Nuther 350TBI question or ideas please,,,

[4xcrazy]

Aight, here's the deal, i am officially lost now, the truck was acting up every now and then, driving down the road it would just shut off for a few seconds, and then get goin again with out me doing anything.

Well, it finally died on me a few weeks back, wouldn't start, i didn't hear the fuel pump in the tank, which i normally could, so i just figured it was dead, Autozone crap, almost 3 years out of it, figured as much.

Was under warranty, free replacement,,,didn't work,,,replaced the pump relay,,,worked for awhile, got in it the next morning to go to work,,,no start.

Not seeing any fuel spray from the injectors, i try to start figuring why no pressurem changed out the oil pressure switch,,,no go,,,fuel pressure regulator,,,no go, ECM (have a friend at the zone let me try it) didn't work, luckily these parts i oaid for, are not that expensive, but it came down to the injector itself that was bad, replaced it with another Autozone crappy,,,,,,runs,,but like crapola, very rich, idles poorly and the spray pattern just wasn't uniform.

Took it back to "the Zone",,, went to Napa, paid like $150 for their top of the line, "new" unit (which BTW, looks identical to the stock unit).....same thing, alittle better spray pattern but still looks like it is "building up" seeing a few little dropletts going shooting off to the side every now and then.

Just thought i'd post up here, and see if there is something i am missing, or forgetting to do, i am pretty knowledgable with this engine and truck, but this one just has me stumped, if i had the correct dianostic tools, i may have been able to finger out the problem first off, which i am working on now, got the laptop, just need the cable

Any other idears??? what am i missing?? do i need to reset the timing or something, the throttle response it a bit better than before, but that could just be from the extra fuel it's dumping.

It DID just start throwing a code 45, which i would expect, rich condition/oxygen sensor thing, did some weird idle thing, up and down a few times, then coded out.

ANYHOO, talk to me fellas, and chickas?

EDIT: to give you an idea as to how it idles, it runs like it has a big cam, loping, smokin out the back, pretty steady lope too, not like an intermittent misfire.

 

[dyeager535]

No vacuum leaks, especially to the MAP sensor?

 

[dogdaysunrise]

i have a somewhat similar although not as bad of a problem, mine idles like poop, but runs fine once the revs are up. I have narrowed it down to what looks like the same thing, drips coming out of the injectors. I have tried a few diffrent types of injector cleaner to see if it helps, but nada. so I am also intrested to find out some insight to this issue.

 

[4xcrazy]

No vac leaks, i suspected this as well, checked everything...

 

[shane74]

Ok, sounds like you checked EVERYTHING but the one thing that could be causing all of your problems. It is so often over looked, but is one of the BIGGEST contributors to major engine problems in TBI rigs. Have you checked your EGR valve? If it's bad you will have all kinds of problems. You will get codes for surging/rough idle (it'll run like it has a lopy cam) you will get ECM, MAP, O2 sensor, knock sensor, idle too rich, idle to lean, etc. etc. etc.

I have an '87 burb that I just went through this on. I'd lay odds that it's your EGR that is messing everything else up. It will even shut your rig down and not let it start if it's not working properly. Wanna know the best part? The EGR is NOT hooked to the computer. It is hooked to the MAP sensor through a vacuum line. Guess what registers as bad when the EGR messes up?? Yup...everything else. If the EGR is bad, sometimes it won't even let fuel through the TBI unit. How's that for frustrating.

The EGR is prolly the cause of 90% of the runability issues w/ TBI rigs. It's another one of those things you'd really like to kick the crap out of a GM engineer over.

Oh yeah, I have been through this so many times w/ TBI rigs that I have a spare EGR in my garage in case something goes nutty on me and I can't get to a parts store.

One last bit of advice, it if is your EGR, spend the $$ on an OEM unit. Parts store units suck monkey nuts. I went through 4 parts store units in less than 2 years. Hmmm..the OEM unit lasted 18 years. Since I replaced it with an OEM unit, no more issues.

Oh yeah, if you replace the EGR, clean out all the carbon and build up in the chamber underneath it. I twill make a big difference in how it works/lasts.

Good luck!

 

[shane74]

i have a somewhat similar although not as bad of a problem, mine idles like poop, but runs fine once the revs are up. I have narrowed it down to what looks like the same thing, drips coming out of the injectors. I have tried a few diffrent types of injector cleaner to see if it helps, but nada. so I am also intrested to find out some insight to this issue.

EGR dood..

 

[shane74]

No vacuum leaks, especially to the MAP sensor?

Hey Dorian, I'm suprised you don't remember all our posts about this. How long did we exchange info about this? I think we had a good week long conversation about this before

 

[4xcrazy]

As far as the EGR, i highly doubt it, it basically ran perfect until the injector issue, the EGR is only about 2 yrs old, still basically new.
Not saying it ISN'T the problem, but that would be just too weird for something like that to die that same time an injector decides to.

Will have to look over it, heck, it isn't even really dirty, as mentioned, it was replaced not long ago, when i had other issues, came out to be a faulty fuel pump.

 

[dyeager535]

Yeah, guess we could look at the EGR.

I would *suspect* if it's as intermittent as it sounds (not consistent in how things are working or not working) that disconnecting the EGR vac line if/when it's idling OK, should result in the problem not repeating.

If the problem is 100% consistent now, disconnecting the line wouldn't do anything, as if the EGR is the culprit, it's probably stuck in a somewhat open position.

Pulling and cleaning EGR valve never hurts. Pushing up on the underside of the valve at idle should result in poor/worse idle. IIRC, this IS possible on these valves.

The injector issue should be different though. O2 sensor is what tells the ECM rich/lean, if you are getting a rich code, it's because of too much fuel at the O2, and that is evidenced by the smoke. (BTDT) EGR *should* give a lean code if it's "on" at the wrong time. There are enough variables in the system though that I can see a small EGR "leak" as being enough to mask with fuel, which would still result in a rich condition.

 

[4xcrazy]

alrighty then, how's about i add alittle more info as to what was happening while trying to finger out where my fuel was at,,,, and there is a question on a couple of components after the info too,,,

As mentioned, there was no pressure coming from the injectors at one time, i then proceeded to remove the top part of the TBI unit, to replace the pressure regulator, at the same time, i removed the drivers side injector,,, looked at it, nothing really to see, but was just curious, reinstalled it.

Now the next day,(ran out of daylight) i went out to check power to the pump, and a few other little things, i tried to start it, it sounded like it was REALLY retarded in timing,,thinking WTF?? did this about 4 times, and then walked to the front and noticed gas all over the intake,,HMMM,,,WTF?

Stretched my arm into the truck, watching the TBI, turned the key, and fuel came out of that driver side injector so fast, it filled up the intake bore on that side.. Now, this was probably done 6 - 8 times, before i said,,OK, it's dead...

Here's the question,,,would that much fuel going into the engine, do any damage to the Oxygen sensor perhaps? i know the plugs were soaked, it definately acted like it was flooded when i did finally get the new injector installed, and engine fired up. Could this fuel have traveled somewhere else it shouldn't have? EGR area somehow?

I am going to change out the plugs tomorrow, just as something to try, and they are cheap.

I just came back in from starting it again, it doesn't really sound too bad now,,didn't do anything to it, it drives fine, actually has better gitty-up, but does still have idle issues, and very rich odor out the pipe, and does certainly have a misfire now, not steady anymore, sounds like a fouling plug, but not steady.

Sorry to drag this out so long, but i know you guys like all the info you can get to try to come up with a good solution.

Any more ideas?

 

[dyeager535]

Dunno that there is any easy/cheap way to check an O2 other than a scanner/software that lets you see what it's doing.

Then again, you can use a voltmeter, probably "good enough" to prove that the voltage is still changing as it should.