Herriott88

My dad and I are working on a 1991 z28 camaro 5spd. with the 305. I started hearing a slight tick noise (something like valve slap, but a little more arking type) that would be less noisy after shes warmed up a bit. One night me and my buddies were driving around in it. A friend hopped in and took it for a spin. He came back saying there was little throttle response and sure enough, just to get her going, i had to get the rpms up real high just to move. I found out that a spark plug wire was burned up a little so I replaced it with a wire that was 1mm smaller than the set up i have. (8mm is what i have, i used a 7mm for a few minutes). Replaced it with a new 8mm wire and it drove just fine. Then another night i went driving, i gave it full throttle and she started rapidly backfiring and had lost a great deal of power. Got her home and pulled the cap and wires made sure everything was fine and things looked great. Tried to start her after putting everything back and she wouldnt start. She cranked, had good voltage, and of course had fuel. I checked fuel pressure and it sat at a solid 20psi then dropped fast to 0. So we replaced the fuel pump and Icm and she fired right up. Took her for a drive and drove beautifully. Next morning i tried to start her and did the same thing she was doing before. I replaced the fuel pressure regulator and saw that i was getting around 44ish psi when cranking and she held it. Ive checked wires, connections, fuel filter, adjusted timing. I have pulled the valve covers to make sure the rockers are in fact moving and they are so the cam is fine. I have spark and fuel it would seem so what is going on? Ive repleced the tps and Iac if that helps.

Tuned Performance

iTrader: (92)

whats the issue now ?
low power ?
lifter tick ?
If one wire was burned to should probably replace all the wires including the cap and rotor.you can ohm them but if your unsure there age it’s not worth the hassle to measure there resistance.

Herriott88

it wont start at all. Cranks, no start. I just bought a new cap and rotor as well as wires not more than a month ago.

Herriott88

itll start when we spray starter fluid into it and keep spraying it to keep it alive but its very choppy and itll die very quickly if we stop

Tuned Performance

iTrader: (92)

Have you checked for injector pulse with a noid light ?
You could have a vats issue.

Lakerman62

iTrader: (3)

just went through similar things, did cap and rotor after fuel pump, ICM, kept cranking not turning over, after got it running, new plugs and the car runs great. It was weird how the fuel pump went out at same time.anyways best wishes for solving things

Herriott88

No, we havent checked that. How do we use the light? Weve checked the ecm and its working just fine.

Herriott88

Ill have to check that. Thank you!

Tuned Performance

iTrader: (92)

You can find noid lights at the auto parts store or harbor freight.
You can unplug a injector and check for power or verify the two injector fuses are good.
put the noid light on one of the unplugged injector connectors and crank the engine over. If you don’t have a blinking light. You can try unplugging all the injectors and try again. If the coils of the injectors fail they can shut off the injector pulse.
a bad icm or vats can also kill injector pulse. Start with the noid and unplug the injectors them move onto diagnostics of the vats. You can find kits cheaper with just the noid lights but harbor freight has this kit.

https://m.harborfreight.com/11-piece...set-97959.html

https://m.autozone.com/test-scan-and...ter/948078_0_0

Tuned Performance

iTrader: (92)

Post 35 check the ecm pin f10 for power with the key on you should get 2.5v if the vats is working.
https://www.thirdgen.org/forums/elec...pass-vats.html

https://tpiparts.net/1227730_pinout_diagram

Herriott88

Okay, ill try that when i get the chance. Thank you for the advice and help! ill get back to you when I try and my results.

Herriott88

I checked vats and theyre working. Reading 2.5 with key on.

Tuned Performance

iTrader: (92)

See if you have injector pulse next. It could be the injectors shutting off the injector driver.
I have seen new icons bad out of the box too.

Herriott88

We hooked up a multimeter to them to check power and they did. different from checking pulse?

Tuned Performance

iTrader: (92)

Yes, pulse happens when the ecm gets a signal from the icm.
with a noid light you can see the pulse. If there is no pulse you can start to ohm the injectors. A shorted injector can stop pulse. The injectors should ohm 15.5-16.5. If they have a grey body they are called multecs.
multecs are prone to shorting.

Herriott88

I checked all 8 injectors and they all read atleast 16. What should I check now?

Tuned Performance

iTrader: (92)

Check to see if you have injector pulse. You can touch a injector while someone cranks the engine over or use a screw driver pressed again the injector and your ear. You should be able to hear it click. If you don’t it’s probably a faulty icm even though it’s new.

Herriott88

I figured it out. One of the icm pigtails was loose. She fired right up. Thank you for the advice!

Tuned Performance

iTrader: (92)

Purple with a white stripe is my guess.

Herriott88

this ones connector broke off

Tuned Performance

iTrader: (92)

It’s hard to see in your picture what broke. If you need a new connector here’s one.
https://www.ebay.com/itm/GM-8-Pin-IC...EAAOSwMNxXXhjQ