Try Ack's FAQ for Tracker factory service manuals, I'm not certain if they have for your model but they might.

 

Thanks! I think I found something that will help but if someone can eli5 that would be great.

I forgot to mention it idles and revs perfectly, it just doesn’t switch between the two well at all

 

Update: TPS tests good.

Is there a chance it’s my ecu? I’m running out of ideas so please anyone help!

 

Is your check engine light on with the key on, and off once the engine starts? Do you get a code 12 from the ECU? The ECU in the 89/90 vehicle, as far as I know, does not intricately monitor spark. How have you determined that the engine ‘literally stops firing’ when you have your issue? During that hesitation, do your revs drop (do you have a tach??)? If, for example, your radio is on, do you lose connection during that hesitation, which might indicate that this is an electrical issue? How have you determined that this is not a tranny hesitation?

 

That’s a great idea, I’ll test that next!

I don’t hear the engine actually combusting (exhaust noise dies)

No codes but I haven’t put many miles on it, gonna drive it for a while and check again

 

Took it for a good drive- still no codes.

I realized I haven’t checked the valve lash yet- could that cause the engine to die right at throttle? This happens no matter what rpm

 

And it’s definitely the engine or possibly something to do with the trans. Revs do drop immediately with pedal push and then after one second or less climb as they should. If you very very slowly press the accelerator it doesn’t do it. Does not go away with ac/radio/lights running and no interference with any electrical components

 

Here’s what it looks like from the interior (Ignore the noise of the fan pulley rubbing on the belt cover)

 

Are you pressing on the gas pedal while in neutral, and the rev goes up slightly (about 400 rpm or so) and then jumps up further (while your gas pedal remains in the same position I)??? If so, I would suspect that perhaps you have a dead spot or issue in your throttle position sensor. The purpose of that sensor is to signal the ECU as to the position of the throttle, and the resistance in that sensor should ‘sweep’ according to the ‘sweep’ of the gas pedal as you continue to slowly depress it. It appears from what you say that the slow sweep is working as it should, but when you quickly rev the engine it ‘hesitates’ and then catches. As you are in neutral now, this would not be a tranny issue. There are tests you can do with a voltmeter on the TPS, with it still in place in the car. The TPS often needs to be calibrated for idle. Your idle appears to be ok, so disregard the first test below regarding resistance between C and D. See if the resistance between A and D, and B and D have the correct resistance. A=grey/red, B=grey and D=grey/yellow. However, if these tests pass, then we can do a fast ‘sweep’ (better if you have an analog ohm meter as the sweeping needle is easier to see), and we can try sweeping quickly to see if the TPS has any dead spots. Doing the calibration is a bit more detailed, so maybe start with the two resistance tests below first.

 

TPS tested good under this criteria minus the sweeping test. If it were a dead spot on the TPS would it effect it at any rpm? This happens even at 3000 RPM while driving

Good to know it’s not the tranny.

 

It’s not the tranny if you confirm that the above video is done with your engine in neutral, and confirm my impression of what was happening in the video……your gas pedal in one position, the rev goes up about 400 rpm and then jumps up, correct???

 

Confirming all the above.
The same thing will happen while driving at any rpm if I take my foot off the accelerator all the way and put it back down

 

One other question. You say in your first post that this happens after it warms up. So it does not happen when the engine is cold???
The TPS calibration for the 8v engine is in post #7 here:

https://www.suzuki-forums.com/threads/code-44.280030/?post_id=1636671#post-1636671

This basically calibrates the idle switch. But rather than locking down the TPS when your ohms first register, instead continue to sweep the TPS counterclockwise, and confirm that the sweep of the TPS conforms with the sweep of your ohm meter. See if the ohms hesitate, even though you are still sweeping the TPS (which would basically mimic what is happening with the rev vs your gas pedal position).

 

I’ll try this next!

I did set the tps and idle according to that process so we should be good there. I check resistance along the TP opening but wasn’t looking for dead spots, just rising resistance.

When I had the tps loose I did sweep it all the way and the engine would die at one spot but I can’t remember where. Would that be where the dead spot is or was I just pushing the throttle plate shut?

 

You do the TPS calibration with the engine off normally. It’s very possibly that you may have been hitting a dead spot by doing that with the engine running. I’d try the calibration by sweeping slowly, the first time, which is the way that it’s normally done. Then bringing the TPS all the way back clockwise to start again, and then attempt to recreate your rev hesitation by sweeping faster to see if the TPS can keep up.

 

for the TPS sweep test, try to use an analog voltmeter with a needle, not digital. even a very cheap analog will be better than digital

 

I’ll order an analog ohm meter and let you know how it goes!

To elaborate- I did the engine-on sweep before calibrating the tps engine-off so it’s set right where it should be as of now.

I could order a $250 tps for tomorrow from Oreillys?

 

Update- I back probed the tps on the output side and the voltage increased even at the dead spot. It did this every time and I tested it many many times.

is there a chance this is a computer issue? Could it be the vacuum advance on the distributor?

 

I doubt it’s a computer issue. There are a number of circuits that could cause a hesitation….from a clogged fuel filter to an EGR circuit that needs cleaning, etc. I’m not quite sure how you accomplished the TPS test…..normally you’re testing the sweep on the TPS with ohms, not voltage.

 

I tested the TPS Iike usual (measuring resistance with the engine off) and then confirmed that it was operating correctly by measuring the voltage on the output side while it was running

 

There’s a fairly definitive list of the various circuits you should test, in order to find your issue: https://axleaddict.com/auto-repair/Why-My-Engine-Hesitates-During-Acceleration
You can disregard #7, 8 and 10, as they don’t relate to your engine. Sadly, this hesitation/stumbling at low rpm is not something that has just one potential cause.

 

Update: I'm an idiot.

After looking over the engine a thousands times I just noticed the PO drilled holes in the top of the airbox. I taped them off and the problem almost completely went away. I ordered a used airbox and will reset everything once I have that installed.

Thank you so much for your help guys. Sorry I'm blind.

 

PO drilled holes in the top of the airbox.

it's a classic "engine will breathe better = free power" urban myth....

 

I’ve seen in a thousand times on motorcycles. I work at 5000+ ft and people don’t understand that it’s not their airbox that’s making their engine run shitty, it must just need a bunch of red dirt to score the shit out of your cylinders!

 

work on motorcycles too.... classic "more powa" bonehead mod

 

Okay so I’m still having the same problem. I’ve tried everything on fixkick and maybe I’m not understanding the sort-of broken-English/confusing orders it’s written in but I can’t fix this issue

IAC tests good but when I try to set the duty cycle using a multimeter the % jumps all over the place. I can get it to around 100Hz and that sets my idle at 850 but it still has the same issue as before. I’m about to drive it off a cliff

The TPS is new and set properly. There don’t seem to be any air leaks. Timing is right on. Everything else that’s supposed to be checked is checked.

Could it just be the ECU is broken?