Engine Surging

[agabriel]

Hello All,
I'm new to this forum and 911's; I have a few questions about my 911. I have an '86 911 Coupe w\ 80K miles. The engine seems to surge a little bit when it comes back to idle. Most of it went away when I dumped in some injector cleaner into the tank, however it still does it a little bit - just not as bad. This doesn't seem healthy to me so I'm curious to see what people think...

Thanks,
Anthony

[scottb]

Check your records, and if the following haven't been done you might consider doing the work:

1. O2 sensor should have been changed at 60,000 miles.

2. The cylinder head temperature sensor should be updated to the new 2-wire version.

Also, sometimes the idle control valve goes bad. It's a very easy fix.

I hope this information helps. Good luck!

Scott

[agabriel]

Okay - I'll check that. I was also checking out the throttle cable and it has a bit of slack in it at idle. Could this be part of the problem or should the engine idle properly anyway?

Thanks,
Anthony

[Dan Owens]

Anthony,

The "throttle cable' your seeing with the slack in it probably isn't a throttle cable but your cruise control cable and is suppose to have some slack.

Dan O

[agabriel]

Ok - so if my cruise cable is on top of the engine, where is the throttle cable?

Anthony

[Rot 911]

Originally posted by agabriel
Ok - so if my cruise cable is on top of the engine, where is the throttle cable?

Anthony

There is no "cable" it is actually a metal rod and you can find it down below the cruise control cable.

[pbs911]

Disconnet the 02 sensor. If that doesn't work, check for vacuum leaks and check the fuel mixture is you have an emissions analyzer. My hunting problems were a result of too rich of fuel mixture.

[agabriel]

Okay - I can do that.

Since were on the subject of fuel which grade should I run? I have 89 in it right now.

Anthony

[Lucky]

Also check your plug wires. I had a bad wire which caused the idle on my car to surge between 800 and 1100 every few seconds. I suggest checking resistance from distributor terminal (on the inside of the distributor) to plug contact -- you should see ~4k ohms.

[CrossT]

I can sympathise. My 86 Cpe went a surging episode which was diagnosed and fixed (with the help of those on this bbs).

It would mildly surge at idle as well as during driving. The engine also exhibited a flat spot(s) around 2700 - 3000 RPM.

Replacement of the O2 sensor cured it entirely. Others have not had it so easy as this though.

Check for other threads w/the search ('surge' ought to yield a few hits).

Todd
------------------
86 Cpe GPW

[JavaBrewer]

Originally posted by agabriel
Okay - I can do that.
Since were on the subject of fuel which grade should I run? I have 89 in it right now.
Anthony

I run the very highest I can get which is 91 here in San Diego.