Best way to remove plenum on a 1985 C-4

[BGJ]

I have a code 32 that my 1985 coupe is displaying. From my research here, I have decided to replace the EGR switch and the little switch next to it.

On this car, the EGR is roughly under the center of the plenum. I have taken ALL the screws out and disconnected everything...the plenum refused to budge. I used a 2 and 1/2 foot pry bar on the intake to push up on the plenum, but it still wouldn't budge. Does anybody have any tips for getting it loose. I was afraid I was going to puch a hole through either the plenum or intake.

 

[Edmond]

I'm curious to see the responses to this question as I'm going to switch out the EGR next week as well.

Did you take the throttle body off?

 

[BGJ]

I didn't. It looks like you can remove the plenum with that attached

 

[jmccloud]

1985 plenum

My son had an '85 Firebird Formula and tried to get the plenum off. Wouldn't budge. Using a dental mirror he found another set of bolts (I think near the center and under everything else). He talked about having to use a universal socket to reach them. I'll ask him about it but won't see him 'til next week.

 

[Vettefan87]

I didn't. It looks like you can remove the plenum with that attached

Yes can remove the plenum and the TB as one piece, but I do not know how. I do know that you can remove it as a unit, because the place pulling my motor to have it rebuilt again did. It may also be a good time to pull the TB off and clean it, and if you want you can port out the little ridge on the plenum.

 

[582Boat]

1985 Plenum removal

Sir: What was the final results of removing the plenum on your 1985 Vette, what all did you finally have to remove in order to replace or repair the EGR. I am having a problem of my engine running ruff or shall we say it is running on 7 cylinders and shows up badly at 900-1100 RPM. I have replaced wires, distributor cap and rotor, still have a miss. I now think the EGR might be causing some of the problem or an injector. Running premium and injector additives has not helped. Help

 

[Edmond]

Sir: What was the final results of removing the plenum on your 1985 Vette, what all did you finally have to remove in order to replace or repair the EGR. I am having a problem of my engine running ruff or shall we say it is running on 7 cylinders and shows up badly at 900-1100 RPM. I have replaced wires, distributor cap and rotor, still have a miss. I now think the EGR might be causing some of the problem or an injector. Running premium and injector additives has not helped. Help

Injector additives will not help if the injector is too dirty or if it's leaking. There are two common solutions to injector problems:

1. replace them-they are not cheap, in the $60 range for each injector.

2. take them off and have them cleaned. I believe that the professionals use sound waves to disolve any contamanents in the injectors and then they do a flow test. www.TPIS.com is one such company, as well as Witch Doctor.

It isn't expensive to have that service done to your injectors; ~$120 range for all 8. However, the work to get to the injectors would be the same as the EGR, you have to take the plenum off.

 

[Mart]

Are you trying to remove the plenum and the runners as one unit or just the plenum.

The plenum is all you nees to remove in order to replace the EGR, just loosen the lower runer bolts so they are loose (do not forget the 2 hidden bolts 1- is on the lower front pass side you can reach it from the drivers side, #2 is on the rear drivers side reached from where the breather tube connects)

Once those two bolts are loose everything should wiggle and the plenum only should just slide up, there is a tube at the back of the plenum you need to disconnect along with the MAT sensor connection.

Hope this helps.

If you need more info let me know.
Mart

 

[BGJ]

I wanted to remove the plenum seperately from the runners. If I remember correctly, I removed the four torx bolts on either side of the plenum, the vacuum line at the drivers side rear, and the throttle cable connections. It didn't want to budge. I'm going to make another attempt on my next day off, next Friday.

So, your are saying that I should loosen the lower runner bolts as well to get this loose..?

Thanks so much for your replies. Everyone has been real helpful here.

 

[Mart]

My thought is that it is easier to remove the plenum with them loose. IMHO.

Especially if it has been there for 100k.

You can leave the TB on but disconnect the coolant hoses and Vaccum lines, now would be a good time to clean theTB, if not done allready.

Mart

 

[plumcrazy]

i had the same problem when fixing my thermo housing bolts. the lower
bolts must be loosened as well to get it out and to reinstall the plenum.
might i add if you plan on puttin an adj feul pressure regulator, DO IT
NOW or you will have to rip the plenum back off.

 

[Hrtbeat1]

To remove my plenum I loosened the seven torx bolts that hold the runners to the plenum and the one stud on the drivers side. I then loosened the lower runner bolts on the passenger side. Remove all the upper torx bolts and the stud. Remeber to disconnect the vaccuum lines and the brake booster from the rear of the plenum on the drivers side. One other thing to remember is the small connector on the underside of the plenum.

Maybe a gentle rap with a rubber mallet will help loosen up the gaskets.

Hope this helps.

 

[AlcHEmiE]

I just got done replacing my EGR 10 min ago. The plenum on my 91 came off easily. The hardest part of getting it off was the tub at the rear drivers side. Other than that it came off easily. My computer threw a code 32 so i replaced the EGR to solve my rough idle problems, But from the test drive i just did.. I think they are still there Also, my oil Pressure seems to be very low.. Around 15-25 PSI, is that normal?

 

[JPS]

Nope that is too low. How is your oil usage?

@BGJ; Perhaps in terms of trying to understand, is it an idea to post some pictures? We then know what you did and people can help you by pointing things out to you by editting the picture for you.

By the way, I've disabled the EGR and removed the Catalatic converters...the sound is awesome!

 

[AlcHEmiE]

Oil usage? I dont have any leaks at all.. The oil level is fine.. Other than that, i just got the car two weeks ago and havent driven it that many miles. Im going to change the oil either tomorrow or wed., so maybe that would help?

 

[JPS]

Oil usage? I dont have any leaks at all.. The oil level is fine.. Other than that, i just got the car two weeks ago and havent driven it that many miles. Im going to change the oil either tomorrow or wed., so maybe that would help?

I don't think so. You need the pressure to avoid the oil from overheating. I'll look it up in the shop manual what the temp should read. Back in a minute....

 

[JPS]

The oil pressure should be between 50 to 60 psi @2000rpm. You should have this checked. I don't believe that changing the oil and filter could matter that much. It could be a sensor or worse but I'm not a technician.

 

[AlcHEmiE]

Yeah true.. I havent looked at the PSI @ 2k rpm, only idle.. I'll take a look at it tomorrow.. Could the oil pump be bad? Or would that not give me any pressure at all?

 

[Vettefan87]

When it goes to 15 does it stay that low for a long time? Mine if I am driving and slow down to idle it will hit about 25 and then go straight up to 30 and stay around there.

Justin

 

[AlcHEmiE]

Im not to sure if i am reading it correctly.. When i go out tomorrow i will take a picture and let others interperut the number. But it stays at about 20 at idle, and when i get on it it goes up, but not sure how much, as i never really paid attention to it.. But i can say that it doesnt go up to 50-60 PSI like JPS said..