The_Fox

Ok, I recently aqquired an FC3S that was running, but it back fired. A lot. After fixing every vacuum leak I could find, I was able to drive it around a bit, and it has NO POWER. Going up hills in first gear has a max speed of 10mph with my foot on the floor, and it doesn't seem to pull after 4k rpm. Car has all emissions deleted(including no cat), and the metal baffles were pulled out of the exhaust side of the irons. I've read everything I can find here and elsewhere, and I am still having trouble. Oh, and I tried adjusting the ignition timing, and the car flooded out. Now it won't start at all.

What should I be checking and looking for? More vacuum leaks? Fuel pressure regulator? New plugs?

RotaryRocket88

iTrader: (7)

Compression test: http://www.banzai-racing.com/compression_test.htm

A badly plugged exhaust system can also cause similar power loss, but it's typically a plugged cat.

TheGloriousTachikoma

The following is not directed at you, it is directed at whoever owned the car before you.

NO!!! Why do people do stuff they do not understand!?!

Now that that is out of my system;

The problem is is that people will remove all emissions equipment without understanding why. One example being people removing EGRs off piston engines, when the EGR doesn't work at WOT anyway.

Barring a massive exhaust backup as RR88 suggested, I think something in the emissions removal was fudged and the ECU is getting some seriously wrong input. If the compression was so low that the engine couldn't get the car up past 10mph then I doubt it would start or hold idle well. just to be sure, make sure the OMP lines are still there and delivering oil. One suggestion; there are two cats in the exhaust, one where joe-I-don't-deserve-a-rx7-sixpack would normally look for one, and a close-coupled unit right at the exhaust manifold. That may be plugged. Backfires are torches in the exhaust and if yours backfired constantly (from messed-up emissions equip) it could destroy a cat.

As to flooding it, hook the batt up to a plug-in charger. Remove the spark plugs, clean them well, remove the 'EGI' fuse from the fuse block, and turn the engine over for 30secs or so to dump the fuel out of the engine. Dribble a few CCs of oil into each chamber, crank it another 30secs, and dribble a few more CCs in for good measure. Put the spark plugs back in, replace the EGI fuse, and try cranking it.

The metal baffles in the exhaust ports are to maintain proper exhaust flow and a substantial power loss is seen after removing them. You'll need new irons to see proper health out of your engine even after the emissions-removal issue is sorted.

The_Fox

Both cats are gone. I checked. The good news is that I have two unmolested irons, and I may be wrong about metal baffles being gone.
Yes the OMP lines are there and delivering oil.
I will take the risk of making an *** of u and me(assume) that compression is good. It revs fine. Also, according to the videos I have seen and previous driving of this car, it ran great, pulled great. The previous owner told me that the fpr is out.

TheGloriousTachikoma

Oh well...no fuel pressure would certainly cause you to be down on power. Is this a S4 or S5? S4 you can replace the FPR as it screws onto the rail, S5 you need to cut and fabricate a mount or replace the secondary fuel rail.

Get the engine cleared and running again (standard de-flooding. No NOT use ATF, just use engine oil and hook the battery up to another running car, and turn the engine over for a minute to clear the gas. ATF attacks the rubber side seals in the rotors).

The_Fox

Motor is running. Adjusted the timing, it pulls a little better. No breaking up issues, unless I'm UNDER 2500rpm, where it WILL idle, at 1100-1200 and its lumpy at best. This only happens after it has warmed up some.

Fpr maybe? CTS? I have a spare cts, but the fpr is difficult to find, and rather expensive. Would I be able to use an adjustable fpr that I have? I will hunt a good fpr down if needed, but I don't see the hurt in stepping up to an adjustable with a gauge on it if the fpr needs replacing anyways.

TheGloriousTachikoma

Well, if the seller told you that the FPR was bad then that seems like it's the problem based on your symptoms. Like I said, if you have a S4 (86-88) then you can just unscrew the old one and thread the new one on. If you have a S5 (89-91) then the FPR is integral to the secondary fuel rail and you either have to cut it off and braze on a bung for a new FPR, or replace the entire fuel rail. But I see no problem with an adjustable unit and a fuel pressure gauge if you have spicy plans for this engine down the road.

The_Fox

Spicy? I hope for A hair over 200hp at the wheels without having to go turbo. I just spent my last two years restoring a Mitsubishi Starion, and would like to stay n/a for a bit.

The_Fox

Well I will update this thread as soon as I can get an fpr in hand and on the car, but thank you very much for the help everyone!

The_Fox

Ok, I have the adjustable fpr in hand, and have no idea where to start. Nor do I really know how to test the factory fpr...

TheGloriousTachikoma

-Well, I asked earlier, do you have a S4 or a S5? S4 is 86-88 and S5 is 89-91. In both cases, the FPR is on the secondary fuel rail.

-The difference is, as I said earlier, the S4 has the FPR as a separate component from the rail, whereas the S5 has it welded on permanently.

-The FPR is controlled by vacuum. To test it you will have to remove the intake tract and the intake manifold plenum (the uppermost of the three pieces the intake manifold comprises). This gives you access to the secondary fuel rail and injectors.
-Disconnect the vacuum line from the FPR. With no vacuum the FPR should be fully closed. Unbolt the fuel rail, carefully lift the injectors out of their bores with the rail to avoid dumping fuel all over the place. Remove the return line off of the FPR and set some container under the spout.
-I am unsure of how the S4 differs if that is what you have, but the S5 has a yellow connector around the passenger side shock tower. Bridge the two contacts and the fuel pump will full-field.
-If the FPR is functioning then there will be no fuel released from the return side. If any fuel leaks...you know your problem.

The_Fox

My apologies, I thought I had answered your question. I have an S4.
Now one question I think I know the answer to, but will ask anyways: Do I need to go get another set of intake manifold gaskets? These are relatively new...

TheGloriousTachikoma

I didn't replace mine, mainly because the one between the plenum and the upper intake manifold had become hard and completely fused to the UIM. For awhile I just left it, I never had any vacuum loss, when warm she would idle rock-steady.

RotaryRocket88

iTrader: (7)

That's a complicated way to test the FPR. Fortunately on an S4 NA, the secondary rail should clear the TB unlike on an S5 NA, which means no need to remove the plenum if you want to try that method.

If you were to remove any intake pieces, it is a very good idea to replace the associated gaskets. If they're hard enough to stick to the manifold, there's a very good chance of a leak.

The FSM procedure for testing fuel pressure requires tee-ing a pressure gauge into the fuel feed hose, and then letting the engine idle. At idle, fuel pressure should be approx. 24-30 psi (~15-20 inHg vacuum applied). With the vacuum line removed, fuel pressure should be approx. 34-40 psi. If you see the appropriate pressure change, your FPR is fine. If fuel pressure is very low, the fuel pump itself may be dying.

http://www.rotaryheads.com/PDF/2nd_g...systems_na.pdf

Fuel and emissions, 4A-67

TheGloriousTachikoma

Well, last time I had it apart I used a very thin layer of black RTV on the surfaces.

The_Fox

It seems that its just dumping fuel. But I just found something very interesting a few hours ago: The lack of any sort of gasket inbetween the intake track and the throttle body. and there seems to be air... leaking in after the air meter... hmmm...

sctRota

iTrader: (2)

I had the EXACT same problem with a FC that I purchased a while back. Look where the starter is located, the bolts that hold the starter have a BIG ground thing behind it. If that thing is loose or missing, then the car will backfire ALOT and will feel like something is plugged. Trust me, I have had this problem and this was the solution.
PM mr if you have no clue what i'm saying hehehe


EDIT: There could be many reasons, but I believe that this is the solution due to what you have been saying

The_Fox

If that ends up being the problem, you're officially my new best friend.

RotaryRocket88

iTrader: (7)

There isn't supposed to be a gasket between the TB and plenum. There should only be the black plastic throttle body spacer.

That would be the main battery ground, so if it's missing or loose, you'll have lots of electrical problems including with the ECU and its sensors.

The_Fox

You misunderstand what I said. Between the intake tract, as in the black plastic stuff coming from the filter, to the throttle body. The black plastic intake tract is warped at the throttle body, and allowing air in. I'll try and post a picture of what I mean shortly.

RotaryRocket88

iTrader: (7)

Ah, the only "gasket" at that junction is an o-ring on the TB. That black plastic elbow is hard plastic, so it'd probably take a torch to warp it.

The_Fox

Thar be an o-ring thar? I wonder if mine is actually there...

Only one way to find out!