Signal in Sound out...

[rossfree]

Hi all,

I have a problem... with my car. I'd like to find it with a pic and picbasic pro. My car runs great... and then it dies. Just dies. But... alas... it starts right back up! Every time. And runs great again! Until... it dies again. About 15 times a day. It has been doing this for YEARS folks. Sometimes it only dies once. Sometimes 20 times. You never know when you get in the car. But it always re-starts (sometimes it grumbles but most times it re-starts right away).

I can't afford to have a garage shotgun this problem. I know the expense of doing that.

Without a long explanation... I think the computer is the culprit. Either, it's being reset or one of the I/O lines is sending bogus information and the computer is shutting the engine down. Most likely one of the wires is shorting out or I have a dirty connection on a cable somewhere. SOMEWHERE.

Ok... thank you for letting me get that out.

So my thought is this. I'd like to connect a pic to one of the pins of the processor of the computer and observe the data while I am driving. But I need to do this simply. So how about outputting a sound. I know this sounds crazy. Stay with me a min.

If an input should suddenly change states, or vary drastically, maybe I could output a tone that would track the change during the event plus a few seconds (and then go silent again). This would be an audible signal (a warble) that I could listen for while driving. If the audible signal preceeds a stall or happens during a stall, I would jot it down as a possible culprit of the problem. Each day, I would try another input. (I think I'd start with the power pin to the car's processor). Call it the "poor-man's data-warbler".

After doing this for a period of time I might at least have a direction to go in... trouble-shooting this problem.

Ok... bash it. I'm ready! I'm also desperate. After the last few weeks of rain, it has really gotten bad. I'll be sitting at a stop light and the engine will just die. Invariably as the light turns green. People trhing to get in to Walmart really hate that!

I bow to the guroos of picbasic pro! I have it... use it... ain't good at it... but love it!

Ross

[schu4647]

Sounds like you are going to spend months on a project that will take a dealer 5 minutes to diagnose. What kind of car is it? What year?

[schu4647]

I would say it is more likely you have a bad ground or battery feed somewhere. Or it could even be fuel delivery. I had a fuel pump go bad that would do the same thing. I would say it is a power or ground. In all my experience in the automotive industry, I have not seen many engine computers go bad.

[mugwamp]

That computer that you're spending many hours trying to figure out also has a memory. As was just said, a dealer would take about 5 minutes to plug in and tell you what's going on in your engine. But in the meantime, could you please post the year, make, and model so the rest of us will know not to buy one?

[schu4647]

I don't know if you are in the US or jolly old england, but most auto parts stores in the US will read your codes for free. You can then type them in a search engine and learn all you need to know. Even if you don't have a check engine light you still may have a code.

[rossfree]

The vehical is a 1996 Chrysler Town 'n Country. It's a wonderful vehical with crap for electrics. There are more electrical bugs in this car than you could believe. If I didn't know who I purchased it from, I'd swear it went through a flood.

Truth be known, I did take this in once a couple years back to have the computer hooked up to an analyzer. They charged me a $150 and gave me no answers nor clues. They started talking about replacing the computer for $500 or so... yeah right! So I purchased a OBDII analyzer for another $100. It tells me I need a new MAP sensor. Other than that nothing. I plug it in from time to time hoping something will clue me in. Nope.

If the computer is resetting, I'm not sure it's going to log the event for an analyzer to find. I absolutely agree that the computer is likely fine.

I've never heard of an auto parts store reading the codes for free... will check into that.

I've never blown any fuses, so I'm not sure this is a wire shorting to ground. I suspect the problem may be in the steering column such as the ignition switch or shift lever position switch but that doesn't jive with rain or hot weather making this problem worse during the year.

I'm not made of money and I've been badly burned every time I've gone to a dealer. This problem is so intermittant that unless their analyzer points directly to the problem, I'm in for the money ride of my life.

Seriously need help. I thought watching the pins of the 'puter would at least give me a clue. If the computer is resetting, I would at least see that.

Ross

[schu4647]

I am actually an automotive engineer and not a mechanic, but I beleive a bad MAP sensor will cause your vehicle to stall. I might actually listed to the code on that one. I usually either bring a tool home from work, or I will go to Autozone to get my codes checked.

[Acetronics2]

Hi,

In my near family there is a Fiat diesel that used to cut the engine on the left lane of the highway ....
time to stop, and it was ready to run ...

Just a connector pin that was badly crimped ...

I know ... lots of investigation to find it !!!

Alain

[Ioannis]

You surely will spend a lot of time to build and test your auto computer. I thing that the electronics in the computer are the last to look for problems.

I would suggest to spend an afternoon checking on all the electrical connections, sockets, cables that could stop the engine including spark plugs cabling (be careful, there are dangerous Voltages...). I am sure will will find it within a few hours (or minutes if lucky!).

Ioannis

[Pic_User]

I had a compact car, that ran virtually without maintenance, for over 100 thousand miles.

The only problem it ever had:
Sometimes, the engine would "cut out" when I went fast around a traffic circle (round-about). When the engine lost all power the car would slow to almost a stop. Then, it would re-gain power and exit the circle. This happened without regard for weather. There was never any other engine problems.

One day, I found there was a wire (harness) that had been moved, by a mechanic, early in the service schedule. An ignition wire was pulled by centrifugal force, to chafe on the engine. When the chaffing wore a bare spot through the insulation, the bare part would short out, each time the centrifugal force (round-about) would re-appear.

Two cents worth of electrical tape, and back to flying around the traffic circles!

Not that this is any help, I just like telling the story.

-Adam-

[rossfree]

I wanted to get back to all of you for your help and encouragement. I ran across a good website for mopar repairs and it seemed to point to several possible faulty sensors. The second sensor I replaced... the MAP sensor, did the job. The faulty MAP sensor was causing the stalling. It hasn't stalled since... over a week now. Thank God it wasn't a harness issue! Ye Gods and Little Fishes!

CUDOS to schu4647. You were spot on!

After years of stalling I have a van running peachie again. *dancing a little jig* (sorry you can't see that... :-)

Again thanks to all.

Ross

[schu4647]

I don't really deal with the controls side of automotive, but I beleive once a vehicle gets warm it enters a closes system mode. Fuel delivery is then calculated by the engine computer based on the O2 Sensor and MAP sensor. A bad MAP sensor will cause the engine computer to decrease fuel which will cause it to stall. It is all a pain in the but, but it significantly improves fuel economy.