Hi Third-Genners! I have an issue with a '92 3.1L Firebird here. Kinda long here.... After starting the car, and when it's sitting at a stoplight, etc. the car idles just fine (except for some occassional shaking, but nothing major). After the temperature reaches a certain temperature, (which I assume is closed loop), acceleration bogs down nightmarishly. I really have to put effort into pressing the accelerator to keep the car going, but power is still gradually lost. This is even more evident when going uphill. It feels as if fuel is being restricted back or choked off. But bizarrely, the car GUZZLES gas. To give you an idea, I filled up yesterday, ran an errand or two around my small town, and it's already down to half a tank. (Scary, huh?)

This is what has been done: Spark plugs 2 through 6 have been replaced, (I haven't yet taken that bar off the back of the alternator to reach the first sparkplug, since I don't have a socket extender that rotates). New fuel filter, new air filter. New distributor cap/rotor. Oil and tranny fluid are good all around. Now, I'm in the process of replacing the TPS, but someone before me stripped one of the screws holding it in. I also intend on replacing the O2 sensor.

The car has intermiddently thrown the CEL light with the codes: 13, O2 sensor; 22, TPS voltage low; and 24, Vehicle speed sensor, (I may be wrong on that one). The codes have only come on once or twice each, and each time for only about 10 seconds. I appreciate taking a second to read all of this, and I'd really appreciate if anyone had any insight into this!

 

The first issue is that it's a V-6 hahaha. Yeah anyways, You may just need a tune-up, I would say spark plugs/wires, but the TPS sends the throttle position to the ECM to adjust the amount of fuel into the combustion chamber, but when the voltage is low the computer runs the vehicle rich (more fuel than air).. This happens normally when the car is at Wide Open Throttle (WOT).

*O2 sensor change fuel and air mixture from exhaust gases.

*If you have a Mass Airflow Sensor (MAF) you can remove it and take some MAF cleaner while your at it, and spray into the metal honeycomb, wait for it to dry afterwards. It's $10 a bottle, but it's related to controlling Air + fuel.

*Coolant temperature sensor has the same concepts.

*The Vehicle Speed Sensor (VSS) sends speed data to the Engine Control Module (ECM) which determines when to activate/deactivate the torque converter clutch.

Hope this gives you a better idea on what to do. A good idea would be to check for obviously frayed wires or dirty connections, filled with dirt or oil..

 

If you have any luck with it let us know.

 

Thanks for the insight. I'll be certain to follow up this thread as soon as I find a way to break off the screw to that darned TPS. I'll get on some MAF cleaner, too. The snow made a wasteland of my town, and has sidetracked everything for the moment!

 

If you have a gauge, you should also check your fuel pressure. Should be about 42psi key on engine off, high 30s with engine idling. It should fluctuate slightly in proportion to manifold pressure.
Try warming it up with the gauge connected, try to reproduce the problem and see if the pressure is staying correct or if it's falling off.
Something else to check if you do this: With key off, it should hold pressure. It shouldn't lose more than a few psi in 15 minutes. If it leaks down quickly then it's leaking somewhere, likely through an injector. I don't think that's causing this issue but it's still something you'll want to check when the gauge is on it.

When the car is in the failure state, you might also try checking the supply voltage to the TPS. This is the input voltage which gets reduced by the TPS in order to produce a throttle signal. The input voltage should be 5.0V anytime the car is turned on. If I'm not mistaken, that voltage supply goes to multiple places, not just the TPS, so if it's low it could be causing multiple problems.

Anything that causes problems with engine management will hurt your mileage, even low fuel pressure could have that effect because the fuel you get is wasted when it misfires.

You can check the coolant temperature sensor with a multimeter:



The TPS can be tested by probing it's resistance, and watching that it gradually changes as you open the throttle. I don't know what resistance range it's supposed to be in though. Another way is to backprobe the signal wire with the key on and watch the voltage change. Closed throttle should be less than 1.0V. As you open it the voltage should smoothly increase, but I'm not sure how high it will get at WOT.

 

when my tbi 305 did the same thing (and i do mean the exact same thing) it was the cat. a chunk of the inside broke off and plugged the exit ... it took me 2 hours to get to st. louis ... it plugged about an hour into the trip home, and it took me 6 more hours to make the last hour worth of the trip ... used well under 1/2 tank of gas to get there, and a full tank to get home

 

That's interesting, I know that a bad catalytic converter will give you performance issues and typically the car will throw an engine code for a bad catalytic converter. If the catalytic converter is restricted, but still working efficiently, I suppose that could be possibly responsible for your performance issue, but also I am not completely sure.. I've never hear of that. If you have tried all other options with no luck you can take the car to a muffler shop and maybe they can give you an answer. Sometimes they charge you sometimes they won't.

 

If you have a fluke I believe that most of them automatically adjust the appropriate range, with cheaper Ohm meters you do have to find the range or guess the resistance value sometimes, I think there are 5 or 6 ranges and I believe they go from 2 to 20 to 200 to 2000 to 20000. The number of digits are the only thing that changes....

 

I forgot to mention, replace your PCV too. they are cheap and easy to replace. $3 for the Positive Crankcase Ventilation valve and $3 for the grommet that goes with it.

I remember working on a Mazda truck and it ran like garbage after coming to slow down, found out a rubber piece fell off that was blocking another part of the PCV, cuz it had two ports on the top where the one port went into the air filter and the other was just pointless.. But I got a new PCV and grommet anyways, instead of just the small rubber thing. Ran great afterwards though.

 

So I made a pretty big discovery. I performed a test that I had heard of along time ago. I took a screw driver and reached around the openings on the plenum(?) and placed the end of the screwdriver on top iof each individual fuel injector. (I heard of people putting their ear to the screwdriver while doing this, but I could clearly feel the injector just through my hand). Anyways, all injectors were clicking away, EXCEPT for injector #1. Totally dead.

So: dumb question, would this likely be the culprit? Is it the injector itself that has failed, or could it perhaps be the spark plug or wire that is causing the fault? Perhaps an ECM issue? I wanted to ask before anyone advises I purchase a new injector, etc.

Oh, and I had forgotten to mention, the cat in this car is gutted out. It's louuuuud =]

 

Yes it would likely be the culprit, If the injector is totally dead there would be a misfire, there are ways to test it, you can take an ohm meter to it and measure the resistance, but though it may have good resistance and power on the electrical side, the fuel injector may not be releasing the fuel (mechanically), because there may be something blocking it or it's just old.

The ECU could be the culprit, but if it was, there should most likely be more components failing as well.

I wouldn't bet on a spark plug or wire failing just yet, If you have an ohm meter, you can measure voltage on the electrical connector to see if it's getting power and whether or not those two wires are broken or corroded.

I would check the resistance value for that injector and test it if you can After that see if your getting power to the connector for it (the vehicle should be running for this).

If those check out, then you can remove the injector and test it various ways. If you go on youtube.com you can find videos of fuel injectors being tested.

If you have any questions, I can get diagrams and resistance values for you if you need them.

Make sure the injector is plugged in all the way too...

 

Thank you so much! There's definitely something going on that's causing the car to kind of rumble and rattle. The owner of the car before me fell asleep at the wheel and crashed the front-passenger end into a ditch (they were ok), so I wonder if it caused any sort of damage or issue related to the first injector. I'll also be hopefully getting a volt meter in my hands at the end of the week. If I get to replace the injector, I will follow up.

 

just a suggestion, if you are going to replace an injector....do yourself a favor and replace all of them especially if they are stock

 

It's possible as far as I know especially with plastic pieces. That would be great though. Good luck!

 

Ok guys, so after all the delays such as work and crappy Virginia weather, I've finally gotten hold of a new injector (maybe more injectors later) and am ready to go at it. The only question remains before I begin; what tools are needed in order to get to the injector? I know that I need to remove the bolts holding the upper plenum thing, but there is also the fuel pressure regulator. Will an allen(?) wrench remove those? Are they Phillips-head screws? Bolts like on the plenum? Sorry for my bad terminology. I only have but so much time to change out this defunct injector, and just want to ensure I have my tools in line before I change it out.

 

Usually you don't have to remove the fuel pressure regulator since it doesn't seem broken. You should be able to leave alone and just remove the intake and relieve fuel pressure for the most part. Also you may need lots of rags.. There's an attached picture at the bottom of this post to take a look at also!

This will be fun. This may take awhile depending on the motor.

I'm not sure of your experience with engines, but I will keep checking this thread, this will help others with the same issue.

Before you start I would recommend watching some videos. I know you probably don't want to, but Here's a few videos I believe bring out some good knowledge/tips.

The engines may be different, but the same principles still apply (wiggling, relieving fuel pressure, testing, being fragile etc.)



You can skip to 7:33 if you want to skip to the fuel rail.

 

If you have any questions just post back here.

*Remove the negative battery cable.

*Then fuel pressure from the fuel test port on the fuel rail, that's how I do it, just do it slowly as not to wear the needle inside and don't forget to put a rag near the port while carefully pushing down on the needle, don't have open flames or sparks around either...

If you can't see the attachment that well, just save it to the computer and view it.

GoodLuck!

 

Well, strangely, I was out and was about to take everything apart and replace the injector. Before changing it out, I tested the #1 fuel injector one more time using the screwdriver method, and found that it's now clicking again. It feels weak, but it's as if it came back from the dead. This leads me to wonder if it's an electrical (perhaps ECM issue)? I thus still don't have a means of testing with a voltmeter. But the car still runs like crud =/

 

Yeah I hate intermittent issues, test the connector when you can, have you gotten the chance to replace the o2 sensor? I would add that to the list since you have a code.

 

Injectors 1, 3, 5 are all on the same circuit, fired together by the ECM. If I'm not mistaken they join up to literally the same wire at the ECM side. So if injectors 3 and 5 are working, I don't think this would be an ECM problem.

I suppose if the ECM was mostly working but having trouble sinking enough current, maybe one injector might struggle to operate more than the other two. I think that's an unlikely explanation though.

More likely either a bad connection, a sticky injector, or maybe something damaged in a location of the wiring which only affects that injector.

 

Sticky injector would be possible here. A Good rule of thumb is that you want to diagnose circuits/components that are closer to the intake and work your way down towards the exhaust last.

This is because one sensor can affect other sensors to operate abnormally/erratically, including the MAP, MAF, TPS, O2, coolant temp, Crank/cam sensor, IAC valve, ect.. EGR vacuum depending on the car.

Sometimes the connectors are just dirty and sometimes they are melted, check wires near exhaust manifold and where ever heat is displaced, and where there is is much dirt build up.

Could be something that simple, hopefully your injector works just fine, but it probably won't hurt to take a peek at the wiring. If it is your injector is acting that way, then you may end up replacing it down the road.

 

Thanks for the information! I was skeptical of an ECM issue as well, but have run into those problems in the past. I've checked the wiring around all connectors and around the plenum, upper engine, etc. relating to fuel injectors and all connectors within that general area. All seem to be in fine condition, (besides the fact that I still haven't yet been able to test anything using a volt meter).

A piece of information I had completely forgotten about until now was coolant. This car is using the fan bypass (the fan is running all of the time). The previous owner did state it has overheating issues. With that: the car never has coolant in it. If you put coolant in it, the car drinks it right up within the first couple of days, leaving behind a gooey, dirty gunk in the coolant reservoir. So, for a time, I stopped putting coolant in the car, which in itself wasn't a great idea, but the car has never become overheated while I've owned it. It just has this acceleration and power nightmare.

Could this be coolant related? (Sorry for the information overload)

 

Absolutely, if your car gets too hot it will run like garbage, newer cars shut down if they reach a certain temperature to save the engine. I'm surprised your motor doesn't smoke and hasn't been overheating/shutting down randomly.

*If you can get a hose (from your house), I would spray and clean out the cooling system with it through all the hoses, the heater core inlet/outlet hoses, big hoses, remove the thermostat/housing, flush all the all the gunk out, remove the coolant reservoir and wash that out with hot water if you need to.

*There's a few things you should know before flushing a cooling system though as some idea why it doesn't have coolant and possibly brownish goo. there may have been a leak in the past and somebody put a 'stop leak' product to save a repair, so if you clean your cooling system out, you may find that maybe you have a head gasket leak/bad heater core/ or radiator.

You may not have to deal with any of those, just possible.

*You can remove any radiator hose and force water through the radiator hoses and clean as much of that stuff out as you can. flush the cooling system one way then back the other direction a few times.

I had this same issue recently with a 97 camaro, except the radiator was leaking onto the battery and had a blown head gasket, but mainly the issue was keeping the car from running more than 20 minute drives.

And just the other day I found out my cooling system was contaminated so I removed and flushed the radiator, then flushed water through the water pump, and heater core/hoses until I saw clear water coming out.

Third gens usually doesn't take long to flush it out. I probably spent 2 or 3 hours making sure my hoses were clean and getting the radiator clean, I replaced my thermostat while I had the thermostat housing off also.

I can type a lot too hahaha. Hope this information helps, now that you mention it I feel confident this is your problem if not most of it. Post back with any questions or results..

 

Thanks so much! I was finally able to buy a jug of holy water that is coolant. After filling the reservoir, there's already a noticeable improvement in acceleration and power. It also runs much more consistently going down the highway. I'll have to see how the gas mileage amounts now. I hope I can get a chance to clean out the system before too long, and I hope this improved performance will remain as well! I just feel silly for not realizing I had forgotten about coolant after all this time.

 

Hahaha my memory isn't so great either, but I seem to have many epiphanies...

I hope this works for you, get back here if you have any issues/questions!

 

Well, sadly, the improved performance was relatively short lived... haha. I'm back to where I was beforehand. Another oddity I've noticed is that the inside of the car fills up with the smell of exhaust fumes, (I don't recall if I mentioned this before or not). I'm not sure if there's a crack somewhere, or if there's a clog somewhere in the exhaust system. I've confirmed that the catalytic converter is gutted out, it's totally empty. Also when I get out of the car after driving, the car is completely surounded in a pungent fuel smell- harking back to the fuel leak theory. I'm really scratching my head on this one. I don't want to get rid of the car, though the gas it uses is blowing a hole in my wallet =/

 

The coolant is definitely needed, I would replace the TPS since you have the code, it's important and it's $30-40, Some that I see go for $200-300, have you checked for any vacuum leaks? The EGR is known to clog up and cause poor performance.

Here's some great information regarding EGR http://sethirdgen.org/egr.htm

The smell is most likely from an exhaust leak with too much fuel running through it, but like my Camry, fuel is very slowly leaking from a fuel hose on top of the fuel tank, so sometimes when I get out I can smell 87 octane hahaha.

If you have a code for an Oxygen sensor I would take a look to see if it's the one after where the catalytic converter was and see if it's still there. If it is then, (If it was my car) I would have someone make a chip to put into the computer to bypass that Oxygen sensor in Bank 2 or 3 whichever one it is, so the computer doesn't come up with the CEL and so the car doesn't adjust the air/fuel ratio from something that doesn't exist anymore.. just an idea.

Let us know if you remember anything else, try looking for vacuum leaks, replacing the other spark plugs, TPS, watch video before replacing O2 sensor.

Vacuum leaks take a peak

 

Thank you! I have a predicament with the TPS; one of the screws holding it in have been stripped out, so I'm trying to look for a way to get that screw out. I'm going to get an O2 sensor later on this week and try to see where I can go with that. For my 3.1L V6, I've only seen one sensor on it, are there two?

It's odd because there was about a week there where the CEL came on constantly, so I don't know if the light comes on whenever the problem persists, or whether it's stored as a one-time occurrence.

 

I have a 91 camaro with the 305 tpi. The car runs fine but only under heavy acceleration the motor will bog down vibrate and backfire but only happens occasionally at random times then will be fine for a day or so?

 

Yes, there is only one O2 sensor for your motor.

The light is suppose to stay on even after the problem is corrected until you delete the code (By removing the Negative battery cable for about 5 minutes or using a scan tool), but I don't know when they programed the ECU to shut the light off when issues are corrected or maybe only for certain issues or whether it's always been like that, I don't know for sure...

Typically I would believe an intermittent problem either way, knowing that a bolt/screw was loose holding onto the bracket of the TPS, maybe the sensor was moving/vibrating slightly, making the car indecisive hahaha.

When that occurs, notice whether the car is going over bumps, when you hit the brakes, going mudding, drifting, going through water, car is warmed up or cold. Sometimes can help diagnosing.

 

Could be almost anything with just that to go off of, from EGR, Fuel system parts, Vacuum leak, weak coil, spark plugs/Wires, leaking oil into spark plugs/cylinders, clogged PCV, TPS sensor, clogged Catalytic Converter, Timing, that's all I can think of at the moment that's common... Pretty much anything wrong in these areas can cause your issue..

You may get your answer faster by starting your own thread. Just post year, make, model of your car, any tests you have done, noticed anything about when it happens will help too.

Keep an eye on this thread if your curious though. Could be a relative/similar fix.

 

Car threw another 13 today. I yet haven't been able to get around to getting an O2 sensor, or knocking out that TPS. Wanted to let you guys know that I'm still here and working on the issue, so I'll be sure to post things as they happen.

 

The TPS/VSS may just be dirty too.