84 Fiero 2.5L Losing power and stalling out (Page 1/2)
ironpuke84 OCT 29, 09:48 PM
So I have been daily driving my 84 fiero for a few weeks now that I have my license (it's the 4 speed manual and that has been one heck of a challenge for me but I'm doing pretty good with it). However, unfortunately I have come across a terrible problem, which has happened to me a few times now and left me in some interesting situations. The best way I can describe the issue is that when it happens (when is only when the engine is warmed up) it loses power completely with no response from throttle, no matter if it's 1/4 or wide open, and then the power will come back, for about a second or 2, and this fluctuation with continue to occur until the engine stalls (if it's idling) or is turned off. The previous owner removed the EGR, and the catalytic converter has also been removed. This most commonly happens to me when I come to a stop after driving, though if I let it idle for long enough (~30 minutes) it will also happen. I'm honestly a little bummed out on this one, so if anyone has any good ideas on what might cause this please let me know. Not sure if this has anything to do with the issue but just in case, this morning when I was throttling down on the engine, and then suddenly hit the brakes, which caused the low oil light to come on (despite the oil being full), and after restarting the engine the low oil light was gone. any help or advice is greatly appreciated. Thanks!!
Patrick OCT 29, 10:48 PM

You don't say whether or not the engine will immediately restart after it's stalled.


quote
Originally posted by ironpuke84:

Not sure if this has anything to do with the issue but just in case, this morning when I was throttling down on the engine, and then suddenly hit the brakes, which caused the low oil light to come on (despite the oil being full), and after restarting the engine the low oil light was gone.



If the engine stalled, then it's normal for the oil light to come on.
Dennis LaGrua OCT 30, 02:06 AM
Friend, its always nice to talk about issues with a 41 year old antique vehicle and discuss repair tips but there needs to be a starting point on your end.
Losing power and stalling out could be any number of problems. Problems such as you have reported are usually based on lack of fuel or poor spark. If you have good fuel pressure Then you focus on the ignition system. if the problem is Spark replacing the ignition module often does it but just throwing on parts to solve a problem without proper diagnosis doesn't usually cut it.
Time to invest in a few tools, and a good repair manual. that will point you to the diagnostic steps. IMO, If you are looking for daily driver/rock solid reliability sadly an antique 41 year old car won't provide it

------------------
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82-T/A [At Work] OCT 30, 06:46 AM

quote
Originally posted by ironpuke84:

So I have been daily driving my 84 fiero for a few weeks now that I have my license (it's the 4 speed manual and that has been one heck of a challenge for me but I'm doing pretty good with it). However, unfortunately I have come across a terrible problem, which has happened to me a few times now and left me in some interesting situations. The best way I can describe the issue is that when it happens (when is only when the engine is warmed up) it loses power completely with no response from throttle, no matter if it's 1/4 or wide open, and then the power will come back, for about a second or 2, and this fluctuation with continue to occur until the engine stalls (if it's idling) or is turned off. The previous owner removed the EGR, and the catalytic converter has also been removed. This most commonly happens to me when I come to a stop after driving, though if I let it idle for long enough (~30 minutes) it will also happen. I'm honestly a little bummed out on this one, so if anyone has any good ideas on what might cause this please let me know. Not sure if this has anything to do with the issue but just in case, this morning when I was throttling down on the engine, and then suddenly hit the brakes, which caused the low oil light to come on (despite the oil being full), and after restarting the engine the low oil light was gone. any help or advice is greatly appreciated. Thanks!!




There's a few things it could be... the first thing I would ask is, are you getting any error codes?

This website lists out all the codes: https://www.pontiacperforma...icles/OSG/codes.html
(Instructions at the bottom on how to retrieve them)


Report back and let us know if you have any error codes.

Next, my first thought is that it's like a fuel pressure issue... but let me know first if you have any errors. I will say that, when running well, the Iron Duke is lots of fun to drive with when it's a 4 cyl. My daughter is almost done completely restoring one, and it drives absolutely fantastic. Doesn't have the same power as the V6 does, but it's still a lot of fun to drive. You just have to work out all the bugs because of how old the car is.
ironpuke84 OCT 30, 11:01 AM

quote
Originally posted by Patrick:


You don't say whether or not the engine will immediately restart after it's stalled.

If the engine stalled, then it's normal for the oil light to come on.



The engine didn't stall when the oil light came on, I just turned it off immediately after it came on, fearing the worst. Also, the engine usually won't start first crank after it stalls out, it just cranks, but on the second try, it starts up and sometimes still has the issue, sometimes not. When it stalled on me in and intersection (not a great time), it started up and was lurching forward the same as when it stalled, but thankfully I was able to limp it home. Another time when my dad drove it, it started right back up like nothing (albeit the first time it was low on gas). On that not I should have mentioned I don't have a working fuel gauge and I think I ran it very low on gas yesterday (when it happened) but then after filling it up it still does it.
ironpuke84 OCT 30, 11:13 AM

quote
Originally posted by Dennis LaGrua:

Friend, its always nice to talk about issues with a 41 year old antique vehicle and discuss repair tips but there needs to be a starting point on your end.
Losing power and stalling out could be any number of problems. Problems such as you have reported are usually based on lack of fuel or poor spark. If you have good fuel pressure Then you focus on the ignition system. if the problem is Spark replacing the ignition module often does it but just throwing on parts to solve a problem without proper diagnosis doesn't usually cut it.
Time to invest in a few tools, and a good repair manual. that will point you to the diagnostic steps. IMO, If you are looking for daily driver/rock solid reliability sadly an antique 41 year old car won't provide it




Not my daily driver, I have a second (more practical car), however after getting my license I've been driving daily driving the car for fun considering I've worked to even get it somewhat road worthy for the past 3 years, just kind of having fun with it at the moment. I plugged in an old GM OBD 2 tool to it and it doesn't really appear to be a problem with the O2 sensor or Map sensor I don't think. Pretty sure it's a fuel issue (though I could be wrong). My best guess at the moment is that the oil pressure switch is bad, so today at some point (preferably when it stops raining) I'm going to jump the wires and bypass the oil pressure switch and see if it still does it. In conclusion, I don't think it's an issue with spark or air, pretty sure it's a fuel issue (should have mentioned in the original post, my bad).
ironpuke84 OCT 30, 11:22 AM

quote
Originally posted by 82-T/A [At Work]:
There's a few things it could be... the first thing I would ask is, are you getting any error codes?

This website lists out all the codes: https://www.pontiacperforma...icles/OSG/codes.html
(Instructions at the bottom on how to retrieve them)


Report back and let us know if you have any error codes.

Next, my first thought is that it's like a fuel pressure issue... but let me know first if you have any errors. I will say that, when running well, the Iron Duke is lots of fun to drive with when it's a 4 cyl. My daughter is almost done completely restoring one, and it drives absolutely fantastic. Doesn't have the same power as the V6 does, but it's still a lot of fun to drive. You just have to work out all the bugs because of how old the car is.



I do find the 2.5 duke to be quite a fun little car do drive around, especially paired with the Muncie 4 speed, which has a bit more pep than the automatic version. Many a V6 Fiero owners like to say nasty things about the duke, which is unfortunate, yet besides the point. I have no codes at the moment, just a recurring one that comes on on long decelerations because of the EGR delete. I am pretty sure it's a fuel pressure issue, and my best guess at the moment is that the oil pressure switch is getting finicky at standard operating temperature and the oil viscosity change is throwing it off, making it cut the power to the fuel pump since the fuel pump is run through the oil pressure switch on Fieros. I should mention that not too long ago I put a thermostat in the car, and prior to that I was driving it without a thermostat, which made it run cold and it usually never got past the 2nd line on the temperature gauge. Thanks for the assistance once again.
1985 Fiero GT OCT 30, 12:27 PM

quote
Originally posted by ironpuke84:

making it cut the power to the fuel pump since the fuel pump is run through the oil pressure switch on Fieros.



The fuel pump is run by both the ECM and the oil pressure sender, in parallel, as a "backup"system. The ECM should be what controls the fuel pump 100% of the time through its relay, the oil pressure switch only provides an additional path for more current to flow, or in the event of the ECM fuel relay failing, as a backup power source. A bad oil sender won't do anything unless the ECM relay is also damaged.

(I'm not 100% certain what's what on the 84s, I could be wrong, but I'm fairly certain)
olejoedad OCT 30, 12:27 PM
The oil pressure switch will not turn off the fuel pump on a Fiero.
It acts as a backup circuit in case the fuel pump relay fails.

The oil pressure light comes on when oil pressure falls below a certain value, that circuitry in in the gage assembly, and has nothing to do with the switch.

Neither the oil pressure sending unit nor the switch interface with the ECU.

You can completely rule out the oil pressure sensing system from your diagnosis of the problem you are having.


quote
Originally posted by ironpuke84:


I do find the 2.5 duke to be quite a fun little car do drive around, especially paired with the Muncie 4 speed, which has a bit more pep than the automatic version. Many a V6 Fiero owners like to say nasty things about the duke, which is unfortunate, yet besides the point. I have no codes at the moment, just a recurring one that comes on on long decelerations because of the EGR delete. I am pretty sure it's a fuel pressure issue, and my best guess at the moment is that the oil pressure switch is getting finicky at standard operating temperature and the oil viscosity change is throwing it off, making it cut the power to the fuel pump since the fuel pump is run through the oil pressure switch on Fieros. I should mention that not too long ago I put a thermostat in the car, and prior to that I was driving it without a thermostat, which made it run cold and it usually never got past the 2nd line on the temperature gauge. Thanks for the assistance once again.
82-T/A [At Work] OCT 30, 12:29 PM

quote
Originally posted by ironpuke84:

I do find the 2.5 duke to be quite a fun little car do drive around, especially paired with the Muncie 4 speed, which has a bit more pep than the automatic version. Many a V6 Fiero owners like to say nasty things about the duke, which is unfortunate, yet besides the point. I have no codes at the moment, just a recurring one that comes on on long decelerations because of the EGR delete. I am pretty sure it's a fuel pressure issue, and my best guess at the moment is that the oil pressure switch is getting finicky at standard operating temperature and the oil viscosity change is throwing it off, making it cut the power to the fuel pump since the fuel pump is run through the oil pressure switch on Fieros. I should mention that not too long ago I put a thermostat in the car, and prior to that I was driving it without a thermostat, which made it run cold and it usually never got past the 2nd line on the temperature gauge. Thanks for the assistance once again.




Yeah, the EGR delete definitely wouldn't cause that. Can you tell me what error code it does show (regarding the EGR)?

The EGR on the 4 cyl Fiero isn't computer controlled, so I'm wondering what error code it shoots. As you know, it's just a direct vacuum port to the throttle body. But yeah, I'm definitely thinking the fuel pump. It's hard to check fuel pressure on these things since there's no Schrader valve, but my guess is that the pump is either failing, or the hose that connects the pump to the pickup tube (in the tank) is deteriorating and thus ... not able to maintain pressure since it's just squirting all out.

Another thing you could try is rebuilding your throttle body. It's super easy to do, and the kit to do it is $50 bucks on Rock Auto. My daughter has a nice video she put on YouTube on how to rebuild the Rochester 300 TBI:





She also has other videos for removing the fuel tank, etc... so if you need to see that, check out other videos (she has one for removing the tank, and also replacing the pickup tube).