Question : car stalled and won't start again. my 3400 Monte

[narutov2]

ok, so my car is down at the moment, it's a 3400 turboed Monte Carlo with 42lb injectors. I was driving in highway and it stalled while I was driving around 55-60 and I managed to coast it through an exit and up a hill somewhat enough for a couple friends to help push me to a parking lot.

most recent things I have done was put seafoam in oil,gas and intake. and installed a adjustable fuel pressure regulator. I was still running lean after the afpr so was experimenting couple things on cars since it kept flashing 20 afr in my o2 wideband. so I unplugged the maf sensor, and idle went to 14.3-14.9 or something like that so I though I take it for a test drive with and shortly after it stalled. but I noticed that when I drive it stayed at 14.7afr even at around 2-3k and when I let go of the pedal the afr jumps to about 13-11 afr, which makes me suspect fuel may be flooding engine?

It cranks and seems to start for a split second or so, and dies. I replugged the maf sensor. I tested fuel pressure and it was reading about 42-45lbs. I dunno if ignition is fine, but going to check the plugs tomorrow. I tried everything I could think of tonight. I disconnected battery reconnect, relieved fuel pressure through valve, check all vac, waited gave it an hour to 2 and restart etc. Also battery and alternator is good.

Tomorrow I plan on borrowing a obd2 reader to check it, and also check the plugs to see if it was flooded or so. Another theory is that the pcm died? is that possible and on the side is all 3400 pcm swappable? like can I go to a junkyard and get a grandam or malibu 3400 pcm and plug and play?

anyone else that broken down like this? I mean no puddle of anything, and when it stalled no loud breaking poping sounds, it was a silent deaf or so. Normally if sometime major is broken it would show a sign right? as in the pushrod, piston etc isn't blown?

[SappySE107]

Have you checked your fuses? Could be something basic. I wouldn't run a turbo on a 1 bar MAP sensor. It needs to be tuned with the MAF at least but that didn't necessarily blow the motor up, especially if it still starts. If its not a fuse and the computer is seeing all sensors and acting normally, do a compression test and check the spark on every cylinder.

[narutov2]

well today I noticed, my fuel gauge was reading 20 psi even though it wasn't plugged in, so after tightening afpr for more pressure, car started. so my bad, cheapo gauge from harbor freight didn't last a week....sighhhhhhhhhhhhhh

[TGP37]

He unplugged the MAF to see if the AFR returned to stoich, and they did, as a test. I suspect a vacuum leak somewhere since the engine goes lean 20+ AFR with the MAF plugged in.

So speed density is doing alright calculating the airflow at idle and light cruise. Your MAF should do the same........but running REALLY lean instead. My guess is vac leak or a dying MAF sensor.

Would a dirty (coated) MAF sensor go richer or leaner? Thinking it views a hotter wire making it think there is less airflow then there really is. But I could be wrong, not sure how that would effect the frequency of the signal.

[narutov2]

question, maybe I just remembered. I did extend the maf plug to the sensor, but adding like 5inches of wiring to it, would that have anything to do with it? well today I asked a friend to help me get a maf sensor while he is at the junkyard if he has enough money left over. I actually have a maf sensor laying around, but just the sensor, and will have to swap the sensor housing.... since I got if off ebay for like 4bucks and I though maybe one day I could use it etc.......
Well I will be getting the fuel pressure gauge replaced one of these days possibly since I do not know what my fuel pressure is reading at all now...... Sigh this lean problem will be solved one day.

[TGP37]

How did you extend the MAF wire? A lot of sensors can be sensitive to such things. Make sure those wires are crimped or soldered well. Sometimes crimps fail or wires break from vibration/motion at the crimp.

Is it possible you mixed up the wires? How about the type of wire used? Is the gauge large enough?

A weak connection could create a voltage loss feeding the sensor, screwing the readings up.

If you fix the MAF, get your car to operating temp and unplug the O2 sensor. Adjust the AFPR until you are idling at 14.7. Then plug o2 back in. Your PCM will make fueling changes to keep 14.7 steady. More or less pressure in the fuel rail will translate into fuel trims. You want your fuel trims to be as close to zero as possible. This way your WOT fueling is not skewed, as WOT doesn't use the skewed fueling trims.

Example, if you fuel pressure was low, the PCM would command more fuel to maintain stoich. When you floor it, that added fuel wont be there for the WOT and then you go lean. So while you test drive the car, after the MAF issue is fixed, you will remain 14.7 but your boosted AFR will change according to fuel pressure changes.

So keep that in mind, you don't want to boost up extra lean. 11.6-11.8 should be safe for 5-8 psi.

If you unplug the O2, you go into open loop and you won't have fuel trims adjusting for stoich. It is then adjusting the AFPR until you idle at stoich which will get you close to 42.5 psi. Of course, having the gauge is always better.

[narutov2]

I am sure that it was with the right color and I just used butt connectors and crimped on. I will also check that today too.