter was recently changed, so that is not a possible point of concern. In the case of FL cold weather doing the same thing, it is possible that a trans filter in need of replacement could be causing the same problem at a higher temperature than it took for mine to act up.

I will still be cleaning the battery terminals, as any help with reducing drag on the engine will help reduce the problem, especially when the air conditioning pump kicks on and off when the heater is used.

I did replace my tranny filter and fluid not too long ago. I probably should double check the fluid level again just to make sure, but it was fine the last time I checked it.

You're right, cold here probably isn't cold to anyone else in the country.

This morning I did crank the truck and leave it in neutral for a couple of minutes before I backed out of the driveway. And it didn't have a single problem....I'll be damned. But that was just one time. I'll keep an eye on that.

I have 95k miles and still have the stock alternator. I'm trying to recall if I had this issue before I added all of my amps and speakers. It's not a huge system by any means but if the alternator was getting weaker maybe it was enough to push it closer to the edge. I haven't had any other issues that would seem like an alternator problem though.