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08 GP starting issues

B

bluebsh

New member
I've been having an odd issue with my 2008 Grand Prix base model. Sometimes it will not start in the morning (strangely usually after it rained all night). If I try to start it a few times with a pause in the middle between tries it eventually catches and starts.

Example of problem:

  1. Car starts and runs fine for days or weeks.
  2. Car sits over night, seems to co-inside also with rain over night
  3. Go to start car, turn key to start let go, starter runs, engine turns, sounds like engine has compression from the sound it makes, engine doesn't catch engine continues to try to start for about 5-10 seconds then stops automatically.
  4. Wait for a second, turn key to run so fuel pump can prime in case that is the issue, fuel pump is clearly heard running then stops when primed
  5. Turn key to start again, same engine starter running noise, clearly has the pistons moving can hear the noise and compression noise from it, 5-10 seconds system auto stops trying since it didn't catch and fire
  6. repeat step 4 and 5 again, same result
  7. repeat step 4 and 5 again, engine catches and starts fine and will work for weeks again until this randomly happens again

What I've tried to do to solve the problem or other maintenance work done recently:
  1. Changed plug wires but not plugs, plugs didn't seem like they needed changed yet, car only has 69,000 miles on it
  2. EGR valve was replaced a year ago, was throwing codes, solenoid valve was stuck and valve wasn't working, codes stopped after replacement
  3. Cleaned MAF a few months ago, I do this about once a year
  4. Replaced intake air filter and cabin air filter with OEM filters
  5. Oil changed with full synthetic oil
  6. Coolant was flushed and replaced with dexcool coolant again
  7. Back flushed the heater core due to low heat (good bit of junk came out)
  8. Last time this happened I thought the fuel pump was going out, so had it replaced, so it's under a year old
  9. Replaced relays for fuel pump (just in case they were going bad) with OEM ACDelco relay
  10. Replaced Headlight beam relay (had an odd issue where the headlights would just turn off out of no where at night)
  11. Removed ground from chassis to negative battery jumper from chassis, cleaned it in case it was corroding, sanded the paint of the chassis where it touches to improve the ground since it had very little clean contact minus the nut and bolt connection. after that was on and tightened back up covered it with dielectric grease to keep water off it
  12. Cleaned battery terminals and wire connectors with acid cleaner / indicator, wire brushed them clean also

So, what is left? Fuel line somehow plugging up? bad injectors? CAM or Crank position sensor? since this happens so randomly but eventually fires trouble shooting it has been a pain

Edit: more info

* There are no check engine lights, never seen one after the EGR valve was replaced
* Gas mileage is down to 13 MPG city, use to get 18+ MPG city, highway I get still about 22 MPG
 
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I have had rough idle a few times, and have had the RPM during acceleration drop from like 2-3k rpm down to about 1k rpm when going up hills... then pushed the gas more and it jumped right back up...

was looking at symptoms of a bad ICM and they seem to match, car not wanting to fire at start but then randomly will fire... not sure if it's the icm or not, it and the coil packs have never been replaced before.
 
well, something more is going odd now... I just drove home for lunch car started up fine ran fine, got home fine (about a 5 mile trip and engine was on for about 15 minutes)'

go to leave to go back start car up, it starts but the engine is running extremely rough now no check engine lights though, running so rough I just turned it off... waited a little turned the car to run to see if I could hear the fuel pump prime, heard nothing assumed it was already primed... turned to start, engine starts up and goes right back to running rough again...
 
Well, someone suggested the coil packs, now its running rough..I would say its something to do with the air/fuel/spark.

I didn't read your whole list, but I would check fuel filter, air filter, coil packs, spark plugs and wires. Its possible your fuel pump is going out, or your tank was dirty and pulled dirt from bottom of the tank into the fuel line, I had a malibu that ran really rough because of junk in the tank, fuel pump and cleaned tank fixed it for me.

Is is possible the fuel pump is going out already? I replaced the plugs+wires in my 01, it had 62K miles and the plugs looked worse than the ones on my G6, that had 95K miles when I did those.
 
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J57ltr said:
Check the fuel pressure.
Click to expand...

this morning when it wouldn't start the pressure was normal, later when it was running rough I think the pressure dropped and tonight the pressure was zero... the fuel pump is new, the relay is new, the fuse is good...

something hit me tonight though that there is a wire in the trunk under the carpet to a hatch, thought that was the line to the fuel pump... I moved it some looking at it to see if it was damaged, tried to start the car again and boom came right on... went back to the wire moved it some and as I moved it the pump got higher or lower in pitch and the engine changed rpm at idle some.... starting to think somehow that line is damaged... but why does this only happen after long rain storms?... it rained here all night and this happened... when the fuel pump got replaced it rained all that night before and the pump wouldn't turn on (why they replaced it the 1st time)
 
well replaced the ICM and coils today to do a little tune up, took the coils off and the ICM looked like it was leaking something greasy... replaced with ACDelco ICM and ACDelco "pro" coils.. seems to rev smoother now at least
 
J57ltr said:
What was the fuel pressure?
Click to expand...

if you read above you'd of saw it was zero.. I figured out the problem though the wire that goes through the trunk has something wrong with it... if you move it the pump wont work, move it again the pump works... and the pump will change tone as you move it
 


after some more investigating today, I took the cover plate off on the wire hatch in the trunk where the wires go through the floor of the trunk for the fuel pump... started the car up and moved the wires around some where they go into the plastic harness that is held in place by the metal cover. as I moved the wires the pump tone changed, and moved them enough the pump went out completely...

at this point I am 99% sure the problem is the connector that is in the trunk floor that the fuel pump plugs into under the car....

question is, how hard is this to replace or fix? not sure what exactly is wrong with it yet, but it is definitely not holding a connection as you move the individual wires that go into it
 
bluebsh said:
if you read above you'd of saw it was zero.. I figured out the problem though the wire that goes through the trunk has something wrong with it... if you move it the pump wont work, move it again the pump works... and the pump will change tone as you move it
Click to expand...

actually I read it and at one point you said it was "normal" what I wanted to know was what was "normal"? I realize you had it drop to 0 and all that but you never answered what the normal pressure was?

Obviously you have a connection issue but if someone asks you to clarify, please do it. Had the pressure been low I would have immediately told you there was a connection issue based on the rest of your information. Most people don't even know what normal pressure is on an 04+ you want info on 03 prior then there is a ton of info on, 04+ there are very few that know.

Jeff
 
J57ltr said:
actually I read it and at one point you said it was "normal" what I wanted to know was what was "normal"? I realize you had it drop to 0 and all that but you never answered what the normal pressure was?

Obviously you have a connection issue but if someone asks you to clarify, please do it. Had the pressure been low I would have immediately told you there was a connection issue based on the rest of your information. Most people don't even know what normal pressure is on an 04+ you want info on 03 prior then there is a ton of info on, 04+ there are very few that know.

Jeff
Click to expand...

sorry, I assumed you meant what was the pressure when it wasn't working. it was zero at that point.

When it is working, with the line primed but engine not running it is 60 PSI at the rail
 
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