this question is regards to my 85 L98 tpi corvette, all of my f bodies have been carbed.
it is running rough and has a miss. i have replaced plugs, wires, rotor and cap. set the time and replaced the fuel filter. still no improvement. where should i go from here? a burnt or stuck valve maybe? a bad injector? what order should i be checking this stuff in? please help a felow f body owner!

 

any codes?

pull the vac line off the egr and see if theres an improvement.

Othere possibilites are the maf may have gone bad (im a speed density guy though, so someone else will be able to better help you with something like that)

also check the fuel pressure and see what you got there too..

 

You might want to take a look at the fuel injectors and all associated wiring. I had a simuliar problem and it ended up being a bad fuel injector plug connector.

 

on a hunch i decided to remove plug wires while the car was running one at a time to see which cylinder made a difference.
cylinders 1 and 4 made NO difference at all and cylinder 8 made very little difference, the others made a very noticable difference. does this point me toward injectors?

 

im going to run a cranking compression test on all cylinders to see if there are any large differences. im also planning to check plugs in the non firing cylinders for traces of fuel. any other bright ideas?

 

past what you've just stated, is it still the 85 ecm? if so, the stinkin' MAF module may be bad. If so, do a search on here about the ecm conversion to 86 and up. It's the only way...

 

Try your ignition control module

 

i considered the module until i removed wires one at a time and had great spark. givin the nature of the distributor, the module couldnt throw my timing off to a degree that would cause this problem, still i love any ideas as it gives me base points to begin diagnosing the syptoms, heh, symptoms.

"but maybe the rain, isnt really to blame, so ill remove the cause. BUT NOT THE SYMPTOM" anyone recognize that quote? anyways, throw me more ideas!

 

i compression checked all the cylinders and came up with very close numbers, so i dont beleive its a burnt or stuck valve. any help on how to check the injectors would be great.ive heard i should check for spray pattern but how do i do that, also ive searched for forums on how to test injectors for resistance, one thread said 14-16 ohms less than 10 is junk, another said 2 ohms is good, so im wicked confused. please help!!!!!!!!

 

I'm also having problems with idle myself. My injectors ohm out at 16.8, and the lowest HC count I have been able to get on NY state dyno test is 1.4, and the require .8 to pass emissions these days. The idle is rough in drive, and the temp. will run up to 220 degrees when the car sits at idle, and occasionally it will stall when you put it into gear. I think it may have fouled an O2 sensor, because it stopped the overheating when it was brand new (the sensor). The Haynes manual states 11 to 14 ohms for injector resistance. I am looking to change mine, just need a good price on them, they aren't cheap. Any info posted would be welcome!

 

summit racing sells a set of venom injectors for around 220-280, not a bad price. i was curious as to how i test the resistance of the injectors, what setting do i use on the multimeter?

 

Set your multimeter to the resistance scale, the one that indicates ohms, looks like the greek letter omega. push in the retaining clip and remove the connector. Take a measurement across the two pin connections. Take measurements cold and hot, just to compare readings, dirt, corrosion, or oxidation can seriously screw with resistance measurements. You also need to be careful about what injectors you choose depending on your motor setup, fuel pressure, and most importantly your state emmisions regulations. My 'bird goes for a simulated driving test on a dyno, so it is going to be stock for the next four years, until it is emissions exempt. (25 yrs old)

 

luckily for me i live in east tennesse where they dont give a damn about emitions. i have all sorts of heavily modded, smog emmiting monsters in the drive and every one is tagged! thanks for the help, ill go check it now and let you know what i get

 

I'll keep my eye on the board till I turn in...

 

16.2 to 16.4 ohms all around, even the two dead cylinders... i know i have compression, spark and a timed engine, all i can think is lack of fuel. i swapped two injector harneses to see if the problem would move but it didnt. clogged possibly, how do i check for that, ive heard people saying to test for spray pattern but i dont know how to do that, someone help please!

 

dude, your injectors are way over on resistance, they might even be the originals that came with the vehicle. I found mine this evening, they ran 500 bucks, but they are OEM, and I need the 19 lb/hr injectors to keep the car on the road. No inspection, NO registration. I think yours may be 22# injectors, but I could be wrong, you'll need to do some research into exactly what you need.

 

i thought 16 was around the norm, thats what you had stated your ohmed out at, and besides, even my working cylinders test about the same.. they do llok complelty original and at 163,000 miles my vette has probably seen better days, so what should they ohm out at?

 

One other thing I did was pick up an "Autoxray" scan tool. The model 5000 does everything from ODB-1, up to and including the new CAN protocols. It covers all domestic and imported models from '82 to present.

 

the resistance measurement should be somewhere between 11 and 14 ohms. Other things to check while you are at it are fuel pressure, and your TPS adjustment. You may want to pick up a Haynes manual for essential specs you will need.

 

i got the manual but not terribly helpful on the vette. ive been refering more to my trans am manual for extra info. corvette manual has alot of "see dealer" bs. if they are all right around the same ohms it cant be that bad though, and like i said, look to be original. im still stumped

 

being around the same resistance is simply due to similar age. All an injector really is, is a coil. The injector is opened magnetically just like a relay, only it snaps open and closed very quickly in milliseconds. This is called "pulse width", and it is determined by the computer according to input from the sensors, oxygen, mass air flow, or manifold absolute pressure , manifold air temp, vehicle speed sensor,coolant temp sensor, throttle position sensor, and in newer models there are crankshaft position sensors, and a host of others, but those are the basics. The specs in chapter 4B in my Haynes have been very useful.

 

The range on your injectors sounds fine , when they go bad they will have less resistance. Gm states over 10 ohms is good, but it isn't a bad idea to replace the multicraps to prevent future issues.

 

electrically speaking, increasing resistance in a coil will actually impede it's function. voltage applied to the coil at higher than design resistance will not have the desired result. In short, the pulse width on the scan tool will probably show a pulse width that doesn't reflect the actual function of the injector. The injector not opening or even spraying properly for that matter, will cause a rough idle, and even possibly an incorrect mixture. If the computer reads lean on the 02 sensor, an attempt to richen the mixture will occur, or a lean mixture can make the motor run hotter than normal.

 

its been a little while but ill post whats going on in case anybody ever uses search and needs the info.
it was clogged fuel injectors, i pulled alot of rust from the fuel sytem and the tank. the rubber seal up top had failed and due to the fact that the car was sitting allowed rust and water into the tank. i replaced the injectors with lt1 units and got everything back together. tomorrow i will finish blowing out the fuel lines and cleaning the tank.i also bought a bunch of super strong rare erath magnets that i will place in the tank to catch any future rust particles that might want to cause problems for me. i thank everyone for there time and patience and will post back when i fire her up and see how she runs

 

ewwwwww, some of the rust tapped out of the injectors on the magnet

 

Wow, looks like all of them are about 20 years old!!!! Original Rochester numbers on the side of the injector too. I'll wager she runs alot better these days, no missing or rough idling!

 

Seeing this made me think you had ignition wire issues . Or were you pulling the injector wires?

So , how does it run now ?

 

i was pulling plug wires,, i had already swapped injector wires on good and bad injectors with no change,,, anyhow thats in the past.

i finished the install today and the car is running much better still has a miss on 1 cylinder but it changed, and thats better than the 3 dead cylinders i had last time. so,,,, it would appear the used injectors i got had one bad one in the set. overall the car runs much better than it ever had before, i was out peeling *** all day long! still need to pick up a single injector to replace the one that isnt working now, but it should be easy now that i know what im doing thanks to everyones help