2G Problem

[madracer247@aol]

Ok i just got my car out for its 6 bolt swap and everything is good but i noticed whe i go on the freeway and keep it at a constant RPM like in 4th at 3000 rpm for about a min or so it starts to bog out and it gets a little shaky. Do you guys have any ideas,I have hks 272's, eliminated Balance shafts, prothane motor mounts i know these things add vibration but can this be the problem.

 

[JuiceGsTurbo024]

Does your Check Engine Light come on? and does the car lose any power? it might be bad wires or spark plugs! check that and if thats not the problem you might have a boost leak does not sound like it would be a boost leak but who knows! check one thing then another! thats how you fix your car! well good luck and get back to us! latez!

 

[Agent Ezzard]

What you are experiencing is the notorious Random Misfire condition that happens to some 2Gs when a 1G cam angle sensor is used for crank angle input on 2Gs (ie 6bolt swap). The only real cure for this is to either get a standalone or the next best thing to it which is a DSMLink. The DSMLink has a function designed to inhibit the ECU's ability to look for a random misfire. I had this same situation when I got my first 6 bolt, but I read up on it before the swap and new of its possibilty to occur. I have also done the Magnus Potentiometer mod which I have had success but I didn't keep it on for long due to lack of engine monitoring ability at the time. I have also disconnected the TPS or Throttle Position Sensor and I put over 20K (mostly highway) miles on my car using this method before finally getting a DSMLink without having the RM happen. The downsides to having no TPS input is under rapid deccelaration the engine has a tendency to stall out. Like braking right after the 1/4 mark at the track and when using an S-AFC you cannot have any Hi settings. Visit the Magnus website for more info on RM.

 

[Scrymerr]

I have had the POT mod on for about 6 months with no problems at all.

 

[Silver2GST]

What you are experiencing is the notorious Random Misfire condition that happens to some 2Gs when a 1G cam angle sensor is used for crank angle input on 2Gs (ie 6bolt swap). The only real cure for this is to either get a standalone or the next best thing to it which is a DSMLink. The DSMLink has a function designed to inhibit the ECU's ability to look for a random misfire. I had this same situation when I got my first 6 bolt, but I read up on it before the swap and new of its possibilty to occur. I have also done the Magnus Potentiometer mod which I have had success but I didn't keep it on for long due to lack of engine monitoring ability at the time. I have also disconnected the TPS or Throttle Position Sensor and I put over 20K (mostly highway) miles on my car using this method before finally getting a DSMLink without having the RM happen. The downsides to having no TPS input is under rapid deccelaration the engine has a tendency to stall out. Like braking right after the 1/4 mark at the track and when using an S-AFC you cannot have any Hi settings. Visit the Magnus website for more info on RM.

I have one question: Is the Random Misfire CELs that occure after a 6-bolt swap a real misfire or just something about the 1G CAS that the 2G ECU thinks is a misfire, and then throws the code?

I was starting to think that if it is just a CEL then how would the RM affect the cars handling or performance? Or does the 2G ECU retard or limit the car after throwing that code? Or does the car really misfire?

The reason i ask is because i have just swapped a 6 bolt engine into my 1995 GST and it misfires (you can hear it hiccup) at idle and its pretty damn random. i hooked up my datalogger and the only code i got was IAC (idling at 1100 RPM because the engine shakes the car pretty bad at 750 RPM) and P1400 (EGR, i have a blockoff). No random Misfire code, but i'm misfiring. i used a '94 black top CAS.

My O2 sensor is dead, i'm still trying to tune the MAFT and my ignition timing isn't perfect so alot of things could cause that misfire. if thats the case and i don't throw the actual CEL then it sounds like i might have beat the RM problem with my 6-bolt? it doesn't happen all the time correct?

 

[Silver2GST]

Did you guys rotate the injector wires 90* like RRE's website recommends? It says to rewire the injectors 1>2 2>3 3>4 4>1 ... did it help? How did you guys dial in your timing? on my datalogger the timing jumps around alot. is there a way to disable the ECUs advance to set the timing correctly like on 1Gs .. what did you guys do?

Sorry about all the quuestions, im trying to tie a few loose strings up and have the car running nicly! THANKS for your help in advance!!!

 

[myblack98gst]

I think what you are feeling IS the missfire.. mine did it, but was bad enough the car just started missing completely till I shut it off and restarted.. I did the POT mod and have not had a seconds trouble for a month now.. the mod WILL make the car run leaner so you will have to re-tune but it is worth it..

I THINK the only ones you have to switch the injectors/ coils on is the 95-96 model.. because their angle sensor is 90* out from the 97-99 sensor..

I have put ?? 13,000 miles on a swapped car and the injectors ar hooked up normally and the wires are hooked up factory style..

 

[blackGSX2g]

I'm very interested to hear more about the injector/coil switch. I'm about to drop a built 6-bolt in my '95, and for some reason I can't log on to Magnus' website. Anymore info on this?

 

[Silver2GST]

I'm very interested to hear more about the injector/coil switch. I'm about to drop a built 6-bolt in my '95, and for some reason I can't log on to Magnus' website. Anymore info on this?

Basically the plug wires are real easy, just swap the wires from one coil pack to the other. from left to right the wires use to be { 4 1 } { 2 3 } now you will make it like this { 2 3 } { 4 1 } ... that has to be done on any year 2G.

At RRE's website under the CAS section you will see where they mention that the injectors are 90* out on the 95-96 ECUs. Now its not a big problem they say but they mention it will allow the car to start and idle better and overall run smoother. you'll need the ECU pin out from www.vfaq.com but basically you have to rearrange the injectors like so:

Injector wire 2 becomes injector 1
Injector wire 3 becomse injector 2
Injector wire 4 becomes injector 3
Injector wire 1 becomes injetcor 4

Check it out on RRE just be sure and to get the wire colors. I haven't fixed my dead o2 sensor and have not done the injector wire swap but plan on doing both tomorrow

 

[blackGSX2g]

Alright, so you don't HAVE to do the injector wire swap but you do have to do the plug wire swap.

Doesn't sound hard, thanks.

 

[myblack98gst]

how is it that you have to swap the plugs to the different cylinders.. yet my car has been running for this long hooked up the right way????????

98 gst
I used a 2g coil pack.
90' CAS

 

[Silver2GST]

I think this may only apply to 95-96 turbo DSMs. RRE has explained it alot better then i can so check there. www.roadraceengineering.com or close to that

 

[Silver2GST]

Just in case you don't want to look it up i'll post it here:

"Due to the inverted Cam signal, injector trigger wires will need to be switch on 95-96 year ECU cars with this wiring diagram in order to bring the signals back into phase. The difference is subtle, but the motor will start easier, provide smoother idle, and have less hesitations during mild acceleration.

Use the following diagram: http://www.vfaq.com/mods/ecu-harness-2G.html

When removing the pins on your ECU wiring harness be patient and delicate. It requires no force to remove the pins. Consult the diagram in the front of your electrical service manual regarding the proper way to inspect and remove pins. You will need a tiny jewelers screwdriver, (1/16 in) to release a plastic catch holding the pin's in. Use a flashlight and take a good look at the harness before beginning.

Green: Pin 1 is now 14
Green w/ yellow stripe: Pin 2, is now Pin 1
Green w/ red stripe: Pin 15, is now Pin 2
Yellow w/ black stripe: Pin 14 is now Pin 15

The spark coil signal is inverted. Looking at the coils, label each wire A,B,C,D. Change the spark plug wire locations: A is now C, B is now D, C is now A and D is now B. Another way to do this is to change the trigger wires to the coil, (3 wire triangle plug, next to the igniter). Switch the two blue wires. One is blue with red stripe, the other is blue with black stripe. The third wire that remains unchanged is black with white stripe.

Don't take shortcuts in the quality of your connections. Solder everything. Use shielded cable if possible. Do not use wire taps. "

There you go ... ...

 

[blackGSX2g]

Sweet, thanks alot! I'll probably do that tomorrow before I start droppin in the 6-bolt.