I have a serious problem guys. I put on the new headers and broke a sensor off of the side of my block. Now my check engine light comes on and my car runs HOT. It was on the passenger side right under the header. It must have gotten hot (duhhh!!)and just got brittle because it broke not only the sensor in the block but also broke the plastic clip from the ECM. Does anyone know what this sensor is and how to replace both ends of the connection? Thanks in advance guys.

Eric

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Teal 1991 Camaro R.S., T-Tops,
Leather, Re-worked 700r4 also w/kit,
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MSD Coil, ADS superchip, Open element air cleaner,
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Edelbrock TES headers, March 3piece billet underdrive pulleys
3.73 gears
http://www.geocities.com/gitarz2/camaro.html
I was shocked to see that companies sold a taillight
set for a rustang! Since when do they have taillights????

 

I assume you are talking about the knock sensor, and I assume the code that sets is a code 43 for the ESC system. You will need a new knock sensor, and I would snag a connector from a junkyard. I have an extra connector that I could send you if you are that desperate, but make sure it is the knock sensor connector that you really need.

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I was told that it is NOT he knock sensor. I was told today it has something to do with my fan. Could there be another sensor there?

Eric

 

Not on the passenger side. The ONLY sensor that goes directly into the block (on either side) is the knock sensor. It's near the terminals on the starter. The coolant sensor that your fan depends on is in the front of your intake manifold, and the temp sensor that your gauge uses is in the driver side cyllinder head between cyllinder 1 and 3.

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View the restoration of an 85 IROC</A>
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I thought so. However it is NOT near the starter. It is directly under the header in the center of the block under the spark plug directly under the head.

 

What you just described IS the knock sensor.



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Mike Metzler (Desert86Roc)
Mike@SpeedworldMotorplex.com
[*] Webmaster: SpeedWorldMotorplex.com[*] Click Here For My Racing Page[*]86 IROC 305 TPI (406 build in progress)
ET's @ 1250 ft[*] 14.28 @ 95.461 mph (uncorrected, NOS, no headers)[*] 15.365 @ 86.785 mph (uncorrected, Headers, no NOS)

 

And it IS near the starter. The knock sensor is only a few inches from the electrical connections on the back (front???) of the starter.

------------------
The IROC Homepage
<A HREF="http://www.rit.edu/~jli4307/camaro" TARGET=_blank>
View the restoration of an 85 IROC</A>
"I didn't know a bored out Ford could go so slow" -Shenandoah

 

OK, here are the facts. If you are posative it is not the knock sensor the only other sensor on that side is in the head right next to the header, actually between cylinder 6 & 8. This is the one that I broke when doing headers, granted mine is a carb. but it still ran really hot. To test this sensor get a long piece of wire and while the ignition is in the run positition touch it to a ground on the motor/frame and if the fan turns on then you know what it does. Also another way to tell is if you can see the connector easily from the top of the motor, then it is in the head. If your car is a TPI then Jim85IROC is right and there shouldn't be a sensor in the head.


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'86 TA, T-tops, T-5, 3.73, 4 wheel disks
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perf. friction pads, Hypertech ignition, Earls brake hoses, Hotchkis springs, Tokico Illumina 5 adjustable
shocks and struts, Lakewood panhard and trailing arms
14.73 @ 95... traction still a problem

 

If you have an RS with a 305 VIN E (TBI), the single electric cooling fan is controlled by three things. The A/C high pressure switch, the A/C on / off switch, and the coolant temperature sensor in the passenger side cylinder head, between cylinders 6 & 8. That is what you must have broken, if the fan is not coming on (unless the A/C is turned on). The connector is available from Pep Boys, and the sensor is available from Auto Zone, however, the Auto Zone sensor protrudes from the head further than the GM sensor, so it may interfere with a header tube - it will with SLP headers, anyways.

Also, '91 TPI (VIN F & VIN 8) cars do have a fan switch in that location, as well. It controls the secondary cooling fan.

The knock sensor & cooling fan temperature sensor connectors are the same - don't get them reversed!

Tim

 

How can you tell the differance between the 2? What color is the wire for the knock sensor? My temp gage wasn't working when I picked it up and it overheated(from the "mechanic")just need to know the right plugs.

 

The knock sensor wire is dark blue, and the secondary cooling fan switch wire is gray. The temperature gauge sender is on the driver's side cylinder head, between cylinders 1 & 3, and its wire is dark green.

Tim

 

Hey Tim,
I just recently rebuilt my 305 "e" engine in my 91 Camaro...I replaced engine temp sender(driver side), fan switch ( between 6 and 8 plugs) and knock sensor..The car is running great but over heats and the single electric fan won't come on. I've checked all the plugs into the sensors to see that they're all connected which they are. I replaced the fan relay next to the windshield wiper motor. The only time the fan will come on is when I turn on the air conditioning.The engine temp will max out if I'm not driving the car. I checked the wire colors of the knock sensor and the fan switch and they are correct..Any help would be greatly appreciated..I'm at a loss.
Thanks!

 

Why did you bring up a thread from 12 years ago?? For all we know, Tim might dead by now. (j/k)

You can use this troubleshooting article for the cooling circuit: http://www.austinthirdgen.org/index.php?pid=36

Are you sure you replaced the cooling fan relay and not the fuel pump relay?

Follow the article and you'll find your problem in no time. And next time you might want to start a new thread.

Lou

 

Sorry, I just did a search for what i felt like the "symptoms" were with my car. Didn't realize it was from 12 years ago. Thanks for the link though! I'm gonna start reading through it now.

 

You should be able to short the fan switch wire (passenger's cylinder head between #6 and #8) to ground and the fan should run when the key is on. If not, then there is a wiring problem with that wire. If the fan does run, then the sensor may be broken. It doesn't turn on until the coolant reaches 228F which is pretty hot.

 

How's the best way to ground this wire?

 

Just disconnect it from the switch and touch it to the block, head or exhaust.

 

Thanks again guys! I hope you all have a great thanksgiving! I don't know about you all, but I actually love working on camaro on days like today!

 

You too. Enjoy the good food. Gobble gobble.
I would love to work on my broken-down Cheby but I got a much more serious duty: the turkey. It takes precedence over my cars.

 

Okay guys, so I grounded out the wire and the fan worked. The end of the plug was degraded pretty bad so I put a new end on it. The switch between cylinder 6 and 8 is new as I replaced it during the rebuild. The fan still doesn't come on and the engine still over heats. Does the coolest temp sender on the manifold have anything to do with it?

 

That's good news, the coolant fan circuit works as expected then. Now to address the switch issue.

Overheats? Did you let it get hot enough to get to 230+? The switch has a very high turn-on temperature so it does not kick in until the dash gauge shows close to red. It sounds like too late but it is good enough to keep our cars from overheating.
Also, did you verify the engine temperature with anything else besides the dash gauge? That one can easily lie.

Nope. The CTS simply provides a temperature reading to the ECM to adjust mixture etc. It has nothing to do with cooling fans on TBI engines.

 

Yes I let it get hot enough. I have an infra red temp gauge that I can test with. Also, I ordered another new fan switch. ( maybe this one is faulty). Thought I would try that. Could it be the ECM not sending a signal to turn on? I know I'm asking a ton of questions. I just finished a 3 year restoration on this car and would like to drive it on the daily. I have a couple of other things that need fixing ( fuel sending unit, and faulty turn signal ) but other than that this is one of the last things to be fixed.

 

Infrared thermometer helps, that's nice.
Did you let it heat up past 240? And it still didn't turn on the fan? I would suspect the temperature switch or the connector in that case.

The TBI ("E") engines do not use the ECM to control the fan. Only the temperature switch in the passenger side head and the A/C can turn on the fan.

Lou

 

If you put too much teflon tape on the sending unit, it might not ground. Otherwise it sounds like a bad sending unit since grounding the wire turns on the fan. You should be able to measure the resistance between the threaded brass part sticking out and the engine block and it should be 0 ohms. If it's a high value then the tape is interfering with the sending unit making a ground connection.

 

Hehe, you beat me to it.
I realized it right after I posted my reply that sealing tape might be interfering with good connection.

 

It surprises me that it's even possible for it to NOT make a ground somewhere along the threads since it's pipe thread and literally jams into the threads. Alas, I've been there when I put just a little too much tape on a temp sender. Amazing that the teflon can surround the thread so well preventing metal to metal contact.

 

Yes, it is no problem to jam the threads full of tape if you try hard. If you use enough tape, you can prevent metal-on-metal contact easily since the tape has nowhere to go when squeezed in the threads and won't allow the two metal surfaces to meet.

Now if you use cheapo Harbor-Freight teflon tape for sensor threads like I do, the tape will seal enough but still rip and allow contact in the threads. So the trick is in NOT using quality tape.

 

hey guys,
ordered and installed the new switch..replaced the plug..still nothing! I have no idea what I'm doing wrong! I also replace the temperature sender unit on the manifold. I'm still at a loss. I didn't use any tape on the new switch just to make sure it would ground ( dont worry no coolant leak)

 

It must be the switch itself or its connector then.
What temperature is the new switch rated at?

 

Well, both have been replaced. switch and connector.. the switch is from factor air, it was the one that advance auto recommend through their system.

 

They should be able to give you a temperature rating for the switch.
If it is not the switch or plug, it must be the actual temperature in the head.
What temperature did you see on the IR thermometer when you were testing the engine?

 

Okay so they didn't give a temperature rating on the switch. I had to buy some antifreeze since I lost some coolant during the coolant fan switch replacement. So while it was low, I replaced the thermostat as well. So now all the sensors on the block and heads are new and have been replaced. I filled the coolant levels back up and let the engine heat up. It took quite a whole for it to get hot. But it went to red again. I took multiple temperature readings. At the water inlet, it registered 260°. The exhaust manifold was above the highest reading on the gauge at 428°. Where should I take a good reading at? I know their probably gonna vary. It would be too difficult to get one where the switch is.

 

260 is more than enough to trigger the switch. Reading the coolant temperature at the thermostat housing is the best spot.

As I said before, if the fan circuit works but is not coming on, the fault must be either in the switch or its connector.
You can try using a piece of jumper wire (any wire will do, even thin doorbell wire) and with the ignition on, just ground one end of the wire and touch the other one to the switch connector and then the switch plug. If the fan comes on, it must be the switch.

 

Well I grounded the wire.. Fan works..I'll try tomorrow grounding it to the switch and see what happens. I just replaced the switch yesterday.. I'm wondering if they got paint on the inside of the threads of the block when I had it machined. If they did, could that keep it from grounding?

 

Yes, paint would be a problem, especially if it's the sticky kind that cannot be easily scratched off.
You could pull the sensor again (yes, I know, I'd hate that too) and use a battery terminal brush to clean out the threads. Or even better, you can use a pipe tap to chase the threads.

A test you could do before you even pull the switch out.
If you can see any of its metal threads, try wrapping bare wire around them and ground the wire somewhere on the head, block or exhaust. That should provide enough ground to the body of the sensor. Heat up the engine again and if the fan comes on, you sure have a bad ground in the threads.

Let us know what you find.
Lou

 

Okay guys, I know it's been a few days but here's and update...I just replaced the fuel sending unit yesterday, the fuel gauge wasn't reading at all. Then, it would turn over but not start. No fuel.. Fuel pump relay ended up being bad. I found this out when it thru a code. While I had it hooked up to the computer I had them check engine temperature. Engine ran fine at 205 - 210 degrees. It finally got to 230 and voila the fan kicked on. I replaced that relay as well. So the fans working now and the engines not over heating. What does this have to do with the fuel sending unit and relay? The gauges are reading the wrong values now. I traced my fuel problem back to the oil pressure sending unit. Somewhere I read that if that unit goes bad or sees "no oil pressure" it cuts the fuel pump signal to protect the engine. I'm going to replace it tomorrow and we'll see if it helps the other issues.

 

Glad to hear that you got some of it sorted out.

Do not believe everything you read on the Internet, lots of people spreading mis-information here - especially about the Fuel Pump Oil Pressure switch. It does NOT cut fuel to the engine to protect it.
The FPOP switch does the opposite: it provides power to the pump when the engine is running (when the oil pressure builds up) in case your fuel pump relay fails. That way, you are not stranded on the side of the road 100 miles away from the nearest mechanic due to a bad $5 relay. That's one thing Chevy did right on our cars.

 

Would it have anything to do with it at all if it fails?( Oil pressure sending unit)

 

If the OPSU fails, the FP relay still provides power to the pump. And vice versa: if the relay fails, the OPSU still provides power to the pump.
So you don't even need your OPSU if your FP relay works correctly.

 

Okay,
So I've replaced the fuel pump, the fuel sending unit the fuel pump relay, and the oil pressure sending unit ( just for good measure) and the fuel gauge is still not working. The car also takes a good 20-30 seconds trying to get it to start, like its not getting fuel.

 

Does your fuel pump prime when you turn the key on? If not, you might still have a problem with the FP relay.
Try this troubleshooting article to see where the problem is: http://www.austinthirdgen.org/index.php?pid=35

When you replaced the fuel pump, did you check that the fuel level gauge wire is connected on the inside of the fuel pickup assembly?
Does your gauge show empty or full?
None of the parts you replaced have anything to do with the fuel gauge, btw.

 

Yes everything on the fuel pump and sending unit seemed to be in place and connected. I don't hear the fuel pump prime. But it seems I hear it run for about 10 sec after the car shuts off?? The gauge reads empty. I know the tank is full.

 

When you had the fuel pump and sending unit out, did you check the sender for free motion? Could it be stuck in the down position? Has the gauge always read empty or is it a new problem?

If the fuel pump runs after the engine is shut down, that is logical since the OPSU keeps it running due to residual oil pressure after engine shutdown.

So you have two problems:
1) the ECM not priming the fuel pump via the relay
2) the fuel gauge not reading the right level

You need to tackle these one at a time and you should be able to fix them both.
For problem #1, follow the tech article I posted and you can identify the source of the problem.

Lou

 

Lou,
Thanks! Hopefully gonna do these after the holiday! Merry Christmas friends!

 

Okay guys, just an update. It had been a little while since I drove my car, so I got it out to blow the dust out of the pipes, sort of speak. Got out on the interstate and looked down and the fuel gauge was working! I'm not sure why. I haven't done anything but fill the car up with gas after I installed the sending unit. But, since it works, I'm not messing with it even though it bothers me I never found out why it wasn't working,