87 2.8l runs for a min then dies!

[cypherbane139]

wow. it started the day i was going for an interview for a new job >_>;;;; sitting at a red light it dies, and wont crank back. after a minute of cussing and fiddling with wires and vaccum lines, i got it to start after cranking an ungodly ammount of time, i had to keep the RPM's high so it wouldnt die, anything below like 2k and i couldnt bring it back up. it sat for a few hours while at work, my friend and i figured it was the MAP sensor, so i went to grab mine, but it would start right up. so i figured it was good, drove off to my interview, and about 3 mins later it starts missing under load, but not dying completely till i let off the gas. tried a bunch of things, different ECM, ended up replacing the MAP, and the distributor (would have just replaced the module, but the distributor is under warrentee =)) no change. checked the coil right after it died and it passed all the tests. i know its not fuel, because it dumps it out the tail pipe lol... hooked a scanner to it and watched everything. CTS is fine, O2 is a little lazy but works fine. MAP, TPS, IAT all good. still dies after it gets warm. i did take a longish trip the day before, about 70 miles round trip, give or take, which is the longest ive drove it at one time. and about 5 mins before it did this crap, i put 5 bucks of midgrade in. anyone come across this or have any ideas? im pulling my hair out =P

 

[Dr. Sievers]

Okay so i suck with technical names but I can tell you that the way this all sounds you have one of two issues not enough juice (electrical wise) or not enough air. Running lean is always easier to diagnose than rich, lol. So when you ran the OBD did you run it after running the engine for a while or was the car sitting for a bit and then you ran it? Because my theories will rely around that information.

If you didn't run the car before plugging it in then I think that it could be your O2 sensor is faulty. You said it was "lazy" so if it was lazy cold it could be sleeping when it's warm. Which would put you in the predicament that you are in.

My other theory has to do with your electrical. Somewhere in/between your supply, relay, and grounds, and plugs you may be experiencing either a loss of power or a lack of power. Like if you have a faulty alternator, corroded lines, bad plugs, wires.

I'm going to tell you to wait for the Fiero Guru to get on here and throw his two cents in because he's the guy that's gonna have the best answer. But, if your in a hurry I'd start by just taking a peak at this stuff.

 

[cypherbane139]

thanks for the reply dude, but the battery is optima, new alternator, new plugs,wires, cap,rotor, pretty much everything... o2 sensor is new, but it was switching after it hit closed loop

 

[Oreif]

Here are some other things to check.

Fuel pressure. You need to check it cold and hot. If the fuel pump is going it could slow down and reduce pressure. Reduced pressure causes the injectors to "spit" rather than "spray" so it will run rich.

The cold start injector could be stuck on causing the engine to run rich as well. When cold the ECU compensates for it but after it warms up it could be too much fuel.

When it starts missing and you rev it up, Does it seem like it is revving slower?
If so this could be a clogging catalytic converter. A clogging cat will reduce the flow and cause the engine to run rich.

Try replacing the ignition coil. They can sometimes get weak when hot.

From the sounds of it, It seems to happen after it warms up. I would start looking into the fuel first. The O2 could be switching because there is raw liquid fuel getting to it. While the sensor may be good, The way it is acting could be a clue to what is wrong.

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[cypherbane139]

mmmmmmmmmmmmmm new coil, new cat, the cold start injector was unplugged till i replaced the distributor.. im gonna check out the fuel pressure after work-ish....

last night i could hold the rpm's at 3~ and it would drop cylinders untill it died.

 

[cypherbane139]

well, its the oil pressure sending unit. lol..... it must have an intermittent short or some shit.

 

[cypherbane139]

....or not? it ran fine for a bit, got it home, went and got gas and food and back. i warmed it up to time it and everything, now it will "hunt" from 400 to 1200 ish and die. thats if it doesnt just die outright... gonna hook up a fuel guage again..

*edit* got a code 45 =P woo

 

[Oreif]

....or not? it ran fine for a bit, got it home, went and got gas and food and back. i warmed it up to time it and everything, now it will "hunt" from 400 to 1200 ish and die. thats if it doesnt just die outright... gonna hook up a fuel guage again..

*edit* got a code 45 =P woo

Error Code 45 is Oxygen Sensor too rich.

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[cypherbane139]

finally!!! =D

LMAO...

*smacks head* its always something stupid you overlook right?

so as im checking the o2 sensor wire, i notice a burnt zip tie, and another one... and find that the main wiring harness is sitting on the back header... lol

fixed that and she runs great^^

thanks for all of your help, u guys are always there when i need a fresh mind on a problem

pontiac rocks ;D

 

[Dr. Sievers]

 

[cypherbane139]

;p