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has a rough idle and dies when i let off gas?

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diamondsm

10+ Year Contributor
107
0
Mar 27, 2010
port orchard, Washington
1995 eagle talon tsi

alright so my problem is a rough idle and the car dies when i let off the gas?


INFO ON THE CAR:

freshly rebuilt engine ( i haven't even been able to set the rings )
standard bore fresh hone and ridge reamed
new pistons/rings
evo crankshaft ground .010
3g hydraulic lifters
eliminated balance shafts
Head was surfaced, pressure tested and i had a couple valve replaced
new C.A.S (cam angle sensor)
vacuum lines were eliminated before i bought the car
gaskets ect....

if you need more please ask


I'm pretty sure my timing is dead on but just in case here is some pics
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I did a compression test

150, 165 ,155,170


checked all my vacuum lines i found one coming off the back of the manifold that go's to the egr valve and forks off that has no plug or line going to it?? anyone know if i need to plug or rout a line to it??

anything besides vacuum lines boost leak and timing?
 
Have you checked the tps, biss screw?
And I know this is pretty basic but are you recirculating your bov? Unless you have a gm maf , link or similar.

As for the line off the mani. If you're not sure where it goes, make sure to cap it. Or take a pic and post it so its easier to identify.

Hope this helps,
Hezig
 
it sounds like you just need to dial it in. biss screw, boost leak test, and cap off that line for now. you already over came the hard part of getting it started so now its just a matter of buttoning up loose ends

btw the pic you posted isnt showing up
 
There is no pic on the post.

Check for any exhaust leak before the front O2 sensor, also check to see if you have a leaking throttle body, clean it up if you haven't done it, but I would lean to leaky throttle body, your tps can cause some issues as well.

For how long it keeps the pressure when doing the boost leak, those it comes right down or it holds for quite a bit.
 
I'm going to do a boost leak test later on today...

but in the mean while i took my throttle body off to clean it up and change out the gaskets, when doing so i noticed the throttle plate has side to side slack making a decent sized gap i was wondering if my throttle body be bad?? would this cause it not to idle?
 
Well, the throttle plate screws onto the throttle shaft, so if you are getting movement, something is loose. Probably the throttle body shaft nut. If the throttle body hasn't been rebuilt, I would suggest you take the time to have it rebuilt. It's pretty easy and you should be able to do it in a couple hours. Just make sure you take pictures of it as you disassemble it, as it will make reassembling it MUCH easier. If anything, you will have piece of mind that you have new TB shaft seals.

But as everyone else says, boost leak test. Also, are you recirculating your BOV? is your MAF plugged in all the way? My car did not like haveing the MAF unplugged. Every time I let off the throttle, it would stumble and die.
 
Well, the throttle plate screws onto the throttle shaft, so if you are getting movement, something is loose. Probably the throttle body shaft nut. If the throttle body hasn't been rebuilt, I would suggest you take the time to have it rebuilt. It's pretty easy and you should be able to do it in a couple hours. Just make sure you take pictures of it as you disassemble it, as it will make reassembling it MUCH easier. If anything, you will have piece of mind that you have new TB shaft seals.

But as everyone else says, boost leak test. Also, are you recirculating your BOV? is your MAF plugged in all the way? My car did not like haveing the MAF unplugged. Every time I let off the throttle, it would stumble and die.

everything is nice and tight it just has slack.....yes the BOV is recirculating and yes the MAF is plugged in.....im just going to pull the throttle body off of my other dsm it and all the sensors are known working if that doesnt do it then ill do the boost leak test just wanted to figure it all out before i out it back together
 
I am currently having the same issues. For the most part, I did everything the same as the OP just a few other things are different. (s90 TB and evo3 intake manifold) It is a fresh rebuild. My car does stay on by itself, but misfires when I give it gas. I checked the plugs after a few minutes of idle time. 3 & 4 came out black and 1 & 2 were clean. I already sent the injectors to get cleaned up. I put the injectors back on along with a new set of plugs and the color did change. Cyl 4 plug still came out real black. I haven't done a boost leak test but will try that the next few days.
 
1995 eagle talon tsi

alright so my problem is a rough idle and the car dies when i let off the gas?


INFO ON THE CAR:

freshly rebuilt engine ( i haven't even been able to set the rings )
standard bore fresh hone and ridge reamed
new pistons/rings
evo crankshaft ground .010
3g hydraulic lifters
eliminated balance shafts
Head was surfaced, pressure tested and i had a couple valve replaced
new C.A.S (cam angle sensor)
vacuum lines were eliminated before i bought the car
gaskets ect....

if you need more please ask


I'm pretty sure my timing is dead on but just in case here is some pics
You must be logged in to view this image or video.

You must be logged in to view this image or video.



I did a compression test

150, 165 ,155,170


checked all my vacuum lines i found one coming off the back of the manifold that go's to the egr valve and forks off that has no plug or line going to it?? anyone know if i need to plug or rout a line to it??

anything besides vacuum lines boost leak and timing?

Mines is doing the same thing.... id what it could be...
 
mass air flow sensor. My car was running fine, then suddenly was idling very low and dying without throttle. It ended up being my mass air flow sensor wiggling its way off
 
One thing I like to do is remove a couple sensors to see if the problem gets worse or better or stays the same. That could help you to see if that sensor is bad without having extras. That also can work for vacum lines too. It's just one of the many ways to troubleshoot annoying problems like this.
 
i would do a boost leak test and also check the iac. the stepper motors over time go bad and cause idle issues. also i would delete the egr if you havent done so already(if your state doesnt have emission laws), the egr causes gunk to build up around the iac and over time will cause the motor to get strained and eventually go out. try taking the iac out and cleaning the black gunk off of it. there is a youtube video showing how to test the iac with a standard multimeter. thats where i would start.
 
I am currently having the same issues. For the most part, I did everything the same as the OP just a few other things are different. (s90 TB and evo3 intake manifold) It is a fresh rebuild. My car does stay on by itself, but misfires when I give it gas. I checked the plugs after a few minutes of idle time. 3 & 4 came out black and 1 & 2 were clean. I already sent the injectors to get cleaned up. I put the injectors back on along with a new set of plugs and the color did change. Cyl 4 plug still came out real black. I haven't done a boost leak test but will try that the next few days.
This one sounds like tipical missfire. First check cables and spark plugs. Also good thing is to clean injectors but will not help in this case.
 
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