94 Zr1 power key makes car act funny

[94Zr1TX]

Hey guys. I have a 94 zr1 that is acting funny with the power key on. I've read a lot on the secondaries and what not but haven't seen much on what this car specifically is doing. It runs as it should in normal mode but with the power key on it acts like it's missing half the cylinders. There is quite a bit of vibration coming from the engine bay. If I drive it easily with the power key on it "seems" ok but when I step into the gas it starts driving pretty rough. This only happens with the power key on. Does this sound like something y'all have seen? I really want this fixed asap so I can enjoy the car again as y'all know a zr1 is not the same in normal mode, lol. The car is all stock, no mods. Thanks in advance guys.

Zach

[Kevin]

there's a few things i'm thinking, bad injectors, bad secondary pump, vac leak. I know it's a bit of a drive but if possible i'd get the car down to cory henderson in new braunfuls and have him look it over.

Welcome to the board

[94Zr1TX]

I appreciate the welcome. My dad had a 91Z about 20 years ago but was scared to drive it for fear of someone messing with it. I just want to drive and enjoy mine.

I have been reading up on the secondary system trying to get more familiar with how it all works. I guess what is throwing my for a loop is why does the car feel like it drops half the cylinders? My initial thought was secondaries not opening but injectors throwing in too much fuel and choking the car, or secondaries opening and injectors not firing causing the car to have too much air and not enough fuel. I'm not sure if I'm even in the ballpark here though just an initial guess.

I have checked the secondary vacuum pump and it does work. I disconnected the vacuum line to see if it was working as the write-up said to do and it does run continuously. Now I do plan on buying a hand vacuum pump to check for leaks as well but I also wanted to get this out there to see if anyone had ideas I had not thought of.

Bad injectors, secondaries not functioning right...will that make the car run ultra rough too? I had not read anyone specifically say their car did this with bad injectors or bad secondaries, it seems like the only real complaint I've found was low power. Now the car definitely makes less power than with the key off but also runs rough like I said.

Thanks Kevin for the quick reply. Just looking for some direction here. Any Corey is about 4 hours or so away from me so if I can't get it whipped I'll have to take it to him...if I can get it to run right I'd like to have him put a set of SW headers on it and tune it but first things first.

[Kevin]

When you say it's "running rough"? what do you mean? when I had bad injectors it felt like driving your washing machine around the kitchen. Vac leak, especially in higher gears makes the car just feel like it's fallen on its face. get on it and it just bogs.

[tccrab]

If secondary fuel pump operational then next items to check would be secondary butterlys operational, and then fuel injectors.
My bet would be secondary butterflys staying shut on one side causing a too rich mixture misfire.

'Crabs

[94Zr1TX]

When you say it's "running rough"? what do you mean? when I had bad injectors it felt like driving your washing machine around the kitchen. Vac leak, especially in higher gears makes the car just feel like it's fallen on its face. get on it and it just bogs.

When I say rough basically I just mean that it feels like not all the cylinders are firing. If you take a car and pull a few plug wires and go drive it...that's what it feels like. Does not bog down it just feels like I lose a few or more cylinders.

[A26B]

May be that one of your secondary actuators has failed.

[94Zr1TX]

If secondary fuel pump operational then next items to check would be secondary butterlys operational, and then fuel injectors.
My bet would be secondary butterflys staying shut on one side causing a too rich mixture misfire.

'Crabs

Could you steer me in the direction to check the secondary fuel pump? What would cause one side not opening? Bad secondary actuator? I did read that failed injectors on the 93-95 Z's is pretty rare but I suppose it's possible.

You guys have no idea how much I appreciate the replies so quickly. Thanks a bunch.

[94Zr1TX]

May be that one of your secondary actuators has failed.

Jerry, Is there a way to specifically check an actuator? I will no doubt be needing to order some gaskets from you though as I'm sure the plenum is going to need to come off. First though I need to get a better idea of what exactly is going wrong.

[94Zr1TX]

Just read that the hand vacuum pump is used to test the actuator functionality so I will buy one tomorrow and start setting up to pull the plenum since it seems like that's the next step. Is there anything special I should know about before the plenum comes off? Aside from needing new plenum gaskets? Thanks guys.

[tccrab]

Here's everything you will ever need to know about your secondary port injection system.
http://www.corvetteactioncenter.com/forums/c4-corvette-zr-1-a/14272-1990-1995-zr-1-secondary-port-vacuum-diagnosis.html

'Crabs

[Kevin]

When I say rough basically I just mean that it feels like not all the cylinders are firing. If you take a car and pull a few plug wires and go drive it...that's what it feels like. Does not bog down it just feels like I lose a few or more cylinders.

Sounds like what mine did when my injectors died. The problem with the dual mass is it absorb any small hiccups until they're really big which makes it hard to notice issues like this

[94Zr1TX]

Here's everything you will ever need to know about your secondary port injection system.
http://www.corvetteactioncenter.com/forums/c4-corvette-zr-1-a/14272-1990-1995-zr-1-secondary-port-vacuum-diagnosis.html

'Crabs

Yeah I've been reading up there too. I appreciate the info.

I've got a vacuum pump on order to be here Friday to check for leaks and then see if my actuators are still good. Also have my gaskets on the way to button everything up at the end.

The previous owner said he had the injectors replaced as a preventative deal but I didn't see a receipt so it's possible they put crap injectors in I don't know. We will see when the plenum comes off in a few days. I'd much rather buy a $100 actuator than a $700 set of injectors. Plus that digs into my header money ;)

[We Gone]

http://www.zr1specialist.com/HAT%20Web/articles/Verifying%20Secondary%20Actuator%20Operation.pdf

[94Zr1TX]

http://www.zr1specialist.com/HAT%20Web/articles/Verifying%20Secondary%20Actuator%20Operation.pdf

You're the man Steve. Thanks a bunch. I've been snooping around Marc's site quite a bit lately.

[94Zr1TX]

Ok so the vacuum lines hold vacuum just fine so that's not the issue. Next is to check the actuators. I hope to get around to checking that soon. Then I'll be back with an update. Thanks again guys.

[94Zr1TX]

Just wanted to update the thread. I kind of let the car sit for a while and then bought a few parts for it. I had decided to just let Corey Henderson figure things out for me, lol.

Turns out ONE bad injector was causing all kinds of crap with the car. It was supposed to have new injectors but the previous owner seems to not have been truthful about that.

Anyways the car got SW headers with hi flow cats, full 3 inch SW duals with the louder mufflers. Corey ported the plenum also, put 16 new injectors in, and dyno tuned the car. Car made 412/385 and sounds awesome. Corey also put a Hurst shifter in it. I will take some pics soon and hopefully make a post with some videos.

[Hib Halverson]

May be that one of your secondary actuators has failed.

I'm with Jerry on this...secondaries on one side may not be working or the port throttles may not be opening fully.

If this is an engine which is not driven on the secondaries very often, it could be, as Jerry says, a bad SPT actuator or it could be one or more port throttles are sticking or the SPT linkage on one side is "gummed" up.

If the secondary pump was not enabling, the engine would have lack of power but not the vibration and, perhaps an MIL on due to a lean code.

If the engine idles and runs nice at light throttle, I tend to think ign. is not a problem.

[94Zr1TX]

I appreciate the response. We got it all fixed now though. Bad injector was the culprit. We had Corey Henderson work on the car and add some goodies. Check the post above yours Hib.

[Hog]

What is the driving procedure to get the Port Throttle injectors firing during a long highway cruise? I suggest that all LT5 drivers follow that simple bit of info.

[Hib Halverson]

I appreciate the response. We got it all fixed now though. Bad injector was the culprit. We had Corey Henderson work on the car and add some goodies. Check the post above yours Hib.

Somehow I missed that.
Silly me.

It was a "secondary" injector, right?

In any event, you picked a good guy to fix the problem for you. Corey is the best i that part of the country.