92swtslvr

I have been trying to resolve this issue for a little while now. I have a manual 92 100s with 128k miles on it. When it has sat in the driveway overnight and I drive it, unless I let it sit and idle for about 5-10 mins to let it settle at 800 rpm, it will hesitate and nearly stall out in 1st gear at about 2000 rpm. Also, it seems that the colder it is and the more rainy it is, I have to wait longer for it to settle at 800 rpm from 1000 at start. Once I'm driving for a few miles, the problem goes away and it runs fine. I checked the black wire on the driver side oxygen sensor with a voltmeter. It fluctuated between .2 and .8 volts at idle and stayed at a constant value when the accelerator was steady. So, that is normal operation, correct? I assume the passenger side sensor is operating the same, but I did not check it. I checked the vaccum lines and hoses and they are firm and not cracked. I replaced the spark plugs when I got it with 116k miles on it. Both cats are rattling and need replacing. I'm not sure if the plug wires have ever been replaced and I'm guessing that may be the problem. But before dropping the dough, I heard you can test the resistance on the wires to see if they do need replacing. Does anyone know the correct resistance values? I am working on getting the Bentley manual, I'm a poor college student and can only afford so much at one time :-/ Could the cats be causing the problem? Also, when checking the epoxy insulation on the coil packs, is there a special procedure or can I just pull the wires from them one by one, like when replacing spark plugs? Thanks very much for the advice.

imo46

Have you cleaned the I.S.V ?
Also try replacing fuel filter

92swtslvr

No I have not cleaned the i.s.v. is that easy to do yourself or do I need to take it to a garage?

imo46

Its quite simple.Also check all vacuum hoses at this time
Ive copied and pasted the procedure.Search forum for 'Cleaning ISV' you bound to find some posts with pictures

Procedure One

The IAC valve is located on the left rear of the intake manifold (the multitube snake thingey on top of the engine)
1) Remove the black plastic top engine cover (4 screws)
2) Remove the large black rubber corrogated duct from the airflow meter, at the airfilter box, to the throttle body. (Two hose clamps). This makes some room for access.
2) Find the IAC, a silver metal cylinder, about the size of a D battery, left (passenger side) rear of the intake manifold. It has a wire/connector on top, square plug, retained with a spring clip. Depress the spring clip, and pull the connector straight up. (NO twist!)
3) Unbolt the IAC from the manifold, there are 3 10mm (or 11mm) nuts.
4) Clean the rotating slotted cylinder with WD40 and some Q-tips. Use a wooden toothpick to rotate the slotted cylinder so you can clean as much of it as possible. Always hold the valve with the connector up, so to minimize any WD40 from flowing into the electrical coil part (the silver cylinder body). DO NOT SCRATCH the cylinder or nick the slot edge. (No screwdivers, just the wooden toothpick).
Replace in opposite order, and you should be good to go for another 50K miles.


Procedure Two

ISV Cleaning/Replacement

All left and right references will assume you are leaning into the engine compartment from the front bumper.

First step is to clear the way to remove the ISV. Take off the plastic engine cover, the four screws are similar to Dutz fasteners. Then remove the accordion hose between the air filter box and the plastic plenum to the throttle body. Stuff a rag into the opening on the plastic plenum. Now look for two hoses, one coming off each side of the plastic plenum, they go to the rear top of each cylinder bank. Carefully disconnect them. Now remove the two bolts on top of the intake manifold that hold the plastic plenum in place. At this point you can push the plenum towards the back of the vehicle and then pull upwards. Carefully snake the two tubes out from the maze of wires and hoses. There are a
Couple of vacuum tubes connected to the plastic plenum, the obvious one is to the left as you lean into the engine compartment, there is also a slightly hidden one just to the right of the throttle body. I didn't know about it until I got the plenum out and saw that I had broken it out. It wasn't doing much good anyway as it was completely clogged. I ended up replacing both vacuum lines that go to the plastic plenum with OEM braided vacuum line. Once you have the plenum out of the way, I would stuff another rag in the throttle body opening, better safe than sorry. Foreign Object Damage can be a real bitch.

Once all that is out of the way, you should see a black cylindrical object with a 2 wire electrical connector on top just to the left and just in front of the throttle body. This is the ISV. Remove the top electrical connector. Feel underneath the ISV, you are looking for another electrical connector. It doesn't connect to the ISV, but you will need to disconnect that in order to wiggle the ISV out. I managed to break one of the two "catches" that hold it in place, so be careful, the plastic will probably be a little brittle.

Now that everything is out of the way, remove the two nuts holding the ISV in place. Yes that's right, nuts, the ISV is mounted on studs in the intake manifold. Make sure you don't drop either of the nuts, if I remember correctly, there are three of them. I would suggest sticking a small magnet inside of your socket to hold the nuts so you don't drop them. Once the nuts are removed, you should be able to pull/wiggle the ISV off the studs and out of the engine compartment. The gasket will probably remain on the intake manifold, leave it there.

Once you have the ISV out, thoroughly clean it with a good O2 sensor safe "carb cleaner" or WD40. I used up most of a can of WD40, and on hindsight would probably go with carb cleaner as I believe it would do a more thorough job.

DO NOT apply any voltage to the ISV to check operation. I've heard that a 9-volt radio type battery will work, but I prefer not to mess with it. 12volts will definitely fry an ISV.

Install is simply the reverse of removal. I also cleaned out the plastic plenum and the attached hoses. Make note, that little rubbery valve in the plenum WILL NOT come out without breaking it. That is not a replacement part, you would have to buy the entire plenum for $90 or more. Carb cleaner did not appear to affect it, so just leave it in place. The vacuum port just underneath there on mine was completely clogged, I had to use a piece of coat hanger wire to ream it out and then flush with carb

92swtslvr

Thanks, I'm pretty sure this hasn't been done within the last 50k miles.