car pulsates under load when in power mode

[zr1man@yahoo.ca]

awesome thanks for the quick response!

[Kevin]

Originally Posted by zr1man@yahoo.ca

awesome thanks for the quick response!

thats what we do here

[Mahogaraunch]

Originally Posted by zr1man@yahoo.ca

I just bought a 1991 corvette zr1 and i dont find any difference when i switch from normal to power mode. in normal mode the car drives fine. when i switch to power mode, the light comes on. car still feels like 210 hp and when i accelerate heavy, the car pulsates and vibrates. when i let off and drive normal, the pulsation goes away.

im thinking its the secondary injectors that may be the problem as i continue to read in the other posts.

I would like to be sure before i invest in them. Also, if it is the injectors, is there anybody you can recommend with a decent price? Im from Canada if that makes a difference. Maybe the local parts shop can order from a major supplier.

sorry, one last thing... any advice or tricks to do an oil change? and is it true the zr1 takes 12 litres?

thanks in advance!

I have the exact problem with mine! I have a 1990 ZR1 with 11,000km on it which was recently brought up from Florida. Needless to say, I got it out on the road after a long Ontario winter to find under the normal load the car drives perfectly. Under full power, the car shudders and there is no performance difference.

I have it going in this Monday for service, but I am not confident my garage has worked on a ZR1 before. What does anyone think the repair price for the injectors may run me? Does anyone have reservations about bringing a ZR1 to any garage? I am near the Peterborough area and am unaware of Corvette service shops in the area.

Thanks for the input.

[zr1man@yahoo.ca]

I JUST ORDERED THE ACCEL COILS - ACC-140017 $41.00 EACH @jEGS AND ACC-150821 SECONDARY INJECTORS FROM SUMMIT RACING FOR $293 FOR SET OF 8.

GOING TO PULL THE PLENUM FOR SECOND TIME WHEN PARTS ARRIVE AND CHANGE THE WIRES WHILE IM AT IT. HOPEFULLY THAT WILL UNLEASH THE OTHER 200HP THAT I HAVE YET TO EXPERIENCE SINCE I PURCHASED THE CAR LAST YEAR.

YOU GUYS ARE GREAT AND ITS NICE TO ASK TECHNICAL QUESTIONS TO PEOPLE WHO UNDERSTAND THE CAR AND KNOW WHAT THEY ARE TALKING ABOUT...AS OPPOSED TO A LOCAL GM DEALER WHO DOESNT KNOW THE DIFFERENCE FROM A LT1 AND A LT5...I DIDNT FEEL TOO COMFORTABLE LEAVING THEM THE CAR TO TRY AND FIGURE OUT AT $85/HR.

[sammy]

Originally Posted by zr1man@yahoo.ca

I JUST ORDERED THE ACCEL COILS - ACC-140017 $41.00 EACH @jEGS AND ACC-150821 SECONDARY INJECTORS FROM SUMMIT RACING FOR $293 FOR SET OF 8.

GOING TO PULL THE PLENUM FOR SECOND TIME WHEN PARTS ARRIVE AND CHANGE THE WIRES WHILE IM AT IT. HOPEFULLY THAT WILL UNLEASH THE OTHER 200HP THAT I HAVE YET TO EXPERIENCE SINCE I PURCHASED THE CAR LAST YEAR.

YOU GUYS ARE GREAT AND ITS NICE TO ASK TECHNICAL QUESTIONS TO PEOPLE WHO UNDERSTAND THE CAR AND KNOW WHAT THEY ARE TALKING ABOUT...AS OPPOSED TO A LOCAL GM DEALER WHO DOESNT KNOW THE DIFFERENCE FROM A LT1 AND A LT5...I DIDNT FEEL TOO COMFORTABLE LEAVING THEM THE CAR TO TRY AND FIGURE OUT AT $85/HR.

everything that you are doing is very easy for you to do. if you have ?s you can ask here before you put it back together . taking it to a dealer is just a waste of cash .jmho

[1990 415]

Originally Posted by Mahogaraunch

I have the exact problem with mine! I have a 1990 ZR1 with 11,000km on it which was recently brought up from Florida. Needless to say, I got it out on the road after a long Ontario winter to find under the normal load the car drives perfectly. Under full power, the car shudders and there is no performance difference.

I have it going in this Monday for service, but I am not confident my garage has worked on a ZR1 before. What does anyone think the repair price for the injectors may run me? Does anyone have reservations about bringing a ZR1 to any garage? I am near the Peterborough area and am unaware of Corvette service shops in the area.

Thanks for the input.

Have you asked this garage if they have ever worked on an LT5? Very unlikely they have. They will very likely make you wish you never took it to them. Only let an LT5 knowledgible person work on your ZR-1. Injector replacement isn't difficult to do yourself. Getting that first plenum pull under your belt is the key to really feeling like you are a brother of the beast. Don't let the inexperienced go near your LT5.

[Kevin]

you'd be better off buying some beer and seeing who in the registry or list serve is nearby to lend a hand. if you're not on the list serve you need to be

[Pete]

Originally Posted by Kevin

you'd be better off buying some beer and seeing who in the registry or list serve is nearby to lend a hand. if you're not on the list serve you need to be

How is the good old list serve?
Last time i was on there all they talked about was politics and advertising for Red Line nothing to do with ZR-1's or LT5's.

You wanna have some fun on the list serve mention Mobil 1 is the best oil and then sit back and enjoy. LOL

Pete

[Paul Workman]

Originally Posted by zr1man@yahoo.ca

I JUST ORDERED THE ACCEL COILS - ACC-140017 $41.00 EACH @jEGS AND ACC-150821 SECONDARY INJECTORS FROM SUMMIT RACING FOR $293 FOR SET OF 8.

Until 93 MY the injectors were susceptible to alcohol. I would recommend purchasing 8 MORE of those same Accel (150821) injectors and replace them ALL now - prolly save you some grief again down the road. Once you have those injectors in, you B good. (You do know about the tabs being off-set on (I believe) the secondary injector, right? You'll have to grind or file off that plastic key on 8 of the Accel injectors before the connector will snap in place - took me about 10 minutes with a Dremel to do all 8.)

While you have the plenum off, one other thing you might consider is cleaning up the (solenoid) contact ring and perhaps the contact posts on the starter. They tend to get pitted and one day you'll have the dreaded "LT5 no-startums"...and another plenum pull. I bought a kit off of Ebay, but discovered the actuator shaft on the replacement was about 5mm SHORTER than the one being replaced. So, I used the new contact posts, but reused the actuator.

With an emery board I was able to easily remove the pitting on the surface of the contact ring and thus restore and retain the actuator "good as new". Start to finish it took about an hour - easily done.

Far as the secondary throttles go, if there is one item that pops up on this board consistently - especially among new Z owners - it is fixing the 16-21 year old vacuum circuit. Although parts to restore the system are available, many (most?) of the FBI gang and others too have pulled the secondary throttle plates, actuators, the whole shee-bang and are much happier for it! It requires the chip to be modified to run on all 16 injectors full time, but drivability, IMO, is enhanced. Once the injectors are changed, the secondaries eliminated, and the starter serviced, and the coils replaced...That is about IT for overhauling the stuff that rings up maybe 90% of the problems that pop up (on the board)! The argument for keeping the secondaries seems to center around passing emissions tests; having the secondary throttle plates in place increases the swirling effect in the chamber. Theoretically, this may help emissions testing, but I have not seen anything written here to suggest passing emissions tests is not possible or even inhibited by their (secondary throttle plates) removal. Just a thought.

Originally Posted by zr1man@yahoo.ca

YOU GUYS ARE GREAT AND ITS NICE TO ASK TECHNICAL QUESTIONS TO PEOPLE WHO UNDERSTAND THE CAR AND KNOW WHAT THEY ARE TALKING ABOUT...AS OPPOSED TO A LOCAL GM DEALER WHO DOESNT KNOW THE DIFFERENCE FROM A LT1 AND A LT5...I DIDNT FEEL TOO COMFORTABLE LEAVING THEM THE CAR TO TRY AND FIGURE OUT AT $85/HR.

Amen!

Welcome to the Brotherhood!

P.

[jrd1990zr1]

Originally Posted by Mahogaraunch

I have the exact problem with mine! I have a 1990 ZR1 with 11,000km on it which was recently brought up from Florida. Needless to say, I got it out on the road after a long Ontario winter to find under the normal load the car drives perfectly. Under full power, the car shudders and there is no performance difference.

I have it going in this Monday for service, but I am not confident my garage has worked on a ZR1 before. What does anyone think the repair price for the injectors may run me? Does anyone have reservations about bringing a ZR1 to any garage? I am near the Peterborough area and am unaware of Corvette service shops in the area.

Thanks for the input.

Sounds like the same problem I had with my 1990 until I installed a set of new injectors.

FWIW, I wouldn't trust any non-GM dealer with a 1990 ZR1 (except the few specialists discussed by registry members). Likewise, there are very few GM dealers I would trust.

I recommend you check the injectors when the engine is hot to verify low resistance. Do the work yourself, there are a number of resources in the technical section.

Good luck