I need some help,


Issue #1.

My Trans Am tends to get very hot while parked or at a stoplight. It will shoot close to 260 before it cools down slightly. it will go below or around 220 (even with a/c on) within a minute or two once i start driving the vehicle. The fan only comes on when it reaches that 260ish point and stays on for a few seconds while the temp drops a few degrees then shuts off. System was just flushed out yesterday and issue continues.



Issue #2. When I first purchased the vehicle it idled and sounded very good. When I would lay into the gas pedal it would put me back in my seat and accelerate without any hesitation. Now when I give it gas it sounds like *censored* and it doesn't accelerate the way it did when I first got it.

I went in to a local GM dealer and had an oil change done. Vehicle at this point was running like a champ.. a few weeks later my vehicle had developed a lack of power, so the plugs were changed and that seemed to solve issue.. two weeks later issue came back and a vacuum line leak was fixed, carb was tuned because it was idling a little off and vehicle ran fine for about another two weeks and issue returned. So the plugs were checked and they were fine so the wireset, coil, cap, rotor, Oxygen sensor and fuel filter were changed and it ran ok until recently again.

So I had the timing check and set and vehicle performed slightly better but still is off.. Every time i try and put my foot down on the accelerator it hesitates or even feels like its going to die on me. I've spent a few Hundred dollars on parts and still can't get this dialed down.

I've tried a code reader but the system doesn't pick up anything..
Only thing I noticed was that the carburetor flap doesn't close all the way unless its done physically.


I'm running out of $ and this issue i can't seem to get rid of it.
Any ideas or input will be greatly appreciated

 

BUMP (this is urgent)

 

I just got done working through an overheating issue on my 84 L69 Z28. My issue was the fan housing was warped and the fan wasn't turning. These cars were made to run hot and my fan was kicking on when the needle hit close to 240. Remember, these gauges are not very precise and may be off up to 60 degrees. The only true way to find out how hot your engine is, is to use a laser thermometer to read the block and see how hot it is. There is a coolant temp switch in your engine block between the #6 and #8 sensor on the passenger side very close to the header. It has a single green wire going to it, its hard to reach. This part costs $10 at AutoZone, only thing is if you pull it out while the coolant is in it, you will leak coolant everywhere. Obviously yours is working since the fan kicks on when it gets hot. Only two ways the fan kicks on, one is through this switch and two is when the A/C is on. Is your fan a single electric fan? I replaced my fan with an aftermarket fan from O'Reilly auto parts. I attached it using the plastic connectors that go through the radiator. It now pulls air across the radiator like it should, but it still gets near 220 or above when at idle or at a stop light.

Regarding your crappy idle/getting on it, you've done all the things I would suggest. Hopefully someone else with much better expertise can help you.

 

Yes, Its a single electric fan. On my way home today it shot the guage up to 260 and it started to drip coolant out of the line that connects from the radiator to the coolant reservoir. i tightened up the clamp and it shot up to 260 again a few hours later without the fan coming on :-/

 

try replacing the fan switch? It sounds like it is working intermittently. what about your thermostat, have you looked at the condition of it, maybe it is sticking.

 

If by 'carburetor flap', you mean the choke, that could definitely be a part of your problem.

The hesitation you describe sounds very much like a vacuum leak. How does your car idle? Get yourself a can of carb cleaner spray and, with the engine running, spray all around the base of the carb where it meets the intake manifold and also around all vacuum hoses while listening closely to the engine. If you hear it idle up a little bit, you have found a leak. Another area to check would be your EGR, since this seems to be an intermittent problem. I'm not too familiar with the EGR system on your car, but I'm sure there is a how-to here on this forum for checking and cleaning EGR valve on your engine.

 

The connection to the fan switch may be bad. When I replaced my switch the wire connector was oxidized, and the plastic around it crumbled. Probably due to engine heat and the elements. My hunch is that the connection was bad, not the switch. I was not impressed with the cheesiness of the connector, since the the life of the engine depends on it.

 

I believe your information regarding what turns the coolant fan on is incorrect. My expertise is in the Fuel injected versions and not carbs though. I could not find a wiring diagram for a carb vehicle that had an electric fan, this diagram (http://austinthirdgen.org/mkportal/m...ine_wiring.gif) is for an 86 TPI with an electric fan. The single wire that you are referring to is only for the gauge. It goes from the sensor over to the bulkhead connector C100 pinout F7 on the driver's side firewall. (http://www.austinthirdgen.org/mkport..._1985_C100.gif) From there it goes straight to the gauge cluster, It does not turn the fans on and is a common misconception. Your fans should be controlled by the coolant temp sensor (the leads are usually black and yellow) that sensor goes to your ecm and the ecm is set at a certain temp to turn the fans on and off. Since the sensor is nothing more than a thermoresistor, it is possible you have the wrong one installed or yours is bad. It should be on the top front of the intake or in the thermostat housing. I would alos go ahead and replace your thermostat while your at it, only usually $5. Possible it could be the waterpump's impeller shaft is broken or there is a coolant bubble. I would not drive the car around at 260* until its fixed.

 

No this is wrong. The sensor on the intake doesn't turn the fan on and off, the block sensor does. It has a green w/white stripe that leads to the fan relay. Both carbed and fuel injected engines have this sensor.

 

Part of your information is incorrect, you should refer to the diagram(s) that I posted before making any further comments, thank-you.

There is a dark green and white wire that goes from the ecm to the fan relay, please refer to this diagram: http://austinthirdgen.org/mkportal/m...ine_wiring.gif The ecm uses the coolant temperature sensor in the intake or thermostat housing to tell the temperature, again it is the sensor with yellow and black wires. When the engine coolant temperature reaches the prescribed temperature the ecm turns the fan on by grounding out the relay (via the green/white wire) which in turn completes the relay's circuit. The sensor in the side of the block you are referring to (plain old green without a white stripe) goes straight to bulkhead connector C100 (please refer to this diagram: http://www.austinthirdgen.org/mkport..._1985_C100.gif, not the relay and not the ecm.
The sensor in the side of the block is a thermoresistor and gives out a constant varying resistance, thats all, it can not tell a relay when to turn on and off. Since the entire engine block is grounded, if you were to run a wire straight from this to the relay, it would act as a ground, complete the relay's circuit and the fan would be on the entire time the key was in the "on position."

 

Hey Tibo, I get where you're coming from. Most GM vehicles with electric fans do operate the fans on command from the ECM with a switch in the passenger cylinder head only as a back up that turns the heavy duty fan on at 240. The 84 however uses a fan switch and has no ECM fan control. There are options available for the switch as it was used in various applications. I don't know the part number by memory but there is an option available that will turn the fan on at 180degrees. With a 173 degree thermostat, this will really cool the car down alot. I have not seen any issues with the CCC system by performing this mod.

It is normal that you have to push the choke butterfly closed when the engine is warm. It is opened by a thermostatic spring and should be held fully open by the time the engine has run 5 minutes. Since your ignition system is pretty much new, I agree that your problem is likely caused by a vacuum leak. The CCC carburetor contains a TPS and fuel management solenoid. These can cause trouble. You also have an O2 sensor that may be shorted. But since your trouble is mostly under power I would start by tracing down any vacuum leaks.

 

I still have the weird issue with the cooling fan,

but the other day the car showed 1/4 tank and died in the middle of an intersection.. apparently it ran out of gas.. tried to fire it up for a solid 10 minutes.. AAA came with some fuel and i got it to chevron. Filled it up and *Poof* the hesitation disapeared