At the end of my rope... rough idle.

[decathect]

So i've been working on idle problems for a while now, with my 93 tsi awd.

I had a loping idle and some boost leaks, as well as a bad ISC motor, all that is fixed now. It idles at a constant RPM, it boosts fine, no huge boost leaks.

However... my idle is rough! My car sounds like it has a high lift cam, but it most certainly does not. I can't quite set the idle where it should be at 750 RPM or so, because it idles so rough that the car just seems to shake violently and i'm worried about it dying.

I have been told I should check the timing, I'm going to do that tomorrow and post results. Is there anything else I should check?

Are there any suggestions about how to proceed?

 

[poonman]

Check your EGR Valve for sticking.

 

[decathect]

Check your EGR Valve for sticking.

EGR valve has been deleted with a plate, no leaks.

 

[poonman]

is this something new or been going on for a while?

 

[ilco187]

got any CEL or unplug the mass sensor and try and see were it idles

 

[poonman]

got any CEL or unplug the mass sensor and try and see were it idles

I remember my first DSM 93 GS I somehow got soap in my MAF and WHAO boy that thing ran like poo

 

[decathect]

got any CEL or unplug the mass sensor and try and see were it idles

I'll try that. I don't have a CEL.

This has been going on a while, i've just been doing a lot of work diagnosing it. Its probably been going on for a month or so, I just got the car.

Could the fuel filter be causing this? Perhaps the coil going bad? I think i'm also going to do a compression test.

Driving the car seems fine, it has plenty of power and seems to rev fine in the higher RPMs.

 

[decathect]

How about power transistor? I just randomly came across someone saying theirs was a problem, its something I hadn't thought of before.

 

[snowborder714]

blah, I wish I could post this thread in a section of the forum that people actually look at

Please do not bump your thread.

 

[95GSXBLUR]

when is the last time you changed your plugs or had them gaped properly?

Clean injectors? fuel filter replaced? fuel pressure @ proper level?

Start simple.

 

[decathect]

when is the last time you changed your plugs or had them gaped properly?

Clean injectors? fuel filter replaced? fuel pressure @ proper level?

Start simple.

plugs were changed about 500 miles ago, gapped properly. How do I verify definitively that my injectors are cleaned? Pay to have them cleaned? I have been meaning to install a fuel pressure gauge, maybe i'll do that.

 

[95GSXBLUR]

Are you running the stock FPR? you need to update your profile so we can see what you've got.

Any tuning capabilities? WB A/F Gauge or any logging? Any way to adjust fuel or spark?

Injectors would have to be uninstalled and cleaned properly. FIC does it for a small fee. You could seafoam your engine/fuel system. or run an Injector cleaner through it and see if it helps.

What about the fuel filter?

 

[decathect]

I've been considering doing the fuel filter, though i've never seen a fuel filter actually affect idle or anything, really. Is it worth running some injector cleaner through the system?

Car is basically bone stock. Stock FPR, no real tuning capabilities. I have MMCD on a palm, I'm gonna get that up and running here and look at things. Also going to check timing, because it appears that the Cam Angle sensor is turned to the left quite a bit.

 

[91PlymouthLaser]

If it was a fuel filter it would be doing it at all times i.e. not just during idle. If I was you I would check your MAF.

 

[decathect]

I unplugged my MAF while running, and the car runs DRASTICALLY different. Idle jumps up and down, it freaks out. So I assume its at least partially working. How do I check it? Just swap out with a known good unit? I almost wanna say you may be on to something...

 

[ilco187]

try a different mass, and see what happens, a crapped out mass will make a car run $hitty, but when you unplug it it will run somewhat better.

 

[25391tally]

chech your tb gasket thats were mine was leaking and it was bad

 

[rush2252]

So i've been working on idle problems for a while now, with my 93 tsi awd.

I had a loping idle and some boost leaks, as well as a bad ISC motor, all that is fixed now. It idles at a constant RPM, it boosts fine, no huge boost leaks.

However... my idle is rough! My car sounds like it has a high lift cam, but it most certainly does not. I can't quite set the idle where it should be at 750 RPM or so, because it idles so rough that the car just seems to shake violently and i'm worried about it dying.

I have been told I should check the timing, I'm going to do that tomorrow and post results. Is there anything else I should check?

Are there any suggestions about how to proceed?

I think the problem maybe simple.. @ curb idle w no accessories on you should be set at 850-900 if your trying to get it to idle down to 750 then its going to idle rough. Adjust the SAS slowly and see if raising the idle a bit helps. Also does it run fine if you idle it up w the throttle to around 1000 and does it misfire while driving?

If you have a boost leak on the charge side before the throttle body it can cause it to idle like shit. Also try tapping the MAF lightly and see if the idle changes. This is a way to test the MAF if you dont have a datalogger. If the idle changes the MAF is bad.

 

[MichaelSuch]

Have you checked the ignition timing? It needs to be at 5 degrees BTDC.

 

[decathect]

Have you checked the ignition timing? It needs to be at 5 degrees BTDC.

actually, just checked it today with a timing light.. however I know i'm supposed to ground a plug or something, but i couldn't find it. Can anyone tell me where it is? That being said, the timing was a bit on the retarded side, just under 5 BTDC with the computer still controlling it. I advanced it to closer to 10, and it idles a lot better now... but its still a bit rough.

I think something is still going on with the idle. I've never really used a timing gun before, but when I was using it today, the when the light flashed, the timing mark on the crank pulley wasn't always in the same location. It was 'jumping' around and the light was hitting it in different places. It was funny, i could even see it change as i heard the idle make a similar jump. Should I be concerned about this? Is something wrong?

 

[MichaelSuch]

That's most likely because the computer was taking control still. You definately need to ground it and try again. I'm not sure what car you have whether it's 1g or 2g, I'm not certain on 2g's since I've never owned one but on a 1g check this. It should help. The plug you ground is close to the firewall, it's just a 1 wire plug that goes into your harness with a little cap on it, pull the cap off and ground it.

 

[decathect]

wait... I dont think this was my computer. I'm saying that on every revolution of the engine, the timing advance was different. For example, on one revolution it would be 8*BTDC, the next it would be 5*BTDC, then 10*BTDC, and so on. Make sense? Is that really the computer manipulating it? That almost seems to me like an ignition problem.