Studder/cutting out on heavy gas pedal

[SmokingRocks]

I doubt its that. A starving fuel situation is not an on off feeling, plus it's a pretty rare issue in the US. I'm much more inclined to think its an intermittent ground fault in the injector wiring, much much more common of an issue.

 

[bicycleagent003]

I would unplug the O2 sensors as described above and see what happens. That is free and requires no tools or anything else. If it runs better (CEL will be on, ignore it) that will tell you a lot. I had a lazy O2 sensor for almost a year that was driving me Crazy. Replacing it solved everything. The nuts holding mine on were also totally disintegrated, I had to get creative to remove them. But if that's your problem you'll hate yourself for not having tried that sooner. I did. I was ready to give up on my truck, even the technician I took it to could not figure it out because it was very intermittent.
Good luck. Please post up your solution once you find it, for the benefit of others.

 

[Zhowardfzj80]

I would unplug the O2 sensors as described above and see what happens. That is free and requires no tools or anything else. If it runs better (CEL will be on, ignore it) that will tell you a lot. I had a lazy O2 sensor for almost a year that was driving me Crazy. Replacing it solved everything. The nuts holding mine on were also totally disintegrated, I had to get creative to remove them. But if that's your problem you'll hate yourself for not having tried that sooner. I did. I was ready to give up on my truck, even the technician I took it to could not figure it out because it was very intermittent.
Good luck. Please post up your solution once you find it, for the benefit of others.

Anyone here have a link to what o2 sensors I should buy? 1993 so it seems like there is some issues with the compatibility across the years. I mainly need a brand and part number and/or website.im going to unhook them now and see what that does for me.

 

[Zhowardfzj80]

I would unplug the O2 sensors as described above and see what happens. That is free and requires no tools or anything else. If it runs better (CEL will be on, ignore it) that will tell you a lot. I had a lazy O2 sensor for almost a year that was driving me Crazy. Replacing it solved everything. The nuts holding mine on were also totally disintegrated, I had to get creative to remove them. But if that's your problem you'll hate yourself for not having tried that sooner. I did. I was ready to give up on my truck, even the technician I took it to could not figure it out because it was very intermittent.
Good luck. Please post up your solution once you find it, for the benefit of others.

Unplugged the o2 sensors. Seemed to be running great for the first 3 or so minutes then the sputtering returned.

 

[Zhowardfzj80]

Ok since my last reply I've changed the charcoal canister, cleaned the IAC, fixed a couple more bad vacuum lines and removed the pair valve system and added the new o2 sensors there at that spot. Check engine light went away immediately without even resetting and Truck is running better overall but still has an occasional sputter. It's a way different sputter and not even at the same times or locations on inclines and such. Its more of a small and random sputter since new o2s installed and it's way less often. So my question is should I keep rolling with these o2s or eventually should I try a different brand? I'm gonna replace the fuel pump sock before I I buy new o2s but just trying to Gauge my next steps.

 

[ozarkmud]

Ok since my last reply I've changed the charcoal canister, cleaned the IAC, fixed a couple more bad vacuum lines and removed the pair valve system and added the new o2 sensors there at that spot. Check engine light went away immediately without even resetting and Truck is running better overall but still has an occasional sputter. It's a way different sputter and not even at the same times or locations on inclines and such. Its more of a small and random sputter since new o2s installed and it's way less often. So my question is should I keep rolling with these o2s or eventually should I try a different brand? I'm gonna replace the fuel pump sock before I I buy new o2s but just trying to Gauge my next steps.

I think I'd probably leave them in for now. Can baseline further and if nothing else is showing progress, then maybe do OEM O2 sensors.

Glad you're having some luck, though!

 

[TWILLY]

Ok since my last reply I've changed the charcoal canister, cleaned the IAC, fixed a couple more bad vacuum lines and removed the pair valve system and added the new o2 sensors there at that spot. Check engine light went away immediately without even resetting and Truck is running better overall but still has an occasional sputter. It's a way different sputter and not even at the same times or locations on inclines and such. Its more of a small and random sputter since new o2s installed and it's way less often. So my question is should I keep rolling with these o2s or eventually should I try a different brand? I'm gonna replace the fuel pump sock before I I buy new o2s but just trying to Gauge my next steps.

Check fusible link? They go bad, causing such symptoms. Worth replacing if you haven't.

 

[Zhowardfzj80]

Check fusible link? They go bad, causing such symptoms. Worth replacing if you haven't.

Any suggestions on checking it? Or replacing it? Part number? Website?

 

[Zhowardfzj80]

I haven't had any trouble at all starting it up. You think it could still be that?

Check fusible link? They go bad, causing such symptoms. Worth replacing if you haven

 

[Zhowardfzj80]

I think I'd probably leave them in for now. Can baseline further and if nothing else is showing progress, then maybe do OEM O2 sensors.

Glad you're having some luck, though!

Toyota dealer said they just went discontinued. No longer available.

 

[ozarkmud]

Toyota dealer said they just went discontinued. No longer available.

Might have to try another dealer or buy abroad, like Amayama or Partsouq.

 

[Zhowardfzj80]

So past 2 days has been up and down symptoms. Engine performed horribly 2 days ago, sputter all over the place. Yesterday it was pretty good. Very few sputters and felt like improving. Well this morning I hopped in it and back to sputters. I dropped the kids off and pulled over on way home and unplugged both new o2 sensors and it felt back to full power basically and not a single sputter all the way home.

 

[SmokingRocks]

You need to buy yourself an Oscilliscope and back probe your injector wires while driving. The scope will show you if there are any issues with the injectors wiring (which I'm suspecting is the issue). You can also check your O2 sensors with an O-Scope.

Otherwise you are just firing the parts cannon at it.

Here is a great website that helps you set up the O-scope for different test Automotive guided tests get a Pico 2204 or Hantek 2C42 Handheld Oscilloscope Multimeter 2 in 1

Like I said in my post on the first page this seems similar to an issue I tracked down.

IAC wouldn't cause issues at heavy throttle. I suspect there's a wiring issue, possibly injector wiring. I'd probably break out my oscilloscope and start dataloging the injectors during a pull.

I had a similar situation documented here: Calling all you Diagnostic Gurus

 

[ozarkmud]

If symptoms come back, I'm going to keep thinking it could be the fuel pump sock with intermittent low pressure. Otherwise, hopefully that did the trick!

 

[SmokingRocks]

So past 2 days has been up and down symptoms. Engine performed horribly 2 days ago, sputter all over the place. Yesterday it was pretty good. Very few sputters and felt like improving. Well this morning I hopped in it and back to sputters. I dropped the kids off and pulled over on way home and unplugged both new o2 sensors and it felt back to full power basically and not a single sputter all the way home.

It should have no studders at all, our ECU's don't learn so if it's studdering there's still an issue. It won't 'clear up' as if it were adapting.

Unplugging the O2 sensors just puts the ECU into an open loop condition where it runs a richer fuel map that also pulls timing out, basically its the 'safest map' it can run. When the O2 sensors are plugged in and functioning correctly the ECU will run in closed loop mode where it selects a fuel trim & timing from a preset table based on the data the sensors provide.

If symptoms come back, I'm going to keep thinking it could be the fuel pump sock with intermittent low pressure. Otherwise, hopefully that did the trick!

A clogged fuel pump sock or fuel filter presents as a reduction of overall power not a studder. In all the USD 80's I've worked on through the years I've never come across a fuel sock that was plugged up.

 

[Zhowardfzj80]

You need to buy yourself an Oscilliscope and back probe your injector wires while driving. The scope will show you if there are any issues with the injectors wiring (which I'm suspecting is the issue). You can also check your O2 sensors with an O-Scope.

Otherwise you are just firing the parts cannon at it.

Here is a great website that helps you set up the O-scope for different test Automotive guided tests get a Pico 2204 or Hantek 2C42 Handheld Oscilloscope Multimeter 2 in 1

Like I said in my post on the first page this seems similar to an issue I tracked down.

You think it's injector wires with running fine immediately after unplugging o2 sensors? I was thinking the other way. I was thinking this kinda eliminates other things from the equation if it's back to normal just by unplugging the sensors. Bad Plugs or injector wires wouldn't only be bad while o2 sensors are plugged in. Or a fuel pump wouldn't be giving me problems only when the sensors are plugged in. They would still show symptoms after unplugging. So I felt like it was telling me very likely sensors or ECU.

 

[Zhowardfzj80]

It should have no studders at all, our ECU's don't learn so if it's studdering there's still an issue. It won't 'clear up' as if it were adapting.

Unplugging the O2 sensors just puts the ECU into an open loop condition where it runs a richer fuel map that also pulls timing out, basically its the 'safest map' it can run. When the O2 sensors are plugged in and functioning correctly the ECU will run in closed loop mode where it selects a fuel trim & timing from a preset table based on the data the sensors provide. Thats it.


A clogged fuel pump sock or fuel filter presents as a reduction of overall power not a studder. In all the USD 80's I've worked on through the years I've never come across a fuel sock that was plugged up.

Please try what I suggested above.

You are the first person that has told me the ECU doesn't learn the trims with new sensors. There are threads on mud that guys are saying it takes 30-40 drive cycles for them to be straightened out and other guys saying need to drive it for 20 min etc. So I'm not sure what to believe at this point but many others have said otherwise.

 

[SmokingRocks]

You think it's injector wires with running fine immediately after unplugging o2 sensors? I was thinking the other way. I was thinking this kinda eliminates other things from the equation if it's back to normal just by unplugging the sensors. Bad Plugs or injector wires wouldn't only be bad while o2 sensors are plugged in. Or a fuel pump wouldn't be giving me problems only when the sensors are plugged in. They would still show symptoms after unplugging. So I felt like it was telling me very likely sensors or ECU.

Keep an eye on it, I'd be willing to bet a shinny nickle your problem come back even with the o2's unplugged. It is possible they are the culprit but I'd be surprised. Do yourself a favor and get that oscilloscope I posted previously and you can actually test the o2 sensors while the engine is running and you can see if they are indeed providing the correct waveform or not. O-scopes are one of the best diagnostic tools you can buy yourself, its worth having.

O2 sensor waveforms look like this

You are the first person that has told me the ECU doesn't learn the trims with new sensors. There are threads on mud that guys are saying it takes 30-40 drive cycles for them to be straightened out and other guys saying need to drive it for 20 min etc. So I'm not sure what to believe at this point but many others have said otherwise.

they are all wrong. Our ECU's are 100% non-learning preprogrammed units. I guarantee it.

 

[Zhowardfzj80]

Noticed today the rpms are consistently sitting around 2000 rpm while accelerating then almost skipping over 2100 and jumping to 2200/2300 when I'm accelerating.

 

[MickeyB]

Noticed today the rpms are consistently sitting around 2000 rpm while accelerating then almost skipping over 2100 and jumping to 2200/2300 when I'm accelerating.

Depending on age of your LC, miles, and overall condition a full tear down may be in order. I have a 94 and with numerous oil leaks and interment issues. I Had the motor rebuilt and replaced cleaned as much as I could after getting it back. You prolly don’t reliaze how marginal or in bad shape things are until you tear into it.