cheese_kake

I have a 95' LT1 swap into my 92' Z28. I have hedman headers and full 3" exhaust. MSD 8mm plug wires, and all new AC Delco stock platinum plugs. The motor has only 38k miles on it. I noticed that at lower RPMs it seems sluggish and lacking in torque, and even sounds rough. Although at higher RPMs it seems to pull alot better and sound great. At idle it seems ok, but I just noticed something as the headers started to shed the initial black paint as they get hot (only been running about 2 weeks brand new headers ). The second from the back cylinder on the passenger side, its' primary still has all of its paint and is not even chipping. All of the other primaries have long since lost their paint. One day I started it and wanted to see if it was even getting hot, after about 30 seconds you cant even touch the other primaries, but the one primary in question remained just warm or slightly hot. But I was still able to hold on to it for while without burning my hand. I'am not noticing anything else out of the ordinary, other than the fact that it doesnt run as good as I know an LT1 can. The motor does not seem to be running on any less than 8 cylinders, but the loss of low end power could deffinately be that.

Any help or ideas would be greatly appreciated.

Thanks,

-Phil

sofakingdom

iTrader: (1)

You clearly have one cylinder not working.

When you pulled that plug as your initial troubleshooting step for a dead hole, what did it look like?

grumpyvette

check the plug and ignition, check your getting a good spark, first, replace that plug with one from a good cylinder and see if the problem remains or moves, if it moves its that plug,(replace it with a new one) if it stays in the same cylinder ,then thats generally a plugged/clogged injector symtom

check the electrical connection to that injectors a good contact, add a pint of MARVEL MYSTERY OIL and a CAN of INJECTOR CLEANER to your next full tank of gas and replace the fuel filter, if it doesn,t clear after a few hours run time youll need to pull and clean,and or replace the injector


BTW

http://www.professionalequipment.com...d-thermometer/

spoting problems with one of these is a breeze, it helps a good deal on carb tunning & jet changes and finding problems quickly

cheese_kake

The marvel mystery oil, that goes in the tank correct ? What type of injector cleaner do you suggest, there are so many ?

Since both you guys pointed out that this is deffinately one cylinder not firing, I'am just amazed at how it still runs with just 7 clyinders !!
I would figure the car would be shaking really bad if a clyinder was out.

grumpyvette

"The marvel mystery oil, that goes in the tank correct ?"

YES, add 1/3 of the fuel. pour in the MMO then fill the tank to make sure it blends with the gas

"What type of injector cleaner do you suggest, there are so many ? "

use TEXACO, or SHELL,or GUMOUT
, buy any two, and add to the tank of fuel, between the MMO and the INJECTOR CLEANER the injector SHOULD clear if its mildly fouled, if not youll need to pull & replace that injector

Damon

Remember a cylinder needs 3 things to fire: fuel, spark and compression. A plugged injector would have to be just about completely plugged to prevent the header from heating up at all. Lack of spark is even more likely (bad plug, wire, etc.). Last would be compression (physical engine damage or misadjusted valves).

Start with a compression test- make sure that cylinder is close to the same cranking compression as a known-good cylinder. If it's down quite a bit (or significantly higher) it's definitely the problem.

Next easiest thing to check is the ignition. The last thing to check is the fuel side of the situation.

cheese_kake

Thanks guys, Iam gonna try some of those things and see what turns up.

cheese_kake

Well I had my dad do the compression check while I went to work, and he said they all checked out fine. Each cylinder was within less than 10psi of eachother. I checked the plug, it looks white, like it was in a lean condition. So I'am only assuming that it is getting spark and has good compression, and it just isnt getting enough fuel.

F-BIRD'88

Try feeding some propane from a propane torch into the throttle body inlet. If you have a lean cylinder the extra fuel will allow the cylinder to fire properly. The extra propane will not harm the motor otherwise. If the header on that cylinder now runs more normal, you either have a bad injector or a intake manifold leak. Swap the injector for another one. If the problem moves with the injector swap the injector is bad. if the problem stays on that cylinder you have a manifold leak.

DENN_SHAH

iTrader: (1)

its not uncommon for the injectors to stick closed if they have sat up for very long.
with the motor running, take a long screw driver & put against the injector on the cylinder thats not firing & see what it sounds like, for a comparison do the same to another injector so you know what you should hear. if the injector isn't clicking, with the motor still running try tapping on the injector body with the screw driver & see if it helps. you don't need to beat on the injector, tap on it with about the same force as if you dropped the screw driver down on the blade from about 6~8 inches is enough.

MyMaro89RS

The screwdriver tricks works well but you can also check the resistance of the injector using an ohmeter.

cheese_kake

After work today, I'am going to try listening to the injector and then try tapping it. If nothing changes, I will probobly try using some propane.

But like DENN_SHAH said about the motor sitting for awhile and the injector just sticking closed. That could very well be the problem.The motor had been sitting from September until January. And I only just started it 2 weeks ago. Also there's no way to tell how long it sat in the warehouse before I bought it.

Sonix

iTrader: (1)

I'm just gonna grab the ball and run the other way here;
Can grumpy, or anyone else expand on this? I was going to pick up a digital thermometer, but mostly to find dead cylinders sorta thing. How can I use it to help with carb tuning??
Thanks

grumpyvette

simple, lean cylinders tend too run hotter than rich cylinders, between reading the condition of the plugs and useing a IF thermometer on the headers just outside the heads you can get some IDEA of the exhaust temp, and a/f mix ratio, if you have experiance and know that ignition timing also effects results.
example if the temps over about 1270F your REAL LEAN, rev the engine up to 1000rpm, then 2000rpm then 3000rpm and hold it a few seconds,at each, zap the headers with the IF temp gun and youll quickly get some idea as to the exhaust temp/a/f ratio if the power valve and jetting is close.
vacuum leaks and other faults also tend to show.
generally youll want the header outside temps in the 1000-1100F range max, if the rear cylinders tend to run hotter the rear jets or transfer slots or accellerator pump shot may need riching, ETC.
its just one more tool that helps isolate/detect info you can use

xomega

iTrader: (1)

i had this issue. same cylinder, i bought some noid lights, and saw the injector harness was calling but i still had a dead cylinder, so i layed the fuel rail upside down and turned the key, come to find out the injector wasnt pumping i could see them all squirting but that one, then i put the inject in a different location on the raid and it didnt pump, so i soaked it in wd40 i think it was overnight, and it worked! been working 6 months since

Sonix

iTrader: (1)

Thanks for the tips grumpy!