MPI relay? SAFC dead, car idles, runs very rough

[manrightchea]

Well, where do I begin with this car.. Ok I recently finally finished my 1G CAS swap and the car was running like ass. Found that injector wires at the ECU harness weren't getting continuity, so I fixed that issue and it ran decent for a while. The other day I was driving, car dies all of a sudden and I swing it into a business driveway that God must have ordained for me to see. Pop the hood, and the ENGINE fuse (or MPI fuse for the 2G as I've been told) is blown. I take a 30 amp from some random accessory to limp the car home. I take a look at all my ECU wiring and underhood wiring, but can find no bare wires grounding. I start the car the next day, and the idle is terribly low. I drive the car and get a major stutter at about 3000rpm that the car does not seem to be able to bypass. About 30 - 45 minutes into the test drive, the fuse blows again. This time the SAFC dies with it, car runs like ass and I have to limp the car home again, it runs similarly to how a car runs after you've blown an intercooler pipe. Car doesn't rev over say 2500 rpm. I do my research and notice that the ENGINE fuse is also referred to as the MPI fuse. So first I diganose the SAFC, and notice that all of the wiring is still intact from the install, it just doesn't come on. I've checked and recheck for a grounded wire but have not been able to find any as of yet. Tomorrow I will pull the rear seat and check the fuel pump rewire.

So at this point I suspect one of the two relays under the center console, mainly because researched showed that they were the fuel pump and MFI relays. When I pulled the one on the left, the car wouldn't start at all (as if it has a bad starter), when I pull the one on the right, I notice it idles and revs in the same fashion as before, so I suspect this relay. When doing my CAS swap earlier I noticed a third triangle shaped plug down there by the timing cover area. When I pulled it and reinserted it, I heard a buzzing sound. I just recently did this again the other day when I still have both of those relays connected, but I didn't hear that buzzing. I know it was there before. This may seem trivial but I'm beginning to believe that the buzzing has something to do with the fuel pump.

This is basically where I am at this point. Dp either or these relays control the ECU? Any idea why the SAFC went out? Any help is greatly appreciated.

 

[manrightchea]

Well?

 

[manrightchea]

So does anybody have any idea what blew to cause my SAFC to die and my car to idle and run terribly? I it won't rev past 2000rpm. I just don't know what to do with this car anymore.

 

[kahl23]

There is a way to check those fuses. As you can see, I thought my MFI was dead. Turns out it wasn't, one of my crimp connectors had pulled out underneath the dash. Pull it and test it. Listen for the clicks.

http://www.dsmtuners.com/forums/problem-diagnosis/263224-mfi-mpi-relay.html

 

[manrightchea]

I appreciate your response but I believe that MPI relay is for the 95 model only. I spent all of yesterday looking for this issue, mainly because someone said something of the MFI or MPI powering the ECU and in turn the AFC. Problem is, there are so many different people saying the MPI or MFI is this or that. I looked for the one in your pic, but its not there in my car. The mounting area is not even there. At this point, I am not even sure the ECU is seeing power. I have tried my eprom ECU and my stock one. They both do the same thing. So at this point I doubt its the ECU. I've checked the CAS, have fuel pressure and spark, compression is 182 all the way across, timing is dead on. It idles which is better than nothing, but misses and won't rev past 2 grand. I'm about to go check the entire ECU harness for 12v at the pins and see if that will show me something.

 

[manrightchea]

AHH! Nevermind, I found what was broken...my common sense! Unbeknownst to me, my harness to the SAFC had disconnected from the daughterboard inside the case itself. So you know the engine was running with a good bit of necessary signals missing. I swear sometimes I can be so smart and so stupid! Even so, I can't help but feel relieved that my car is back.

 

[steve]

The only signal you loose is the MAF when the SAFC doesn't run.
The fact that the car idled was proof that the MPI and fuel pump relays (and the fuses the attach to) worked. That pretty much left a bad SAFC power connection or dead SAFC.

 

[kahl23]

Why is it that you always discover it's the simple fix after going through all the hard work?

 

[92awddsm]

Why is it that you always discover it's the simple fix after going through all the hard work?

Because it is a dsm and everyone always expects the worst.

 

[kahl23]

Touche