Hey guys....
I'm about out of ideas on this one, and before I throw some $$$ at the problem, I thought I'd see if anyone has seen this before.

I've got a freshly rebuilt J20, 2.0L DOHC engine (less than 100 miles on it), out of a 2000 Tracker.

After the rebuild, it starts and runs fine, but has a low idle (~650-700) and a slight/decent miss at both idle and higher rpm's.  Occasionally it will not want to start at all, and might take 4 to 5 tries before it does.

Even though it's missing, it is NOT throwing a code.  I did get it to throw a code once (random/multiple missfires), but I believe it only did that because I disconnected the harness off of a couple of coil packs while it was running to see if I could single out a cylinder.

I've replaced (well technically I didn't replace them, but they are brand new):
Coil Packs
Plugs (w/ iridium's)
Cam sensor
Fuel filter

Cleaned the IAC, EGR and tube.
Tested IAC operation.
And I've OHM'd out all the major sensors that weren't replaced (all within specs).
OHM'd the injectors (all good)
Test fuel pressure (good at ON / IDLE / shut off)
NOID checked the injector harness
Tested continuity between injector harness and ECU
Tested continuity between ignition harness and ECU
Cleaned and verified all the engine/harness grounds
And I've played swaptronics with different parts trying to get the missing to follow the part, but no good.

I put an O'scope on the injector lines at both the ECU and the injectors, and I'm seeing a nice steady firing pulse in both spots.  At this point, I know the injectors OHM'd good, but am seriously thinking about just replacing them.  The truck does have 190K on it, so probably wouldn't hurt, BUT it's still a couple hundred $$ and I hate throwing money at a problem unless I know it should fix it.  Unfortunately, I don't have a test rig to test the complete operation of the injectors (fuel spray pattern / flow testing).  I know they're getting a good pulse, they ohm good and I can hear them clicking nicely away ( using a stethoscope ).  I've taken them out and tried cleaning them a couple of times, but still no good.

The ONLY other things I can think of are:
Fuel pressure regulator.  I tested line pressure before the fuel rail, so I guess it could be the regulator
OR
I might have some bad gas in the tank.  The truck sat for a couple of weeks at the old owners house before I got it, and then it sat for a month or so while I got things together for the rebuild.  After I got it running I did go fill the tank.  I suppose it possible that either I got some bad gas, or maybe, for whatever reason, the PO poisoned the tank with something.
OR
Bad ECU.  I'm not seeing anything odd on the scope though, and other fuel related functions, like the high rpm to low rpm fuel injector cut off (shuts the injectors off when throttle is closed above 3K rpm until rpm drops to below 1K rpm), is working correctly.

At any rate, before I go get new injectors, anyone have any ideas about this?  I'm pretty much boggled....
Thanks for the help!   
NV

Vacuum leak?

Vacuum leak?

DOH!

I should have mentioned that i checked for that too.  While running I sprayed starting fluid over the intake side of things.  No changes in idle speed or rpm.
NV

I wonder if you're getting insulation breakdown in the ignition noise suppressor.  Its near the battery, and has a Black/white wire and a Black wire.  If you disconnect the wires and the problem goes away....

Run it and immediately pull the plugs, noting carefully their individual condition. Try narrowing down your prob to a specific cylinder in other words and go from there.    Fuel delivery or spark issue?    

Suggest a cylinder leak down test after that in an attempt to locate a possible weak one.

Smoke of any nature out of the oil fill cap or tailpipe? 

when the rebuild was done could the timing belt had been installed one tooth off??

Maybe it is the iridium plugs.  Mine ran horrible on some of the fancy ones.  I just get cheap NGK's now.

I've been running Iridiums for two years w/no problems. 

Hey guys!

Thanks for all the input....   sorry for the delay getting back to you, but we're just back from a 3200 mile (WELL OVERDUE) vacation around Montana, Wyoming, South Dakota, Wyoming (again) and Idaho!  Here's a quick sample....   
(bonus points if you can tell me where we went     )







They seem to be pondering something.... but I'm not sure what.....  hmmm....





But....getting back on subject...
Let me address all the input:
Noise suppressor:  no change..   

Cylinder leak down:  well I have the tester.... but it's a fresh rebuild, so no I haven't checked that...  but I did notice black plugs (fuel) across the board.  No smoke.

Timing belt tooth off:  2.0 has 2 timing chains.  I followed FSM to the T, and manually spun the motor probably 10 times to verify correct chain position and always coming up dead on when coming back to TDC....

Iridium plugs:  I've swapped out for new NGK's with no change.  Although it IS interesting to note the while the FSM initialy insists on irdiums.....  buried deep inside it DOES say that NGK's are better at lower temps...   

I should mention that I did find one f'up on my part....  usually Zuki is pretty good about one plug will only fit one sensor....but I discovered that the fuel tank pressure regulator plug will also fit the fuel tank purge valve and vice verse....  much better operation after correcting....

but still running poorly... soo.....

Since I got back, I had a long talk with SWMBO.... we both agree...  the truck has 190K on it... BEFORE I take it to the dealer ($120 just for diagnosis), I should replace everything that should be replaced at 190K anyways.... so....

I replaced the cheapest thing I thought it might be first....  the fuel pressure regulator.  Which didn't fix the issue  BUT....  it does run a bunch better.... still missing, but not quite as much....

But tonight I ran the truck for about an hour, with in-line spark checkers installed, noid lights on all injectors, AND I had my o'scope (with new and improved FSM o'scope reference traces to refer to    ) and I'm not seeing anything odd.

BUT!!!  I did pull the spark plugs and found them to be pretty much fuel fouled!  So this is definitely a fuel issue (or so I hope)

I'm thinking leaking injectors....

So taking this back to troubleshooting 101..... 

The engine does not miss at idle while cold...  makes sense... the ecu is already telling the engine to be rich  (increase injector pulse) and is adjusting the IAC to make up for that and for any 'extra' leaky fuel.....  when it warms up, the ecu reduces the IAC air and cuts back on injector pulse, but injectors are still leaking.  So now the engine is getting proper amount of air for a warm engine, the injectors are getting the correct pulse, but since they are leaking, mixture in each cylinder is hit and miss....always a bit rich....but not quite enough to trip the O2 sensors..... (car still isn't throwing a code unless I pull connectors and plugs...)....
So.....  I threw money at the problem...
I ordered rebuilt injectors from rockauto.com  $32 each plus core, so about $200 before core return.  Since I'm more than a bit miffed at myself for not figuring this problem out, I put them on 2 day shipping.....  You guys (and the guys at the Zuw) will be the first to know if this fixes it....
IF it doesn't....  the truck will go to the local Chevy dealer next week.  I went down and made a drop off appointment today.  Interesting conversation....
Service gal got all the basic info, and then called the "national awesome technical person of total awesomeness of mechanical ability" to come over and talk to me....
(him. me)
Rebuilt huh?  yep.
Do it yourself?  yep.
Should've had us do it.  Uh....no
MIL on?  (techno speak for check engine light) No the Malfunction Indicator Lamp is not displaying a code
Oh
Broke the t-chains?  Yep.... (detailed the whole story of the car and what I've done)
You're not like most of the people the bring their cars in.  Thanks!
You set the timing? (ah, trick question.... the lay person would normally need the Suzuki "Scan Tool 1"...  Yep, installed bypass jumper and it's within spec.
Oh
Uh.... bring it in and we'll see what we can find.
(me to service lady)... so if you can't figure it out, there's no charge right?
(waiting....waiting ....waiting...turns to other service guy) well?   pause.....  "oh we'll find something"
me... ya.. that's what I thought....

So I'll post in a couple of days when I get the new injectors installed....  I do hope this fixes it.  I'm REALLY tired of working on this.

But HEY....  it's STILL cheaper than a new car payment!

NV

Curious...the engine IS coming up to normal (proper) temperature, right? Correct thermostat operation, allowing for optimum performance and satisfying all sensor / ECU temperature requirements, in other words?

Curious...the engine IS coming up to normal (proper) temperature, right? Correct thermostat operation, allowing for optimum performance and satisfying all sensor / ECU temperature requirements, in other words?

Yep.... that's what was really odd about this....

BUT.... see my next post!

Hello!

Well I have good news!!  As my last post stated, I threw some $$$ at the problem by ordering all new injectors.  I installed them, and while the truck ran a LOT better, it was still missing.  However, the truck was now throwing a CEL every time I ran it    Just the random multiple misfire.  I did a bunch more googling and came across a SINGLE post on one of the suzuki car domain sites about a tracker misfiring.  They ended up replacing a mechanical part to fix it.  So I dug out the FSM and started going through all of the troubleshooting stuff again.  I realized that there was one item I hadn't tested..... the 'camshaft synchronizer'.  This is basically the housing that the cam position sensor sits in, and has magnetized points on a disk on the end of a shaft that is connected to the exhaust cam shaft.  As the disk rotates with the cam, the points pass under the sensor sending a position pulse back to the ecu.  Going through the testing procedure revealed that the sensor was not always sending a pulse when a point passed under it.  Since this was basically the very last piece I could replace before taking it to the dealer, I went ahead and ordered it.  I got the part at NAPA (listed as a crank synchronizer) for about $120.  I got it installed last night, and the truck is running perfectly!!   
Why did it fail?  I'm not sure, but here's my theory......  these engines are known for killing the cam sensor with heat.  I'm thinking that for 10 years and 185K miles that magnetic disk has been going through a hot-cold-hot-cold cycle....  My thought is that this cycle caused some, if not all, of the points to lose enough of their magnetism, that they didn't always trigger a position pulse for the sensor.  Not enough to always throw a CEL, but enough to make the ecu not fire random cylinders..... 

So now all that is really left is to make sure the timing is set correctly.  This does pose a slight problem as the FSM calls for either using the Suzuki Tech 1 tool (~$1300    ] ) or jumping the 'monitor plug' to make the ecu fire #1 at TDC, you then adjust the position of the cam synchronizer to get the proper timing.... pull the jumper and you're good to go.  Since I'm not going to buy the Tech1 tool, I thought I'd use the jumper..... except I can't find the plug.  For right now, I'm assuming that everything is working correctly, and figure that if the timing is correct, the RPM should be what the FSM says it should be.... so I adjusted the synchronizer until the engine is at 750rpm. 

Here's what the part looks like:



Yes, it comes with a new cam sensor as well....  so now I have a spare 

I know I might have been able to save some cash by not replacing the injectors, but the truck has about 185k or on it, so they were probably ready to go away....  and the new ones should last quite a while.

So....  even with the new injectors, pressure regulator and synchronizer, I'm still only into the engine about $2k....  but the truck should last me another 10 years or so....   

Thanks for all the suggestions and help, and I hope maybe this info will help someone else out in the future!

NV

That's proly the #1 part failure item over here (along w/02 sensors) on the 4-banger and is well documented on "the other" forum. Typically they die when hot only though.

It's gotten so bad / prevalent that you can buy "reman" ones now!

Glad you got it sorted out.