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2G Is the base timing really adjustable on a 95 GSX?

GSXRunner

Proven Member
150
33
Feb 24, 2013
Queens, New_York
I can't seem to get a definitive answer on this. I've always assumed that it was fixed because it is hidden behind the cam sprocket. However, I watched one of Jafro's videos
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According to him (at the end of the video at 6:25) it can be adjusted by loosening the screws and sliding the sensor forward or backward. When I replaced this sensor, I just bolted it on without any regard to its position because I assumed it wasn't adjustable. After all, how could you set it without running the engine and using a timing light when the sensor is buried under the cam sprocket? It's a conundrum. Is there some paint mark that I was supposed to set it to when I installed it? or is Jafro mistaken?:confused:
 
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GSXRunner

Proven Member
150
33
Feb 24, 2013
Queens, New_York
WOW. So there's not a single person that has an opinion or concern on this?
 

19Eclipse90

DSM Wiseman
5,309
1,177
Sep 29, 2003
OKC, Oklahoma
He's not technically incorrect. But the amount you'll actually be able to adjust it ought to be minimal. The specification is 5 degrees, plus or minus 3 degrees. I wouldn't expect you'd be able to mount it outside of this range regardless of how much you move the sensor. Hence the statements you see about it being "fixed". I've never tried to move the 2Ga sensor around to check just how much of a range it might have in its different installed positions.

My $0.02.
 

GSXRunner

Proven Member
150
33
Feb 24, 2013
Queens, New_York
He's not technically incorrect. But the amount you'll actually be able to adjust it ought to be minimal. The specification is 5 degrees, plus or minus 3 degrees. I wouldn't expect you'd be able to mount it outside of this range regardless of how much you move the sensor. Hence the statements you see about it being "fixed". I've never tried to move the 2Ga sensor around to check just how much of a range it might have in its different installed positions.

My $0.02.
So it is adjustable then? If this is true, then anyone replacing the sensor would have to move it to the correct position before tightening the bolts, which I'll assume was set at the factory. Does this mean there is a paint mark which shows where it's supposed to be tightened? I'm not looking to alter the factory setting; I just want the stock 5 degrees. The reason I brought up this topic is I thought it was fixed and just bolted it on the last time I replaced it, so the angle is randomly set. Had I known this, I would have set it correctly when I replaced it.
 

Mello

15+ Year Contributor
1,484
642
Jul 4, 2003
Albuquerque, New_Mexico
By design the 2G (A or B) timing is not adjustable. There is a little bit of wiggle with the bolts in the holes (which are not slots) but it's not enough to make any timing adjustment. I have no idea what Jafro is talking about.
 

19Eclipse90

DSM Wiseman
5,309
1,177
Sep 29, 2003
OKC, Oklahoma
You could take a moment to check your ignition timing and see where it's actually at. And then worry about it if it falls outside of that original specification. My money bets it won't fall outside of spec.
 

steve

DSM Wiseman
15,010
1,809
Feb 3, 2002
Boulder, Colorado
it does not adjust timing like a distributor, because ya know, its not a distributor.

the ecu sets base timing. The coils firing is not manually adjustable

I'd word that a little differently.

The ECU drives the timing but it relies on the Crank and Cam sensors to know where TDC is. On those engines where you can adjust the sensors you need to do so, so that the ECU matches the actual position.

That's what your doing when you set the base timing, synchronizing the ECU to the mechanical position.
 

Mello

15+ Year Contributor
1,484
642
Jul 4, 2003
Albuquerque, New_Mexico
Mitsubishi made the 2G's with a separate crank sensor on the crank and the ecu using it with the cam sensor to synchronizing the ignition & fueling events. 1G's crank & cam sensors are packaged together and need mechanical adjusting with the timing mark on the balancer to set crank position for the ecu.
 

GSXRunner

Proven Member
150
33
Feb 24, 2013
Queens, New_York
The whole reason why I brought up this topic is because I think I have a possible valve timing issue and I want to minimize as many variables as possible.

Here is my dilemma. Hunting down a random misfire that occurred sometimes when driving, never while idling, among other things I replaced my CPS. This did not clear up the problem, however, I started to notice when idling, I'd get a random stumble from the exhaust. I held a paper towel by the exhaust and every now and then it would suck the paper towel in. This could only happen if an exhaust valve wasn't completely sealed on an intake stroke. I did a leak down test and found less than 5% on all cylinders; so my valves are all sealing well. Interestingly, I'm getting acceptable compression, but readings are not consistent when repeating readings on the same cylinder. It could be because it's a cheap HF compression tester, but assuming it's not the tester, I have come up with a theory based on this evidence.

Since the leak down test shows perfect sealing and the test is independent of timing belt issues, yet the compression test which relies on the timing belt keeps varying in psi, I'm thinking that either the timing belt is stretched or the tensioner loosened or weakened and is causing the play in the belt to move around, which is then intermittently shifting the valve timing, thus giving me an intermittent leaking exhaust valve. When I replaced the CPS, I had to pull on the belt a little to get the old one out and the new one in and in the process I may have created an issue, either with the belt or the tensioner.

I checked the base timing using a timing light with and without the connector grounded. Either way the timing jumps around and is impossible to read. If I pull the injector connectors off and just roll the engine with the starter, I get approximately TDC using the timing light. BTW - I am aiming the light at the marks of the cam sprockets, rather than the crank pulley.

Right now I am using a cheap amazon timing light, which I don't really trust and I'm supposed to get a "better"(?) one in today; but I'm not holding my breath. Based on what I am seeing, the belt/tensioner is prime suspect and a full inspection of the timing belt is warranted; but I will be checking the timing again with another supposedly better timing light before I go in for the kill.
 

chrysler kid

20+ Year Contributor
2,613
579
Dec 20, 2002
Mckinney, Texas
The whole reason why I brought up this topic is because I think I have a possible valve timing issue and I want to minimize as many variables as possible.

Here is my dilemma. Hunting down a random misfire that occurred sometimes when driving, never while idling, among other things I replaced my CPS. This did not clear up the problem, however, I started to notice when idling, I'd get a random stumble from the exhaust. I held a paper towel by the exhaust and every now and then it would suck the paper towel in. This could only happen if an exhaust valve wasn't completely sealed on an intake stroke. I did a leak down test and found less than 5% on all cylinders; so my valves are all sealing well. Interestingly, I'm getting acceptable compression, but readings are not consistent when repeating readings on the same cylinder. It could be because it's a cheap HF compression tester, but assuming it's not the tester, I have come up with a theory based on this evidence.

Since the leak down test shows perfect sealing and the test is independent of timing belt issues, yet the compression test which relies on the timing belt keeps varying in psi, I'm thinking that either the timing belt is stretched or the tensioner loosened or weakened and is causing the play in the belt to move around, which is then intermittently shifting the valve timing, thus giving me an intermittent leaking exhaust valve. When I replaced the CPS, I had to pull on the belt a little to get the old one out and the new one in and in the process I may have created an issue, either with the belt or the tensioner.

I checked the base timing using a timing light with and without the connector grounded. Either way the timing jumps around and is impossible to read. If I pull the injector connectors off and just roll the engine with the starter, I get approximately TDC using the timing light. BTW - I am aiming the light at the marks of the cam sprockets, rather than the crank pulley.

Right now I am using a cheap amazon timing light, which I don't really trust and I'm supposed to get a "better"(?) one in today; but I'm not holding my breath. Based on what I am seeing, the belt/tensioner is prime suspect and a full inspection of the timing belt is warranted; but I will be checking the timing again with another supposedly better timing light before I go in for the kill.
I dont have the factory service manual memorized, yet, but it should cover cam sensor replacement and have notations of how to correctly install the sensor if it does require adjusting.
 

Mello

15+ Year Contributor
1,484
642
Jul 4, 2003
Albuquerque, New_Mexico
Your description of the misfire you have makes me lean towards an ignition of fueling problem but not a TB mechanical problem. I would be checking things like plugs, plug wires, coils, PTU, injectors, & injector wiring. Are the plug wires arching on anything? TB is in tension while running and the valve events aren't changing from revolution to revolution. What make is the replaced CPS (Crank Position Sensor? Cam Position Sensor?).
 

GSXRunner

Proven Member
150
33
Feb 24, 2013
Queens, New_York
Your description of the misfire you have makes me lean towards an ignition of fueling problem but not a TB mechanical problem. I would be checking things like plugs, plug wires, coils, PTU, injectors, & injector wiring. Are the plug wires arching on anything? TB is in tension while running and the valve events aren't changing from revolution to revolution. What make is the replaced CPS (Crank Position Sensor? Cam Position Sensor?).
I never made the claim that the misfire was caused by a belt issue. In fact, the random misfire isn't even my concern right now. My main concern is the exhaust sucking in air.

The plugs, wires, PTU, coils were all replaced and the plugs are firing. The injectors are working perfectly. The sensors I have checked with an oscilloscope and the signals are perfect.

The belt issue came AFTER I replaced the CPS as I explained and I did put some tension on the belt to get the CPS out/in so that may have been the cause. So far everything points to a belt issue. An ignition problem isn't going to cause the exhaust to suck in a paper towel. Only an exhaust valve that is not sealing on an intake stroke would do that. I ruled out a leaking valve with a leak down test (less than 5% leakage). So either an exhaust valve is sticking (I doubt it with less than 5% leakage) or there is an issue with the belt. A compression test shows different readings every time on the same cylinder, which I would expect to happen if the valves weren't closing at the right time. I'm thinking the gap in the tensioner widened when I installed the new CPS and so the belt is giving me unstable timing. Since the crank drives the cams, if there is a little slack in the belt, the cams will lag and that lag won't be constant. So imagine at the end of an exhaust stroke, the exhaust valve should close by TDC, but if there's a lag, due to slack in the belt, the cam will keep the exhaust valve open a little past TDC, which is the intake stroke. Obviously that would suck in air from the exhaust. The fact that I'm getting unstable timing readings with the timing light only presents more evidence on my thesis.
 

Mello

15+ Year Contributor
1,484
642
Jul 4, 2003
Albuquerque, New_Mexico
Since the crank drives the cams, if there is a little slack in the belt, the cams will lag and that lag won't be constant.
This is not correct. The crank pulls the cams (& oil pump). The only slack in the timing belt is between the crank & exhaust cam. Exhaust cam to intake cam, to oil pump, to crank is in tension (no slack) and does not fluctuate. You can only pull a rope, not push it.
 

GSXRunner

Proven Member
150
33
Feb 24, 2013
Queens, New_York
The only slack in the timing belt is between the crank & exhaust cam.
That's exactly what I mean. If the tensioner is not tight, it will bounce as the slack is taken up from the tension of the crank. Remember that the tension varies due to valve springs fighting one another. This will most likely cause the timing to be unstable and would SOMETIMES cause the exhaust valve to be open SOMETIMES on an intake stroke, causing the exhaust to SOMETIMES suck in air.
 

steve

DSM Wiseman
15,010
1,809
Feb 3, 2002
Boulder, Colorado
This will most likely cause the timing to be unstable and would SOMETIMES cause the exhaust valve to be open SOMETIMES on an intake stroke, causing the exhaust to SOMETIMES suck in air.

Check out cam overlap, it's actually normal for both the exhaust valve and the intake valve to be open at the same time and the main reason you can't do a boost leak test at TDC. On a stock DSM Turbo 4G63 it's about 30* of overlap.


There is little play to be had but you're correct that the cam and crank can shift somewhat do to the harmonics of the belt. It's not much but does happen and is thought to be one of the causes of the random misfire fault on 6 bolt swaps.

If you had 30* of belt vibration it would pop off and valves would crash.
 

GSXRunner

Proven Member
150
33
Feb 24, 2013
Queens, New_York
I'm aware of the fact that there is some overlap, but when the piston just starts its travel down on the intake stroke, there is not enough vacuum to overcome the pressure from the hot gasses that were just released from the exhaust, at least not enough to suck a paper towel into the exhaust. Now if there is enough shift of valve overlap do to the flexibility of a belt that is not tight enough, the vacuum could be strong enough (at least in theory) to pull in a paper towel.

I'm only going on theory here. It's the best exclamation I could come up with based on the evidence I'm seeing. Do you have any other ideas why a paper towel will SOMETIMES be sucked into the exhaust? Remember, the head has less than 5% leakage across all cylinders and when the engine is running, the timing jumps all over the place with the timing connector grounded. Isn't the ecu supposed to not intervene with the timing when the connector is grounded? Shouldn't I be getting 5 degrees timing, being that timing is fixed on this engine? If you have any other ideas of what could cause this exact phenomenon, I would love to hear them.

I know this video is not of a dsm and I'm sure I don't have anywhere near this much slack, but it's interesting to see what a loose timing belt looks like when it's running. I bet you the timing mark would be all over the place on this engine and the exhaust would probably suck in a paper towel.
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GIB

Probationary Member
18
2
Jul 9, 2012
Chicago, Illinois
I can't seem to get a definitive answer on this. I've always assumed that it was fixed because it is hidden behind the cam sprocket. However, I watched one of Jafro's videos
You must be logged in to view this image or video.

According to him (at the end of the video at 6:25) it can be adjusted by loosening the screws and sliding the sensor forward or backward. When I replaced this sensor, I just bolted it on without any regard to its position because I assumed it wasn't adjustable. After all, how could you set it without running the engine and using a timing light when the sensor is buried under the cam sprocket? It's a conundrum. Is there some paint mark that I was supposed to set it to when I installed it? or is Jafro mistaken?:confused:
It's not adjustable to make any "fixes" to the sensor behind the cam. The 1g style that sits on the passenger side is adjustable. I've never fixed my cam issues on the sensor behind the sprocket.
 

pauleyman

DSM Wiseman
8,451
2,958
Nov 19, 2011
oklahoma city, Oklahoma
I'm aware of the fact that there is some overlap, but when the piston just starts its travel down on the intake stroke, there is not enough vacuum to overcome the pressure from the hot gasses that were just released from the exhaust, at least not enough to suck a paper towel into the exhaust. Now if there is enough shift of valve overlap do to the flexibility of a belt that is not tight enough, the vacuum could be strong enough (at least in theory) to pull in a paper towel.

I'm only going on theory here. It's the best exclamation I could come up with based on the evidence I'm seeing. Do you have any other ideas why a paper towel will SOMETIMES be sucked into the exhaust? Remember, the head has less than 5% leakage across all cylinders and when the engine is running, the timing jumps all over the place with the timing connector grounded. Isn't the ecu supposed to not intervene with the timing when the connector is grounded? Shouldn't I be getting 5 degrees timing, being that timing is fixed on this engine? If you have any other ideas of what could cause this exact phenomenon, I would love to hear them.

I know this video is not of a dsm and I'm sure I don't have anywhere near this much slack, but it's interesting to see what a loose timing belt looks like when it's running. I bet you the timing mark would be all over the place on this engine and the exhaust would probably suck in a paper towel.
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I think you're over thinking this. I've seen many cars including dsm exhibit this behavior. There was nothing wrong. Your initial question was the 2ga cam sensor adjustable. No it isn't. I would suggest a new thread for further discussion on a different topic.
 

Mello

15+ Year Contributor
1,484
642
Jul 4, 2003
Albuquerque, New_Mexico
Years ago the "dollar bill" test was a scam trick used to get work. At idle there is not enough exhaust gases to fill the exhaust system making it low pressure. When the pressure gets low enough the dollar bill gets sucked into the exhaust and the pressures equalize with the outside air; then the cycle resets and starts again. You can stop the paper towel from getting sucked into the exhaust if you shove a potato up it, otherwise use a compression or leakdown test to diagnose things.
 

GSXRunner

Proven Member
150
33
Feb 24, 2013
Queens, New_York
otherwise use a compression or leakdown test to diagnose things.
Read the thread and you'll notice that I mentioned several times that I did a leak down test, which turned out less than 5% leakage (about what a brand new engine would read) and I did a compression test that had acceptable numbers, although I would get inconsistent readings on cylinders.

Now a potato, I haven't tried that yet. :hmm:
 

We're on Boost

15+ Year Contributor
1,641
454
Aug 25, 2007
Seattle area, Washington
it's a cheap HF compression tester,

I hope your leakdown tester is not also a cheap Harbor Freight one. They sold a really crappy one for a while.
Just to clear this up, could you tell us the make and model of your leakdown tester?

Crappy tester:
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Good tester:
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GSXRunner

Proven Member
150
33
Feb 24, 2013
Queens, New_York
I have that OTC tester. I also have that old HF tester which I retired many light years ago.
 
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