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Car running bad at idle and low rpms no boost leak?

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Dawson159

5+ Year Contributor
164
16
Nov 13, 2017
Billings, Montana
I recently replaced my turbo on my 98 eclipse gst I had bought the car with a bad turbo and only drove it once before buying and taking it home and taking it apart. I got it running but it is running super rich and really bad at idle. Is idles at about 800 rpms but sometimes idles at 1000 randomly but usually at around 800. It doesn’t constantly go from 1000 down to 800 and back so I’m pretty sure it’s not the tps? I ordered a new cone filter for my intake and an idle air control valve hoping that it will fix it but I want other opinions on what’s wrong I already checked for boost leaks and there was one but I fixed it and it runs the same. I’m a noob at this as well so plz be understanding :ohdamn::hmm:

Oh and it sometimes gets to about 2200 rpms and doesn’t want to go any higher than that idk if that has to do with this but I thought I’d add it since it runs bad at low rpms and idle.

Thanks for the help:dsm:
 
The first question I have is whether or not the car completely stock? If not, what mods have been done. No check engine? Id say unplug the maf and see if the car is better or worse. If the car gets better there is your problem.
 
Any check engine lights?
No check engine lights

The first question I have is whether or not the car completely stock? If not, what mods have been done. No check engine? Id say unplug the maf and see if the car is better or worse. If the car gets better there is your problem.
It has an upgraded fuel pump, turboback exhaust, a bov that is vented to the atmosphere and a few other things(all this was done by the previous owner) I think the bov might be my problem but idk what do u think?
 
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It's hard to diagnose over the keyboard, but if its running pig rich I would assume it's a spark problem.

Make sure the vacuum lines are all connected correctly, large vacuum leak can have similar symptoms

Make sure your spark plug wires are connected in the correct order, cylinder 1 is on the very right. Wires go to the coil as cylinder 4,1 to coil 1, cyinder 2, 3 to coil 2.


My recommended approach is to put the car back to as close as stock as possible to narrow down problem areas. I would suggest recirculating the blow off valve first, it might not solve the problem but it would help it run better
 
It has an upgraded fuel pump, turboback exhaust, a bov that is vented to the atmosphere and a few other things(all this was done by the previous owner) I think the bov might be my problem but idk what do u think?
You can test the run issue with the bov. Just put your hand over it at idle. Im betting your idle immediately improves. Recirculate the bov please.
 
Order it, what kind of BOV do you have? Go to Home Depot or similar and find a hose that fits it if it’s stock BOV...
 
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Order it, what kind of BOV do you have? Go to Home Depot or similar and find a hose that fits it if it’s stock BOV...
It’s a Greddy s bov and my biggest question is where does the hose go into the intake? I have an Aftermarket Apexi intake and there is a hose that has a bolt in it (I’ll take a picture) is this where it recirculates into?
 
Definitely a start to your issues. so you can recirculate it. The intake pipe should have a specific area for a re-circulation hose like the one pictured here. since your intake pipe doesn't have it, you could possibly customize yours and add one!
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Definitely a start to your issues. so you can recirculate it. The intake pipe should have a specific area for a re-circulation hose like the one pictured here. since your intake pipe doesn't have it, you could possibly customize yours and add one!
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I’m so confused on why mine doesn’t have one?:ohdamn: Do u have any idea on how to customize it so it is like in the picture?
 
if you can't drill a hole and insert a small diameter tube and seal around it for your BOV hose I would look for a stock 2G intake tube which accommodates that re-circulation hose.
 
https://www.millerimportparts.com/A...Eclipse-Talon-Turbo-TSI-GST-GSX-P2519925.aspx
This place is nice for used OEM replacements. I agree with the BoV being vented, that would be a good start. You can set the car up for venting but usually isn't done/recommended because it's more trouble then it's worth for a fancy noise, other then that I'm not sure why you'd want to.. Don't care to look into it cause I'll never do it :D. But that would be why aftermarket intakes have the option for recirculation or venting. Did you try what pauleyman suggested?
 
Can someone confirm or deny if the type S BOV had issues with cracking open slightly at lower pressures? If so, kinda like everyone is suggesting, that could be your issue. I'd go back to what Pauleyman suggested and cover the outlet up with your hand while it's idling to see if that improves the idle.
 
He needs to recirculate it first if he doesn't have a way of venting to the atmosphere correctly. He can then proceed from there.
 
He needs to recirculate it first if he doesn't have a way of venting to the atmosphere correctly. He can then proceed from there.

If you're talking about fixing the engine for doing actual driving, I'm totally with you on that. I'm more talking about a quick and dirty way to give some extra evidence that the vent to atmosphere is causing his problems. If you block off the only vent path of the BOV to atmosphere like Pauleyman suggested, you're back to a closed system where all the air that's gone by the MAF has nowhere to go but back into the engine (assuming no leaks anywhere else). So at idle, if the type S is old enough to be cracking open slightly, he blocks off the outlet with his hand, and idle smooths out, that's a strong piece of evidence to indicate that the vent to atmosphere is, in fact, the route cause issue needing to be addressed, right?

Am I missing something?
 
Order it, what kind of BOV do you have? Go to Home Depot or similar and find a hose that fits it if it’s stock BOV...
It’s a Greddy s bov and my biggest question is where does the hose go into the intake? I have an Aftermarket Apexi intake and there is a hose that has a bolt in it (I’ll take a picture) is this where it recirculates into?
He needs to recirculate it first if he doesn't have a way of venting to the atmosphere correctly. He can then proceed from there.
i replaced the iac valve today and it helped a little bit but the car is running super rich and I’m hoping that recirculating the bov will take away the running rich problem and help the idle more to where it can run well enough to daily drive
 
Your losing metered air at idle which would be going towards the rich side.:D:hellyeah::cry:ROFL:rocks::thumb:

Fix that hose and you’ll have your metered air back!
 
I’m so confused on why mine doesn’t have one?:ohdamn: Do u have any idea on how to customize it so it is like in the picture?
It doesn't have one because they were available with and without. That is not an APEXi unit. It's an injen intake.
Somewhere above somebody is asking about BOV leaking at idle? They don't leak, they're open at idle/vacuum. That's how they work. If you have one off a car you can apply a vacuum to it and it will open.
 
It doesn't have one because they were available with and without. That is not an APEXi unit. It's an injen intake.
Somewhere above somebody is asking about BOV leaking at idle? They don't leak, they're open at idle/vacuum. That's how they work. If you have one off a car you can apply a vacuum to it and it will open.

I was asking about his because modern recirculation valves don't use pressure differences quite like the older mechanical ones do. The ones I have most recent experience with are electromechanical and there were some intermediate architectures from Bosch, Continental, Pierburg, and even HKS that functioned similarly in that they were completely shut at idle due to clever routing of gas flow around multiple valve faces (not too dissimilar from the way the HKS SSQV works:
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)

I just pulled up a diagram of the Type S and, yeah, you're bang on, they'd definitely be open at idle due to the delta P across the diaphragm and valve face for lift throttle and idle conditions, I just couldn't remember off the top of my head weather or not the type S had the clever valve arrangement or not. As I'm sure you're aware, this exasperates the metered air being lost to atmosphere problem at idle, which is why I was using the word "leak", which is not a universally true assumption of all bypass valves.
 
Dawson159 there is nothing on your intake you can recirculate to. Not the hole with a bolt, no spot at all.. you'll have to replace your intake with one like Chrysler kid shared a picture of with that little tube. If you'e not looking to spend a other 250-300 for the pipe then you can reinstall a factory one for 30ish and keep the filter or you can do some handywork and cut a hole where to normal recirc tube would attach And epoxy one in. But again, there is nothing on your intake you can recirculate to right now.
 
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