This thing was running beautifilly then it sputterred on two seperate occaisions while going up a fairly steep grade, the following day it stalled twice at idle, the following day it acted just like it was running out of gas resulting in pushing it to the pumps on a quarter tank of fuel. Wouldn't start after that. Tested fuel pump - operating - Fuel pump relay - operating - plenty of spark while cranking - error codes 33 - IAC motor - 35 - Map sensor and - 44 - 02 sensor - lean mix. Put in new IAC motor, Map sensor and TP Sensor just for good measure. Cleared codes now its flashing 12's all the way but it only runs for about a half an hour and then its done for a couple of hours and is a real !@#$ to get started again after that. I'm eyeballin the fuel pressure regulator next then I'm all out of ideas - please help!

Um...you didn't mention a fuel filter??

Change the filter if you haven't already, then see if AZ will loan you a fuel pressure gauge, and see what kinda pressure you've got at the rail when the car acts up.

Yep changed out the filter right off figured it was plugged, then drained the tank figuring I got a load of crap - refilled - no change - Pulled the fuel rail this morning and I'm going to replace the FP regulator. While I had it all apart I replaced the O2 sensor too - Thanks for your input I'll keep ya posted. Keep your ideas comming - I read all the archive posts before posting and you gave the best advise - Thanks again

Please do let us know whether that fixes it or not. If not, we will go from there.

Still a No Go - Idles like a champ - warms up - gets a little warmer than usual then starts to break up. I hooked a timing light to #6 cause its the easiest to reach and at about 3000 RPMs I'm getting some black spots on the scope when its really steady and bright ast 2000. Could be just overloading my light I guess - I'm grasping at straws here - I read somewhere in the archives about the coolant temp sending unit giving bad info to the computer(confuser). Also read that the ECM could be bad. I ran the code reader again and got a 33 but it was probably because it stumbled during runup. I don't get it this thing ran like a top - I put about 10000 miles on it in about six weeks always 30 MPG - mr goodwrench put an alternator in about 1500 miles back hated it but was way away from home.

It sounds as if the computer is shutting off the engine after it warms up. Then the injectors will not operate -and no gas into the engine. This could be the ECM itself (as I have seen this failure), or possibly the Ignition Module (sometimes located under the coil packs), or it could be the Crank Position Sensor. All can fail with temperatue/vibrations, then work again after cooling.

I'v seen quite few Crank Position Sensors fail this way and just recently replaced one on a "92 Olds 3.3L (similar ignition components to the Lumina).

You can check the Ign Mod and Crank Pos Sens by waiting for the car to warm up to the near failure stage and the tap on it. The car may stall suddenly. Once it gets warmer and fails completely, then blow on the Crank sensor or Ign Module with an air hose for a minute to cool it down. The car may start right back up, until it heats up again. The Crank Position is cheap to replace- $25.00. The Ign module and ECM (core exchange part is normal) are about $100.00 ea.

Also check/disconnect/bypass the low oil pressure switch and temp sensor.

Replaced ECM today - what an ordeal drove an hour and fifteen minutes to get to NAPA - pick up the ECM - drive home - hook it up and its in diagnostic mode - no check engine light no start. I call them and we check numbers - whoa that ECM is for a standard transmission - So back I go and swap it for one that should actually work in my car - drive back with the new one - same deal - it seems to be locked into diagnostic mode - makes all the same noises - fan etc but NO check engine light at all - tried resetting all the buttons and whistles - more broke now! So tell me sage ones - besides trying the ECM gig again tomorrow what else should this grasshopper do?

I hope you realize that many new replacement ECMs do not come with the engine (software) program chip inside. In most cases you need to remove it from your old ECM and then put it into the new ECM. This program chip contains the operating parameters for your specific engine (timing, advance, tranny shift points, etc.). GM (and others) make many of its ECMs as a standard platform and then tailors each with engine specific software to run it.

This is where aftermarket vendors can make money by selling a swap out "performance" chip. The program chip is under an access cover on the ECM box. It is installed into a socket on the ECM mainboard with two latches to hold it in place. Release the latches and it can be pulled out easily- much like the memory in a desktop computer.

Be careful when swapping the PROM chip. Static or mishandling can ruin it.

Thanks for the ideas - Yeah put the MEM/CAL chip from the original into both the replacements - Very gentle - Still think I got a second bad REMAN computer - gonna try a third today - Keep your comments comming - I'm really outside my comfort zone here - strictly old school - If it gets gas and a spark it oughta run - quite an education.

Also check/disconnect/bypass the low oil pressure switch and temp sensor.

Now where might one find such a widget - I did an oil change just prior to all this hoopla - used a can of engine flush - maybe it ate something besides sludge - ??? - cant find any mention of this particular thingy in my Haynes manual.

If the engine has very low oil pressure, or thinks it does because of a faulty sensor, then the fuel pump can get shut off. This is a safety innovation on newer fuel injected cars- with the idea that if you get into a car accident and the engine dies- then the fuel pump won't potentially keep spraying gas onto a hot engine and start a fire. Temp sensor can has simialr effects- for heat related reasons.

I think you will find both the oil and temp sensor are located almost side-by-side on the front end of the Intake manifold. Look directly up from the crank pulley higher up on the engine. They are somewhat hidden under the top of the intake, so you will need to bend down and look generally back behind the pwr steering pump at the front of the intake. Use a light to see them better and look for the wire harness' gonig there from the main wire harnes bundle along the intake.

Your right that Haynes forgot to pinpoint their location- I don't think he found them either!

your oil sender is just above the oil filter on the front of the engine. Check vacuum to the fuel pressure regulator. If the factory plastic vacuum hose is cracked, it will cause a false reading and the regulator will not work properly. I assume the "black spots" with the timing light refer to a miss in the spark, if so, it's a good chance the crank sensor is the problem.

Thanks a bunch - gotta fly -- be back in about a week and start tackling this out again

Try something simple. Change your spark plug wires. Sometimes when they get hot, if they have been slightly damaged, it can affect how well they are able to transmit the spark voltage the the sparkplugs. Sounds odd, but my wifes 93 had very similar problem and a new set of wires made a new car out of it.

Nobody's mentioned the CPS yet. Can't hurt to check it at the least.
EDIT: oops nvm, maybe I should take my own advice and read the whole thread first. :grinno:

that's ok Kooter, it was at the end of my post

I was just thinking, you mentioned up a steep grade, 1/4 tank of gas, then trouble. Could the strainer on the pump have picked up a load of crud while climbing a hill, and is now collapsing, cutting off fuel flow? Seen that happen in older cars with mechanical pumps, drives you nuts trying to figure it out!! Don't recall seeing it on a newer car though.