Some of you know me others don't. I was an S2000 pilot for awhile. Have driven other cars and now I own the soul of an S2000. It sits in a Lotus 7 clone with total weight of 1400lbs. You would think it would be sick fast but engine issues are keeping my eyes for peeling off of my head. Any local engine experts?

Here's the info:
New plugs and MAP sensor
Honda S2000 ECU
Fuel is getting to the engine
Not getting fuel back into the return line on the tank
donor car 2002 w/ 48K miles
aftermarket gauges and speedo (still having speedo issues)

Engine starts and idles w/o issues
Under light acceleration engine will pull fine sometimes bucks
Will slowly climb to 9K seems to pull better at 7K, not sure if VTEC is kicking in. Been awhile since I drove an S2000.
On highway engine will lose power and slowly drop, blipping throttle does not help, most allow it to idle down before applying power.

Could lack of return fuel indicate not enough fuel? If so why does it seem to pull stronger in the upper RPMs?

Would non-functioning speedo impact ECU? Limp mode? What is limp mode and what does it limit?

Thanks

Pictures soon.

 

Limp mode limits the max RPMs, IIRC. I think it limits them to 3K or somewhere around there.

I've never experienced it, but I believe there's also a "free-rev" limiter. Basically, if you are revving the engine high without load (or while not in gear), then the ECU will drop the revs back down. Sounds similar to your highway experience. I don't know anything about the triggers for this, and I've only heard rumors that this actually happens, because I don't personally know anybody that would sit there free-revving their engine for any length of time.

BTW... it sounds like you need to get an OBD2 datalogger and start monitoring your ECU to see what it sees and get a better idea of what may be the problem.

Also, if you don't get an answer here, you may want to get this thread moved to Under The Hood, as there are a lot of knowledgeable people over there, and probably someone has seen this exact issue.

 

It is not limiting the revs, just hesitates and blogs down. At 1400lbs I should spin the tires when I floor it but does not, it just climbs out of the hole.

 

Ahh... I must've misunderstood your comment above^.

 

I'd start by troubleshooting that return line. If the fuel pump is fine and the return line isn't blocked, you should be getting plenty of return fuel. Fix the known problems first, and they often eliminate the unknown problems.

Is there a port on the fuel rail for a pressure gauge or a fitting you can tee off of? I'd hook up a gauge and do some research to see if the rail is seeing the proper pressure as well.

 

It is the stock S2000 engine. Not sure if a port exist.

 

There should be a maintenance port you can use. If you have a Helms, you can probably look at the procedure for replacing a fuel filter and it will tell you to loosen a particular maintenance plug on the fuel rail before removing the filter. You should be able to plug a fuel pressure gauge in there.

This is all an assumption, though, because I haven't done this on the S2000, but that's the way it works on my Accord.

 

Found it in the Helms, thanks.

 

Whatever you do, don't get frustrated and sell the car.

 

B&M makes cheap easy to install fuel pressure gauge. Here it is installed on my ex S2000. I agree with Altian, fix the knowns and the unknowns will often fall in line.