Hunting Idle problem diagnosis help

[alf]

After a spirited drive in the rain with the Seattle Pelicans on Sunday and a day's rest, my 88 is having some strange ignition problems...

On the first start up, she fires up, then dies. On second try, no problem.

Idle is a little high when cold, but stable.

When warm, idle will hunt for about 3 sec (1100-1300rpm) then settles itself at 980. But the oil pressure continues to goes up and down, and i could hear the engine rev fluctuate. Seems like the DME is compensating for something but manages to keep idle stable.

In the last 1000 miles, i have replaced the cap, rotor, O2 sensor and cleaned the ISV. This was to fix another idle problem after driving in a rain storm for 2 hrs (the O2 sensor got fried).

PO never drove the car in the rain, but i do not want a garage queen but a car that could get wet.

Any ideas?

thanks
alf

[alf]

I've done a search and it could be a number of things from the vacuum tubes to the cyclinder head sensor.

Some questions, where are these vac tubes and how do you tell they are leaking?

Where is the cyclinder head sensor thingy?

thanks
alf

[CrossT]

Head Temp Sensor is top left back hard to even see let alone string a new one in. I bought one and took one look and had a wrench put it in. Wiring snakes in and out of the sheetmetal. Pretty amazing.

Possible other thing to look at is water in cap and new ing wires. Discussion on these should show up in search.


good luck,
todd
=-=-=-=-=-=-
86 cpe

[Quicksilver]

The cylinder head temp sensor is on the front side of the #3 cylinder. It is accessible from underneath the drivers side of the car. The wire attached to it runs through the engine tin into the engine compartment and ends up connecting to the wiring bracket that is just below the heater blower on the drivers side of the engine.

The temp sensor has been superceded by a better unit and is generally one of the first things to swap when you have weird things happening with the engine management.

You can get one here -> http://www.pelicanparts.com/catalog/shopcart/911M/POR_911M_fuelMO_pg6.htm#item17

Because the sensor has a wire attached to it requires a special deep socket to deal with the wire. I can't remember what size the socket is but making one is really easy. To remove the old sensor just cut the wire off. Once you know what size of socket you need, go buy the cheapest one you can find and also get a 1/4" wide grinding wheel that you can use with an electric drill. Use the grinding wheel to cut a slot all the way up the side of the socket. This will let the wire hang out while you are tightening it. The sensor needs only about 6 ft/lbs of torque so don't over tighten it.

BTW, the upgrade replacement sensor has 2 wires where your original probably only has one. Don't worry about it. The additional wire is a ground lead and doesn't require that you hook it up.


Wayne

[alf]

I think i fixed it with a full tank of gas and a little more spirited driving We'll see what happens tomorrow morning.

[stlrj]

then settles itself at 980

Big clue here: the idle rpm on an 88 Carrera is 880 rpm not 980 rpm. Throttle the idle rpm down to spec, that should take care of your hunt.

Cheers,

Joe