Hi,

I need some help working through diagnosing a car that stalls under load.

It idles fine and revs ok under no load, but will buck and stall going up the slightest hill. It's barely drivable right now so it's going to be hard to pull any OBD codes. The last time I pulled the codes for the engine I believe I got a bank 1 too rich (P0172). I also pulled a cylinder head about 3 months ago for a broken valve spring. We're right at 98k miles.

I'm pretty new at fixing cars and would really appreciate your help so I can get my wife back on the road! Where would you start?

 

I generally don't drive my vehicles if it's doing something weird like you mentioned. What all did you do when you did that cylinder job?

I'd see if you can borrow a scan tool or buy a cheap bluetooth - it will pay for itself many times over if you start repairing you vehicle.

 

make sure all the sensors are plugged in snug. check the vacuum line on the fuel pressure regulator.....sometimes that rubber elbow cracks and leaks.


According to OBD Codes, receiving error code P0172 may result in no drivability problems, or it may cause misfiring. Some possible solutions to resolving the error include inspecting vacuum hoses, cleaning the mass air flow sensor, inspecting fuel lines for cracks and damage, checking the fuel pressure or cleaning the fuel injectors.

 

Thanks for getting back to me.

WBody, I went and bought a scan tool today and I pulled the following codes:
P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
P0172: System Too Rich Bank 1
I just pulled the rear cylinder head and got it decked. All it really needed was a replacement for a broken exhaust valve spring but I figured I'd get it checked for warpage while I had it off. I tried to put everything back the way it was with new gaskets and it ran really good for 3 months following the repair. Thanks!

Sharpie, I'm going to go investigate the MAF sensor and some vacuum and PCV hoses. Do you think that would cause it to stall out like that? It drove with that code for a while. Thanks!

 

I think its possible . the MAF may just need to be cleaned also...very easy to do with a special cleaner you can buy at any local auto parts store. worth a try to clean it.

as for the other code ...that indicates a possible faulty thermostat....air in the cooling system or a faulty temp sensor. my guess its either air or the thermostat. did you replace the thermostat when you did the head repair? it may even be an old code that was tripped shortly after you did the repair and then resolved itself after the cooling system got back up to par...a soft code its called.

at any rate tackle one issue at a time. if it was me id clean or have someone clean the MAF for you. then clear the codes and go for a drive and see what comes up. and if the fuel filter hasnt been changed id swap that out.

its even possible the coolant sensor is faulty and causing both codes. that is another cheap and easy repair.
but anyhoo clean the MAf and see if it helps . thats where id start if all the connections and vacuum lines are valid. after that id suspect a plugged fuel filter or faulty temp sensor.......

 

My 02 would stall under load when my MAF was dirty. Cleaned it and have had no more problems.

 

I think I may have figured it out. While I was looking at all my PCV and vacuum hoses I noticed my spark plug wires were really cut up in places. There were a few spots down to the center conductor and I think it was just arcing under load. I replaced them and did a test drive for twenty minutes with no issues. Also the CEL is out. I'm hoping that's all the problem was.

As for how the wires got so messed up... I have no idea. Thanks for the help! I'll post back if it was something else.

 

good to hear I'm surprised that didn't trip a misfire code glad ya got er fixed tho