Some type of solenoid on the firewall??

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garzas23

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Can anyone recognize what this is? The vacuum hose attached to it is running to the EGR valve. Its an 85 GMC with a 350 and a quadrajet. Where should the EGR valve be running to anyway? The truck hasn't been running very well, it hesitates when I hit the gas from a stop. And on a cold start it wont idle, the only way it stays running is if I constantly feather the gas until its warm then it will idle. Im wondering if misplaced vacuum lines could be the problem.
 

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MadOgre

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where do the wires go to ? The transmission ? If so its the TV lock up switch or else its a tip in switch. @Hotrod knows all about those. lol
 

garzas23

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where do the wires go to ? The transmission ? If so its the TV lock up switch or else its a tip in switch. @Hotrod knows all about those. lol

Not real sure, but the wires tie into another bunch of wires lust below the solenoid to the right, then some go thru the firewall and some go down. I will get in there and look. Either way what are the function of those you listed? Should the EGR be running vacuum to them?
 

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Something does not look right to me there. Isn't that solenoid for controlling the transmission kick down or overdrive?

Don't you have an emissions label under the hood showing how to route the vacuum lines?
 

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Something does not look right to me there. Isn't that solenoid for controlling the transmission kick down or overdrive?

Don't you have an emissions label under the hood showing how to route the vacuum lines?

That one should be tip in switch

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Boone83K10

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That is completely wrong. Normally that side is the tip in vacuum switch for timing. It is totally unrelated to EGR. Here's what should happen.

1. Unhook that vacuum line at the switch on the firewall. It should be running to the carb, and the port should only supply vacuum when the throttle is opened. Not sure where that is on a qjet.
2. Check for any other open lines that would cause a vacuum leak.
3. If you are running a 700r4, there should be a switch that looks almost like the one you are taking about. But it should be at the 10 o clock position above the brake booster. In the first pic, to the left of the egr, there are two wires. Yellow and green. That is the wires for the egr bleed solenoid which is tied into the 700r4 overdrive wiring. Follow the green wire until you come to another connector. Note it should be blue and green wires. Follow that until it comes to a connector that will not be hooked to anything. That is supposed to be hooked into the overdrive vacuum switch.
4. If the green wire leads up to the switch that you have pointed out, then some one had moved it. If that is the case, you need to run a vacuum line from a full vacuum port on the carb. This would also apply if you found another switch laying in the engine compartment from step 3.
5. If you dont have a 700r4, only do step 1 and 2.
 
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That one should be tip in switch

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Yup, I concur. The vacuum switch that's right above to the left of the booster, that looks almost identical to that one, is your lock-up switch. HotRod started an info. Fail thread on it, if I remember correctly.
 

garzas23

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That is completely wrong. Normally that side is the tip in vacuum switch for timing. It is totally unrelated to EGR. Here's what should happen.

1. Unhook that vacuum line at the switch on the firewall. It should be running to the carb, and the port should only supply vacuum when the throttle is opened. Not sure where that is on a qjet.
2. Check for any other open lines that would cause a vacuum leak.
3. If you are running a 700r4, there should be a switch that looks almost like the one you are taking about. But it should be at the 10 o clock position above the brake booster. In the first pic, to the left of the egr, there are two wires. Yellow and green. That is the wires for the egr bleed solenoid which is tied into the 700r4 overdrive wiring. Follow the green wire until you come to another connector. Note it should be blue and green wires. Follow that until it comes to a connector that will not be hooked to anything. That is supposed to be hooked into the overdrive vacuum switch.
4. If the green wire leads up to the switch that you have pointed out, then some one had moved it. If that is the case, you need to run a vacuum line from a full vacuum port on the carb. This would also apply if you found another switch laying in the engine compartment from step 3.
5. If you dont have a 700r4, only do step 1 and 2.

Ok. The carb is a Q-jet. I have a TH350 so I do not have a lock up switch. So I need to make sure my EGR valve is working properly and route it straight to the carb. Now that I know its a Tip in switch I need to route it straight to my carb also. That being said I know for sure something is hooked up wrong as for as vacuums because I have NO free vacuum ports on it. My Idle is horrible hopefully I can get these vacuums correct an it will be my idle problem.
 

garzas23

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Also, the mixture control solenoid on the front of the Q-jet has only one wire connected. The other is cut short. Can the wire cut short be just a ground? Would that solenoid also hurt my idle or does the carb Function fine without it, because It has idle mixture screws as well?
 

Boone83K10

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Ok. If that tip in switch is still wired to the computer and you're still running an ESC distributor, then it needs a vacuum hose from the carb too.
 

garzas23

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ok thanks. What do you think about the mixture control solenoid on the Q-jet?
 

flyboy1100

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Do you have the tps plug as well? If you don't then it isn't mixture control

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Boone83K10

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ok thanks. What do you think about the mixture control solenoid on the Q-jet?


as much as I know about these trucks.. I don't know diddly poo about Q-jets with their mixture controls and all that. Edelbrock & Holley are my forte although I am looking at trying to learn about Qjets and maybe rebuild one and put on my truck just for gits & shiggles.
 

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