Please help before I sell this car! (long)

Pats-GN

Member
Car runs fine but, about 30min into a trip it backfires and dies. Usually start right back up, on hot days it might not start for 10min or so. Its not a quick stall, it starts with a backfire, and loss of power like its starving for fuel, give it gas and its more backfiring even flames out the exhaust then finally it dies. Its much worse in warm weather. I'm getting good fuel pressure at all times, even when it wont fire back up. It usually fires back up so I cant get a spark or inj pulse reading, only strange thing from the scanmaster is the BL's hit 150 when mash the gas during the problem, no codes. I've been chasing this problem for months with no luck, i've changed ECM, Coil pack, Mod, Maf, Cranksensor, Cam sensor looks ok but dont know for sure, still quits if you run with it unplugged. Sometimes the car will stall in the same area so its definately heat related. Please help, any ideas on how to diagnois this problem would be greatly appreciated.

thanks
pat
 
Hmmmmm....

Does the problem start when the car goes into closed loop mode. Once it warms up it will start to read from the o2 sensor and if its bad it could be running really rich causing it to run like crap. From the 150 blm's it sounds like its running rich. What do the plugs look like? Don't sell the car its got to be something simple.
 
I changed the O2 sensor and problem is still there. The BL's are normal until the car starts to lose power, when I try give it more gas they jump to 150, but all the car does is backfire. It happens in closed loop, the hotter the outside temps the sooner it acts up. I'm totally stumped. :confused:
 
Yeah, could definatly be a bad chip. Also does your tps sensor read correctly on your scanmaster once the car is warmed up and the problem starts? If that sensor started jacking up once it got hot it would probably cause the problem too.
 
I have tried two different chips, but havent looked at the TPS readings at the time of the problem. I'll check that out. Thanks
 
stallout

Hi Pat,
Check the Reference and crank sensor inputs. If you have a Snapon Vantage, take a picture of them while driving.I suspect that you have a wiring problem, specifically in the shielded places. Check the harness behind the motor. Good luck!


PS It's a pain, but will turn out to be simple stuff Dale
 
I dunno Pat, mine was doing almost the same as yours. I finally found that pin C-16 (that's the orange BATT wire) on the ECM was missing. :eek: Every time I turned the key off, on restart it had to relearn all over again. And yes, it would start and run without the orange wire! I had to get a new ECM, so I can't be sure if the problems were due the BATT missing or a bad ECM. Have not had ANY electrical problems since. You might want to check and be sure the orange wire is intact and undamaged.
 
Spent all day checking wiring, i'm yet to find anything strange. Orange wire to ECM looks good, crank sensor wiring looks ok. Problem seems to consistent to be a wire, sometimes the car will stall in almost the same place when the outside temps are similar, which makes me think some component or sensor is getting hot. If its backfiring flames the injectors should be pulsing right? I'm stumped.:) Thanks for the help.

pat
 
Hmmmm

Were the tps readings good when the problem started??

Talking about wiring, I worked in a shop once where one of our mechanics had a problem with a buick century. After using a snapon scanner and replacing every concievable sensor and electronic part includind the ecm he was starting to get pretty nervous. Pretty soon both mechanics were working on the car and low and behold it was one little wire that had broken inside the insulation and was making contact when the car was cold but not when it heated up a little bit. 1000 dollor repair bill over a broke wire. They spent almost 2 days working on that POS. This was at a state motor pool so no actual individual got screwed except for the state lol. Check that wiring really good. Good Luck.
 
wiring

Hello,

I am not sure of this will help. But when I bought my GN it would not run, it turned out to be a bad pin A6 wire (the other ECM power wire.) Oversized tire rubbed through the pass. inner fender and through the harness, water got into it and you can figure out the rest. Anyway, there are splices within the harness (a big one under the heater box) basically bare wires with a piece of metal crimped around it.

I spent $3.99 on a powered test light and it was the best tool I ever bought. Get one of those and access to the wiring diagrams, check for continuity on stuff that matters like ECM power, MAF signals etc.

Q: does your check engine light work? Does it come on when you have key on, engine off?

I Agree that it is something dumb, it is just a matter of finding it.

Bill
 
Thanks for all the input, engine light does work. Checking my wiring again, only strange thing I found was the relays on the drivers side fender. All three have a good amount of black goo on the connections where they plug in. I cant tell if this is the connector itself melting down or just some type of grease. Dont see how you could get a good connection through it. I know one controls the fan, not sure about the other two. Is this normal?

thanks
pat
 
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