dredre08

iTrader: (2)

OK guys here is the problem, I just got my 88 iroc-z a couple months ago, and I have been getting her together over the last few weeks (Headers, Y-Pipe, Tune Up, etc....) It's seems to be running fine but Im have problems with the gauges. The speedometer is reading to high, It will say im going like 80 or 90 and I will really be going like 60 or so. The rpm hand I believe might be reading too high as well. Last, is the temperature gauge. At first It wasn't doing anything at all and would just stay at the very end on the cold side, so I put another temperature sensor in, and it started to move but now all it does is randomly go all the way up to Hot side then while driving will randomly go back to the Cold Side. Every once in a while it will stop somewhere in the middle like it is reading correctly but then it will spazz out again so I really dont know if it is reading to temp or not. My questions are:

Has anybody experienced any of these problems?

Do you guys think that the speedometer, rpm, and temp gauge are all caused by the same problem? and if not what are the possible causes of each?

I ask these questions because a guy I know said I need new gauges for all and I just wanted to know before I went and bought all new gauges because that could get expensive....

All input would be greatly appreciated, I want to get this fixed so I can drop her off at the paint shop

Ozz1967

iTrader: (4)

The speedo, that's easy. Do you know what gears are in it? Were they changed from what was original to the car? Also, Check the tire size. If that's not factory, it will also throw off your speedo. The tire size + gearing help determine what drive/driven gears go with your transmission to let the speed o read right. If their not matched correctly, this is the most likely cause of your issue.

For the temp gauge, have you replaced the thermostat? Have you replacd all of the fluid and made sure there are no air bubbles in the system? Do the fans work correctly? They should come on around 225*. You said you replaced the temp gauge sensor on the drivers side bwteen the #2 and 4 cylinders, is the wire to it good? What you describe is reminiscent of an air bubble in the system.

For the Tach, if you can get (borrow) an after market one and rig it inline, you can check it against your factory tach, that would be the best way to determine if your tach is off.

Hope this helps!

dredre08

iTrader: (2)

As far as the gears I really have no clue, I don't even really know where or what the gears are, where would I check the gears at, I'm a bit of a novice when it comes to the mechanical side of everything....

As far as the temperature, I don't really think that the car is overheating, it doesn't seem to be and I always pop the hood to make sure everything feels fine when Im done driving it but hey I could be wrong. As far as the fans the guy I got it from had the fan hooked up to a toggle switch so I just leave it on whenever I'm driving it......... I think its a problem with the actual gauge itself not with the car actually overheating

dredre08

iTrader: (2)

Anybody else got any input???, I really wanna get this tackled this weekend...... Any comment is greatly appreciated.....

Ozz1967

iTrader: (4)

When you have an airbubble in the cooling system, it'll spike "HOT", then "COLD", then settle in the middle until the airbubble comes around again. It's common when you swap motors, radiators, do a drain/flush of the system.

For the gears, unles the previous owner knows, the only way to tell for certain is to pull the diff cover and count teeth unless you can read numbers on it with the diff cover off. There is also another way you can figure it out by wheel diameter/spin at a certain RPM, but I don't know that formula. Your best bet, is to get an original set of wheels, put the factory size tires on, and see where the speedo reads. The tire size should be listed on the door frame of the drivers door, near where the latch catches.

dredre08

iTrader: (2)

Well getting the temp guage fixed is my first priority, so how do I go about checking to see if its an air bubble in the system and getting it fixed??

And as far as the wheels concerened they are the factory wheels with factory size tires......

Ozz1967

iTrader: (4)

So what are the tire sizes? 205/60/15? 235/60/15? Etc. Need to know this in order to calculate.

If you have 205/60/15, 700R4, and 3.73 gears (Unknown at this time), you should be running 2K RPM at 55mph. 2600RPM at 70mph. This is what I have. We can figure out your gearing based on the other factors. (Speed and tire size and transmission).

To air out any bubbles, take the radiator cap off and start the car. Once it gets hot at operating temp (The temp the themostat opens), you'll see the fluid move. If you have an air bubble, when it does this it'll bubble up suddenly, then as the air bubble passes the cap, your fluid level will drop. It'll cycle like this until all the air is out of the system. Make sure your heater is on high when you do this. This is also called "burping" the system.

Watch your temp gague, or have someone else watch it. As the air bubble moves around, the temp will spike hot as the hot air passes it. Then when the coolant gets to it it'll cool back down and stabilize.

You'll need to fill the radiator after it bubbles up and down a bit, once it levels off, that "should" cure your gauge from doing it's flip flop. if it doesn't, then you've got bad wiring or a bad gauge, only way to fix that is to get a HELM manual and start troubleshooting from there. THat's about the only thing we can't do over the internet. We can give you ideas to "look" for, but diagnosing without being on the car is very difficult. Sorry if I"m not more help.

seawolf18

iTrader: (1)

Have you checked the grounds? there should be a body ground attached to the back of the passenger side head, and two grounds on the back of the driver's side head. If the grounds are bad your car will do some very funky things.