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| 3.4 runs bad cold (Page 1/3) |
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Jim Jimenez
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SEP 20, 03:30 AM
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So this is a problem that I have been fighting for the last 20 years! I have a problem with my 3.4 . When the engine us cold, it runs like a carbureted engine where the choke is not closing Usually have to restart 8 - 10 times, until the engine warms up, and then it runs great!
I think I have tried just about everything, but nothing has worked, so I need help!------------------
Corvairo
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Patrick
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SEP 20, 05:04 AM
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There are two different 3.4 engines which have been swapped into Fieros. Which one do you have?
| quote | Originally posted by Jim Jimenez:
I think I have tried just about everything, but nothing has worked, so I need help!
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What's "everything"? Have you had a scanner (or a laptop running WinALDL) connected to allow you to see what the sensors are reporting. Perhaps the MAT and/or CTS are telling the ECU that the engine is something like 250° when it's actually more like 60°.
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82-T/A [At Work]
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SEP 20, 07:46 AM
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| quote | Originally posted by Jim Jimenez:
So this is a problem that I have been fighting for the last 20 years! I have a problem with my 3.4 . When the engine us cold, it runs like a carbureted engine where the choke is not closing Usually have to restart 8 - 10 times, until the engine warms up, and then it runs great!
I think I have tried just about everything, but nothing has worked, so I need help!
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If you're using the stock ECM and everything else on the engine is essentially stock other than the short-block and injectors, then my guess is that it's probably the cold start injector that's failed and / or failing. This often causes the issues you're talking about in a normal 2.8 in the Fiero.
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sleek fiero
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SEP 20, 10:18 AM
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It could be a bad temp sensor for the cold start injector. sleek
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Patrick
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SEP 20, 02:25 PM
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It's my understanding that the cold start injector has no bearing on the engine once it's started. In other words, it wouldn't have anything to do with the multiple stalls.
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82-T/A [At Work]
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SEP 20, 03:30 PM
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| quote | Originally posted by Patrick:
It's my understanding that the cold start injector has no bearing on the engine once it's started. In other words, it wouldn't have anything to do with the multiple stalls. |
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It seems to be a constant point of discussion on Pennocks, as to whether or not it runs just while cranking, or if it provides fuel up to a certain temperature. I don't personally know or have an opinion either way. EDIT: I wonder if it's discussed in the service manual. I have one, so I'll check it out at some point tonight if I get bored.
But I figure you could rule out the cold start injector by testing it, but either way, as you say... the temperature sensor can certainly cause this behavior as well.[This message has been edited by 82-T/A [At Work] (edited 09-20-2023).]
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cvxjet
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SEP 20, 03:38 PM
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I don't like "Temp" ermental sensors.....
I think that someone should prove how the Cold start injector works by Hooking up a light to the wire that powers it- install on the dash- and then you can see when it is activated...Or you could go fishing in the computer program to see what it says......
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Patrick
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SEP 20, 03:50 PM
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| quote | Originally posted by 82-T/A [At Work]:
It seems to be a constant point of discussion on Pennocks, as to whether or not it runs just while cranking, or if it provides fuel up to a certain temperature.
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Keep in mind the OP has made no reference to hard starting. The problem, as reported, is the engine running rough and stalling while cold.
Another thing to check if the MAT and CTS readings proved to be satisfactory would be the fuel pressure. I suspect low fuel pressure might affect an engine more when it's cold, as it needs to be running richer.[This message has been edited by Patrick (edited 09-20-2023).]
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Raydar
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SEP 20, 04:55 PM
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I would be looking at coolant temp readings, and intake air temp readings, with a scanner.
This, as a first step.
| quote | Originally posted by 82-T/A [At Work]:
It seems to be a constant point of discussion on Pennocks, as to whether or not it runs just while cranking, or if it provides fuel up to a certain temperature.
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It absolutely is only active while cranking.
The big purple wire that causes the solenoid to pull in, when the key is turned to start, is the same wire that supplies power to the CS injector circuit.
The temperature switch affects when it's activated when the key is turned to "start".
/ hijack
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82-T/A [At Work]
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SEP 21, 08:19 AM
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| quote | Originally posted by Raydar:
I would be looking at coolant temp readings, and intake air temp readings, with a scanner.
This, as a first step.
It absolutely is only active while cranking.
The big purple wire that causes the solenoid to pull in, when the key is turned to start, is the same wire that supplies power to the CS injector circuit.
The temperature switch affects when it's activated when the key is turned to "start".
/ hijack |
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I totally believe you guys... it just seems like a lot of people in the archives / other (in search) seem to still think it did otherwise (as I did). I didn't look it up in the service manual last night. But odd to me why they didn't see the benefit of controlling it from the ECM via the temperature sensor. Maybe it was just too much effort to program at the time and not worth the cost?
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