I've owned my IROC for about 12 years now and still love it! Anyways, the car always ran well but there were always a few issues with it. First off, the car would crank a little longer when it was hot. Second, the temperature gauge doesn't really move at all and third, blue smoke on startup. I know that the smoke is most likely the valve stem seals. Also, my battery gauge will go down low for some reason while I am idling but will never shut down...new alternator, battery never fixed that. Umm, let me think of anything else...oh yes, the gas tank will kinda hum after I shut the car down from driving a while...when I release the pressure in the tank it goes way. Any suggestions?

 

For starters ill mention that these gauges arnt really the best and being that there not the best and 20 something years old i wouldn't trust their reading too much.

1. Cranks longer when hot:

How much longer? We may want to look into the temp gauge issue first because if the temp is reading correctly and its running very cool this may account for it.

2. Temperature gauge:
When you say it dosnt really move on an average day where you run the car for a bit what is the range of temps it hits according to the gauge (if any)? Try measuring the resistance to ground or the temp sensor for the gauge well compare that reading with what temp that should correspond to and see if it matches what the gauge reads or if what it reads is reasonable for how hot the motor is.

3. Smoke:
You guessed it probably valve seals so i wont really get into that too much.

4. Voltage dips at idle:
Again the gauges are not the best i wouldn't necessarily accept this a true just yet I would start by measuring the voltage at idle with a volt meter and compare to your gauge. I suspect the gauge reading will be off.

5. Gas tank humming:
When you say you release the pressure to you mean it blows out or sucks in? How loud is the humming?

 

I can't recall now how much longer, but it doesn't fire right up like when the motor is cold. The temp gauge used to work and gave a proper reading but now, even after I replaced the coolant temp sensor, it doesn't even move. The voltage drop never used to happen, just started recently...goes very low and lights dim out. Lastly, it's a noticeable hum from the tank but when I release the pressure in the tank, hum goes away. Lots of pressure comes out of gas tank. Also, do you think my timing chain jumped which caused my motor to not start anymore? Now it starts but it's just waiting to jump again? Does this make any sense?

 

Well even with a tew temp sensor there could be wiring issues or a gauge may have failed. Since the temp sensor is new ide say its would be a reliable measure of engin temp. What should be done is measure the resistance of the sensor and compare it to the gauge reading. If the temp sensor says the car never warms up over 100 degrees than your running too cold and that should be corrected as that may cause other issues with the car never getting out of open loop operation. If the sensor says the cars getting up to normal operating temps then the gauge or something associated with it is bad. For the voltage try this with the car off measure the battery voltage then start the car and re-measure the battery voltage. With the car off it should be somewhere around 12V and when started should jump to say 14V. If the charging system isnt working the voltage will remain at 12V or maybe less from the electrical systems loading the battery. For the timing although its possible the cam may have jumped a gear I kinda doubt it. Reason being if the timing jumps a tooth i don't think that would be enough to make the car go from running strong to no start at all. Plus a timing chain is a very reliable piece of equipment and unless you had a ton of miles on your car its not likely it would be that worn out that it could jump a tooth. An easy way to check would be with a timing light if you measure the timing (with the ECMs control over timing disconnected) the timing should be steady reading. If the reading is jumping all around your timing chain is probably worn out.

 

I did the timing, set it to 6*BTDC..runs good..but after I connected the EST, the timing went waaayyyy before BTDC. Is this normal? Also, my passenger side fan always runs for some reason??

 

Well when you say it went way back before TDC to about where? For the most part though from what I have observed this is normal. The 6 degrees is only the base timing that the ECM adjusts from what it will adjust to is based on whats programmed into the PROM which I dont happen to know off hand. If you really wanted to know if it was correct. I would measure the timing and them compare that to the timing table thats programmed into the stock PROM. The passenger side fan i don't recall which one is which but i can say this. 1 fan is controlled by a temp switch and the other is controlled by the ECM. It could be that one of them has been rigged to run always a wiring fault, a bad relay, or something like a bad temp switch or temp sensor(for the ECM not the gauge).

 

The car runs good, I was just wondering why it didn't stay at 6*. Right now for some reason, both fans run as soon as the car is started, never happened before. BTW, how do you backflush the engine/rad?

 

Well it wont stay at 6 thats only where the ECM adjusts from so no worries there. If both fans are running the second you start the car the both fans have to be looked into. All the same things apply as mentioned above. I would start by measuring the resistance of the temp sensor for the ECM and also the resistance of the temp switch for the fan. These are most likely the problem followed by the relays themselves assuming the wiring hasn't been modified.

 

Oh and also on the flushing of the coolant system. Its easy just buy a kit from your local autoparts store or walmart that will allow you to connect a garden hose to your cooling system. All it is really is a t-fitting you patch into your heater core hose. From there just turn on the hose open up the radiator cap run the motor turn the heat on full blast and be prepared to see some awful things come out lol. From there just keep in mind when you do this and youve drained all the water out as best you can there will still be a fair amount of water in the engine block. So if you just put in 50-50 antifreeze water mix it will be diluted with the water that was left behind from the cleaning. I would mix it alittle strong with some extra antifreeze, run it for a bit, and then test the coolant with those cheap coolant testers you can also get at walmart.

 

Can't I just put the garden hose in the top rad hose and run the car with the bottom hose disconnected as well?

 

Well the advantage of putting it in the heater core lin is its forced to circulate through the entire motor, heater core, and radiator. If you dissconnect the bottom hose the water will drain out faster than the hose can provide leaving nothing for the motor which could cause damage. Plus if i remember correctly (not 100% on this) thats the inlet for the water pump anyways and the top is the return line so it would never cycle through the motor anyways.

 

Hey thanks again for your time.

 

No problem at all. Best of luck.

 

Your temp guage runs of a sending unit that is installed in the drivers side head between and below the no1 and no3 spark plug, and not the coolant temp switch.
The humming in the gas tank could be the fuel pump running, on my car the pump would run for a few seconds after I shut it off, if yours doesn't stop after a few seconds it could be a bad oil pressure switch.
As far as the spark timing goes, the computer adjusts the spark timing according to engine load, I think the spark table goes as far as 45deg. The computer uses the 6 deg as a starting point, as long as your base timing is at 6 deg with the est disconnected your good to go.

 

I don't think it's the fuel pump...it hums until I loosen the gas cap, then comes back seconds later. It happens when I drive for a while and shut the car off.

 

Are you confusing the engine temp 1-wire sensor in the driver cylinder head for the temp gauge with the ECM coolant 2-wire sensor in the front of the intake manifold?

Dimming of lights assuming good alternator & battery is an indictor of internally corroded battery cables and, or faulty ground connections.

Tank releasing pressure? Hold some threads close to the gas cap as you open it quickly to tell whether it's pressure or vacuum. Also need to know time when cap is opened; morning, noon, or night.

If timing chain has jumped it will always start the same way and not run properly and run with a loss in power

Sorry John didn't see your #14 post.

 

My heavy duty (secondary) fan will come on with the A/C high pressure switch.

On the pump humm, I once had a bad oil filter that was holding pressure and the pump would run on (humm) when I turn the ignition off until the pressure dropped off, because it did it consistently I started testing all oil pressure related items and found the filter to be bad.

 

Hey RJ, the humming comes from the gas tank...I'm positive. It can be at anytime after I drive for a while. If I drive right now for about 30 minutes, get home, shut her down, the humming begins almost instantly.

 

The oil pressure switch is in paprallel with the fuel pump relay and are powered at all times, turning off the ignition doesn't kill the power to those devices. If the relay, or switch contacts fuse together (not likely) the pump won't shut off.
If the oil pressure for whatever reason slowly drops the pump will run untill the pressure drops below about 4psi.
How much fuel is in the tank determines how loud the humm will be along with the ambient noise existing at the time you turn the ignition off, door open, or window up/down, Eye candy in the passenger seat...etc.

 

If I release the gas cap, it goes away.

 

There is a TSB on that problem depending on the production number.