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Discussion Starter · #1 ·
This has been going on for 3 days and I've troubleshot a ton of stuff and I have not come up with a problem. I did search but no one was really having the identical problem I am.

Basically if I'm driving the car, or cruising along, it's fine - shifting through the gears at a speed (accelerating) it's fine...it's when I come to a stop, or a very slow rolling stop, where the car will just shut off (all lights stay on, though). It will not turn on instantly, either. I have to sit there maybe 1 full minute before I turn the key, then the car fires right back up. If I try to start it too soon after it stalls out, it will just keep turning over but never fire up. This only happens at a stop, when I'm waiting on a red light, or taking a slow turn or when rolling very slowly with the clutch pedal in at a very low speed. If I'm on the freeway there are no problems, nor are there any when I get on it even to redline. A/F still looks good and zero KR.

Fuel pump primes and there's appropriate fuel pressure at the rail (gauge is spot on). I have checked every fuse in the car and all are fine. I replaced coil, spark-plugs and wires, battery is spot on with voltage, alternator is working fine, etc. I see no shorts or anything and there's no unusual noises. I have not done anything to the car recently, and it's throwing no codes.

Any ideas would be greatly appreciated.
 

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This has been going on for 3 days and I've troubleshot a ton of stuff and I have not come up with a problem. I did search but no one was really having the identical problem I am.

Basically if I'm driving the car, or cruising along, it's fine - shifting through the gears at a speed (accelerating) it's fine...it's when I come to a stop, or a very slow rolling stop, where the car will just shut off (all lights stay on, though). It will not turn on instantly, either. I have to sit there maybe 1 full minute before I turn the key, then the car fires right back up. If I try to start it too soon after it stalls out, it will just keep turning over but never fire up. This only happens at a stop, when I'm waiting on a red light, or taking a slow turn or when rolling very slowly with the clutch pedal in at a very low speed. If I'm on the freeway there are no problems, nor are there any when I get on it even to redline. A/F still looks good and zero KR.

Fuel pump primes and there's appropriate fuel pressure at the rail (gauge is spot on). I have checked every fuse in the car and all are fine. I replaced coil, spark-plugs and wires, battery is spot on with voltage, alternator is working fine, etc. I see no shorts or anything and there's no unusual noises. I have not done anything to the car recently, and it's throwing no codes.

Any ideas would be greatly appreciated.
My saab had the exact issue, I know not the same but it is a 2.0T, Turned out to be a collapsed vacuum line. I replaced it and all issues went away. May help may not GL
 

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Discussion Starter · #3 · (Edited)
I also forgot this tidbit - if I start the car, and let it idle, it will just shut off after maybe 3 minutes of idling just fine (like starting it in my driveway, then going back into the house to get something). RPMs aren't erratic or anything. Boost gauge showing the appropriate vacuum and boost but I can check the lines. Thanks for the advice.

**EDIT**

All vacuum lines look good and are solid. Damn this is pissing me off, and numerous times it's done this in city traffic. The SRT-8 Jeep gets such shitty gas mileage, but I may have to go back to driving that as a daily until I figure out the issue here. :\
 

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I also forgot this tidbit - if I start the car, and let it idle, it will just shut off after maybe 3 minutes of idling just fine (like starting it in my driveway, then going back into the house to get something). RPMs aren't erratic or anything. Boost gauge showing the appropriate vacuum and boost but I can check the lines. Thanks for the advice.
Dude, the more you add the more it literally sounds like my saab. Check all your vacuum lines.
 

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Pull the Idle Air Control Valve from the throttle body and check to make sure it's relatively clean and the plunger moves relatively easily. Next, I'd recommend hooking up a lead to the IAC voltage line and see what it does when the car dies. If the voltage drops when the car dies, then you know the valve is closing.
 

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Bad iac causes symptoms close to this.when I had a bad connection electrically with the plug it wouldn't start unless I had my foot on the gas.iac could be worn or stuck in your situation,swap with a local or buy new and report back
 

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Discussion Starter · #9 ·
Looks like I'm going to have to take the throttle body off to get to this. It's torqued down good, and it's at such an odd angle, I can't get pressure on the torx bit and it just slips out.
 

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Discussion Starter · #11 ·
Take tb off hit it with some penetration oil and an easy out.if u get it off rePlace hardware that holds it
Yeah gonna' have to do that. I'm tired of being in the garage troubleshooting this so I will have to get to it tomorrow. I have a spare IAC sensor around that's good so I'll be happy if this one is fubar'd and that's the issue. I'm just amazed how damn tight that bolt is on there, and now I think it's been rounded out a bit by slipping so I really have no other choice but to take off the TB. :flame:
 

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Discussion Starter · #12 · (Edited)
Alright, I took off the throttle body and got the IAC sensor bolt out by taking a grinder and making a slit in it for a flat-head screwdriver. So anyways...it's in perfect working order. I blow on the end and no air comes out, and the piston (whatever) moves up and down freely. Just for a comparison, I took an older unit that I had and blew on the end and I could feel air coming out. The one in there now is tight as can be.

So, with that, any other ideas? I've also looked at all the vacuum lines and I can't find any that are collapsed. The wiring into the IAC was fine, too, as I tracked it all the way down and found no cuts or anything. Plus, when I wigged it with the car on, I could not produce the same symptoms. Ugh...I was really hoping it was the IAC...

**EDIT**

It is quite dirty, so I took some brake cleaner and got off all the grime. Not sure if that'll help, but I read here that cleaning it has helped other people.
 

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Discussion Starter · #13 ·
Well I can't do much but laugh at this point. Fired the car up and it idled fine...got on the road and was cruising and went to stop (put clutch in) and RPMs went up and the brake went stiff, though I was still able to stop. Went back home and checked under the hood. Everything is hooked up properly, so I took the TPS off and made sure it was on there right and it was.

Started the car up and the same shit...high idle with clutch in. Removed connector from IAC and it started to run a bit better (brakes worked again) but the idle is high in neutral, but not if it's during engine brake. Clearly my IAC is screwed up but now what's the deal with this high idle bullshit? Wiggled the TPS wires and couldn't reproduce the problem (it's rewired). Only SES light on is for the IAC sensor.

Car didn't just turn off, though.

So, any ideas? Bad sensor(s)? I have an extra TPS that's brand new layin' around. Obviously I need a new IAC even though testing it yielded no problems (ugh).
 

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Discussion Starter · #18 ·
Tested it, yes. Couldn't hear squat. Brake booster line is also connected perfectly on both ends so it's not that. It has to be one of the sensors that's fubar'd, because I'm also out of ideas.

I will BL again tomorrow to see... Had to wait for the motor to cool back off to do anything. It's something before the throttle body, though, not after. I'll also have to jack the car up again I guess. Bleh.
 

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Yeah, with the brake issues at the same time, there's definitely a vacuum issue but where? Do you have a vacuum pump? If so, you could take off various lines and test them one at a time to see if you can identify what it is. Of course, if its electrical, it may only leak under certain conditions, so then you'd have to vacuum test when the problem is occurring which may be a bit harder. Lot's of one way valves on our cars though, so if you know which way air should travel, it's pretty easy to check them since if those are getting stuck, you could be leaking within the system which would be harder to detect by sound. Your problem is under vacuum and not boost though, so remember that those valves, can mask leaks further down the system if you only check with pressure and not vacuum.
 

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Discussion Starter · #20 ·
Yeah, with the brake issues at the same time, there's definitely a vacuum issue but where? Do you have a vacuum pump? If so, you could take off various lines and test them one at a time to see if you can identify what it is. Of course, if its electrical, it may only leak under certain conditions, so then you'd have to vacuum test when the problem is occurring which may be a bit harder. Lot's of one way valves on our cars though, so if you know which way air should travel, it's pretty easy to check them since if those are getting stuck, you could be leaking within the system which would be harder to detect by sound. Your problem is under vacuum and not boost though, so remember that those valves, can mask leaks further down the system if you only check with pressure and not vacuum.
It's just weird the brake issue went away when I unplugged the IAC. That makes zero sense to me. Anyways, today I'm going to install the new TPS I've had for a few years to see if the problem goes away. If not, back to square one. I cannot find a single boost leak at all, but may start spraying with carb cleaner for changes in idle for a vacuum leak.
 
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