FC RX-7 V8 swap assistance (also HP Tuners help): Grassroots Motorsports forum: Grassroots Motorsports Magazine

Subscribe get a full year for only $23.95 Sample Free Test Drive—no strings attached

Oct. 20, 2010 9:12 a.m. dyintorace SuperDork

So I've having some issues with my FC RX-7 convertible V8 swap. The car will start and run, but, after a few minutes of running, especially under throttle, it starts to bog down and eventually simply dies. It won't restart for some time, but, eventually will restart and run again for a few minutes. Given my low level of mechanically know how, I'm scratching my head when thinking about what the issue could be.

One thing I would like to check is to see if any fault codes are present. The PO, who performed the swap, used HP Tuners and told me the computer is "unlocked". He installed a port under the steering column that should allow a laptop to be plugged in, but I'm not sure what to do from there.

Some background on the swap. It is a 2005 L33 5.3L V8, a T56 and an ECU from a 1998 F-body. Evidently that ECU was particularly useful, given that folks figured out how to unlock it.

Does anyone have any HP Tuners experience? Any suggestions are welcomed!
Oct. 20, 2010 9:52 a.m. 2002maniac HalfDork

I'd put a fuel pressure gauge on it and make sure the pump isn't crapping out.
Oct. 20, 2010 10:01 a.m. RossD Dork

My thought was along the same lines, fuel lines that is: where they replaced with larger ones?
Oct. 20, 2010 10:16 a.m. pres589 HalfDork

My first guess is fuel; what's the pump like, the feed lines to and from the regulator (I assume this uses a bypass style fuel pressure regulator at the fuel rail) and what sort of filter is in use.

Would be curious what the hall effect sensors are like after they get warm, like the camshaft position sensor, I've seen this a couple times on cars in shops I used to work in where a tech would let the car get warm and it dies. They then use a blow gun & compressed air from the shop compressor to blow cooling air on the camshaft sensor. If doing that while having someone crank the car allows the car to start, they'd start digging to see what the signal out of the position sensor is like.

But I think the smart route would be to get a fuel pressure gauge, tap the test port on the fuel rail, and see what sort of pressure is getting to the rail before going further.
Oct. 20, 2010 1:04 p.m. dyintorace SuperDork

Thanks guys. I'll start by looking into the fuel pump, fuel pressure, fuel lines, etc.
Oct. 20, 2010 1:42 p.m. dean1484 Dork

Does i have a catalytic converter on it? If so see if ti is clogged. I have seen many a cat killed (taste like chicken) while tuning a vehicle.
Oct. 20, 2010 7:32 p.m. dyintorace SuperDork

dean1484 wrote:

Does i have a catalytic converter on it? If so see if ti is clogged. I have seen many a cat killed (taste like chicken) while tuning a vehicle.

I don't think it does, but I'll check again.
Oct. 20, 2010 7:50 p.m. Appleseed SuperDork

LS motors still use mass airflow sensors? I had an LT1 with a bad one that was sending input to the EMS that it was flowing 3 times the amount of air that it actually was, so it was dumping 3 times the amount of fuel into it. It was flooding the engine.
Oct. 20, 2010 10:39 p.m. RexSeven Dork

Well, you've crossed the canoeing line, that's for sure...