I have a rebuilt vortec v6 in my 93 chevy s10. For probably about a year now I have had an issue where one of the fuel injectors will intermittently stop spraying. I've visually confirmed the injector not spraying. When this happens the engine stutters and bucks, the rpms vary, and there is a huge loss of power. The fuel injector will kick on and off while this is happening. At first it happened once or twice every 6-8 weeks. Now it is happening weekly, sometimes several times a week. It eventually will stop and return to normal but this takes anywhere from a few seconds to a few minutes. Usually it happens when I start the engine but sometimes it happens while I am driving. Doesn't matter what the weather is like or if the engine is hot or cold.

I also recently changed the spark plugs and coil pack because it was misfiring really badly. I had noticed the wires were deteriorating and the spark plugs were black and eroded. Now it is hesitating and misfiring again.

I took it to a mechanic and had the codes (OBD1) pulled:

33 MAP sensor
35 idle air control
44 lean exhaust
43 esc module or censor circuit

Mechanic said that the fuel injector not spraying was causing these codes. I asked what was causing the fuel injector to fail and he kinda shrugged and said to replace the injectors. Others have said it could be a bad oxygen sensor.

Could it be that bad sensors are causing the injector to not spray? Should I start by replacing the injectors or the sensors? Note that the injectors and sensors are from the old engine.

Thanks in advance for any help and insight!

 

Homeslice,
I would pay the guy that shrugged his shoulders an hour diagnostics to figure it out.

 

Do you know if the injector is getting receiving the electrical impulse to inject? = a faulty injector
If there is no electrical pulse at the injector? Then yes, replace the sensor.

 

I just bought a multimeter to test this. I read a thread on here where the guy was testing the resistance across the injectors so I am going to try that.

I looked at the injectors with the engine idling and both injectors are dripping.

 

resistance on both injectors came in at 1.7 ohms, cold.

 

So, I replaced the injectors on Thursday last week, and the problem is worse with the new ones! It stalls after a few seconds of idle, there is a loud vacuum hiss, and the engine doesn't sound right, like it's struggling for power. I couldn't even test drive it with the new injectors because it stalls at idle. Also noticed that when I give it throttle in park the digital cluster displays random speeds.

So I put the old injectors back in and the truck at least runs. I can drive it. The idle is a little rough, and it hesitates and sputters. So, not sure what to do at this point. The new injectors (BWD, assuming refurbs) also came in at 1.7 ohms so does that mean they are bad? They were $73 each, so maybe I need to get the more expensive ones?

I also took apart, cleaned, and rebuilt the TBI with new gaskets and fuel pressure regulator diaphragm, got a new CTS connector (wasn't reading temp), a new MAP sensor connector, and a new IAC connector. All the connectors were corroded and bad looking. Also replaced all the pre-molded vacuum lines with vacuum hose and a new pcv valve.

 

I think the first thing you probably need to do is to figure out were that vacuum leak is coming from and seal it. Then we need to resolve that electrical issue.

 

I replaced all the premolded vacuum lines with hose. Seems to have fixed the leak. What do you think the nature of the electrical issue is?

Okay, so it's been running okay for a while, but recently it's been having a problem with hard starting and a rough, low idle. So when it started stalling I replaced the MAP sensor and IAC valve. It ran great for about two days then started stalling again. It stalls as soon as I start it, and I have to give it gas or it just cranks without turning over. Once I get it going I have to give it gas or else it stalls.

I looked at the injectors while it is doing this and they are definitely dripping. When it finally stalls the injectors continue dripping for a few seconds. Is this a problem with the injectors? Or could it be something with the throttle body that houses the injectors?

I just made a video to better illustrate the issue:

 

Also, why was this thread moved to the Ford heavy duty forum??? I am working on a Chevy light duty.

 

I'm not sure... I'll move it.