Hi y’all. Bought my 03 R53 a few weeks ago from a friend. He bought it 4 months ago with a known bad head gasket. He pulled the head, had it resurfaced and installed all new valves. He then reassembled the top end, parked it and let me have it. He is an ASE certified Master Mechanic so I’m 99.99% sure that what he did was good.

I picked up the car on a Saturday and felt it miss before I backed out of the driveway. He said he felt the same thing and saw an error code 302 but assured me it was fine.

I drove the car 35 miles up the road and it was fine. But when I hit the interstate, it bucked several times and went into limp mode. I had it trailered home.

so, car is at home and I pulled the 302 misfire code. Replaced coil, wires and plugs. Cleared the code and it was awesome for about 5 minutes. What happens is that it is starved for power. The harder you press the gas, the slower it goes.

I replaced the fuel filter thinking it was a fuel issue. Tested the FP pressure. It hits 45psi running. Next I pulled the fuel rail to check regulator and injection seals. The FP regulator seals were leaking. So I replaced them both and the injector seals. Took it for a test drive and it was great. No codes and barking the tires 1-3.

found a barley used header on line down the street. Added that. Ran awesome but 10 minutes later I get a lean code bank 1, o2 sensor code, and 302 misfire on #2 again.

I don’t know if I’m looking for a vac leak or a fuel problem at this point. I did find a broken vac line weeks ago and have hit every visible vac hose and junction w NO results. Like I said, fuel filter is new and FP is w in spec.

also pulled TB hose and found no leaks. Air filter is new.

what next? Intercooler hoses?

 

When my fuel pump started to fail it would do almost the same thing. It would run like junk and throw lean codes.

 

See how much fuel pressure you have on your rail.

 

I have 44 psi on the rail while it is running. The book says it should be 53. But I read a lot of posts from other mini owners that say 44 is normal

I left the gauge on for 10 minutes after I shut it off. It stayed rock solid.

 

thanks for the reply chief. I’ve been reading you build thread. Your depth of knowledge about minis is astounding and you are the poster child of dogged determination

 

One more thing to note. When I pulled the fuel rail off, I notice that one of the fuel injectors has been replaced. It was on cylinder #2. I was getting a code 302 for cylinder 2 misfire. When I changed the injector seals, I moved the odd injector to cylinder #3 thinking that if it was the culprit it would foul and give me a code 303 for cylinder 3 misfire.

instead I have a 302 code (again) for cylinder 2 misfire (plus bank 1 lean code and O2 code)

 

I think I am just a glutton for punishment most of the time. I just really love that R50 for some strange reason.

 

Would the addition of the headers cause the O2 code? It has a straight pipe (no emissions here). So no cat.

it came w a bung extender but I took it off since it interfered with the installation of the rear sensor.

Both sensors are plugged directly into the header. Would that freak out the Ecu?

 

Absolutely, no CAT is a definite code generator.

You have to remember, the 2 sensors read Pre-CAT and Post-CAT, the computer them looks at that variation in those two signals to determine how to adjust the fuel trims and if there's a problem in the system.

 

[QUOTE=BlwnAway;4631988]Absolutely, no CAT is a definite code generator.

You have to remember, the 2 sensors read Pre-CAT and Post-CAT, the computer them looks at that variation in those two signals to determine how to adjust the fuel trims and if there's a problem in the system.[/QUOTE

Thanks BlwnAway for your info. It got me to thinking so I jacked up the car and put the bung extender back in (w creative application of a hammer to get the heat shields to cooperate). My thought was that by pulling the second sensor further away from the exhaust stream, it would see a difference pre and post cat. Happy to report I was right.

after I reinstalled the bung sensor and cleared the codes, the R53 ran great. I took it for a drive w mild acceleration and went out to a secluded spot and beat on it. All was good for the first 15-20 miles. Then I felt it (the ECU) start to fight me. It will do hard pulls through 3rd but also give me a bit of popping from the tailpipe.

it is a sweet gentle lady when I drive like a granny

when I got home I pulled codes and it went from 7 to 1. It’s still giving ma a 302 for the second cylinder misfire. So I’m now thinking wiring to the #2 injector or the ECU. The spark plug is new. The leads are new. And the coil is new. Plus I swapped injectors so if #_2 was bad it would have shown up on #3 (where I moved it).

any suggestions?

 

Here are the plugs from cylinders #1 & 2. #2 is definitely wet