I was wondering if a cracked manifold could change the idle. Its cracked were #1 goes into the main pipe. Its before the oxygen sensor so I didn't know if it could mess stuff up. It idles at like 2000rpms.
I was wondering if a cracked manifold could change the idle. Its cracked were #1 goes into the main pipe. Its before the oxygen sensor so I didn't know if it could mess stuff up. It idles at like 2000rpms.
The high-idle problem on V6 Fieros is almost ALWAYS the result of a cracked EGR tube.
It looks like this:
... and you generally wouldn't even notice it because it's usually located underneath a heat shield fabric (like this beat up looking one)
But it's almost always here where that happens, and it's like having the throttle body open at all times. The biggest problem is that this immediately causes more air, but does NOT lead to more fuel... so the engine ends up running lean, and gets extremely hot... which almost always leads (during a prolonged period) to cracked exhaust manifolds.
This is the replacement part you need for this (once you confirm that this is your problem): https://www.fierostore.com/.../Detail.aspx?s=67019 ... it's $119, and will outlast the original (it's steel braided, not just a steel pipe).
This tube is located just behind the throttle body. It attaches underneath the red intake plenum, and attaches to the EGR which is off to the side beside the starter and ignition coil. Here's a good picture of a Fiero V6 engine that shows the tube well... it's that silver tube off to the left that looks like it's coming off the distributor (which it isn't).
Hahah... shoot. Ok then in that case, it's either something directly on the intake manifold (some huge leak)... or it's possibly leaking from the brake booster. How do the brakes function?
Second question, do you have a check engine light on, and have you checked the codes?
Before when I pushed the brakes it would run rough and stall.(I took the booster off and put it back on and it stopped doing this) If I let it sit idling for like half an hour it will go down to 1000 it tries to go lower but when it hits 800 it runs rough or stalls. Also if it's at like 2250 I can step on the gas and it will drop to 2000.
Before when I pushed the brakes it would run rough and stall.(I took the booster off and put it back on and it stopped doing this) If I let it sit idling for like half an hour it will go down to 1000 it tries to go lower but when it hits 800 it runs rough or stalls. Also if it's at like 2250 I can step on the gas and it will drop to 2000.
Hmm... I'm trying to think... it's definitely either a vacuum leak, or a problem with something on the TBI unit (like the idle air control valve. or TPS).
Can you tell me what year it is? Is it an 84-86 or an 87-88?
All of the vacuum lines (including brake booster and everything else) attach to the intake manifold. It's all accessories basically, so there's no concern for anything else that affects engine performance other than the EGR. Because you said that after an hour, it tends to smooth out to 1,000 rpms (fully warmed up), it's possible that it could be the EGR valve has failed, and is allowing it to suck in too much air. When the EGR is closed, this would be less of a problem.
Can you try something? Try unplugging every single vacuum line off the intake. I don't have the intake in front of me, but there should only be a few. One large one on the side, and a couple of smaller ones. Plug them with vacuum line gaps if you have them, or some other way to ensure they're actually capped (like a piece of vaccum hose with the end cut off and a screw stuck into it. Whatever you can do to ensure that the vacuum lines / intake is sealed. If you're still getting a very high idle (after say... 5 minutes), then there's probably something else going on.
You'll want to check the seal for the EGR valve, as well as the gasket for the TBI unit. Either could be bad and allowing air into the engine when it should not be.
Let me know how that works. Can you take some pictures too, and possibly a video of the engine starting when cold (with a walk-around)?
Chances are, there's probably a few things going on with this car, especially if it's been sitting for a while.
I ran my '84 SE 2.5L 4 speed for years with both #1 and #4 exhaust manifold pipes broken off from the center #2 & #3 section. It didn't seem to affect idle speed. I wondered if it might affect the oxygen sensor readings for fuel metering.
I left it that way anticipating that removal attempts would result in broken bolts that would be awkward to get out. It would be a little noisy sometimes when cold, but quieter when warmer as the broken joints would close up. Last year I had to replace a failed head gasket, so I replaced the 3 piece manifold with a good one while the head was off. https://www.fiero.nl/forum/Forum2/HTML/146435.html I was surprised that all the bolts came out cleanly, even the ones with the heads practically corroded off. https://www.fiero.nl/forum/Forum2/HTML/146459.html
[This message has been edited by David Hambleton (edited 05-11-2023).]
I tried capping the lines. It went to about 1100rpms right as I started it.(it started way faster too) It's a 87. Also when I move the bolt in the the line it changes the idle little bit.
[This message has been edited by GabeBjerk (edited 05-12-2023).]
Oh **** ! You have an 87 SE/L4... that's like one of the rarest Fieros made. People will balk at this, because it doesn't in fact mean that it's more valuable... but there were only 1,401 of those ever built. I've only ever seen one in person, and there was one other person on here that had one. All of them were medium metallic red (what yours is).
I mean, that doesn't help you, but it's kind of cool. Basically, they took what would have essentially been a 4 cyl coupe, and then stuck all the V6 stuff on it, including the dual exhaust, aero-package (like on the 84 Indy), with all the SE trim, and many of them even got the auxiliary gauge cluster.
I don't know if it'll ever be worth more or less than any other Fiero... but it was essentially the rarest / lowest production number Fiero out of any of the models... so long as you're not counting a Fiero MERA, or a T-TOP Fiero as a model (which it isn't because it's an option).
Anyway, back to your problem...
Going to 1,100 rpms on startup is actually quite normal until it warms up (and should drop to about 700-800). But the easiest way to diagnose this problem now, is to start the car at various points after it's cooled off, and each time, have a new vacuum line reconnected back onto the intake manifold. As soon as you start the car and it jumps back up to 2,000 rpms... you've identified the SOURCE at least of your vacuum problem, and then you can follow / trace that vacuum line to wherever it's connected to on the other side. My guess is likely the brake booster or something like that.
So I started hooking up the lines to find the leak and I found that when you hook up the map sensor it revs back up to 2000rpms. So i'm guessing it's broken.
So I started hooking up the lines to find the leak and I found that when you hook up the map sensor it revs back up to 2000rpms. So i'm guessing it's broken.
Yes, either the MAP sensor is bad, or the map sensor vacuum line itself is bad.
You can diagnose this by disconnecting the pigtail on the MAP sensor (with the vacuum line connected), and then starting the car. If the idle is fine, then the MAP sensor is likely bad. If the idle is still high, then it's the vacuum line itself that's bad.
I capped all the vacuum lines and it went to 1500rpms. then I hooked up a good map sensor without the plug and it stayed the same but when I plugged it in it went right up to 2500rpms. I don't know why it does that.
I capped all the vacuum lines and it went to 1500rpms. then I hooked up a good map sensor without the plug and it stayed the same but when I plugged it in it went right up to 2500rpms. I don't know why it does that.
If I'm not mistaken, disconnecting the MAP also puts it into "Limp Mode," which means the ECM is defaulting to the use of some other sensors, like the O2, TPS, and one other (I think). I guess the good news here is that you don't actually have a vacuum leak... which is usually the culprit. But I'm kind of at a loss.
The only thing that I think is frustrating though, is that most new sensors that you buy are going to be made in China, so they produce garbage voltage results which often cause erratic behavior. I think you said the check engine light doesn't come on either, right? So it sounds like it's just running a bit high and trying to warm up... though that is certainly not ideal for the engine to be blasting to 2,000 rpms the second it cranks over.
Gunna hope that some other people have some advice too...
Okay, full disclosure. I've been ignoring this thread because it ticks me off that people don't indicate in their opening post what year Fiero they have and which engine it has. So much time and bandwidth is wasted with people giving advice for the wrong engine and/or year Fiero. Totally unnecessary.
Alright, with that out of the way, read this thread... '88 2.5L Duke high rpm on start-up normal? Except for the oil filter mount and internal balance shafts, the '87 and '88 dukes are very similar.
As stated in that thread, I had an '87 duke (was my first Fiero)... and I hated that engine.
And make sure to also click on the two hyper-links I posted in that thread.
[This message has been edited by Patrick (edited 05-14-2023).]
So I let it idle at 2500rpms and after 2-3mins it went to 800-1200rpms then it dropped to 600rpms and died now it won't run it starts goes to 1000rpms and right away dies.
Never mind it just ran out of gas!
[This message has been edited by GabeBjerk (edited 05-14-2023).]
