89 IROC, car was left to me by a buddy who passed last year, it's been molested. Edelbrock top end, runners, manifold, air box, bkk throttle body, MSD ignition. I have spark, engine cranks, fuel pump replaced and functional, pressure at rails. Seems to have no injector pulse, plugs are dry. Looks like maf and map are disconnected, it did run and was driven to its previous location. I had it towed to my shop.

 

It’s maf if tpi no map. Check for pulse with a noid light . Could be stuck injectors or vats or is ecm isn’t getting signal from icm.

 

What type of signal am I looking for at the ecm from the icm? I could see stuck injectors, but all eight? The fuel in the tank was pretty bad, I think it sat for 4 years?

 

If injectors sit in fuel and varnish yes all 8 can stick shut . The signal is on the purple/white wire from icm to ecm. Easiest thing is to start with a noid . No pulse then measure hz signal from passkey module to ecm.

 

B6 is vats a hz signal from passkey module to enable injectors.
30hz iirc .

https://tpiparts.net/1227165_pinout_diagram

 

THANKS!!

 

Ok, it runs, but fouls plugs. It's a 91 vette motor, msd small cap hei. Jet maf, Edelbrock intake and 6085 heads, big tube runners, bkk throttle body, headers, it seems to have only one 02 sensor, single wire. 150 psi compression, ngk fr4 plugs. Put autolites in it last night, ran much better. Drove it this morning and went about a mile and a half and it sounds like the plugs are fouled again. Check engine light came on at the same time. This car has been molested....any ideas where to start?

 

first things first. What does that check engine light have for a code?

 

Can't tell, no diag plug can be seen

 

That's a solid problem. Molested or not, who the hell takes that out? There's no purpose in doing anything to it even if removing the efi, well unless you're fully gutting the car for weight.

Umm ok. Check fuel pressure, check to see if the regulator isn't leaking fuel, and see what the injectors are. With no aldl, I don't know how you'd see values from the ecm. Factory ecm still there? Did they swap to an aftermarket?

 

Reman ecm, hypertech chip, msd distributor had lots of corrosion to clean up, module tests ok.fuel pressure 45psi

 

Injectors are yellow lol all I can tell at the moment.

 

Aftermarket chip and maf are suspect. I'd personally change them but that is just a knee jerk reaction. Impossible to know what the maf is telling the ecm.
Yellow injectors sound like 22lb bosch 3s but that is soley based on color.

Did you check these new plugs to see if they gassed up?

 

Definitely sooty around the base, electrodes were white. Just put the distributor back in after cleaning, checked module, checked air gap.

 

Runs better, sounds like and feels like it's firing on all 8, before it had a slight misfire. Weren't the 5.7 injectors 24lb?

 

5.7 had 22lb injectors stock, the 305 had 19lb.@, hope that helps.

 

Stock 24lb weren't till the LT1. L98s were 22

 

It does have a stuck or low flowing injector on #8, it started to work after tapping on it. Going to pull the injectors tomorrow and clean/test, it's still got the egr hooked up?
it made the whole test drive tonight without throwing a code.....

 

Sounds like it just needs some road time. Run some good gas through the hot injectors and get them cleaned out. Yellow injectors might be Accel brand. I think the Corvettes did have 24 lb injectors with the better exhaust on those cars. Car might be a monster when it gets all straightened out.