Good news about the idle

Sounds like it starts to stumble as soon as it goes into closed loop operation which means it starts paying attention to the sensors. Prior to that it is running a preset situation where I believe the only sensor it looks sad is the e c t s to determine proper air fuel mix.

you will track down the issue much faster if you have access to a real-time data capture scanner. For instance you can watch the oxygen sensor voltage change and you can watch the TPS voltage change as you slowly put the pedal down. By doing so with the TPS, you can see if there are any reversals of direction in the measured voltage which would be the equivalent of a variable resistor with a worn spot in it, causing a goofy change in resistance or lack thereof. Either way, this would show up as a discontinuity or a strange blip in the TPS voltage.

Did you clean the EGR or is it still in the same stat it originally was? I assume you have it plugged in to the harness and connected to the car.

Unless it is no longer hung up, the errors for position should still be there. if it is moving freely, then as long as it is moving to where it is being told to go, it doesn't care that it is not in an exhaust flow and will not throw errors

Oxygen sensors get poisoned with time and react with a voltage that is lower than it should be for the amount of oxygen present. This causes the PCM to richen the air fuel mix to create more oxygen in the exhaust.

With the car at operating temperature, remove the front O2 by the manifold and see if it runs any differently.

you can try to measure the voltage across the O2 sensor with a multimeter but it moves so quickly that you can really catch it with a DVM.

 

I don't have a real time capture, but it sounds interesting.

The EGR is still blocked (it's a nice plate, kinda thick, turned out well), and the wiring harness is still connected to the EGR.

If I go across the pins of the TPS can I measure increasing resistance? I have wondered about that, over 153k with a manual trans it has rocked back and forth quite a bit, so it is possible it has worn in the spots where it rests a lot. When i ran it WOT going through the gears it was smooth, making me wonder if the TPS is up in used territory it was happier.

I will disconnect the O2 on the drive home and see if it makes a difference. I read that the output of the O2 is a sawtooth voltage form that moves quickly, so not all meters will react that quickly.

Thanks, Doc

 

Driving with the O2 sensor did not seem to make a difference...

 

Assuming there is no front O2 sensor input to the PCM. I asked because I need to know whether you still have an attached like the EGR or if you simply disconnected the sensor harness. Should be the latter.

What type of plugs are you running in the vehicle, when were they last changed?

Also have you checked the resistance of each coil pack??

 

Post should have said "driving without the O2 sensor made no difference"... My bad. I disconnected it leaving work and ran an errand to test.

EGR remains with blockout plate but connected to the wiring harness.

Reflecting this morning on the way in, if it was a TPS it should do that when cold as well. When cold, no hesitation/surging.

So, perhaps back to the temp sensor. I replaced it, and checked the connector, which looked fine, Could not see where the sensor had leaked back through into the connector causing corrosion. But, the connector could still be damaged somehow, I will try to check that with a DMM next, or get a new pigtail and splice it in.

I am a telecomm engineer, and work with electronics, and I am constantly amazed that cars and other motor vehicles work as well as they do, knowing how sensitive electronics can be at times, hat's off to some of these engineers who build the systems that survive under our hoods for so many years...

Anyway.

Plugs are probably 2-3 years old.

How do you check the resistance of each coil pack?

 

The fact that your front O2 sensor being disconnected has absolutely no effect on the drivability of the vehicle makes no sense to me. It should not be overwhelming but if the sensor is bad enough you should be able to tell the difference. Of course if the sensor is bad enough it should throw a code telling you in what way it is not properly behaving.

As you have noticed oh, I have not told you to go out and change anything. Yet. We do not shotgun parts on this forum nor do we promote it. Logical troubleshooting.

Keep track of which spark plug wires you pull off of each coil pack. There are two. Cylinders 1 and 4 are on one coil pack, cylinders 2 and 3 are on the other. Measure across the towers on each one separately and report the resistance here.

The other test for proper operation is to remove all of the spark plug wires once the sun has gone down. Disconnect the fuel pump via the fuse.
Have someone crank the engine and watch the coil towers. You should see a narc between posts on h coil which alternates between the two coils. Pay attention to the strength of the arc in comparing them to each other. In your case you will probably want to perform this test on an ice cold engine as well as an engine that is up to operating temperature to see if one of the coils is being affected by temperature, thereby only acting up once the car is warmed up. Usually you get all kinds of misfire codes if the coil is truly messed up because the firing in the cylinders is not consistent. But it never hurts to check.

I asked about plugs because you should have NGK stock plugs in this vehicle. the ignition system does not appreciate Platinum iridium zirconium wismec caziomiom, ruthenium, graphite,, or pretty much anything you can buy at AutoZone.

Go to rockauto.com, drill down to your vehicle, find spark plugs under fuel and air or ignition I don't remember oh, there will be an NGK four digit code in parentheses there will be a letter followed by a bunch of letters and numbers I don't remember. Make sure you are in the dohc subcategory. I believe they are NGK 75 35 or 7744 but now I am just making stuff up because I honestly don't remember. They are like a dollar fifty a piece and change the way the engine runs in a good way so spend the cash.

As far as the pigtail and the ects go: we always advise people to put out the thirty bucks for a genuine AC Delco ects as it is calibrated it's resistance versus temperature that is for this application. The AutoZone crap has a generic resistance to temperature profile to cover as many applications as possible without overheating a vehicle. The temperature monitoring circuit is extremely sensitive 2 additional resistance that should not be there which is why the pigtail can cause problems as you cannot always see damage to it in the form of partially broken connectors or connector to wiring issues. Mini Saturn s cars have a hard time starting or can't be started when the sensor fails. It completely messes up the air-fuel mixture not just at startup but while the vehicle is running. If it goes open circuit, the PCM interprets the temperature as - 40 and makes the mixture absurdly rich switch off installs out vehicles or creates spots in the throttle curve weather is so much gas you are more or less flooding the engine momentarily. Usually this does not happen until around 2200 RPM which is why I have not mentioned it. But since we are running out of other options, you could try that. You could also try another cleaning on the throttle body as it only needs two slightly stick 2 make the TPS pause. I truly believe the mix is wrong and that is a function of either improper fuel pressure, ECTS troubles, ignition glitch, that includes plugs, throttle body issues. Do a loan a tool from AutoZone or similar for a fuel pressure gauge. It is possible that your show pump is weak and it's not supplying sufficient pressure under load or actually completely not under load. Can't remember if you change the fuel filter or not but that is an option to o.

So basically I just told you to shotgun a bunch of parts. Not really. Go through it logically and do what makes sense. I have to go back to work now and I apologize for all of the goofy spellings and word substitutions but I am voice dictating this


PLUGS FIRST

 

Hey, I was going to order some plugs for it, no doubt it needs it anyway, but do you mean to research from the DOHC selection, or the SOHC, the engine in SOHC......

 

Hey, thanks for the troubleshooting tips, I will do all of that this weekend, supposed to be nice weather. I checked the temp sensor that I bought from Autozone, thought it was Delco but it was not. I ordered a Delco and pigtail from RockAuto last night, since most of the troubleshooting has pointed toward that as being a likely culprit.

As I troubleshoot and get results I will post back.

Thank you for your help!

Doc

 

Sl2 = dohc
Sl1 =sohc

Confused

 

Did you pull out the map sensor when you cleaned the throttle body? If not you may have rinsed all kinds of crap into the ports. Pull and gently clean with I'm not sure what. Look on the internet. Not carb cleaner