Injector Failure Signs? - ZR-1 Net Registry Forums

avijay · 11-30-2011

What are some tell tale signs that your injectors / coils are going bad? I have a 91 and it surely doesn't feel right on acceleration and has a little bit of a shuttering on acceleration. I assume it's time to change the injectors, coils, plugs, wires, etc but just want to make sure I'm trouble shooting the right thing.

Kevin · 11-30-2011

well your car is a 91...so you can assume they're bad. when they first start going bad your car will start to run rich before it goes lean then you'll get a knock when the car is warm. you can also ohm them...12.5-15 ohms is what you want

my injectors are bad and while i'm in there in the spring i'm going to do air filter, injectors, wires and plugs

tccrab · 11-30-2011

Remember, there are 16 injectors, two separate systems that integrate on full acceleration.
The symptoms will differ depending on what combination of injectors are going bad and the condition of the "failure", i.e., injector stuck open, injector stuck closed, or simply an injector with bad spray pattern.
Lots of combos to think about.
A primary injector stuck closed or with a bad spray pattern will cause a lean condition with a rough idle and sympathetic dual mass flywheel knock.
A primary injector stuck open will cause a fuel rich condition and the spark plug will eventually carbon up and cause misfires.
Multiple bad primaries will cause rough idle, stumbling on regular (non-secondary) acceleration, dual mass flywheel knock, and if bad enough the ECM will set a SES light because the O2 sensors will read high or low depending on the condition.
Bad secondaries in a closed condition, i.e. fuel lean condition, will cause stumbling on secondary acceleration initiation and significant leaning of the engine at high rpm and O2 sensors reading high.
Bad secondaries in an open condition will cause stumbling on secondary initiation and smooth out as the airflow leans the a/f mixture to optimal.
Mix up the failures and all kinds of good things can happen.

My advice is to replace the fuel injectors, the spark plugs, and while you're underneath the plenum check the coils and replace as necessary.

Just my $0.02

TomC
'Crabs

oricale · 12-01-2011

Thats exactly what Im doing...AMMMOOUUNNGG.....other things!!!!

tomtom72 · 12-01-2011

Use a spark tester, the inline kind to test for coil output or use a DVOM. Please resist the impulse to pull off plug wires while at idle as our Ignition brain boxes, aka the DIS module, doesn't react well at all to that treatment.

You can ohm out the coil + it's wire pair using the two plug ends of the wires, but if you have to go under the plenum the "while we're here" rule comes into play.

If a primary injector goes south from the alcohol in the fuel it will mimic a dead miss. The alcohol shorts the coil and no fuel to that cylinder. You'll get the Dual Mass rattle like Tom said. Also, if you have a scanner you can see the results of the lean mixture by looking at O2, BLM's and Integ numbers. Or, you can use your nose. If she's lean enough you can smell it....trust me! The miss will not go away. Also, it may not miss on cold start, as the coil heats uo the miss will become more pronounced. Also the plug(s) for those cylinders where the injector coils are bad will look like no gas is being delivered.

Tom

carmine · 12-01-2011

I Recomend RC Injectors And Jerrys Gaskets Carmine #357 Black Gray Stock

Hib Halverson · 12-01-2011

Quote:

Originally Posted by avijay

What are some tell tale signs that your injectors / coils are going bad? I have a 91 and it surely doesn't feel right on acceleration and has a little bit of a shuttering on acceleration. I assume it's time to change the injectors, coils, plugs, wires, etc but just want to make sure I'm trouble shooting the right thing.

You can remove all 16 and test their coils.
You also can have an injector specialist, like RC Engineering, test them for flow and spray pattern.

But, if your injectors are original, ie 20 years old, I'd just pull 'em out and replace them with RC Engineering units.

ZR1Vette · 12-02-2011

Are the RC injectors the ones that have to be modified by removing a small tab on the injector?? Or was that for Accel injectors?

Edit- added this pic showing the tab removal so can you ID that the injectors are RC or Accel from the pic?

tomtom72 · 12-02-2011

Quote:

Originally Posted by ZR1Vette

Are the RC injectors the ones that have to be modified by removing a small tab on the injector?? Or was that for Accel injectors?

RC's are plug and play. I'm not 100% on the Accels, I think you have to do the grind to get our harness plugs to plug in to the coil terminal...not 100% sure though

Tom

ZZZZZR1 · 12-02-2011

FIC have stainless steel injectors and look like OEM

http://fuelinjectorconnection.com/shop/

Speak with John. He also carries Jerry's gaskets, so you can get everything at once

We have installed many local Z's with these...

David

11-30-2011	#1
avijay Join Date: Nov 2011 Location: Glen Allen, VA Posts: 49	Injector Failure Signs? What are some tell tale signs that your injectors / coils are going bad? I have a 91 and it surely doesn't feel right on acceleration and has a little bit of a shuttering on acceleration. I assume it's time to change the injectors, coils, plugs, wires, etc but just want to make sure I'm trouble shooting the right thing. __________________ 1970 LT-1 - sold 1971 Vert - sold 1972 454 - sold 1996 Grand Sport - sold 1999 C5 - sold 1969 Mustang Mach1 - sold 1991 ZR-1 - sold 2008 Z06 - current

11-30-2011	#2
Kevin Join Date: Jun 2005 Location: pittsburgh Posts: 4,629	Re: Injector Failure Signs? well your car is a 91...so you can assume they're bad. when they first start going bad your car will start to run rich before it goes lean then you'll get a knock when the car is warm. you can also ohm them...12.5-15 ohms is what you want my injectors are bad and while i'm in there in the spring i'm going to do air filter, injectors, wires and plugs __________________ It's not the car, it's the people - Doug Johnson 90 r/r "KEYS ON" nick named "T.L.B" Last edited by Kevin; 11-30-2011 at 10:41 PM.

12-01-2011	#4
oricale Join Date: Oct 2011 Location: STAFFORD VA, Posts: 576	Re: Injector Failure Signs? Thats exactly what Im doing...AMMMOOUUNNGG.....other things!!!! __________________ 1990 ZR1 #00077 (10Y022 PEP CAR) 1991 ZR1 #00517 ("Irene")SOLD:cry: 1992 ZR1 BLACK RED(2016 2009 Z06!! BLK/BLK rare Linen interior 707HP!! 2006 BLK/BLK Z51 (Just SICK FAST!)SOLD) 1996 BLK/BLK LT4 Grnsprt(sold...Twice!) 1991 RED/REDL98(Fell off the shipping truck:( 1980 BLK/RED L82(Sold) 1990 RED/BLK( sold.....In Japan) 2006 Mustang GT mach 1(sold) 1969 Mach(sold in Japan) 1969 Mach 1#2(sold) WAZOO Member... www.evolution-motorsport.com facebook/evolutionmotorsportengineering Your Local [url]www.Amsoil.com[/url] dealer/user.. Victory Loves Preparation

12-01-2011	#5
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,637	Re: Injector Failure Signs? Use a spark tester, the inline kind to test for coil output or use a DVOM. Please resist the impulse to pull off plug wires while at idle as our Ignition brain boxes, aka the DIS module, doesn't react well at all to that treatment. You can ohm out the coil + it's wire pair using the two plug ends of the wires, but if you have to go under the plenum the "while we're here" rule comes into play. If a primary injector goes south from the alcohol in the fuel it will mimic a dead miss. The alcohol shorts the coil and no fuel to that cylinder. You'll get the Dual Mass rattle like Tom said. Also, if you have a scanner you can see the results of the lean mixture by looking at O2, BLM's and Integ numbers. Or, you can use your nose. If she's lean enough you can smell it....trust me! The miss will not go away. Also, it may not miss on cold start, as the coil heats uo the miss will become more pronounced. Also the plug(s) for those cylinders where the injector coils are bad will look like no gas is being delivered. Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member

12-01-2011	#6
carmine Join Date: Jun 2005 Location: Hanover,Ma. Posts: 180	Re: Injector Failure Signs? I Recomend RC Injectors And Jerrys Gaskets Carmine #357 Black Gray Stock

11-30-2011	#3
tccrab Join Date: Oct 2004 Location: Folsom CA Posts: 1,658	Re: Injector Failure Signs? Remember, there are 16 injectors, two separate systems that integrate on full acceleration. The symptoms will differ depending on what combination of injectors are going bad and the condition of the "failure", i.e., injector stuck open, injector stuck closed, or simply an injector with bad spray pattern. Lots of combos to think about. A primary injector stuck closed or with a bad spray pattern will cause a lean condition with a rough idle and sympathetic dual mass flywheel knock. A primary injector stuck open will cause a fuel rich condition and the spark plug will eventually carbon up and cause misfires. Multiple bad primaries will cause rough idle, stumbling on regular (non-secondary) acceleration, dual mass flywheel knock, and if bad enough the ECM will set a SES light because the O2 sensors will read high or low depending on the condition. Bad secondaries in a closed condition, i.e. fuel lean condition, will cause stumbling on secondary acceleration initiation and significant leaning of the engine at high rpm and O2 sensors reading high. Bad secondaries in an open condition will cause stumbling on secondary initiation and smooth out as the airflow leans the a/f mixture to optimal. Mix up the failures and all kinds of good things can happen. My advice is to replace the fuel injectors, the spark plugs, and while you're underneath the plenum check the coils and replace as necessary. Just my $0.02 TomC 'Crabs __________________ TomC '90ZR1 #792 Honorary Pirate [B]If it ain't FUN, you're doing something terribly WRONG. [/B]

12-02-2011	#8
ZR1Vette Join Date: Dec 2007 Location: Reston, Virginia Posts: 931	Re: Injector Failure Signs? Are the RC injectors the ones that have to be modified by removing a small tab on the injector?? Or was that for Accel injectors? Edit- added this pic showing the tab removal so can you ID that the injectors are RC or Accel from the pic? __________________ Michael :cheers: [I][SIZE="2"]1990 RED on RED #566[/SIZE][/I] [I][SIZE="2"]WAZOO MEMBER[/I][/SIZE] Last edited by ZR1Vette; 12-02-2011 at 12:04 PM. Reason: added pic

12-02-2011	#10
ZZZZZR1 Banned BANNED Join Date: Oct 2006 Location: MD Posts: 3,684	Re: Injector Failure Signs? FIC have stainless steel injectors and look like OEM http://fuelinjectorconnection.com/shop/ Speak with John. He also carries Jerry's gaskets, so you can get everything at once We have installed many local Z's with these... David