i have a 1994 blazer 4.3 vortec with the central point fuel injection.it has a rough idle and stinks like rotten eggs.we have changed the map sensor the idle control valve the plentium gasket still acting up.i tried testing new idle control valve by turning wheel all the way but idle never rose so i turned on ac still no rise in idle with the smell i checked to make sure catalitic converter wasnt glowing red at night and it wasnt,any ideas the mechanic that changed the plentium gasket for me told me injector was good.

 

A rotten eggs smell is typically caused by a failing or failed catalytic converter. One of the most common problems with the CPI motors is a fuel pressure regulator leak/failure. Start with a fuel pressure test, specifically watching the leak down after the pump shuts off. If it leaks down quite rapidly, you have a leak and the FPR is the first place I would be looking. Uncontrolled fuel flow into the intake can burn up a cat very quickly.

 

Smells like you need a new cat... but like Kyle was saying, you need to find what caused it to go bad in the first place.

 

1994 chevy s10 bazer 4x4 cpi ok guys need help this is getting expensive so far i replaced catalitic converter and muffler<muffler baffle went out.changed idle control valve map sensor,tested and cleaned egr had a mechanic check under plentium he said all good but plentium gasket was bad and fixed that found 2 leaking vacuum lines fixed pulled plugs all new.un plugged o2 sensor still runs bad.put in new fuel filter did a fuel pressure test here are results off schradr valve-at key on straight to 60 then instantly to 51 and stays at start up stays at 51 when u rev it it rises 3 or 4 psi then drops to 47 or so before returning to 51 i also did a fuel holding test pressured system and it held 51 psi for 5 minutes + the problem is a rough idle and slightly ruff accleration when u slow to stop sign it stumbles slow to take back off sounds like it will die.if u are acclerating hard this thing runs like a rocket slow acclerating is terrible at take off gas mileage is not great but just got this so not real sure due to odometer and trip counter dont work.cant tell u temp range due to tempratre gauge dont work.any help would be great or things to test.

 

Wow, that post just hurt to read...

Your pressures sound low, but some fuel pressure gauges are not all that accurate.

When you replaced the idle control valve, did you clean the bore it goes into?

Have you tested for further vacuum leaks?

 

i bought a 60 dollar tester from autozone not a cheapy harbor freight one.but they can still be off.i cleaned bore compltely not sure whats up no check lights coming on.cant find a way to check vacuum any better then carb choke cleaner on lines.no one has a vacuum tester in the town i live in.called a dealer in my area and he said that a cpi will not function properly with less than 54 psi i think he might be trying to sell me though thats why i came to the forum if anyone can figure this out its u guys

 

update took off sensors and had tested all good but coolant temp sensor replaced it then drove it still surging looked for vaccum leaks non found pulled new plugs out and driverside has black burns saw something on here about that but cant find it now please let me know if u have any ideas

 

You need to check the fuel pressure again, KOEO, then leave it connected for 10 minutes after you turn the key back off to see what the pressure is then.

If the pressure leaks down significantly after 10 minutes, your fuel pressure regulator is probably bad. If your fuel pressure is initially low (less than 60 psi), then it's quite possible your fuel pump is on its way out.

However, if your plugs are black, you probably have a leak under the plenum. If it's #2, it's probably the fuel pressure regulator. If it's #3, your 'nut kit' (fuel pressure and return lines) are suspect.

The mechanic who said the spider is okay...how does he know? Did he test it or did he just look at it?

 

Only the driver side has the discoloration? This would indicate an overly rich condition affecting that side of the engine. Since the CPI injection system uses a single batch fired electronic injector feeding 6 individual poppet nozzles, this makes it quite difficult to get an overly rich condition on only one side of the engine. The most likely cause would be a leaking fuel line as these are on the driver side of the lower intake manifold. A leak here would dribble down around the driver side poppet nozzle bores. If the leak was on the return line, it may not affect the system pressure. You would have to remove the upper plenum and pressurize the system looking for signs of a leak.

 

well i was there when he pulled plentium top plate no gas in it he primed the system key on he said he didnt want to start it didnt say why.i will pull plugs tromorrow and check it i think either fuel pressure regulator stuck open or closed or fuel pump not sure but my mechanic did tell me to change coolant sensor i said why he laughted and told me to do it so i did and it did help it i dont know why he says that it sends voltage to ecm i dont know i would say i could drive it now but its not right not by a long shot.ill also check fuel pressure over 10 minutes and post results.