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New 86 owner here, did the valve cover gaskets, but in the process I broke the metal pipe that runs from the passenger side exhaust manifold, up and over the rear of the valve cover, and to the block (or intake i guess) right next to the distributor. What is this part called and what does it do? I have done a lot of work getting it to run, redid all the wiring for the fuel pump relay, some wiring for injectors, new fuel pump, all new ignition components, i have spark, fuel, and combustion, its a car that has been sitting for sometimes a year at a time, and it just cannot hold an idle, it is nice and smooth if i hold the throttle down, but when i let off or try to give it heavy throttle it chokes out and dies, could this be the result of this broken pipe? I am thinking that its because its loosing vacuum from there or sucking in too much air for there? any ideas of what that pipe is? Thanks!!!!!!!!

P.S As usual, i have to do the digi dash repair too eheh, its dim but works, can only see it in the sun light, so i think its the main ground or something, and sometimes the gauges go outta control, but when u press on in (not bang) it goes back to normal (still dim).... so something is loose.
 

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oye, just realized what it was, EGR tube.
 

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DC Crew
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Yea that could be your problem. You can make a block off plate for it with no ill effects or you can get another. It's an exhaust crossover tube
 

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also noticed from pictures that there is a wire that runs from the top of the pipe to ??? EGR? mine does not have that, must be broken.
 

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there is a wire that runs from the top of the pipe to ??? EGR? mine does not have that, must be broken.
Most likely you will have a Code 32 up because that sensor ( EGR temp sensor ) tells the computer the EGR is working when the computer operates it

Pull the codes , you may have other faults showing that are the cause of your problems

http://www.digitalcorvettes.com/forums/showthread.php?t=22897

After reading the codes, disconnect the battery for 5 mins to clear the codes.
Then when you have problems,recheck the codes to see what is showing or if anything has changed

Read ( bottom of page) for code description
http://www.digitalcorvettes.com/forums/showpost.php?p=1227169&postcount=3
 

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Discussion Starter #7
ill look at the iac and tps next. I wanna get the egr tube in. how do i go about setting the tps? and is there adjustments to the iacv?
 

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how do i go about setting the tps? and is there adjustments to the iacv?
DC won't let you put links up to other sites so cut and paste for you

How to Adjust your Early C4 TPS and Idle Speed By Lars Grimsrud

This tech paper will discuss the procedure for correct adjustment of the Minimum Idle Speed and for adjustment of the Throttle Position Switch (TPS)

General:
Idle speed and off-idle response on the early TPI systems is determined by correct adjustment of the minimum idle speed screw combined with a correct setting of the TPS. I've seen many of these cars that have had their idle speed "corrected" by well-intentioned mechanice and owners by simply screwing the minimum idle speed screw in a few turns. This really messes up the settings, and will not make your car perform properly.
Doing a correct setup of the TPS is one of the easiest ways make your car feel and respond better.
To maximize the benefit of this procedure, I recommend that you first remove your Throttle Body (TB), disassemble it (it's incredible easy - there are a total of about 5 pieces in it...), clean the TB up really good with some spray carb cleaner, and put it back together. A nice clean TB will really put an edge on the performance improvement you will get by doing this procedure.

Tools and Equipment
You will need the following tools and equipment:
1. A set of Torx wrenches. You can buy a complete set in a nice, genuine plastic pouch at Sears
2. A good digital voltmeter that will read voltages less than 1 volt
3. A paper clip
4. A small screwdriver

Procedure
There are two electrical components on the TB that you will be working with: The TPS and the Idle Air Control Valve (IAC). Make sure that the connectors for these two components are easily accessible and that you can easily disconnect the IAC.
You will also be playing with the diagnostic connector under the dash. Remove the cover (if it’s still in place). Bend your paper clip into a “u” shape. You will be playing with the two top right hand terminals (“A” to “B”) in the connector.

1. First step is to set the minimum idle speed.
Start and run engine until it reaches operating temperature
If nobody has messed with idle on your car before, the set screw will be covered by a pressed-in plug. It’s located on the driver’s side of the TB. Remove this plug if it’s there.
2. With the IAC connected and the ignition “OFF,” stick the paper clip into the diagnostic connector from “A” to “B.” This grounds the diagnostic lead.
3. Turn the ignition to the “ON” position without starting the engine. Wait 30 seconds.
4. Now, with the ignition still in the “ON” position, disconnect the IAC connector at the IAC.
5. Remove the paper clip from the diagnostic connector.
6. Start the engine. The idle speed will probably be really low, and you may have to coax the engine a bit with the gas pedal to keep it running for a while.
7. If your car is an automatic, set the parking brake and put the transmission in “DRIVE.” If your car is a manual, leave it in neutral.
8. Adjust the idle speed screw to obtain 400 rpm in drive or 450 in neutral.
9. Shut off the engine and reconnect the IAC.

That’s it for idle speed. Now on to the TPS.
There are 3 wires stacked vertically on the TPS. You will need to be able to measure the voltage between the two top wires. You can either buy a special harness connector that breaks these wires out (from Min America), or gently pierce the insulation of the wires with the pointy prongs on your volt meter.
You can also stick a paper clip into each of the two top locations of the connector and clamp onto the paper clips to measure the voltage. Whatever is easiest for you.

1. Turn the ignition to the “ON” position without starting the engine.
2. Loosen the TPS Torx adjustment screws.
3. Set your volt meter to the low scale DC volt setting that will accurately read less than 1 volt.
4. Measure the voltage between the two top TPS wires.
5. Adjust the TPS by rotating its position until you get a reading of .54 volts.
6. Tighten the Torx screws and recheck the voltage. Readjust if necessary to make sure voltage is right at .54
7. Turn the ignition “OFF.”

Addition by CorvetteForum Member Charles Warner

As an addendum to “How to adjust your early C4 TPS and idle speed,” I would like to add that checking your WOT TPS voltage is also, potentially, a worthwhile endeavor. Frequently the TV cable that controls shifting pressure to the transmission binds the throttle linkage thereby not allowing for WOT.
After measuring and, if necessary, adjusting the idle voltage (nominally .54 volts) check the WOT voltage and ensure that approx. 4.5 volts is realized. A minimum of 4 volts at WOT are required for the ECM to go into fuel enrichment mode (FEM).
If you are not seeing over 4 volts at WOT you are probably not opening the throttle to the stops and are not seeing FEM. A significant performance improvement is possible with this adjustment.
 

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Yea that could be your problem. You can make a block off plate for it with no ill effects or you can get another. It's an exhaust crossover tube
Mine has broken also, have searched the internet high and low and only come up with Discontinued. The part number for this tube is (14092329), everbody sells the clamps, nobody has the tube. Would any one have any knowledge of where I might find one?
I have plugged the exhaust with a threaded plug and fabbed a blockoff palte for the intake for the time being. Is it true that the combustion chamber temperature will increase up to 500 degrees in addition to what it normally runs without the EGR functioning ?
The car has't thrown any codes without it yet ? But I did notice it run a few degrees hotter under cruise conditions. I am not concerned about the temp right now being it is only 50 outside. My concerns are the summer is coming and the temps will be close to double outside.
Thanks
 

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Hey renegade, how badly damaged is your tube? Mine was cracked pretty wide and I used exhaust putty and it works GREAT! :thumbsup:
 

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I removed all that egr crap from mine and welded closed my exhaust manifolds (AIR Injection tubes). Let me look through my parts pile to see if i saved the egr tube.
 

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The flex part of the pipe was separated. I plugged the header, TPIS has the bung on the header threaded inside for 1/4-18 pipe. I think I'm just going to call them and find out about eliminating the egr in the chip.
I'm starting to see a similarity between the Vette and harleys. I have a feeling this is going to be a long and expensive relationship.
:crazy:
 

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Well, when people have a bad experience with a vendor or another memeber due to a sale you hear about the negative transaction or such.
On the other hand a good transaction also deserves to be spoken of .
I want to thank Jim From TPIS for deleting the EGR function from my PROM. I shipped it to them Tuesday, he sent it back, and I had it installed on Friday evening. I also installed their EGR Tube Block off plate and Air Pump Eliminator pulley and bracket along with a new shorter belt.
Now, can anyone tell me what these two sensors are in the Front of the Intake Manifold? The larger one has a crack in it and I would like to change it, just don't know what it is or called.
Thanks
 

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I think you are talking about the coolant temp sensor and the coolant temp switch.

The coolant temp sensor varies its resistance with temperature its tip is subjected to (The coolant).

The coolant temp switch does this also but its more of a on or a off type sensor which is used to tell the ECM that the electric fans need to come on.

If one or the other is just cracked in its plastic housing and you arent getting any coolant out of them then i wouldnt worry about it. In fact if i remember correctly the plastic housing only goes so far down into the metal part of the sensors and the coolant cannot even touch the plastic so you shouldnt be getting any coolant out of them anyway.
 

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I believe that the coolant temp switch on the front of the manifold is for the 9th injector cold start this is the switch that is not the coolant temp sensor there is another sensor for the fan that screws into the pass side cyl head
 

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I believe that the coolant temp switch on the front of the manifold is for the 9th injector cold start this is the switch that is not the coolant temp sensor there is another sensor for the fan that screws into the pass side cyl head
Yes the larger one is the cold start fuel injector switch. The crack is in the plastic and as remauto says, no coolant would come out. I'm. Going to replace it with a Bosch 280130229, because the GM part #14084318 is discontinued.
Thanks
 
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