Plenum pulled now for the questions?

[White Bullet]

First let me thank everyone here for your experience and knowledge as they have been very valuable to me maintaining my Z.

My car is need of some attention as the idle is ruff and there is oil leaking from somewhere. I decided that at minimum the plug wires would need replacing as they are the wire sets with LT-5 stamped on them. Got to think at least age wise they are very old for wires. But reading around lends me to believe that more than wires will be needed. So with that I pulled the plenum today with the plan to change the wires and plugs and to test the fuel injectors as they appear to be original (1991) and the motor has 102,000 miles on it. I will probably replace them given they are not ethanol friendly. Now to the questions.

1. When installing the plenum how do you keep the new gaskets from moving while positioning the plenum?

2. The plenum and many parts need cleaning; what would be the recommended method/solvents to get it done?

3. The oil leak is showing up at the back side of the oil pan. I thought it was from loose bolts on the pan. When I checked them some were tight as I could not move them and some where not as tight and I was able to move them but not by very much; maybe an 1/8" turn. Is that enough looseness in the bolts to allow the oil to leak out? The leak would allow about a 3" diameter circle of oil to collect on the floor after driving. Or is it leaking from somewhere else on the back side of the motor?

[Paul Workman]

Originally Posted by White Bullet

First let me thank everyone here for your experience and knowledge as they have been very valuable to me maintaining my Z.

My car is need of some attention as the idle is ruff and there is oil leaking from somewhere. I decided that at minimum the plug wires would need replacing as they are the wire sets with LT-5 stamped on them. Got to think at least age wise they are very old for wires. But reading around lends me to believe that more than wires will be needed. So with that I pulled the plenum today with the plan to change the wires and plugs and to test the fuel injectors as they appear to be original (1991) and the motor has 102,000 miles on it. I will probably replace them given they are not ethanol friendly. Now to the questions.

1. When installing the plenum how do you keep the new gaskets from moving while positioning the plenum?

I used that new blue Permatex RTV gasket stuff to tack my plenum gasket down on one (IH) side only. But, before placing the gasket on the injector housings, I sprayed the top (only) of the gasket with spray silicone** - as a "release agent". That way I can pull my plenum time and time again (recently proven) without tearing the gasket; it stays on the IH.

**(Note: I wouldn't want to get any silicon over-spray inside the runners, as silicon will kill the O2s. So be sure if you spray the gasket you do so before installing the gasket to the IH, doancha know...)

Something to consider is cutting off or bypassing the plenum's coolant passages. You do this by tapping the coolant holes in the top of the IH's and screw in brass plugs (available at hardware stores). Then you plug the tubing leading to the pipe on the starboard side of the engine, tuck it away, and install a dummy rubber tube to the coolant pipe, IF you want it to look stock. Otherwise, you can remove all the exterior plumbing and plug the ports appropriately - your call on that. In the end, it will facilitate easy removal and re-installation of the plenum, AND remove the source for corrosion potential around the rectangular access port on the top of the throttle body. When recently discussing this with Marc Haibeck, he indicated having no problem with winter driving after bypassing the TB. (When you think about it, there is no fuel being dispensed in the TB, so there isn't the added cooling that causes carburetors to freeze up - the necessity for "carb heat" just doesn't apply - in all but the rarest of situations. The injectors are nested in the injector housings - where it is very warm. No frost there!)

Originally Posted by White Bullet

2. The plenum and many parts need cleaning; what would be the recommended method/solvents to get it done?

The original gray gets darker with age, and tends to turn a bit greenish (or at least that is what mine and others have experienced). To remove heavy soil, I like Simple Green - spray on and let soak, and then pressure wash it at a car wash, for example.

For stains and such there are many opinions. Some staining and light soil can be removed by scrubbing with a sponge and "Soft Scrub".

Then for nooks and crannies, there is the ol' chlorinated type brake cleaner: probably the best thing ever for removing grease sticky gasket goo, but it is a bit expensive to be washing an entire plenum with. Then again, Simple Green pre-soak and then a hot power wash will do wonders too!.

Originally Posted by White Bullet

3. The oil leak is showing up at the back side of the oil pan. I thought it was from loose bolts on the pan. When I checked them some were tight as I could not move them and some where not as tight and I was able to move them but not by very much; maybe an 1/8" turn. Is that enough looseness in the bolts to allow the oil to leak out? The leak would allow about a 3" diameter circle of oil to collect on the floor after driving. Or is it leaking from somewhere else on the back side of the motor?

With around 100k miles, I would be thinking either the rear crank seal, or the input seal for the trans.

I've not replaced the rear main engine seal, so I'll defer to those that have. But, I ended up cooking a ZF as result of an oil seap. The ZFs do not like to run low on oil. It is very important to keep the level topped off, so you might want to keep that in mind.

I'm not 100% sure, Pete and others would know for sure, but I think maybe the rear main seal can be replaced with out disassembling either the engine or the trans - better verify that with the experts, I recon.

Then too, it might just oil draining out of the valley thru the drain tube. That oil would be coming from the breather box under the plenum (or the gasket around it to be more precise), or the air tubes from the breather box to the IHs are cracked or leaking. That is very easy to check when you have the plenum off. Jerry (Jerry's Gaskets) can provide a gasket(s) as you need them.

Hope this helps

P.

[secondchance]

Originally Posted by White Bullet

First let me thank everyone here for your experience and knowledge as they have been very valuable to me maintaining my Z.

My car is need of some attention as the idle is ruff and there is oil leaking from somewhere. I decided that at minimum the plug wires would need replacing as they are the wire sets with LT-5 stamped on them. Got to think at least age wise they are very old for wires. But reading around lends me to believe that more than wires will be needed. So with that I pulled the plenum today with the plan to change the wires and plugs and to test the fuel injectors as they appear to be original (1991) and the motor has 102,000 miles on it. I will probably replace them given they are not ethanol friendly. Now to the questions.

1. When installing the plenum how do you keep the new gaskets from moving while positioning the plenum?

2. The plenum and many parts need cleaning; what would be the recommended method/solvents to get it done?

3. The oil leak is showing up at the back side of the oil pan. I thought it was from loose bolts on the pan. When I checked them some were tight as I could not move them and some where not as tight and I was able to move them but not by very much; maybe an 1/8" turn. Is that enough looseness in the bolts to allow the oil to leak out? The leak would allow about a 3" diameter circle of oil to collect on the floor after driving. Or is it leaking from somewhere else on the back side of the motor?

Answers:

1. Position the plenum minus the gaskets. Once you know it is in place, lift one side of the plenum just enough to slide in a gasket. Start a few bolts with finger to hold the gasket in place and do the same on the other side. You do not need any sealant.
2. Do not use solvent to clean!!! Use Deep Purple (or something like that...). Spray on and use tooth brush then towel dry.
3. Just because bolts are tight does not mean your pan gaskets are good. If oil is pooling around the edge of the pan most likely it's the pan gasket. Best source is Jerry's gasket.

Have fun!

[White Bullet]

Dynomite, Paul, Secondchance thanks for the input. I will check the fluid level of the transmission to make sure it is full and elimenate it as the possible soure of the leak.

I sure hope the oil leak is not going to require replacement of pan, transmisstion or rear seal gaskets as I do not have the equipment and or skills to get that done. Here is hoping that it is from the breather or the pan and by tightening up the bolts it will stop. I will proceed with the other work and cleaning. Thanks again.

[Corvette95]

DO NOT USE DEEP PURPLE - it contains chemicals that will ruin your fiberglass leaf springs. I do not recommend ANYTHING but diluted simple green.

[White Bullet]

Corvette95 thanks for the info. I will be using simple green for the cleanup.

This evening I checked the injectors and found two that are bad. One measured 3.0 ohms and the other 8.1 ohms. Also had one read 11.9 ohms; chances are it is bad or going bad. Either way it looks like I will be needing 16 new ones as time will get the rest. Has anyone had their original injectors rebuilt? If so would they be ethanol tolerant, what was the cost and where was it done. I have time and if rebuilding is a better cost option I can wait. If not what replacements would be recommended. Originality is not important.

[Corvette95]

F.I.C injectors can test and clean your stock injectors but unless its a ncrs car, they offer a good selection of NEW injectors starting at prices close to rechecking your stock injectors with a lot less risk! BTW , I just learned the hard way that ohm'ing your injectors can miss a bad injector.

[White Bullet]

My thoughts were to replace them with new ones even if my test did not show any problems. This was driven by their age, lack of ethanol tolerance, and all the information available from the forum. In the shop manual there is a method to check injectors however it requires test equipment I do not own so ohming them was used as the best method that I have available to me to test them and it does show several to be in need of attention. I will be getting new ones to replace all 16.

[secondchance]

Originally Posted by Corvette95

DO NOT USE DEEP PURPLE - it contains chemicals that will ruin your fiberglass leaf springs. I do not recommend ANYTHING but diluted simple green.

I meant for cleaning the plenum.

[Z51JEFF]

Nobody is rebuilding injectors,they dont come apart.Jon has NOS sets from time to time,Ive got Accels.When doing the gaskets I set them in place and then got back,lift one side,position the gasket and do the other side.Once the gaskets are set Ill start the bolts.Dont like the idea of lifting the plenum with any of the bolts started.