ROUGH RUNNING 2

[Pat Cooke]

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]

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]

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]

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]

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]

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 (http://fuelinjectorconnection.com/shop/viewcategory.php?groupid=106) 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]

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]

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]

Paul,
Thanks for your thoughts, fascinating !

[Pat Cooke]

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

[Pat Cooke]

Nice to hear from you again. Yes, I am going to do some more diagnostic work before buying parts. I don't have a GM factory manual, I do have a Chiltern repair manual, a GM service manual supplement LT5 and GM 1990 section 8A electrical diagnosis. I am thinking of buying a multimeter and an OBD1 scanner cable and software to connect to my laptop, from Red Devil River in Wisconsin. 111018956789 on ebay. Thanks for your advice,I would welcome more on your thoughts on fuel pressure leakage ?

[Schrade]

Nice to hear from you again. Yes, I am going to do some more diagnostic work before buying parts. I don't have a GM factory manual, I do have a Chiltern repair manual, a GM service manual supplement LT5 and GM 1990 section 8A electrical diagnosis. I am thinking of buying a multimeter and an OBD1 scanner cable and software to connect to my laptop, from Red Devil River in Wisconsin. 111018956789 on ebay. Thanks for your advice,I would welcome more on your thoughts on fuel pressure leakage ?

Fuel pressure leakage, either FPR bladder rupture (allowing fuel through FPR vacuum tube), or leakage from leaking injectors, can cause hard hot restart.

Cold start would still be easy with fuel leak, because fuel readily atomizes in cold environment - think Cold Air Induction.

Chilton's should have a round hollow binder, and should hang in the 'library', where the chair has a big hole in the middle. Tear a page, read, wipe, flush, repeat if necessary. 'Krinkle', between 'read', and 'wipe', if you're tender in the hindquarters :bootyshak

[Pat Cooke]

Fuel pressure leakage, either FPR bladder rupture (allowing fuel through FPR vacuum tube), or leakage from leaking injectors, can cause hard hot restart.

Cold start would still be easy with fuel leak, because fuel readily atomizes in cold environment - think Cold Air Induction.

Chilton's should have a round hollow binder, and should hang in the 'library', where the chair has a big hole in the middle. Tear a page, read, wipe, flush, repeat if necessary. 'Krinkle', between 'read', and 'wipe', if you're tender in the hindquarters :bootyshak

Re : Chilton's, I have ordered a GM FSM.
I will be doing the fuel pressure test.
Thanks again !

[efnfast]

From what I understand, the pre 93 injectors will fail if you run alcohol through them. Do you in England? If so, sounds like it wouldn't hurt to change them, maybe to the wallet, but you're due anyway. Mine are in a box getting ready to go in. New SS FIC's.

[Pat Cooke]

Thanks for your thoughts.

[Pat Cooke]

Yes, I live in Cornwall, England. Great Car !

[Schrade]

From what I understand, the pre 93 injectors will fail if you run alcohol through them. Do you in England? If so, sounds like it wouldn't hurt to change them, maybe to the wallet, but you're due anyway. Mine are in a box getting ready to go in. New SS FIC's.

That's what Mr. W posted; most specific info I've ever known of about ethanol in fuel, solving the coil winding insulators...

VERY interesting.

Still say static FP + leakdown first..............................


ed.:
Wonder if anyone knows the different molecular compound in '93 + winding insulators.

2nd ed.:
Damn that's a good question Uh hUH... http://www.smiley-lol.com/smiley/celebre/einstein.gif