Allright i get a heavy engine vibe at 3500+ rpms when warm and heres the most recent update. Im pretty sure its nothing mechanical and my vibration/loss of power is due to it dropping a cylinder. For some reason the first time i put all new plugs in i put in ngk's and i just tonight went and switched them over to delco's. The delcos seem like theyre firing better but the problem seems worse with them in. At part throttle i hear an audible ticking/sputtering noise. I also think i broke a clamp or two for my exhaust by driving around a bunch with the vibration because it is shaking pretty heavily in the middle section.

All of this said this is what i have concluded (through various forms)
-Every cylinder is getting a spark
-The ticking noise (now noticeable with the new plugs) could be an exhaust leak due to the shaking of the exhaust creating one somewhere but hypothetically speaking if one of my injectors died and the cylinder was only getting spark and no fuel could you hear the ticking of the plug?
-If it is that i have a dead injector is there any way i could go about testing the injectors to figure out which one is dead. (i think if anything its the number 2 cylinder thats dead because me and my buddy went about pulling wires off of the dist. cap while the car was running and it was the only one that had no change in the way the engine ran when we pulled it)

So basically how do i check for a dead injector. Can anyone think of any other possible reasons for my problem based on the symptoms described

 

Use could check them with an ohm meter...they should all be 13-15 ohms. I have taken a wrench and tapped on one before and it started firing.
Good luck.

 

how can you check it with an ohm meter? I'm really bad with how electricity works my first thought was wouldnt this just check to see if the injector was getting power (which i should do anyways) and not check if the actual injector was working?

So how do i check it with an ohm meter (i have a funny feeling if i go out and get an ohm meter and look at an injector itll be self explanatory) and someone explain my thought process to me and how i can tell if the actual injector works because those r expensive

 

One quick thought, what is the condition of your spark plug wires? A bad wire could be arcing, causing the ticking. It will be noticable if you run it in the dark.

 

Check the wires like he said.....then tap on the suspect inj. to see if it will start working.
To test for ohms...remove the wire plug on that inj. and set the ohm meter to 1 ohm and put 1 probe to each prong on the inj. and read the 0-100 scale.

 

Allright im sure i have spark to every cylinder i just replaced all the plugs and ive checked for spark at the dist. cap and i would have noticed a burnt wire when i did the swap. Ill try the injector test when i get home from work.

 

You should check for spark at the spark plug end.

The wire may not be burnt, but the wire or boot could be cracked.

Just a simple check to do before you go and get an ohm meter.

 

ive checked every plug at the plug except for the number 6 and 8 cylinder and were pretty sure its the number 2 cylinder anyways. I think my friend is going to help me check the injectors tonight or tommorow

 

Here is my input, and I'll start with your itemized list:

*I agree with RE82carota that you should check for spark at the plug and not at the dist. I know you did on all but 6 and 8, so I'd just double check those.

*A ticking noise could come from the exhuast, but that would be from and individual cylinder, at the head flange or along one cracked header tube. Nowhere else in the exhaust would a leak sound like an single "tick". It would also get much louder/sharper sounding with throttle and load, and it would dissappear under trailing throttle. If the noise doesn't have these characteristics, then it isn't exhaust, and it is mechanical. How loud is the noise? Also, if a cylinder IS misfiring, it wouldn't make a ticking (from exhaust leak) noise, because it's not generating any exhaust energy to make a ticking noise.

*Checking the injector via Ohms is one way, the other way would be to do what you did (remove spark from one cylinder at a time). I never pull plug wires though for a couple reasons: 1. I don't like getting shocked. 2. It's potentially bad for the ignition coil, and 3. It's hard to hear the engine precisely, when you're flinching and jerking wires.

I use a test light, with the shaft coated with dielectric grease, and I back probe the spark plug boots. I also unplug the IAC, so I can more clearly hear and RPM drop. I recommend re-doing the "cylinder balance test" that way, isolate the misfiring cylinder, and then compression or do a leak down test on that cylinder.

 

well i appreciate the info but i think ive basically given up. Heh when i was pulling wires off the cap i only got shocked once but i was using rubber gloves so it wasnt too bad. It was also a little easier for me to tell if the engine was changing because my friend just stood by the exhaust and said he heard a change in every cylinder except number 2 which we checked twice. I did the test where you put something metal up against your injector and "listen" to wether it makes a ticking noise....i could just feel the tick but every injector was firing. Today im going to make an appointment at the gm dealership to get it hooked up to a scope. Thanx again for everyones help im sure ill need more of it in the future

 

oops didnt mean to put another post but this site doesnt let me delete them.

 

Could you let us know when the dealer figures it out? Just for S&G's? Thanks

 

UPDATE Well i took it to a gm mechanic and its closer to being fixed.....He checked my whole fuel delivery system and its fine so that gets rid of that. Its getting air without a problem. As far as spark he tested my coil and it works. He said #5 cylinder was the worst and that plug if you pull it out and hold onto the metal you can spin the ceramic part But when i got the car i changed the plugs and put in some ngk's.....had the problem....changed them to ac delcos and the problem is still there. The latest mechanic said to fix all the plugs that seem broken and then get a compression test done. He had it hooked up to a scope and said it was dropping cylinders but that it was somewhat random which ones were going although the number 5 was the worst. So im going to replace the plugs that need it and then go get a compression test done. If i was losing compression on 1-2 cylinders then it could mess with all of them a bit. Hopefully a compression test will come up with something otherwise im going to be at a loss

 

DOH!!! so 3 stupid mechanics later none of which have come up with anything substantial (my normal mechanic, the mechanics that my friend works at, and a GM mechanic) and not to mention 186 dollars later it seems like i might finally have figured out my problem on my own. The thing that drives me nuts is that from the second i stepped into the garage it took me less then 5 minutes to have figured out the problem....cleaned up....and was back inside the house and all i needed to figure it out was a 12 dollar tool (well normal priced 50 but it was on sale )

ANYWAYS to the point I went and bought a multimeter. Went out to the car...checked the injectors...one of them had half as much resistance as the rest.....guess i have a dieing injector....that would explain my car dropping a cylinder....WTF WHY DID NO MECHANIC FIND THIS?!?!?! I HATE THEM THEY ARE ALL MORONS!!!! sorry venting but it shouldnt have gone through 3 mechanics undetected thats just sad. Anyways im buying a new injector and im assuming itll fix my problem. I also tried having the car running pulled the injector wiring from the dieing one and almost no difference in performance....put it back on and tried it with a working cylinder and it had a major stumble. I TOOK IT TO 3 MECHANICS AND NONE OF THEM COULD FIGURE OUT IT WAS A DEAD INJECTOR HOW DUMB ARE THESE PEOPLE. well there ya go it seems like problem solved.....knock on wood

 

since u have a 90' i would look into replacing the entire set. u have the Multec injectors(light gray body). these injectors are failure prone and u will only be disasembling the tpi unit again in the next year or sooner. it is a major PITA to disassemble the TPI and reassemble the TPI unit. if your having someone else do it, then you will end up paying double later.

 

okay well first of all injectors are like 150 bucks canadian and im 16 so if i can get away with buying one for now id rather that. And im not sure exactly as to what it is that makes the tpi unti so bad to take apart? The TB is 4 bolts and the plenum is like 5 on each side seems pretty simple to me. And ive never taken apart the fuel rail so that will be a fun experience. But yeah i couldnt see spending 1200 dollars on stock injectors when in the next couple years im going to be upgrading my engine and will need bigger injectors anyways. thx for the thought though

 

$1200 for injectors? at the dealer maybe. try like $220 for new accels at the least. when u start taking the tpi apart and then putting it back together you'll see what i mean. it is a PITA. even more so, very time consuming.


if you had prom burning equipment, or some one that can burn for you, i recommend some used LT1 injectors. they can he had for as little as $75. they are 24# and will easily support 450HP. room for improvement down the road . i've bought around four sets and they have all been in excellent condition. they all have worked superb. i have a set in my 88' IROC and absolutely love them. great & cheap solution.

 

well considering i can pull the plenum off in about 5 minutes and the fuel rail is 2 bolts so im not worried. Anyways i just bought this car and am flat broke so i bought a single injector from the dealership and itll be in after the weekend. My car will work (*knock on wood*)and right now the most important thing is just that the car runs properly.