Mitsubishi 3000GT & Dodge Stealth Forum banner
1 - 14 of 14 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter · #1 ·
So when I’m driving the car and it’s in 4th gear and I’m going around 40mph the car bogs down even on flat land. Not to mention when I let off the gas it backfires. But when the car is above 3500rpm none of the it runs better.

Ive replaced the plugs, wires, distributor cap and rotor, injectors, fuel filter, and the pcm for the car and it still has a weird idle and bogs down.
 

·
Registered
93 NA ATX 3000gt DOHC
Joined
·
4,174 Posts
To me it sounds suspiciously like a timing issue or a fuel delivery issue or injector leaking flooding at idle and low RPM’s.

Being that you’ve already changed everything dealing with fuel delivery (except for cam sensor), You should check spark advance first (easiest), with timing light for 15° BTDC at idle on #1 cylinder. If that’s off by more than distributor slot adjustment allows, distributor could be off by a tooth or more. But if off a lot I’d suggest to first check the mechanical timing of cams to the crank, there’s a chance timing belt has jumped few teeth at crank or cams.
 

·
Registered
93 NA ATX 3000gt DOHC
Joined
·
4,174 Posts
I think you are right the right side is 2 teeth off from where I should be.
By saying right side if you mean looking at timing belt side, that would be back bank which drives the distributor. So if crank is on TDC that means not only is valve timing off on that bank of cylinders but ignition timing is also off on all cylinders, because the distributor if not timed to crankshaft.

Below is diagram for mechanical timing belt timing on SOHC engine.



Crank shaft belt cog gear demple mark lined up with raised indicator on oil pump housing.
 

·
Registered
93 NA ATX 3000gt DOHC
Joined
·
4,174 Posts
I think you are right the right side is 2 teeth off from where I should be.
Just looked at zoomed in version of your pictures, the below right side looks to be off way more than 2 teeth. See below image of timing mark circled in red and dimpled gear tooth circled in yellow.

Either your crank wasn’t on TDC of compression stroke of #1 cylinder or you’ve got a major mechanical timing issue. I suspect you didn’t check it correctly, because I’m not sure engine would run correctly above 3500 rpm as you indicate with that cam 7 teeth off.

Also, keep in mind when talking about right and left side of engine, it’s when viewing from transmission end. So in 3S cars with transverse engines right side is front bank closest to radiator. That helps when understanding timing belt installation procedure from manual above with diagram showing gear marking from belt side, when they say left or right cam sprocket it’s actually opposite sprocket as what you’re looking at.

 

·
Registered
Joined
·
11 Posts
Discussion Starter · #9 ·
I did just recheck the timing on the cam gears and they are in time but I can’t check the crankshaft to make sure that’s good. I did start the car with covers off and they don’t seem to be balanced very well.
 

·
Registered
93 NA ATX 3000gt DOHC
Joined
·
4,174 Posts
I did just recheck the timing on the cam gears and they are in time but I can’t check the crankshaft to make sure that’s good.
The Crankshaft being at TDC of #1 is the most important thing! It’s imperative the cams are in time to the crankshaft. Not the best practice but you can get general idea by turning crankshaft manually, until notch in harmonic balancer edge is lined up with the “T” on advance indicator on lower cover (see below picture of notch on 5° BTDC) just before the “T” which is TDC for #1 cylinder. But keep in mind cams turn once for ever 2 turns of crank, so if cams are about half way around you’ll have to turn crank one more rotation.
Click on image to enlarge

I did start the car with covers off and they don’t seem to be balanced very well.
Not sure what you mean about “don’t seem to be balanced very well”. Do you mean belt is floppy and cam gears jerky?

After all this I’m assuming you didn’t bother to check spark advance with timing light as I suggested first being the easiest starting point.
 

·
Registered
Joined
·
11 Posts
Discussion Starter · #11 ·
I haven’t got a chance to check that since I don’t have a timing light yet, but do you have any idea where the cam sensor would be located? I can’t seem to find anything on it, but there’s diagrams for the crank sensor.
 

·
Registered
93 NA ATX 3000gt DOHC
Joined
·
4,174 Posts
................... but do you have any idea where the cam sensor would be located? I can’t seem to find anything on it, but there’s diagrams for the crank sensor.
Cam sensor is incorporated into distributor, I don’t know if it is replaceable without replacing the entire distributor:unsure:. Prior to ’97 model SOHC engines both sensors were in distributor, they moved the crank sensor to same location as DOHC engines in ’97-’99, but still left the cam sensor in distributor.
 

·
Registered
Joined
·
11 Posts
Discussion Starter · #13 ·
Just did an oil change and the car has copper flakes coming out so I think that means camshaft/crankshaft bearing if I’m not mistaken. So I think I just need to do a full rebuild at this point.
 
1 - 14 of 14 Posts
Top