I have been all over the threads here.... have always found answers to my issues but this time i am stumped... i talked my my 17 yr old son into buying a 92 RS TBI 305 ( all stock except for the open element air filter) for his first car a few months ago and he is having issues at the moment that i cant figure out.

About a week ago he started having issues where it would start cutting out on him. Under normal driving it will sputter like it is cutting out. I took it for a drive when he told me about it and it seemed like it was possibly getting too much gas or not enough air...or i am totally off base, which wouldnt be the first time lol

At any rate when i tried WOT it would just lay down, it would down shift but there was no power. I have a 91 RS i am getting ready to do an LS1 swap in that only has 90k miles on it. So we have been taking parts from that TBI engine to fix the southern engineering the PO had done....and boy was there some doozies. At any rate we have replaced the following, moroso cap, wires, coil, rotor, ac delco fuel pump, fuel filter, stock intake
( all sensors on the intake too) and a couple vacuum lines the PO had tried to splice together.

It ran fine for a few months then all of a sudden it started acting up.

it will idle fine, put it in gear and it is fine but when you drive it and put any load on the engine at all it sputters and runs like crap.

Any suggestions on where to start? Help a dad help his son appreciate these cars we love. He is getting as frustrated as much as me....any help is much appreciated.

 

Check TPS - did it get wet? Wash engine? If it got wet change it.
Check plug wires on correct plug
Check vac leaks everywhere.
Possible jumped timing chain?
Check timing
Check fuel pressure.

 

Check fuel PSI, timing, cap/ rotor and test ign mod/ pickup coil and coil.

 

That's what the symptoms sound like. More like not enough fuel though, than too much.

I'd suggest leaving the "timing" alone. It can't cause the symptoms you describe, and therefore, all you're likely to accomplish by messing with it, is creating more work for when you find the REAL problem and have to go back and put it back wherever it is now, and was before, when the car ran right.

 

Will check the fuel pressure tonight and report back on my findings. Thanks guys

 

OK...finally got around to working on this again. We went ahead and removed all wires and plugs. Found TDC (I think) and replaced all the plugs and wires. Still had the same problem. Checked for Vacuum leaks and found none. Checked fuel pressure and it was good.

After staring at it for awhile I thought I might as well put the other TBI on from my 91 RS. Sure enough it got its power back. which leads me to believe it was either a fuel injector or something else in the TBI. Haven't a clue what it could have been though.

Now that the power is back I've been trying to get it timed and am having troubles getting it timed right. I am now set on 6 degrees as that is the only place it will run without dying.

Does the timing have to be set to 0 or is 6 ok? I also ran the codes and got a code 22 and 23. 22 is the TPS and 23 is manifold air temperature sensor. Are those related to my timing problem as well?

 

Since I had to replace the manifold I had to redo the timing unfortunately. Just wish I could get it back to where it was before.

 

Not too hard...

Adjust it a little bit one way or the other. Doesn't matter which way. Mark where you are now before you start.

Did it get better or worse?

Worse: go back to where you were, and then a bit more.

Better: go a little farther the same way.

Repeat until it's back like it was, or, maybe even better.

This stuff is just not that hard. A "light" and a "mark" will only tell you where it is now, not where it should be. Listen to the engine and let it tell you that. Then once you find it, write it down, mark it, whatever, so you can always put it back.

 

Thanks Sofakingdom....so it doesn't have to be at 0 is what you are saying. Other posts on the boards here were saying it was, but I wasn't so sure.

I completely forgot to remove the battery cable to clear the codes. 23 and 22 are now gone but am still fighting the timing. It seems no matter where I put it the idle is erratic. It will start and as long as I'm giving it gas it stays running. I'm going to play with it some more til I find that sweet spot (taking a break from this Tucson heat). It just seems like once I get it and take it for a test drive it goes back to running rough at idle. I've timed my Chevelle many a times and never had troubles like this. sigh

 

Why did 22 and 23 pop up to begin with if it is not a problem? Did you check the TPS?

 

No; doesn't "have to" be at zero.

First off, how accurate are your timing marks? Don't know, eh? Neither does anybody else.

Second, the engine does not whup out a "light", examine a "mark", and then decide accordingly, how it's going to feel like running. All it cares about, is when the spark occurs, relative to piston motion. And since YOU can't "see" the piston location yourself, you're in no position to improve on its judgment.

Third, the factory's "spec" is the servant of many masters; not only making it run right, but also, some compromise of gas mileage, high- and low-altitude emissions compliance, cold- and hot-weather emissions compliance, emissions compliance, and ... oh I almost forgot to mention, emissions compliance. YOUR personal satisfaction is NOWHERE NEAR the top of their list.

Fourth, somebody will come on here and try to tell you all about how "this is EFI, it's so much more precise, can't use the tune-by-ear method"... Well, the ENGINE ITSELF is no more precise than before EFI. And, the EFI itself has not the vaguest foggiest dimmest remotest hint of a glimpse of a whiff of a clue where the pistons and valves ACTUALLY ARE, anyway; all it knows is, "I got a pulse from the dist, now I look up in my table and wait however many milliseconds it says before sending a pulse to the coil". In the end, it varies the spark according to a pre-programmed set of values that it selects from determined by RPM, engine load (driver input), and a few other minor variables like temps, and produces AN OFFSET from the incoming pulse from the pickup coil. Well guess what... that's NO DIFFERENT from what a mech dist does, using RPM (centrifugal advance via springs & weights) and vacuum advance (engine load) as its inputs. EFI can take engine and ambient temps into consideration, but those are a very small portion of the total input to the process, and certainly don't somehow preclude setting the timing to where the engine runs THE BEST it can, factory "spec" or not.

There IS NO "sweet spot". It's just a car engine, same as all the others. It will work just exactly the same as your Chevelle's, only difference being, a computer is looking up those "offset" values in a table, instead of some mechanical system or other generating them. But the end result is NO DIFFERENT.

If the engine only has a very narrow range of dist body twiddling that it will run in, that's a sign of it being "a tooth off" if you look at it one way, or the plug wires being one hole off if you look at it the other way. Again, same as a mech dist; the same thing can happen. Put all that supposed EFI "voodoo" and "black magic" stuff out of your mind and approach it logically and with reason, using a clear head and a logical thought process; you'll get it figured out easily enough.

Meanwhile, "timing" won't make the idle "erratic". It might make it idle high or low, but not "erratic". Most likely you still have a fuel problem of some sort.

Incidentally, this is why I said to leave the timing alone... all you accomplished by messing with it is, creating a whole other problem that didn't exist before, which you now have to solve. And the original problem is still there, to some extent, waiting to be solved. So at this point, do the best you can with the "timing", then let it be, and troubleshoot the real problem without messing with the timing any more until the real problem has been found, clearly and unambiguously identified, and repaired.

Good luck!!

 

Sounds like Sofa's got a burr in his cushion. But he is right, the ecm does not know where the dist is set compared to the cam/valves/piston. Set the timing as best you can get it and leave it so you can find the real problem(s).

Does it run good above idle in neutral and under a load driving down the street?