Hey all,

This is a second post for my problem as it's been a long time since I last posted about it. Some of you may remember my problem from the previous post.

Basicly, my car is sputtering like a mofo. A couple of weird oddities I've noticed however; it only does it REALLY bad at 4700 rpm and up. By really bad I mean like absolutely no acceleration and funny noises from the exhaust, like a rapid pusling noise. Hard to explain. I also noticed that exactly when the sputtering happens, my fuel pressure starts bouncing from about 80-90 psi very rapidly. If I continue to hold the gas down and make it sputter longer, the fuel pressure drops, and I sometimes get a backfire. Immediately after a sputter-session, I get a blinking CEL. Pocketlogger shows 2 error codes... ignition coil B and multiple cylinder misfire.

I have already replaced the ignition coil twice, and cleared the ECU. I've also changed the plugs (twice) and the plug wires. I followed the coil wires to the ECU to look for shorts. No such luck. I've looks for boost/vacuum leaks and there don't seem to be any. Boost does hold steady on my mechanical gauge, even while in the sputter-zone.

Previously, turning up the boost made the problem worse. Now it has little effect. I've had my car diagnosed by several professional mechanics, and no one has any idea whats wrong. I've checked about everything I know how to check (coil,plugs,wires,map sensor, O2 sensor, cam angle sensor, crank pos. sensor) and I am just really confused.

I am concerned about the fluttering fuel pressure. I don't think thats supposed to happen, and it may be the source of the problem. It kind of feels electrical, so I replaced the fuel pump. That made no difference so if anyone wants a Walbro 255HP, let me know. The way I see it, the only thing left that could cause a fuel pressure flucuation of that magnitude (at least 10 psi + or -) would be the fuel pressure regulator (SFMU in my case). Other than an actual malfunction of the regulator, only a massive flucuation in air pressure to the regulator could cause a deviation in fuel pressure like this. I really don't think thats the case here. I checked all the screws on the SFMU, and inspected the diaphragm for tears. It all looks good. WHAT THE HELL IS CAUSING THIS??? Please help guru's, I've been trying to fix this POS for like 4 months now.

THANKS!


1996 Eclipse RS / 5-Speed / Aerogear Body / Coated in Magnetic Red Metallic rev.2 / T3 Turbo Intercooled @ 8 psi / More at http://home.insightbb.com/~eclipse2nr/
Mark Galyan - Indianapolis, Indiana

If you're positive that the boost pressure is steady while the fuel pressure is fluctuating then it has to be a problem with the SFMU. When its working properly you should see the fuel pressure rise in direct proportion to your manifold pressure.


95 Eclipse RS : 5 speed
15.7 @ 87.9mph
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

Is 80-90 PSI the right ballpark for Fuel Pressure? I know nothing about the subject and that's why I wondered if that wasn't just an easy solution only a noob would see. If that is acceptable fuel pressure then disregard my idea. Also do you have a cat on the car still? Think maybe it's clogged?

I'd check your MAP sensor and it's wiring again.

The car will run with it completely unhooked, but you will be stuck in open loop, it will run rich, the timing will not be advanced much, and the RPM's will be limited. The exact RPM that it's limited to I can't remember.

Nathan you and I have the same problem and what we have in common is our "custom" bleed valve. I find that when I make a straight to 15psi pull from 1st gear, the car would start to misfire because of the engine being flooded with fuel. However, no matter how much i adjust it, it just keeps on happening. I believe the problem lies somewhere within the sfmu, not how it works, but how we rigged it up to work. I don't believe our "custom" bleed valve is working too well. I think it's not bleeding the pressure quick enough to close the diagphram. It's like haveing a 3inch dp mated to a stock exhaust system. The pressue is jammed for that moment, that the diagphram opens up and allows all that excess fuel to fill the engine, causing a misfire. Almost like the sfmu is seeing more than your preset boost pressure. I spoke with 1bill the other night and the best thing is maybe to get an ignition amplifier like the msd.

Originally posted by DSMRoadster
Nathan you and I have the same problem and what we have in common is our "custom" bleed valve. I find that when I make a straight to 15psi pull from 1st gear, the car would start to misfire because of the engine being flooded with fuel. However, no matter how much i adjust it, it just keeps on happening. I believe the problem lies somewhere within the sfmu, not how it works, but how we rigged it up to work. I don't believe our "custom" bleed valve is working too well. I think it's not bleeding the pressure quick enough to close the diagphram. It's like haveing a 3inch dp mated to a stock exhaust system. The pressue is jammed for that moment, that the diagphram opens up and allows all that excess fuel to fill the engine, causing a misfire. Almost like the sfmu is seeing more than your preset boost pressure. I spoke with 1bill the other night and the best thing is maybe to get an ignition amplifier like the msd.

I am not running the bleed valve right now. I tried to use it, but it didn't make any difference. Oh, and the map sensor... I logged the map voltage with my pocketlogger, and its working fine. In boost, it shows a constant 93 kpaA, atmospheric pressure. So the missing link is working fine too.