Yesterday my car started randomly hesitating and bogging while I was cruising on the highway. I initially thought it was cutting fuel, but when I looked at my AFR gauge, the car was actually running really rich dumping fuel in to the engine. It was giving me 8-10 AFR's and I went through almost 1/4 tank of gas in about 10min. I tried figuring out if it only happens on certain maps, but it happens at any low load/rpm map randomly. I tried to re-create it but it just does it whenever it wants.

It happened twice on me, only after I had been driving for about 10-15min. To stop it, I can simply accelerate the car to let more air in and match the fuel, and sometimes it stops doing it completely and sometimes it just keeps hesitating after I let go of the accelerator again.

I don't know what to think of what it could be, I've never had a car dump fuel in like that. If it had anything to do with the fuel pump or injectors themselves I figured it would be cutting fuel not dumping it, but I could be wrong. Only thing that comes to mind is the FPR? Or maybe the solenoid that controls the FPR?

I tried searching on here for hours last night but the only issues I found were with fuel cutting. I'd appreciate any help, the car's my daily so I need to try and figure it out asap. Thanks!

 

I had a similar problem when a fuel injector o-ring went bad. The problem never went away though, and I had to pull the injectors to fix the problem.

 

I just put in some fuel injector cleaner to see what happens. My best guess is they're sticking open for some reason

If an o-ring went bad though, wouldn't it happen all the time? Because mine only starts after 10-15min driving, and it stops, and then happens again randomly every few min after that.

 

I could be wrong, but it sounds to me like your fuel injector is sticking open.

 

Yeah after reading some more I think that's the most likely thing. That's why I put in some fuel injector cleaner hoping that might fix anything in there making it stick. If not I'll have to take it apart

Would I be correct in assuming since it's happening at low load/rpm, that it would be the primary injectors causing the problem?

 

if the injector is sticking open it cold be the primary or secondary... either way you will be getting too much fuel. It may not be as noteiceable at higher loads/rpms becuase you need more fuel there so the percentage of extra fuel is lower...

Could also be an electrical short causing the injector to open, I have had electircal problems in the past related to temperature, as parts warm up / expand the short or open circuit becomes a problem...

Good luck tracking it down...

 

Does sound like a sticky injector, could be oring related but the intermedant symptom ahh, I doubt its orings. When its worse at low rpms, could be secondary sticking partially open, heck could be primary. You havent changed injectors lately right ( in case I missed that above)?

You can shut her down w/to much gas, obviously, so I would be carefull how far away you go until the problem is resolved. I suppose a wiring harness issue could also cause this, but sounds like injector as mentioned above.

Oh yeah, I wouldnt put any additives in my fuel system, just 93/94 octane gas from a station you trust, but thats just my opinion.

 

sure the MAP sensor is ok?

 

As far as i know I think it is. How would I be able to tell or test if it's faulty? And how would is it that would cause the problem?

No I haven't touched the injectors for anything.

Well I had already put in some of the injector cleaner in the morning. I took the car to work and back today, and the car ran fine with no problems this time. I tried to run it in as many different conditions as possible and nothing. So I guess I'm gonna keep trying it out for a little longer to see if it happens again and then take it from there.

I don't think I'll be using the car much the next couple of weeks, so even if it doesn't happen I might take out the injectors and try to check them anyway.

 

I think I might have found the problem. As I was removing the UIM, I found that the TPS connector was very loose almost falling off.

Would the TPS be a reason for that happening? It was surprising to me that I didn't experience any idle issues with it like that.

 

Needed to continue this, I'm still having the same issues.

The TPS not being plugged in was not the problem.

The car's still having the same issues, and now it's actually developed other symptoms. Now I'm having a hard time starting the car.

So far I've checked the following:
TPS sensor is working to spec
MAP sensor is working to spec
All relays are working to spec
Removed and jumped fuel pump resister (Was reading at twice the spec ohms)
Fuel Pump is working good
Fuel pressure is good
No Fuel leaks
Injector resistance is to spec for all 4
ECU has been swapped and still happens so ECU is not the problem

What I want to do is check for a short or a if the injectors are being grounded and sticking open, but I can't find any info on how to test that? I've tried searching for a while and going through the SM, but no luck.

 

bad plugs / leads not igniting the fuel properly?
wouldent explain the low rpm bogging but something easy to test.

 

I replaced all the plugs about 3k miles ago so I doubt it's that, but I'll be removing them and checking

 

isnt bogging like a coolant seal issue? when engine starts to burn coolant

 

check you fuel pressure regulator. i have seen the diaphrams burst and draw in raw fuel in through the vacumn hose into the intake. pull the hose off and smell for gas and look for wetness.

 

I ended up replacing the complete fuel rail/injector setup. After I put it back together and tried to get it started it wouldn't. So I removed the plugs and found they were pretty fouled up and very wet from flooding, so I replaced those and the car started right up and ran like normal. I didn't have time to take it out for a test run so we'll see when I do tomorrow.