Hello all. Pick your brains? I have a 1991 z28. Car burns rich pretty much all the time. Stinky car. Seems to move pretty good. The car was originally a 305. Was converted to a 350 previously/supposedly. I have replaced the ECM /prom,knock sensor, iac,tps, coolant temp sensor, plugs wires cap rotor. Set and reset timing. the car starts well when cold (first start) but cranks quite a bit when warmed up (gasy smell is worse once warmed). All these components replaced are to match a 350 as I thought that that was probably the issue. (305 componants on a 350 car)There are Eddlebrock performer heads on it , headers. The smog pump has been removed( heads , smog pump , headers were from previous owner). Everything I have done has been over the last couple of seasons. The problem has been consistent since I got the car approx 3 years ago. I'm starting to think maybe an oversized or dirty injector issue? Any ideas would be appreciated. I also am unsure what type of heads these performers would be or how it may affect things (202s etc). I'm a novice gear head trying to figure this stuff out thanks for any advice or info

 

Few things to check. For one, you would need to get a scanner to see what the readings are from the sensors. O2, MAP, Injector Pulse, and any other sensor that has to do with the fuel system. The other thing to look for are leaking injectors or clogged air filter. Also, what is your fuel pressure? These are things you would need to look at and this will help determine where the problem is.

 

Hey Birdtojag thanks for the reply. Do you think it can have anything to do with the smog pump(air) being removed or the heads not being original ? I'm not sure what effect these items would have on the car. I'll have to find someone with a scanner or take it in to a shop to get it scanned

 

Hello again just checked my fuel pressure it jumps up to 43 psi when the pump is energized(key on not running) there is no sign of fuel in the fuel reg vacuum line. The fuel pressure immediately starts dropping almost to nothing within approx 5 min. From what I've read it's most likely leaky injectors fuel reg faulty or fuel pump check valve am I reading that right? Anyone else having this issue? I also read that youre supposed to pinch off fuel lines to prove if it's injectors or reg can anyone describe how this should be done to prove what the issue is. Thanks

 

That's a good start. The rubber fuel lines are what you want to pinch off. Start with each one and then both. This will tell you which way the fuel is bleeding off. Fuel pressure is good at the start, so just find out where it is going.

 

Thanks for the info birdtojag I'll do that. Hopefully this weekend and I'll post the results of the test. Just a side note there always seems to be a lot of pressure in the gas tank does this mean anything or is it just the fuel trying to evaporate ? Thanks again

 

Fuel evaporation. This is normal.

 

I pinched off the lines and found the pressure still drops at the same rate and I am able to hear what I think is the fuel leaking. I'm now leaning heavily towards the fuel injectors. What do you guys think?

 

thats a safe assumption, the factory injecters suck, go with Bosch III's....south bay injectors should help you out nicely as they are a vendor here on the site

 

Hello sorry it took so long to get back on here. I finally got my injectors(Canadian postal strike). I finished replacing them and the fuel smell seems to be gone yay! I've been trying to get this for quite some time so I am very pleased woo hoo. Thanks guys for your assistance

 

This is good news. My car is doing the exact same thing. But I wanted to ask you cubby. What ECM/PROM did you use? Did you have one burnt for your car or did you get a used 5.7 auto ecm? I ask cause I also have a 350 with a t5 and was just wondering on how to go about getting a ecm that will work right with my t5

 

Sorry it took so long to reply I've havent been on for a while. I just bought a new ECM and prom for an auto 350. I don't know if it would matter that I have the 5 speed in there I havent noticed any issues. Further to the burning rich issue. The gas smell seems to be gone with the new injectors but it still has to crank quite a bit before it catches. It now starts a smidge better warm than before but a lot worse cold with the new injectors. Anyone have any ideas?