ROUGH RUNNING 2 - ZR-1 Net Registry Forums

Pat Cooke · 11-03-2013

Good Morning !

I am thinking that my rough running symptom when starting with hot engine could be something to do with a cold start system. Can anybody explain how it works on the LT5 ? Also wondering if it is switching to a default mode ? When started cold it will run perfect for hours until it is stopped.

LGAFF · 11-03-2013

I don't think that would be it, cold start just multiplies the fuel being dumped based upon coolant and intake air temp I believe. I would think that would not be your issue. If it happens when hot I would think more likely injectors, wire, coil or maybe DIS

Pat Cooke · 11-03-2013

Hi, thanks for coming back to me.
I initially thought coils and replaced them. This made no difference. I then focused on injectors and used injector cleaner, which did seem to help and I thought I had cured the problem. Do you have any thoughts on what is happening with the injectors, if that is the problem ?

LGAFF · 11-03-2013

Original Injectors tend to go bad, no cleaners etc will help. Check the resistance across the injector to see if they are consistent.

Pat Cooke · 11-03-2013

I believe they are the original injectors, It sounds like I should invest in a new set. Have you any advice on which manufacturer ?
Thanks again.

Paul Workman · 11-03-2013

Hello!

The issue is alcohol; dissolves the insulation of the internal actuator coils in injectors installed before 1993.

Talk to Jon at Fuel Injection Connection and ask for the NEW (not "rebuilt") stainless steel injectors for the LT5.

Or, Summit carries the Accel #150821s (which many of us are using). The Accel units have a plastic tab that needs to be ground off of those to be used for the secondary(?) injectors - no big deal.

XfireZ51 · 11-03-2013

Quote:

Originally Posted by Pat Cooke

I believe they are the original injectors, It sounds like I should invest in a new set. Have you any advice on which manufacturer ?
Thanks again.

Pat,

You have several choices. FIC, RC, and Accels are the more common ones. I believe the FICs are the most cost effective but I would stay away from rebuilts.
I have run the Accels for 5 years w no issues.

Schrade · 11-03-2013

Well, maybe don't replace too many parts without doing some diagnostic work. It ain't no picnic, and it's cheaper.

Do you have FSM and a multimeter? Fuel pressure gauge? Check static FP, and leakdown time...

Pat Cooke · 11-03-2013

Paul,
Thanks for your thoughts, fascinating !

Pat Cooke · 11-03-2013

thanks for that, I am going to do more diagnosis before taking the plunge with a new set of injectors.

11-03-2013	#2
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,180	Re: ROUGH RUNNING 2 I don't think that would be it, cold start just multiplies the fuel being dumped based upon coolant and intake air temp I believe. I would think that would not be your issue. If it happens when hot I would think more likely injectors, wire, coil or maybe DIS __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359

11-03-2013	#3
Pat Cooke Join Date: Oct 2013 Location: England Posts: 35	Re: ROUGH RUNNING 2 Hi, thanks for coming back to me. I initially thought coils and replaced them. This made no difference. I then focused on injectors and used injector cleaner, which did seem to help and I thought I had cured the problem. Do you have any thoughts on what is happening with the injectors, if that is the problem ?

11-03-2013	#4
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,180	Re: ROUGH RUNNING 2 Original Injectors tend to go bad, no cleaners etc will help. Check the resistance across the injector to see if they are consistent. __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359

11-03-2013	#5
Pat Cooke Join Date: Oct 2013 Location: England Posts: 35	Re: ROUGH RUNNING 2 I believe they are the original injectors, It sounds like I should invest in a new set. Have you any advice on which manufacturer ? Thanks again.

11-03-2013	#6
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,466	Re: ROUGH RUNNING 2 Hello! The issue is alcohol; dissolves the insulation of the internal actuator coils in injectors installed before 1993. Talk to Jon at Fuel Injection Connection and ask for the NEW (not "rebuilt") stainless steel injectors for the LT5. Or, Summit carries the Accel #150821s (which many of us are using). The Accel units have a plastic tab that needs to be ground off of those to be used for the secondary(?) injectors - no big deal.

11-03-2013	#1
Pat Cooke Join Date: Oct 2013 Location: England Posts: 35	ROUGH RUNNING 2 Good Morning ! I am thinking that my rough running symptom when starting with hot engine could be something to do with a cold start system. Can anybody explain how it works on the LT5 ? Also wondering if it is switching to a default mode ? When started cold it will run perfect for hours until it is stopped.

11-03-2013	#8
Schrade Join Date: Dec 2012 Location: NC Posts: 1,783	Re: ROUGH RUNNING 2 Well, maybe don't replace too many parts without doing some diagnostic work. It ain't no picnic, and it's cheaper. Do you have FSM and a multimeter? Fuel pressure gauge? Check static FP, and leakdown time...

11-03-2013	#9
Pat Cooke Join Date: Oct 2013 Location: England Posts: 35	Re: ROUGH RUNNING 2 Paul, Thanks for your thoughts, fascinating !

11-03-2013	#10
Pat Cooke Join Date: Oct 2013 Location: England Posts: 35	Re: ROUGH RUNNING 2 thanks for that, I am going to do more diagnosis before taking the plunge with a new set of injectors.