Hello everyone. I have an 86 Fiero SE. I recently changed plugs, cables, distributor, cap, flushed coolant, changed oil, new filters. The car has been sitting essentially since the late 90s. Now, I finally got it to run (yay!) but only in idle, and the idle is high. (2000-2500 [3000 if pretty cold]) The issue I'm having now though, is despite the clean (albeit high idle) when I shift into gear, I get a very rough transition at around 500-1k rpm and then the car sputters and dies as soon as even a drop of gas is given. This happens in drive gears and in reverse. But I can idle indefinitely and even apply throttle while idle without any noticeable issues.
Current engine code is a 15 so I'm planning on replacing the temp sensor and thermostat here in a couple days, but I don't think that would cause this issue because the temp sensor has a fallback, doesn't it? Looking for any help, AstroChemist
P.S. my timing is several degrees ccw because otherwise the car will slowly die in idle. Going based off the harmonic balancer, I have an idle of 1.5k rpm for 30 or so seconds before it slowly dies off. There's also pretty bad throttle lag if I stay at the timing from the harmonic balancer. Even though it has the best idle rpm. ------------------ Vroom, Vroom. -My 86 Fiero
[This message has been edited by AstroChemist (edited 05-06-2024).]
It sounds like a large vacuum leak. First place 8 would check would be the #GR tube that runs from the underside of the upper plenum to the EGR valve. They are known to be a failure point.
It may also be that the torque control solenoid is about to totally fail. Look on the front of the transmission for a sensor and harness wire pointing at the driver's butt. Unplug the harness and see if that will stop the stalling. It won't stop the idle problem, though.
It may also be that the torque control solenoid is about to totally fail. Look on the front of the transmission for a sensor and harness wire pointing at the driver's butt. Unplug the harness and see if that will stop the stalling. It won't stop the idle problem, though.
So I took a look today, (I'm still getting used to the mess the old owner made) and here's what I found:
The egr tube is missing (I knew that) but I have it blocked off with a plate, and the vac line is blocked too. Theres probably an exhaust leak bc of that but surely not a vac leak right?
The connector for the TCC is just gone. So its already unplugged I guess.
The fluid levels are all good. There's no thermostat in (I ordered one already)
I think that's about all I found so far. Despite cranking up all day yesterday with no issues, I can't seem to get it to really run. To be fair, I don't have a working gas gauge so I can't tell when it's out or not. But I put a gallon in yesterday and haven't been driving it so I doubt it's out? It idles rough at just under 1k for a few secs then dies.
The egr tube is missing (I knew that) but I have it blocked off with a plate, and the vac line is blocked too. Theres probably an exhaust leak bc of that but surely not a vac leak right?
Wrong. The missing EGR tube was originally connected to the underside of the top intake plenum. If that's not blocked off/sealed properly, then it's a definite source for a (huge) vacuum leak.
Just so you know, this (as well as your previous threads) belong in Technical Discussion & Questions. No, you're not able to move them now. Only Cliff Pennock can move or delete threads.
[This message has been edited by Patrick (edited 05-07-2024).]
Wrong. The missing EGR tube was originally connected to the underside of the top intake plenum. If that's not blocked off/sealed properly, then it's a definite source for a (huge) vacuum leak.
Just so you know, this (as well as your previous threads) belong in Technical Discussion & Questions. No, you're not able to move them now. Only Cliff Pennock can move or delete threads.
I see, I'll go ahead and check that asap then. Apologies for the wrong location, I'm still new here. I'll be sure to post in the correct spot next time.
I'm just curious... when you blocked off the opening in the EGR valve (or the exhaust crossover pipe if the valve itself is also missing), where did you think the other end of the missing EGR tube might've gone to?
[This message has been edited by Patrick (edited 05-07-2024).]
I'm just curious... when you blocked off the opening in the EGR valve (or the exhaust crossover pipe if the valve itself is also missing), where did you think the other end of the missing EGR tube might've gone to?
... To Narnia I suppose. I see what you mean. I thought the egr system operated backwards to how it actually does.
I went back in and checked all vacuum lines, and made sure the egr port on the underside of the plenum was blocked off. It already had a plate there, I just didn't notice it before. That makes me think it's not a vacuum leak, I can't seem to find any source of one.
[This message has been edited by AstroChemist (edited 05-08-2024).]
Cover the end of the throttle body with the palm of your hand while the engine's running. It should immediately stall. If the engine continues to run, there's a vacuum leak.
Cover the end of the throttle body with the palm of your hand while the engine's running. It should immediately stall. If the engine continues to run, there's a vacuum leak.
It immediately stalls.
I fixed the issue, still have a hard shift but that's fine. Cars running smoothly
[This message has been edited by AstroChemist (edited 05-08-2024).]
Honestly not too sure. I think it has something to do with the exhaust. What fixed it for me was just redoing every vacuum line, gasket, etc. it still occasionally stalls out when in gear if I give it gas too quickly so I'm going to pull the injectors and clean them, then check fuel pressure which I expect is low.
Edit:
Fuel pressure is about 40-45 psi, and very steady. This leads me back to potentially air? I recalibrated my TPS to .55 and that helped a tiny bit but not a lot. I'm massssssively underpowered. I can floor it in neutral and get to 4k eventually but that doesn't happen in gear. It has to be air mixture.
I'm confident in spark, I'm confident there's no vac leaks, I'm confident that I have fuel. What else does that leave? Is there a way to test the MAP? What about O2 sensors? There's two, I bought the upstream one but not the downstream one yet because my local auto parts store didn't have it. I might go to Fiero store again next paycheck.
Any other suggestions are welcome.
[This message has been edited by AstroChemist (edited 05-09-2024).]
....................What about O2 sensors? There's two, I bought the upstream one but not the downstream one yet because my local auto parts store didn't have it....................
Did I miss something? A stock Fiero doesn't have a downstream O-2 sensor.
I'm massssssively underpowered. I can floor it in neutral and get to 4k eventually but that doesn't happen in gear. It has to be air mixture.
You know for a fact that your cat and/or muffler isn't plugged?
quote
Originally posted by AstroChemist:
I'm confident in spark...
You set the ignition timing with the ALDL jumper in place? And you verified that 0° on the ignition timing scale actually lines up with TDC of cylinder #1?
[This message has been edited by Patrick (edited 05-10-2024).]
You set the ignition timing with the ALDL jumper in place?
I'm not certain about the clogged cat, the mufflers been pulled by the previous owner. That's a very good recommendation though. I'll go ahead and pull it to check chances are that's the issue given the age and how long it sat + how poorly it was taken care of.
I did set the timing like that, I manually checked the piston for compression stroke to make sure the timing mark lined up. Timing was set with the pin in.
I noticed my map sensor connector was in poor condition, but I think it's still making good contact. I bought a new one and will toss that in tomorrow. I'm also replacing the O2 sensor because there's no real reason not to.
I just don't understand why it behaves more or less normally (with slight lag) in idle but in gear it's so much worse. What changes mechanically regarding air flow in gear vs out of gear?
[This message has been edited by AstroChemist (edited 05-10-2024).]
Did I miss something? A stock Fiero doesn't have a downstream O-2 sensor.
That's what I thought too, and I'm pretty confident that's the case because of the shape of the exhaust pipe after the cat but leave it to O'Reilly's to try and convince me otherwise.
I'm not certain about the clogged cat, the mufflers been pulled by the previous owner. That's a very good recommendation though. I'll go ahead and pull it to check chances are that's the issue given the age and how long it sat + how poorly it was taken care of.
Here's why I suggested to check for a plugged cat and/or muffler...
I know it’s impossible to tell from simply looking at it, but as stated above, the cat looks good. It’s a newer style hi-flow design. I’ve heard that fellas in my local Fiero club have passed the emission test with ‘87 and older Fiero V6s without a cat, so I was hoping the condition of my cat would be a moot point. One concern I do have though is whether or not the contents of the original cat are currently plugging the muffler. One reason I’m suspicious is that I don’t feel the engine has a whole lot of mid-range to top end power. The engine is smooth, it just doesn’t seem to get up and go above 3000 RPM or so. This is my first V6 Fiero, so I’m not familiar with how well they should go.
So I haven't pulled the cat yet but I'm pretty sure it's at least partially clogged. It seems the main culprit was an O2 Sensor that went bad. Now I get good throttle response, if a little underpowered but now it just feels like maybe a gross fuel system or bad exhaust flow. Either way the issues are minimal at this point. I tossed in a new thermostat today as well.
Ill also be getting a new cable for the map sensor which is cracked so I expect that will help to a degree. Something alarming today though, I was filling up at the gas station today (fuel gauge doesn't work so idk when I'm full. I just refill every 3 or 4 rides. And gas started spilling out of the tank, and not a small amount either. It stopped shortly and I think I kept most of my gas but it's alarming nonetheless.
...gas started spilling out of the tank, and not a small amount either. It stopped shortly and I think I kept most of my gas but it's alarming nonetheless.
Strange. Why didn't the automatic shut-off kick in at the pump?
[EDIT] You didn't say, but I assumed the gas was exiting out the top through the opening... or has the gas tank fill tube rusted out?
[This message has been edited by Patrick (edited 05-10-2024).]
Originally posted by Patrick: [EDIT] You didn't say, but I assumed the gas was exiting out the top through the opening... or has the gas tank fill tube rusted out?
The automatic did kick in, but it was leaking from somewhere under the car, looked to me like directly where the tank sits but it's hard to see given how low the car is. This car is almost completely rust free (it was in AZ since it was made)
Well, it goes without saying (but I'll say it anyway)... that's potentially a very dangerous situation. You need to find where that fuel leak is. Even if it's not normally leaking while the car's standing still, it could very well be pouring out when the car's in motion and the gas is sloshing about in the tank. Check any/all clamps on the fuel filler pipe.
I'll take a look soon, I've been working a lot the last couple of days but I haven't driven it since. Maybe I'll get to it Tuesday. Until then I'm going to install a new map cable and see if that does the trick.
The gas issue is very alarming but it sounds like there's a lot of hoses and gaskets that can present an issue. I wish I had a working gauge to tell when it's full.
