my car raddles not alot but ou can fill it and my car feels like a 6 cly. could a injector be bad, and if so how can I tell?
thanks

 

Diagnosing idle and driveability issues with our old Thirdgens is difficult at best. There are many different things that can have the same symptoms.

Case in point. Three times in the last 18 months my car has developed a terrible idle and ran like ****. I usually cheat and use an IR heat gun to find the errant cylinder.

The first time I found two burnt plug wires. They needed replacing anyway so no real skin off my nose.

The second time I re-checked the obvious stuff like plug wire and plug. I even went so far as to switch the injector on the bad cylinder. Didn't help. Finally ran a compression test. Yup, it was way off. I had bent a valve. That was a bit expensive.

The third time it happened I just knew I had bent another valve because the plug and wire was fine. Nothing weird on the compression test, though. I finally replaced the cap and rotor, voila'! It didn't look bad, but I guess it was. All three times the car acted similar but the problems were quite different.

What it all boils down to (unfortunately) is keeping the car in tune and replacing parts that might be suspicious. The last thing with a driveability problem I would suspect are the injectors because there are so many other things that usually go bad first. EGR and IAC are two of the most common if your plugs and wires are ok. Vacuum leaks and the TPI are common partners in crime, too.

Finally to address you question...To see if the injectors are firing you can literally take each one's pulse. I put my finger on each one and feel it fire while it's running. If you're into the electronics I'm sure someone here can probably tell you the resistance in ohms they are supposed to have. Lastly, you might have to remove them and set up something so you can test fire them.

Good luck.

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Mike

'90 IROC-Z, 5-speed, ZZ4, Trick Flows
Moderator SEThirdgen

 

along the lines of a heat gun is something called a temp stix, from welding supply stores. just run it across each header tube, or the manifold and see which one doesn't melt it. a crayon works to, but not as good. you can check injectors by measureing the resistance each one has. it's best to start with the basic tune up stuff and progress from there when dealing with drivablity problems.

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-=ICON MOTORSPORTS=-

 

My injectors are about 16 Ohms cold, and you should hear 'em clicking with one of those little automotive stethoscopes from Autozone. The resistances of the injectors should all be close to each other too (e.g - 15.8, 15.9, 16, 15.9, etc.). If those two checks pass, I'd look into other things than the injectors like these guys pointed out.

 

EGR and IAC are two of the most common if your plugs and wires are ok. Vacuum leaks and the TPI are common partners in crime, too.

I feel stupid but what is the EGR and IAC? I don't think I have a vacuum leak and what do you mean by the TPI? thanks hopefully I can get my baby fixed

 

EGR = Exhaust Gas Recirculation - lowers combustion chamber temps in order to reduce the emissions of NOx by routing exhaust gas back into your cylinders. Also fills your cylinders with inert gas that results in poorer fuel economy and power production.

IAC = Idle Air Control - just what it says, when the throttle plates are closed at idle this baby is a pintle valve that allows the correct amount of air into the into the plenum.

TPI = Tuned Port Injection - GM's moniker for the multiport, batch fire fuel injection system your car is (hopefully) equipped with.

Hope this info helps! It never hurts to ask questions.

 

so how would I replace/check the EGR? Thanks like my problem! Help if you can thanks!

 

Whoa, man! What are your symptoms? Does it idle rough, backfire, accelerate weak, run rough all the time, stall, what exactly is the car doing? I'd just hate for you to get into the EGR system unless you're sure that's the problem because there's alot of other stuff that causes driveability problems that's easier to rule out first. Personally I would check basic ignition stuff, the IAC and check for vacuum leaks before I did anything else. Do you have new plugs, wires, distributor cap and rotor? To work on the EGR you have to remove the plenum, and that's not the most fun in the world.

 

yeah new plugs/wires. new rotor new cap. My car feels like a 6 cyl. it doesn't drive to rough but it does shake. It feels like it is missing but can't figure it out I have no idea what is wrong with it, can I get a diagnostic done, can they tell me what it would be?
thanks again man, you are helping alot

 

No problem, man. Is the computer giving any codes? You can get it hooked up to a diagnostic scanner for about $30, but I haven't had too much luck with this because I think you will be relying on the experience of the mechanic interpreting the data. You can also do alot yourself with just a good multimeter and a vacuum pump/gauge. If it feels like it's missing, you can do what Vader said in an earlier post and disconnect each injector one at a time with the car running while listening to the idle. You may want to even get someone to sit in it and watch the tach. If the idle does not change when you pull the wires from one of your injectors, you have found a dead cylinder and that injector could very well be your problem. Let us know what you find out.