Hot misfire

[wheelz]

I had tried to search this topic but came up with nothing that relates to the issue. I was a mitsu tech for 2 years in a dealership in South Dakota, but have never came accross a problem this indepth.

I am working on a 1997 GST. The car only has 933 miles on a fresh, 2.3L strocker 4g63. With a 60 trim turbo and a SAFCII. Every sensor seems to be working ok, but after the motor gets to full engine temp, it begines to misfire and want to die. Extra fuel does not help or less fuel for that matter. I have swapped the air meter, and the ignition module, same results. I am not sure of what area to go after next. I am sure it is something electrical just unsure what.

Any and all help would be great. Thanks in advance!!

 

[Patterson]

u check the timing?

 

[blue92laser]

timing belt, exhaust cam?

 

[wheelz]

The timing is perfect. The car will misfire only when it is hot. Even when it misfires, i can shut the car off for 2 minutes and it will start up and run great. That is what makes me thinking it is electical.

If there is a theory behind the exhaust cam timing, please tell me how that would work and create a misfire.

 

[wheelz]

ttt

has anyone every heard of this??

 

[wheelz]

I am running out of ideas to try, i have now changed the cam sensor, and the coil pack with no luck, this is starting to get really expensive.

Please any help will be great!!

 

[Old Mitsu Tech]

Unfortunately in this day and time everything begins with a computer scan for any existing codes. CEL or no CEL you have to scan for codes. If no codes I would use a scanner and check parameters of the sensors while in open loop (cold engine) and again when the engine is messing up. Use the flight recorder mode to possibly help you pinpoint the source of the misfires. Good Luck

 

[Ultimatedsm]

I had tried to search this topic but came up with nothing that relates to the issue. I was a mitsu tech for 2 years in a dealership in South Dakota, but have never came accross a problem this indepth.

I am working on a 1997 GST. The car only has 933 miles on a fresh, 2.3L strocker 4g63. With a 60 trim turbo and a SAFCII. Every sensor seems to be working ok, but after the motor gets to full engine temp, it begines to misfire and want to die. Extra fuel does not help or less fuel for that matter. I have swapped the air meter, and the ignition module, same results. I am not sure of what area to go after next. I am sure it is something electrical just unsure what.

Any and all help would be great. Thanks in advance!!

By any chance is it a 6 bolt? Do you have a 1g CAS? If so that is the infamous misfire you get at cruise and it feels like you are running on 3 cylinders. To cure this problem either get a DSMLINK or try this:

Problems!
IF CHECK ENGINE LIGHTS OCCUR! TRY THIS:

(Blake Heisler's Fix for misfire Check Engine Lights (CELs) when putting a 1G Cam Angle Sensor (CAS) on a 2G)

Many people using the 1G CAS on a 2G head have been running into problems with misfire engine codes while at cruise. Many different things have been blamed for this and many different fixes have been attempted.

This fix will keep the ECU from looking for misfires at all. This is the criterion that must be met before the ECU will start to look for misfires:

1. 300+ seconds of steady state RPM less than 80% throttle position

2. Engine coolant temperature -10C or higher

3. Intake air temperature -10C or higher

4. Barometric pressure greater than 76 kPa

Now if we can get one of these values outside of the criteria the ECU won’t check for misfires. The value that would be the easiest to change would be the barometric pressure sensor. We’re going to add resistance to this value so that the ECU will see less barometric pressure than what there really is. This will also lean the car out so you should see a performance increase as well. Depending on the car and altitude you might need to add more fuel with an AFC.

So let’s get started, Parts needed:

A 10K potentiometer (although a 5K would probably do just fine). These are available at any electronics store, if you go to Radio Shack ask for a volume control knob because they don’t know what a potentiometer is

Wire strippers

Soldering iron

Step 1: Remove the access panel on the driver’s side of the center console. You should now see four plugs with a ton of wires going to them.

Step 2: Pull out the top plug, it’ll be the one that’s the hardest to reach. Locate wire #85. It’s orange with a white stripe.

Step 3: Cut the orange wire in half. Solder one end of the wire to the center peg of your potentiometer. Solder the other end to either the left or right leg, it doesn’t matter which. Turn your potentiometer all the way counter-clockwise.

Step 4: Plug the harness back in and start up the car. It should sound like it did before you did any modifications. If the idle is choppy or the car won’t run you turned your potentiometer the wrong way.

Step 5: Add resistance to the barometric pressure sensor by slowly turning the knob on the potentiometer. Drive the car around; if you get a CEL then add some more resistance. Keep doing this until you no longer get the CELs.

That’s it, special thanks to Marco for pioneering this mod and to all the guys on the DSM1Gina2G Yahoo group for all the discussion, ideas, etc.

-Blake Heisler




Anyway I hope that helps, good luck on your car.

 

[Ultimatedsm]

Update us on this one. Let us know if this helped.

 

[wheelz]

Nope this is still the stock block. I have ran into the 1g head swap before, and will more than likely be doing another one soon.

As for the scan test that is the problem that i am having. I can not sneek the MUT out of the shop as easy as i use to. I was just hoping that someone has come across this before. Tonight i am going to work on it more, and starting with a the head temp sensor, and checking other sensors using fail safe mode on the ecu just by unpluging one sensor at a time to see if it will come out of it. If all else fails i will have to have towed to the shop tomarrow.

Thanks for the help so far and if i figure out what it is, i will post it on here.

 

[Ultimatedsm]

So you 2.3 stroked your 7 bolt? Usually people get the 6 bolt and stroke that. Let me know if its a 7 bolt or a 6 bolt.