HELP!!! Vaccum leak, twitching secondaries and rough idle

[Gerb27]

I pulled the codes and got nothing but 1 1 1. I have been searching really hard for a vaccum leak for the last week.

My secondaries are twitching between 1 and 3k rpms. What is this about??


I pulled the plugs out and they had carbon all over them. I cleaned them and put them back in. The compression test measured 180lbs of pressure in the cylinders.

The car will start everytime but won't stay running without giving it gas. Has anyone had this problem before? By the way I did the upper 60k about 2 months ago.

 

[johndallara]

rough idle

might be the IABP valve (located on the upper intake). Esp if you did 60K recently and cleaned out the intake, I am told that this will sometimes make IABP go bad. Would try a 1-for-1 replacement.

Don't know about the issue with the secondaries. Did you make any modifications when you did the upper 60K ?

JD

 

[Gerb27]

No all I did was clean it. Thanks for replying.

 

[93rev2sev]

I made a housecall to this sick SHO and even if you prop the throttle open a tad, it runs ROUGH. Give it a bunch of throttle and it seems to smooth out but not until about 3500RPM. You have to hold the RPM to about 1500 for it to stay running. There is no knocking. There is LOTS of black soot on the plugs. I also helped gerb with the 60k 2 months ago. I have his old plugs. They are/were very clean.

Something has gone wrong inside this engine.

When we did the upper 60, the valve shims were spot on. No adjustments needed. The heads were nice and clean inside and I was jealous(looked like a very low mileage motor).

Gerb mentioned that he overheated it a while back but not to the point where the engine gave up and stalled. I told him that it might be a head gasket but the solid compression on all cylinders makes me think it's something else.


When you hold the idle at about 1500-2000, the butterflies twitch. They open up when the engine stops and close when the engine is started...but then they twitch.
Anyone have any ideas...
Ideas?

 

[SeanMc]

Propane and a rubber hose. I did this and found a bunch of vac leaks. This works much better than the carb cleaner. I found 4 out of my 6 silicone couplers aren't sealing properly, and won't seal. Yes, I have new ones on the way.

 

[93rev2sev]

The engine dosent idle well enough to hear a change in RPM from propane.

Ever tried that method at 3000RPM...thats where the engine smooths out.

 

[Off Road SHO]

It sounds like you have a major vacuum leak. It's vacuum that holds the secondaries SHUT. When the vacuum is removed, the shaft springs do their job and snap the secondaries open. Major leak somewhere. Air is getting in the cylinders but not being measured by the MAF sensor.

There might be a slim chance that the electrical part of the secondary controller is loose. Unplug and re-plug in the connector on the secondary controller a few times.

Tom

 

[93rev2sev]

There might be a slim chance that the electrical part of the secondary controller is loose. Unplug and re-plug in the connector on the secondary controller a few times.

Tom

Thank for the explaination...it makes even more sence that it's a vac leak now.

Wiggle test...Did that... Maybe a hose melted when it was overheated.

Got a link to the vacuum diagram?

 

[Off Road SHO]

Got a link to the vacuum diagram?

Not handy but it should be on the core support label, it's an EPA requirement.

Tom

 

[JustinSane]

intake gaskets ?? when mine had a small leak there it ran so rough i swore 2 plug wires had been crossed.

 

[93rev2sev]

intake gaskets...We used new ones after the 60k. I suppose it's possible...

 

[Gerb27]

Thanks for the input fells. Thanks 93rev2sev for the house call. I will go and try the wiggle technique.

 

[johndallara]

vacuum leak ? secondaries twitching

come to think of it, when I first removed and replaced the upper intake on the 95 ATX, I had major problems with a vac leak. Turns out I had not seated the cleaned intake properly, and the engine would just die each time I started it up.

Fix there was to disconnect the 4 support mounts, and gently bolt it into place to the lower intake first. Then support it in place with the 4 brackets. I am told that you also can remove the crossover tube when bolting down the upper intake to avoid this problem.

Best of luck,
JD

 

[93rev2sev]

And loosen the rubber couplings.

 

[SeanMc]

And loosen the rubber couplings.

My new silicone couplings are not sealing right. It's entirely possible that this is it. Mine runs so rough, you'd think I had cams.

 

[93rev2sev]

My new silicone couplings are not sealing right. It's entirely possible that this is it. Mine runs so rough, you'd think I had cams.

You don't have cams?!?!

Lemme guess, electromagnetically controlled valves and COPs.

 

[Gerb27]

I cleaned all the main connectors with stp wire dryer the blew them out with my air hose and plugged them back up and the car purrs like a kitten. I sure wish I would have done that earlier.

 

[Off Road SHO]

I cleaned all the main connectors with stp wire dryer the blew them out with my air hose and plugged them back up and the car purrs like a kitten. I sure wish I would have done that earlier.

Score another for the old guy.

Old guys rule! :hdance: