Getting to much fuel

[seabee]

Need some help on this , 1987 R10 305 TBI . Runs great but it’s getting to fuel . I keep getting code 45 running rich, I’ve replaced TBI with Holley 502-5 . When with GM TBI would get Code 45 . Truck is getting 6-7 MPG . Only code 45 no other codes. New fuel pumps in both tanks ,checked pressure at filter getting 15 psi .
Change o2 sensor 2 times and replaced it with 3 wire . Replaced ECM , 2 sets of plugs . Replaced plugs wires , cap , rotor , every sensor and module have been replaced MAP , IAC , coolant sensor, grounds have been replaced. What could be causing it to run rich . I’ve turned down pressure regulator on Holley TBI after talking to their tech department. Is 15 psi too much ? If I unhook IAC to adjust base idle engine will run at 1800 rpm . If I reconnect IAC it will idle back down to 800 rpm . Any help will be greatly appreciated. Thanks

 

[78C10BigTen]

Maybe @Vbb199 could be of some help here...

 

[fast 99]

What is the manifold vacuum? Fuel trim is primarily controlled by the MAP, 02 is secondary. My first thought is a stuck or leaking EGR.

 

[seabee]

Manifold vacuum 18-19 , Egr is removed and blocked off . Replaced map sensor 2 times . Is 15 psi too much for TBI ? Holley said it’s should be max 12 psi . Thanks

 

[Bextreme04]

Manifold vacuum 18-19 , Egr is removed and blocked off . Replaced map sensor 2 times . Is 15 psi too much for TBI ? Holley said it’s should be max 12 psi . Thanks

Why are you asking us if holley already gave you the answer? Yes, 9-12psi is correct for all TBI before 94-95. In 94-95 the 454 TBI went up to 30psi, all others stayed at 9-12.

 

[seabee]

Sorry did not talk to Holley till after I ask the question. But thanks for your answer

 

[Vbb199]

Throw that holley chit in the garbage.

They're notorious garbage and not a replacement for gm tbi

 

[gmbellew]

I am also having a rich condition. but only at idle, in park with no accessory load.

I think 9-13 psi is the spec fuel pressure range. seems like you may be over pressured or have a leaking fuel pressure regulator.

I am waiting on a pressure gauge to check my pressure

 

[gmbellew]

also, to check base idle without IAC, you have to force IAC closed and then unplug it. or remove it and otherwise plug the passage.

 

[Vbb199]

The rubber diaphragm probably just went bad on the OEM tbi, or the injectors aren't spraying in an even conical pattern and dribbling.

All common TBI problems and can be resolved for less than 50$


Edit: curious sake, what's the engine vacuum in/hg currently ?


You can tap into the intake manifold behind the TBI and measure this.

 

[SquareRoot]

Throw that holley chit in the garbage.

They're notorious garbage and not a replacement for gm tbi

Including the POS Sniper. Vince, I knew you were sandbagging on this! @Vbb199

 

[fast 99]

The OEM TBI system is very basic and dependable. Put it back to stock and start over. Yes 15 PSI is high. Enough to cause that problem? don't know.

 

[mshawn]

EGR leak!

 

[fast 99]

EGR leak!

He said the vacuum was about 18 pretty normal. EGR issues will usually lower it substantially.

edit, be sure and check the grounds on the thermostat housing. Also check the AC [not DC] voltage at the battery engine running. If near 1/10th [.100] volt that's too much. Excessive AC could cause all sorts of drivability issues.

 

[mshawn]

Vacuum is at 18 hg to the EGR or idle vacuumn of the engine is 18 hg? Maybe I missed this