Here's the first video of my problem, I have a few more uploaded but they're still processing with youtube.

http://www.youtube.com/watch?v=RR77U2oYBNw

The car starts fine and above 2000rpm it seems pretty smooth. It still pops from the exhaust a little bit but nothing too bad really.

However, the car likes to idle at 1200rpm most of the time even when warm. When it's idling, it sounds very lumpy and small pops from the exhaust are frequent. The tach is pretty stable but you can feel the car vibrating when it does it.

The other weird thing is, as can be seen in the first few seconds, and last few seconds of the video, when I hold the throttle at around 1500rpm or so, it just kind of cuts out, drops a few hundred rpm then comes back on again without my foot even moving. It does not do this while over 1500rpm, and it never does this while I'm increasing RPM, only if I try to hold a steady rpm.

I suspect I have a minor vacuum leak since repeated braking at idle causes a bit of bog down, but would a vacuum leak also be responsible for the exhaust popping and weird throttle cut?

Ideas?

 

Forum won't let me edit, here's the 2nd video of the exhaust

http://www.youtube.com/watch?v=tTdhkU3GH5k

 

Come on guys, you can do better than no replies. Anyone?

 

gahhhh

 

Sounds like a blown motor to me. Either that or you popped off a vacuum line somewhere. Check you map sensor vacuum line. Make sure it didn't pop off. Also do you have a boost gauge or access to one? If you do what is the vacuum reading? Is the motor shaking like crazy? What were you doing before this happened? What mods are on your car?

R.K.

 

If you really want to know if its the motor or not let it go idle where ever it wants and look at a vaccume gage. If the needle "vibrates" or "shutters" at a steady rpm that means you have a side seal or apex seal gone...
Pretty much your vaccume reading will tell the whole story.
On another note we kinda need more information. Did this just start? Did you just buy the car like this? Did you let a buddy drive the car

 

in the first video are you reving it like that or is that with your foot off the pedal??

 

How much of a "shutter" is a bad thing? My engine idles at ~850 with 16" of vacuum but ever so often the needle to go to 16.25" and back. This happens maybe 4-5 times a minute while idling.

 

Do you have a digital gauge? I dont know any human that can see a .25 on the vaccume gauge. The vaccume is a little low but your motor seems fine. Post a video of it idleing at 850 and hae the camera on the vaccume gauge.

 

Check your vacuum lines. Doesn't sound like a blown motor to me.

-Andy

 

agreed /\

 

I have been having that EXACT problem you had in the first video off and on with the surging!! I just found out that I installed my primary rail WITHOUT any insulators, thus not creating a tight air seal and providig a vacuum leak. I will report that this is indeed the issue by wednesday.

 

I agree that it does not sound like a blown motor. I would expect a blown/blowing motor to sound a lot more rough, weak in power and / or guzzling coolant.

#1) My boost gauge reads a little bit high, it's reading about .05 more than it should. So when it's idling in neutral at 1200rpm the vacuum shows 500mg, it's probably closer to 550mg (16.25psi vacuum). This looks ok to me. I am going to have to get a new boost gauge, which sucks because I like the look of the old Japanese Apexi one. Oh well.

#2) I noticed that the car only has the surging problem when the clutch or the brake is being pressed in. This makes me think the problem can only be a vacuum line or a TPS. The car also drops down to about 800-950rpm when I put it into gear with the clutch in. The weird fluttering/surging sound begins. The lower the rpms the slower the surging happens, it's almost as if something is building up pressure then releasing it. Solenoid failure maybe?

#3) I noticed a tube sticking out from what I think is the rats nest?? There was no hose attached to it. I thought it looked odd but it could just be a vent to atmosphere or something. I also noticed another hose in the same area that was not connected to anything. See below pic, the hose was below the black tank with the arrow pointing to it. Is there supposed to be an uncapped/unhosed tube there?



On a related note does anyone have a full diagram of all the engine, fuel, vacuum systems together in the engine bay for a 92/93 FD? Have been checking the service manuals and the diagrams are all broken down by subsytem.