1.6 16v has slight stumble

[ramm440]

Hi I am new to this site and was hoping you could offer a best guess to my problem. I have a Samurai that I put a 1994 1.6 16v in and recently barely failed emissions due to high nox. (The nox was close too passing) I followed the advice and was able to clear the EGR passageway which was plugged and now pass a stall test. The valve passed the hold vacuum test also. This vehicle has a hollowed out cat and I know thats a no no! I have a new cat and will install it along with a new O2 sensor I bought. The question I have is the engine has a little above idle stumble when I let out the clutch and take off but it only occurs during take off like under a load. I disconnected the vacuum line to the EGR valve as a test and the stumble is gone.
Do you think the new cat will take care of this issue because there now be more back pressure?
If the cat does not solve the stumble issue would it now be reasonable to suspect that the EGR valve may have a weak spring causing it to open
pre-maturely?
Thanks for all advice

[fixkick]

welcome, all Suzuki and Geo's are
welcome,

Hi I am new to this site and was hoping you could offer a best guess to my problem.
I have a Samurai that I put a 1994 1.6 16v in and recently barely failed emissions due to high nox.
(The nox was close too passing)
I followed the advice and was able to clear the EGR passageway which was plugged and now pass a stall test. The valve passed the hold vacuum test also.
This vehicle has a hollowed out cat and I know that's a no no! (that kills EGR 2ways (TWC nox funcition in cat) and kills back pressure to EGR modulator.

I have a new cat and will install it along with a new O2 sensor I bought.

The question I have is the engine has a little above idle stumble when I let out the clutch and take off but it only occurs during take off like under a load.
Be sure to calibrate the TPS correctly. but this can be the EGR messing up.
I disconnected the vacuum line to the EGR valve as a test and the stumble is gone. (with it sucking air or plugged up that hose?)
Do you think the new cat will take care of this issue, because there now be more back pressure? (yes, the ECU is tuned for working EGR)

If the cat does not solve the stumble issue would it now be reasonable to suspect that the EGR valve may have a weak spring causing it to open
pre-maturely?
Thanks for all advice

I dont think that spring is weak..
The EGR mod is not working now or is acting wrong or weak.
A good cat will , wake up this old EGR mod and it will work if the red vent path is clear.
the mod never goes bad, just the vent paths can get dirty.
NOX 101:
if the engine is running good, holds closed loop at idle and light flat steady foot cruise, the engine nox will be very low (out to CAT)
and what remains the CAT eats all that up (catalyzes it)
see this guy get NOX 24 and then next guy 1 ?
http://www.fixkick.com/smog/smog.html

the state laws are loose for NOX, one state allows. 800ppm. huge, amounts, and even a weak cat can pass that.
a new cat will zero it. or close if the EGR works, and The EGR modutator works (live test passes)
the 1990 car is not even tested for NOX. (no TWC)
but your's is. and at 25mph on tire load rollers....
Get smog passing first , i bet the tiny hicup's end.




GOOD LUCK!

[ramm440]

So I installed the new 3 way cat and new Denso PnP O2 sensor went to emissions and the readings were:
HC .80 allowable 3.00
CO 6.84 allowable 25.00
NOX 1.23 allowable 4.50
The testing dude only made it into 3rd gear and the dyno test shut down and was complete real short and passed! I still have the off idle sputter and it disappears if I disconnect the vacuum line going to the "P" side of the modulator and do not plug it. So right now I am try to clean the modulator as best I can and hope this cures it. I will find out tomorrow. Any more suggestions for the slight stumble that seems to be caused by the egr opening too soon? How do I calibrate the TPS?

[fixkick]

great news, you're clean ! not too bad for old car, no"?
and thanks for posting numbers, we love hard numbers !
1.3ppm nox, is very low.
the P nipple is plenum side, pulling it, kills egr. (egr is strongest for more load, on engine, the more violent the PUTT the more flow)

yes, it might be hidden some other problem?
id need more info on exactly when the stumble happens, moving in what gears, or if it stumbles even in neutral parked?
1ST post said moving, off from start.
things to try that are cheap
Techron fuel injector cleaner in the tank (I DONT LIKE any additives) but this one is good. its just benzene, a very powerful clearer)
egr MODE, off the lid (mark P on base or P side is lost) clean filter there , just beat it up and dust falls out. then find that red path hole and blow on it
an it must free flow air. if not the RED path is blocked.
the red path blocked causes a very bad failure mode. it allows the EGR mod to stick full on. causing too much egr flow.

last:
TPS might be bad or calibrated wrong.
or your egr main spring theory? i dont think so but fate wins and im wrong.

[ramm440]

great news, you're clean ! not too bad for old car, no"?
and thanks for posting numbers, we love hard numbers !
1.3ppm nox, is very low.
the P nipple is plenum side, pulling it, kills egr. (egr is strongest for more load, on engine, the more violent the PUTT the more flow)

yes, it might be hidden some other problem?
id need more info on exactly when the stumble happens, moving in what gears, or if it stumbles even in neutral parked?
1ST post said moving, off from start.
things to try that are cheap
Techron fuel injector cleaner in the tank (I DONT LIKE any additives) but this one is good. its just benzene, a very powerful clearer)
egr MODE, off the lid (mark P on base or P side is lost) clean filter there , just beat it up and dust falls out. then find that red path hole and blow on it
an it must free flow air. if not the RED path is blocked.
the red path blocked causes a very bad failure mode. it allows the EGR mod to stick full on. causing too much egr flow.

last:
TPS might be bad or calibrated wrong.
or your egr main spring theory? i dont think so but fate wins and im wrong.

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Thanks I'm am most happy to pass too! As for disconnecting the vacuum line the engine will stumble just above idle when moving and in neutral. It's much more noticeable when moving or under load. Is the TPS a much involved test? Thanks again this is excellent help!

[fixkick]

stumbles parked? really? in neutral?
94 engine off a USA car? i have no idea what ecu you run in this sammi.
the 1994 was the first year, for many models to have the new rule for egr , to not open until driving faster than 1mph.
to test this theory ( software) is easy if the VSV opens at idle and egr moves, its an early ECU. early EGR rules.
the later cars, the EGR is dead at idle, not moving and dead wide open throttle.
the early cars, egr will flex (main) gunned at idle.
the red line vent must not be blocked.
the tps is easy.
the tps , you use 3 feeler gauges, go , no go and calibrate. it the switch delays opening at tip-in throttle, the idle controls will cause a fight
with your right foot, imagine you tipping in throttle easy, and the ISC fighting you like that, it feels real weird.


http://www.fixkick.com/sensors/tests/TPS...tml#matrix

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[ramm440]

stumbles parked? really? in neutral?
94 engine off a USA car? i have no idea what ecu you run in this sammi.
the 1994 was the first year, for many models to have the new rule for egr , to not open until driving faster than 1mph.
to test this theory ( software) is easy if the VSV opens at idle and egr moves, its an early ECU. early EGR rules.
the later cars, the EGR is dead at idle, not moving and dead wide open throttle.
the early cars, egr will flex (main) gunned at idle.
the red line vent must not be blocked.
the tps is easy.
the tps , you use 3 feeler gauges, go , no go and calibrate. it the switch delays opening at tip-in throttle, the idle controls will cause a fight
with your right foot, imagine you tipping in throttle easy, and the ISC fighting you like that, it feels real weird.


http://www.fixkick.com/sensors/tests/TPS...tml#matrix,

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Great results with cleaning EGR modulator stumble is gone!!! The Tiny hole must have been causing it to run so shitty once EGR was cleaned but it runs great now with EGR hooked up. Thank You! I hope someone else is able to fix theirs as easy as mine was.

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I used carb cleaner and hooked and blew through all ports which musta cleared something

[fixkick]

wow, that is great. news.
it is amazing how a small vent can be such a big pain.huh?
one drop of dust per day.
but your egr defeat test found it...
happy trails.

[ramm440]

wow, that is great. news.
it is amazing how a small vent can be such a big pain.huh?
one drop of dust per day.
but your egr defeat test found it...
happy trails.

4 wheeled all day today still no stumble! Amazing like you said that tiny ?:/-() could cause me stress. Thanks for pointing out all the possibilities.

[fixkick]

keep that 17mm front pulley bolt tight. and it will run strong.

good luck to you!