1.6L 16V sputtering @ part throttle

[flashboiler]

Hi all, 1st time post here.

I have a 88 Samurai with a 94 Sidekick 1.6L 16V transplant.

Ran for 4 years without problems. About 1 yr ago it started sputtering when I would rapidly move the throttle. Nothing to bad but it got worse and worse. Some days it was barely there, other days worse.

Last week it got very bad, now stumbling at partial throttle w/o moving the accelerator.

I have an in-dash fuel pressure gauge and fuel pressure is good (40psi)

idle always perfect, full throttle always perfect.

So this weekend I changed:
plug wires
swapped ECU with a spare
swapped distributor with a spare
swapped mass flow meter with a spare
swapped throttle body position sensor with a spare (and ohm'd it per the FSM)
checked timing

No improvement.

I pulled codes and got 24 (vss) and 53 (bad gnd/ecu)
The vss has never been installed and it's ran great for years...

53 I swapped back to my original ECU and 53 went away.

I then put in new NGK iridum plugs and in doing discovered my air intake tube near the throttle body was loose. Now the stumble is much better but still there.

I've ordered a new Denso 02 sensor and will finally get off my butt and put in the VSS when I install the 02.

I'm at a loss. If the VSS and 02 doesn't fix it can you offer any other ideas to check?

With the leaky air tube fixed, does the ECU need time to "re-learn" the fuel mixture map? How much time? I only drove it a few miles.

Thanks for any ideas/help!

[Scudo]

VSS works off the speedo. If your speedo is dead or problematic then VSS is dead or problematic. WOT and idle require no input from VSS IIRC.

It mentions why it is sick so it is not necessary to throw parts at it.

Do all the free (free apart from your time) checks and diagnosing first and then when you have figured it out move onto repairs.

Does your speedo jump or make noise? Does it work?

[mgbgt]

Scudo,

Can you go into the speedo jumping and noise further and how it relates to the sputtering and stalling? I have a 98 Tracker 16V Auto 4WD that does the same ting thing when it's cold and it does have noise in the speedo and it does jump a little up to about 25 MPH. I just beginning to learn how to diagnose things on the tracker so this will be a learning tool for me and hopefully others.

Thanks

[xxx]

sputters , exactly when? aka; Misfire. ( 10 to 20mph, 20 to 30, 30to 40 , 40 to 50, etc, see? Tipin works at all speeds and loads, flat ground and up hills.) and is a big clue.
never cold.
never wot.
only on tip in, right? (if, yes, moving under load, right? in gear, does it misfire, at only the low end or all ranges steady cruise , the to be more descriptive of when)
sleep, before the misfires.

could be flakey TPS. ( 1 of 5 functions of TSP is called TIP=In enrich)
if you move your right foot fast , and the TPS fails to report this, AFR goes lean. (AFR means Air Fuel Ratio. or aka. fuel mix, the whole purpose if EFI is just that..... mix.)
this is aggravated by any illegal induction air leaks on the low end and the MISSING VSS (going faster with and then accelerating (tipin) air leaks are less damaging to AFR)
the VSS helps the ECU see LOAD. no vss, the ecu thinks there is no load. and will be lean. on enrich mode. i bet you have 3 issues. not one. (you did help it.... get worse)
the scan tool would show added fuel if you had an air leak with large + LTFT showing it idle and it low speeds. but no scan tool, we miss this vital fact.

at tip-in , the 02 drops out during ENRICH mode, and at wot. so is NOT IT.
at Tip-in, it's MAF input + load. ,+ RPM , +speed. and related. (AFR)!

think like this, when you move your right foot fast , downward to floor, the 02 drops out of closed loop now.
a huge air slug its the valves, nearly instantly (goes lean for sure and misfire for sure) BUT, the ECU sees this fact with the TPS< and heads off the misfire.
but activated a fast CALCULATED, enrich of the 4 injectors.
this is how it really works. (jeff hartman ,my mentor)

the learn mode is fast, and is 1 driving cycle.
once hot, its done after 1 drive.
get a scan tool and watch it and the 02 and see the ECU go lean and why.
guessing is very hard on old pre 96s... (10,000 posts to prove that, here)

read my pages on topic.
53 is corrupt memory in the ecu, (a hard dead failed ECU)
or running a cal ecu in a fed body or the reverse, my ecu dead page has the full eCu p/n pdf, read that to see why calif ecu dont work

[flashboiler]

Thanks XXX, awesome website!

I will get the VSS hooked up (actually repaired as I hooked it up originally and it didn't work) I tore into it last night and the reed switch was broken. Not sure how that happened as it's very protected in there.

[xxx]

the knee jerk $200 TPS , is costly
id use scan tool (and log the TPS data as you drive) look for glitches, or dead tps.
or DMM connected to the TPS TP PIN ,
To see, if the voltage holds steady with a steady right foot
and that it advances with right foot usage,and no glitching.
for got to say...that...

[flashboiler]

Hi xxx,

Not to costly in my case as I have a spare engine in the shed!

Could you recommend a scan tool? Are they somewhat affordable?

Thanks,
Andy

[Bex]

There is no scan tool for OBD1 computers, other than the highly unaffordable Tech 1 tool.
That being said, you can use your laptop and a software program designed by forum poster Rhino, along with hardware that you can buy from him, so that your OBD1 computer can spout out just about as much info as an OBD2 computer. Rhino's site is here:
Suzuki Diagnostics
I have purchased this, and highly recommend it.

[xxx]

you are lucky to have such a spare... very rare in the wild.
and after 20 years, long sense worn out.
but sure , try that... it might be good.

we get lots of posts here , new TPS, and after you that and its not the TPS
the $200 sounds better in your Spyder fund...

[flashboiler]

Follow up:

I tore into my speedo and found out my vss reed switch was broken. I imagine vibration got to it or maybe I broke it putting it in as it never worked. I put in a new vss and it runs great now.

Seems to have more mid throttle power now. Maybe more mileage but to early to tell for sure.

Thanks again,
Andy