I've got a 1991 camaro with a 305 tbi, and 221,000 miles. When I start the car up, it cranks over for about 5 seconds, and when it does start, it runs like crap for a few seconds, and then surges for a few minutes, and then runs relatively smooth - rpm wise. It just about dies when i turn on the a-c. When i take it out to drive and I floor it, it accelerates at a somewhat leisurely pace, until it hits a certain rpm(no tach) and then it goes like a rocket.

I had the aircleaner off and I noticed that one injector was pulsing, I then opened the throttle by hand and apparently got it to the point at which the engine gets its ***** and the other injector started pulsing.

I tested the tps, and its voltages where normal, with a linear increase.
I cleaned and tested both injectors.
The throttle body is clean.
The IAC is clean and working.
I couldn't find any vacuum leaks.
I cleaned the EGR too.

So, are both injectors supposed to be firing at idle, and if so, what needs to be done to fix my condition? All symptoms seem to point to a lean condition from my experience.

If its not fuel, is this an ignition timing issue or something like it?


Thanks,
A-C

 

Check fuel pressure. That is the easiest thing to check that is commonly the problem

 

Both injectors should be firing at all times. Check your fuel pressure. I suspect that to be your issue. Either way something on your fuel system is the culprit

 

Yeah, these tbi motors will run on very low fuel pressure. Just not very well.

 

Yeah, I was wondering about fuel pressure, but it performs better at higher rpms than low, which confuses me (not that that's hard to do). I just ran it through the rpm range, and it sounded, to me, almost like a 4 or 6 cylinder until you hit the point at which both injectors fire, at which point it sounds like an 8. I tend to think that its got enough fuel pressure, it sounds like its doing somewhere around 3000 rpm when the passenger side injector kicks in.

 

Again check pressure

 

Just out of curiosity, I went out and switched the connectors to the injectors, and hey presto - they both pulsed and the engine had full power, so what in the world is causing that?

 

Went out this evening and started it and only one injector was firing again, switched the connectors and the same one kept firing. I checked resistance, and they where both 1.7, so should I go ahead and buy new injectors, or try and clean them again?

 

No, you should go ahead and buy a fuel pressure gauge and test the FP! I'm not saying that it 100% the problem, but 98% of the time, it is.

 

i believe you can also rent one from autozone

 

I am completely mystified as to how fuel pressure can cause ONE injector to not fire, while the other one works just fine.

If the problem is that one injector doesn't fire at low-load, and it's always the SAME injector even when you swap the harnesses from one injector to the other...yeah, you have a defective injector.

 

Re-read post #7.

Op states that after switching connectors they both fired. Then the next day the issue arose again. I don't understand why some fight the idea of checking the fuel pressure. The gauge is inexpensive and will come in handy. Second, we all know our cars are notorious for the fuel pump to sending unit hose failing, causing low pressure, causing symptoms like this.

Again, I could be wrong, it could be electrical, but why not rule out pressure instead of taking the "throw money at it" approach.

 

Since I am WAAAY to cheap to spend the 20 bucks on an adapter (I do have a gauge) to test the pressure, I have to put a three-way in place of the fuel filter. So rather than get the car up on ramps, get gas on myself, and find out how well "stop-drop-and roll" works, I disconnected the offending injector, started the car, and put a 9 volt battery on the fuel injector terminal and the fuel shot out nice and hard, and the other injector's spray wasn't affected. I assumed then that the injector was dirty, so I took it out, and got injector cleaner all up in there. Put it back in the car, and it pulses, albeit slightly weakly, and the engine runs on all 8 cylinders. I may just go ahead and replace the injectors anyways though, I don't want to end up stranded somewhere. I'm assuming that since the car had 221,000 miles on it when the odo broke, I would guess and hope that since this seems to be a common problem with these cars, the fuel pump busted awhile back, and was replaced.