Ok guys, I'm stumped. Went to get my 92 LT1 out of storage/paint shop over the weekend. It had an awful miss when I started it. So, limped it home to the old man's place, and started pulling plugs and replacing them. No dice, 8 new plugs, still runs like garbage. I should point out that within the last 2k miles I've replaced the wires, opti, coil, water pump, and both o2 sensors.

Then, I started pulling plug wires one at a time to see if I could nail down which cylinder had the miss fire. again, no dice for the most part. Here comes the STRANGE part. out of curiosity, I started pulling injector plugs while it was running. If I pull any of the FRONT FOUR injector wires, it nearly kills the car. HOWEVER, I can pull ALL FOUR REAR INJECTOR PLUGS at the same time and leave them hanging there, and the car runs exactly the same with no sign of getting worse. I'm at a total loss. I didn't have my manual with me, so I had to leave the car at the old man's for the week. I need to ohm the injectors, but I have a hard time believing I'd lose the two rear injectors on both banks at the same time. I'm beginning to think the computer may be fried, but maybe one of you has had the same problem and can point me in the correct direction. Thank you in advance for any help guys, I'm totally defeated on this problem.

 

you must have a coulple of leakers, so fuel is getting into the cylinders but at a unmetered rate. I doubt its your computer. the injectors are batched fired. Sounds like the classic multec failure. Do an ohm test. Leak test can be done on a lt1 easily by taking the rails off leaving the injectors hang. make sure the clips are good. Disconnect the wires and pressurize the rail. if they are leaking you will see fuel coming out the bottom of the injector that is bad/ use a pan just in case they are leaking. be careful with fuel. use a battery drop light or floresent.

 

Opti.

 

ya think the opti with 2000 miles went bad.. he pulls the injector wires and it still runs on 4 injectors.. the others have to be leaking enough fuel to keep it running. but, it runs like crap!

 

So you're thinking it's the injectors? I'm just wondering what would cause those four to plug up pretty much all at once? Of course, they are the first ones to get fuel since they're at the back of the rail. Well crap, guess it's time to start pricing injectors.

Edit : just checked my records, the fuel filter was replaced when I did the opti and everything else. So like july'ish of last year. Also, I looked up accel injectors..price isn't bad. Anyone have experience with them?

 

we sell the new style bosch injectors for your car.. 169 for the whole set.. watch the video in this link
http://forums.corvetteforum.com/show...t=FICINJECTORS
thanks
jon

 

FICinjectors.....the one telling you what is wrong with your car is the place to buy them!!! I doubt you'll beat his price and he knows what he's doing. Give him a call, you won't regret it!

 

Before you buy parts, swap injectors - front four into rear cylinders, and rear four into front four holes...

 

 

 

The injectors are a dual batch setup, 1,3,5,7 and 2,4,6,8 are fired in batches. There are two fuses, Inj1 (20 amp) and Inj2 (10 amp), check those first.

If you suspect leaky injectors, put a pressure meter on the fuel rail, turn the key on and note the pressure. Turn the key off and see how long it takes to bleed down the pressure by 10 lbs. It should take >~3-5 minutes. If it drops much quicker, something is leaking.

 

Thanks Shawn, I had the old man recheck those fuses this afternoon. They are both fine. Even had him pull both of them one at a time while it was running and doing so killed the engine. since the LT1 is batch fired left and right banks (if I'm reading my manual correctly?) then I'm starting to agree with just about everyone else. I'm still, however, at a loss as to why those four, and mostly all at once. wonder if I got something bad in the fuel tank and they were the ones it got to first. anyway, I'm planning on calling FIC if they're open when I get home from work and placing an order. It's hard for me to explain to the old man what I want him to do over the phone...I'm thinking best bet will be to get the injectors and take them with me this weekend. If anyone can think of anything else I may be missing here, feel free to chime in, and thank you to everyone!

 

Ya! throw another opti-spark at it!

 

That sounds like an awsome idea Road Agent!

I think my opti (GM part, not ebay special) is probably fine after only 2k miles.....

Doing the opti once is one time to many in my book. of course, having access to a lift and tools was a super help. but thanks for the input jsup!

 

Do you have a stethoscope (or a long screwdriver to your ear)? Can you listen to the suspect injectors and compare them to the others? I would feel more comfortable narrowing it down to the injectors before throwing money at it.

Do the leak down test, quick and (nearly) free.

 

OOPS, didn't see the first opti...

 

I dont think you are at a loss here or defeated, It sounds like you did some pretty good diagnostic work and you have almost answered your own question.. I agree with the poster that mentioned how the multec injectors are horrible and this does sound like a classic case of them failing.

Since it is an LT1 and not a TPI, the easiest thing to do to verify the injectors are dead is (BE VERY CAREFULL DOING THIS) unbolt, then lift the fuel rail and have someone crank the ignition briefly, you can usually see that a couple injectors wont spray gas at all...

Good Luck!

 

So you're gonna' buy a set of injectors?

Makes perfect sense.

If your house is dark because 4 of 8 light bulbs are out, dont check the switch for the 4 that are out. Also, don't take the 4 good ones out and put them in the other sockets, and don't put the 4 bad ones in the good bulbs sockets to see if they come on, and don't put a multimeter in the socket to see if there's power in the bad sockets.

I just don't get it.

 

I'm not entirely sure what you're asking here Schrade. Are you Flaming me because I haven't done enough checking, or are you flaming the other guy? If you're flaming me because I haven't swapped the injectors, let me point out that the car is exactly 159 miles away from me currently, and swapping injectors from that distance is a little difficult. It makes sense to me to at least have the injectors on hand when I get back to the car JUST IN CASE (since it's the logical solution) it's the problem. Anyway, not sure what you're saying, or asking, so we'll leave it at that, and thanks for the input!

 

From my interpretation of his response, I would say that he is criticizing the other responses, not your diagnostic work. His point is that you may have a more global problem than simply 4 dead injectors, that it could be an issue with the signal going to the injectors perhaps.