I connected the fuel pressure guage to my gas rail on my 89 TPI 350 IROCZ. The pressure reads 40 PSI, is this correct? Thank youhttp://www.camaros.net/forums/images/icons/icon6.gifhttp://www.camaros.net/forums/images/icons/icon10.gif

38-42 is fine.

It's important that the pressure hold (with key off) for at least 30 minutes or so.

The reason for asking is that the car idles and only at idle it runs erractic when warm. I changed the fuel filter. check all sensors, connections, good spark, distributor, MAF,IAC,O2, throttle senor all good and working. I have no engine codes except the 12. I will change the spark plugs, oil and time it this weekend. Any other suggestions? Thank you!

Yeah, the spark plugs are a real possibility on that.

How are the plug wires?

Thanks I will check all that.

vacuum leaks are a real PITA with TPI motors and could be the issue as well. The vacuum system runs through the heater control, cruise control, TPI/TB unit, Dizzy, etc - all over the stinking place. This will cause the warm rough idle. Basically, until your car warms up it's in bypass mode ignoring the sensors and such. Check out thirdgen.org for lots of tips.

-Dan

Thanks, I'll check vacuum. I which I could bypass everything, so i could just drive and no worries. Thanks for all the help!!!!!!

I changed the spark plugs and there was the normal use on 7 of the 8. The number 4 spark plug was totally new. I know there hasn't been spark in that one. The wires were put on when I last put the spark plugs, about a year ago or less. I checked number 4 wire that goes to the distributor and there was spark, now I don't know if it was weak or strong spark but there was spark. Still running the same. I will put on a wire that have just to test it. What else could it be? Thank you

I would start with the wire, the dizzy cap, and then the injector. If it doesn't even look to have fuel on it, then it may be the injector. You could also do a compression test to make sure - open the throttle all the way for the compression test if you do one.

-Dan

Ok, if it looked new, it wasn't getting fuel.

It should have an injector balance/drop test done on it.

Without that, you can get an inexpensive node to test the electrical signal from the ECM at each injector. You can also check the resistance with a digital VOM.

It won't show fuel flow however, for that you will need a special tool to use with your fuel pressure gauge. You can watch the gauge while working each injector and watch the drop.

I changed the spark plug wire and it seems to idle better.I'll see how it acts up after a couples of days I'll then pull number 4 spark plug in a week or so and see how it looks. I'll still replace all the wires.Thank you so much guys.

From a post on www.thirdgen.org boards:

Leaving the pressure gauge hooked to the test nipple, find a way to SAFELY clamp off the fuel hoses. If you clamp the larger one and the pressure holds, there is a problem with the anti-drainback valve in the fuel pump. If you clamp the small one (only) and the pressure holds, the FPR leaks. If you clamp BOTH and the pressure still drops, then the injectors are leaking. The system SHOULD hold pressure for 20 minutes, at least, without losing more than about 2 PSI of pressure.

I have an 89 camaro/tpi/350/5.7. I have replace fuel pump and 23 lbs.bosch injectors and adjustable regulator, fuel pressure is 47 psi motor idiling. when i shut off the motor the fuel pressure drops to zero immediately. It starts on the second try, runs good. no codes, don't know what it is. Need your help, please. thank you.

Check valve at the fuel pump. Cycle the pump a couple of times and it will start but the pressure bleeds off after a time or immediately. PITA to change the pump.