Car died/no start thread
 

Haven't really had a chance to tear into anything yet, just wanted to see if I could get a little help before I start.

1998 Trans Am, minimal bolt ons, what is sticking out to me as relevant are the longtubes to open y pipe (:bomb:), I think I burned out my o2 sensors but don't want to just start replacing shit I don't need to. Haven't checked the wires I extended yet but that's gonna be my first task...

First off, I was driving the car around like normal, about 35 mph when it started bogging down any time I hit the gas pedal. No power, couldn't get back up to speed when it started doing this. I pulled over right away and once I had it stopped it died. Tried starting it and it would briefly run, maybe 2 seconds at most, then die. I pulled the codes and accidentally cleared them. I can't remember what they were number wise, but do know that know that the front o2's aren't getting any power/signal, the rears are disconnected, and a code for the map sensor came up. No tune, so the SES was already on.

When I do try starting it I can smell and see the raw fuel coming out of the exhaust, where should I start, and is there a way to test the o2 sensors?

Bump for the move and anyone feeling like helping lol?

The engine should run, even with 02 sensors that hardly work. It should just be very rich. maybe you burnt through a wire completely. Check that.

Maybe the PCM died on you.

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Leaky gas tank / fuel lines? I had a similar experience one time then felt dumb after I filled the tank and got home to find a gas waterfall coming out of the back...

You seem like you have alot going on that will be remdied with a tune.

Bad 02 sensors or if they aren't getting power won't bog your car down and cause you stall or prevent starting.

You said one of codes that came up was for map sensor, leads me to believe either your map sensor is bad OR its just might be giving whacked out readings in combination with much needed tune. We don't know that yet.

A simple way to test if map is bad, unplug it and trying turning the car on.
Leaving it unplugged and driving the car (NOT EVERYDAY) but for very short period of time until you fix the problem is fine.

The way it works is that a bad map will give false readings and car doesn't act quite right.
If you unplug it, default readings are used by PCM. - Don't quote me on this, its how I understood it.

I was in similiar situation not too long ago, when it felt like power was cutting out. Within half a mile, It went from bogging down to couldn't start anymore.

I verified fuel pressure and spark were good and scanned for codes.
Code for map sensor came up, I unplugged it and car fired right up!
I replaced the map sensor, cleared the code and its been great.

Again keep in mind your map sensor itself can be bad or causing issues with lack of proper tune.

Check if your air filter is dirty,likely dirt/debris went upstream past the filter and got the map sensor dirty or just plain faulty.

Maybe , but thats very rare.

Another good point. Check for gas leaks and if possible check for fuel pressure (needs 58 PSI) on the fuel rails with key to accessory.

True, it is rare. But my factory PCM fried itself from the inside out.....so I thought I'd throw it out there.

People have chased sensors, wires, grounds, vacuum leaks, etc.....to find the PCM is just failing.

Another rare item with the 1998's......that will cause the engine to start for a second or two, then stall out. Or if it does stay running it will backfire, spit raw fuel out the pipes and sound like there's broken rods in the engines......failing or failed "Coolant Temp Sensor." I've had that happen too.......it will make you chase many things.

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Wow thanks for the replies guys, going to try the map sensor out first and see if that does anything for me. Out of curiousity, do they just go out in a hurry like that?

And yea, been meaning to get on a tune just haven't really felt the need to just yet and haven't had the car out much this year yet. Will update later on, thanks again.

first thing I would do is unplug the MAF. Then try and start the car. Sometimes having no o2's/fried o2's will really jack up a car. Unplugging the MAF sends the car into SD. It wont have a lot of power and will be in a sort of "limp" mode, but it should start and run. easy to check as well.

For some reason I poste on my buddies account in the first post lol, but yeah, nothing changed when I unplugged the map and the maf sensor.

Speed density is not a limp mode. Can easily make just as much power. Lots of people actually tune for speed density. It just isn't as fuel efficient. Don't be spreading misinformation.

Sounds like a no spark condition if you're shooting raw fuel out the exhaust.

Gonna check for spark and fuel pressure tomorrow, as well as chase down the o2 sensor lines, is there a decent way to test the pcm?

And about the coolant temp sensor, besides just replacing, is there anything I can do? Trying to stay as low budget as possible, bit of a tight time for me lol.

On the no spark - it seems to want to fire when I first crank it over, then dies down almost immediately afterwards.

You can check the ECT (engine coolant temperature) for a certain resistance based on ambient temperature. I'll see if I can find the chart.

For the PCM, it's pretty much throw a known good one in there and see if it resolves the problem.

Here it is. Pain in the butt to find. http://shbox.com/1/4th_gen_tech2.html#ect

http://carprogrammer.com/Z28/PCM/LS1/Holden_LS1.pdf
This may be better. Just check the bookmarks on the side for Engine Coolant Temperature Sensor.

Can't tell you how I appreciate it man, thanks, will get back tomorrow with more info.

Glad to help. Looking forward to hearing the results.

Oh, when you check for spark, pull the injector fuses so you don't flood your cylinders more and wash down into your oil.

Totally forgot to check up on this, it ended up being a bad fual pump.