TRANSSPORT

I've had my 1991 bone stock 305 Auto TBI since mid 2008. About 3 years ago I suddenly lost power similar to others whose threads I have read. Worse than a four cylinder on takeoff,once up to speed will do 70 on the freeway but throttle response is hideous. Barely climbs hills (even small grades).
When it happened 3 years ago I suspected bad gas as I am fairly religious about tune-ups (plugs wires cap and rotor is the norm about every 2 years. Last tune up was less than 1 year ago...also have new air filter, pvc valve and filter, new factory thermostat and 3 core all aluminum radiator, replaced the electric fan in 2010). I tried fuel injector cleaner etc. nothing helped. After about a week the problem went away and did not return until last Wednesday.
I drive 25 miles to work (50 miles round trip) every weekday, car has 180,00 + miles on odometer. After driving to work on extremely hot day, I parked it for 15 min., then decided to go pay my phone bill before clocking in. Car reacted exactly as described above, as it is all surface streets it barely crawled along shaking and shifting roughly into gear. I limped it back to work, parked it for 2 hours until 1st break. I started it to move it closer to door after day shift leaves as always, still no change. On last break (4 hours later)I decided to disconnect battery to reset the computer in case it got a bad code saved. 2 hours later, shift was over, I connected the battery and it ran and drove normally until tonight.
Tonight on the drive home (after another hot day in the 90's) on the freeway it lost power again. I was mainainting speed, but flooring the gas pedal did very little, slight grades hard to climb, surface street driving barely crawls along, etc. etc. I dropped my co-worker off at his place, shut the car off, disconnected the battery for 5 min but this time NO CHANGE. When I limped it home I disconnected the battery again and am letting it sit overight to see if engine temp plays a role in whether or not it will GO AWAY this time.
So anyone have any ideas? Could it be related to heat wave weather as others have wondered? Since it went away for 3 years we can rule out most of the usual culprits, after all either a cat is clogged or it isn't right? Parts don't fix themselves for 3 years and then crap out again. What is the most likely cause? an intermittent bad code thrown from a sensor? if so which one?
I work swing shift so I will check back tommorrow around 10 or 11 A.M. and let you know if the cooldown/disconnect reset the computer this time. I really need to fix this without throwing a lot of money at it. Any suggestions you have will not only benefit me but the gen3 community as a whole.

ex-x-fire

Check the fuel pressure.

bigal55

iTrader: (1)

Sounds like it is going into Limp mode. Check the eprom to be sure it is not loose in its socket. Does the check engine light come on when this happens?

TRANSSPORT

Thanks for the suggestions guys, I appreciate it.I reconnected the battery this morning and started it but no change this time.
I do not have any electrical or mechanical measurement tools and am working with basic handtools and little money in the driveway of my apartment. I have read many threads on similar issues, one of which advised to see if the fuel injectors are working properly. The Driver's side is spraying like mad, but the passenger side is BONE DRY. Yahoo answers talked about underhood fuses for these injectors, I have yet to locate them. I DO have both a 1991 and a 1992 GM service manual (the 92 has updated torque specs). The thread also talked about grounding issues with these causing the injector not to fire. I am contemplating switching the injectors from side to side to make sure it is the injector and not a fuse or ground issue on the passenger side. The fact that it happens and goes away smacks to me of a short rather than a failed part.
Have not checked Eprom socket yet, but the check engine light DID come on last night (it is not on now).
Right now I am trying to arrange a ride to work for the balance of the week and may have to table this til the weekend. If I cannnot get a ride, I shall be forced to tackle it immediately. Stay tuned...

Eagle223usa

Did you pull the codes yet?

Damon

Yeah, that would be your problem right there. I'd suspect a bad injector rather than a wiring problem, actually, in this case (and it's not a fuse issue). Your idea of swapping them L/R would be a good diagnostic tool, but you might just as easily be able to find a junkard TBI unit (any 305 TBI should use the same sized injectors, and GM built scillions of them) and just swap the whole thing for some back-to-back testing. Even if they are not the exact same injector size, it's gotta be better than only one working injector.

steve87ta

iTrader: (4)

Ditto.... Went through this with my 454 in my truck a couple of months ago.
I replaced the injector.
Its like they malfunction and then finally give up the ghost. Funny thing was the bad injector would still fire with a 9 volt but not the ecm.....

TRANSSPORT

I haven't gone any further with the car as getting thru the work week is most important right now. About a month ago I drove my buddy from the Portland Oregon area to Tacoma in my 91 so he could aquire a 2002 LS1 z28 (Predator hood, SS rear spoiler). When it turned out the steering column needed rebuilding I gave him one I had bought for $100 out of a 94 Trans Am and told him to fix his ride. Guess what I'll be driving to work this week.
We will tackle the car together this weekend. I will post a progress report saturday night.

TRANSSPORT

Hi guys. Here is the promised update.

The patient (right) and the Z28 (Z style hood, not Predator as mentioned in previous post).
Spent the last week getting up at 5:00 A.M. to ride to work with my buddy Jake (who works dayshift), going back for my shift that starts at 2:30. He then had to come back for me at 11:15. But I got to drive the awesome LS1! Gives me ideas that must wait until I smog my car one last time in August.
Today Jake came over to help me operate on the patient. The first thing we did was switch the wiring harnesses to the 2 fuel injectors. As there was no change (fuel on the drivers side with the passenger side harness, no fuel on the passenger side with the known to be working driver's side harness) we quickly eliminated the possibility of any electrical or computer issues.
Changing the bad fuel injector was fairly painless (it appears to be the original, 25 year old injector). Car runs like a champ (no check engine light so checking for codes after disconnecting the battery would be futile. I suspect the code thrown was a result of running the car on one injector, not a contributing factor...I.E. a symptom of the actual problem, not a cause). I also had a slight stumble at idle that is not currently present. I mention this because I have yet to read a suggestion in other threads on that issue that idle stumble may be attributable to either a failing injector or bad gasket on the TBI injector cover (it fell apart pretty easily).
Only time will tell if the stumble is gone for good, but I thought mentioning it might be helpful to someone else.
Thanks for all your help guys!

Damon

Glad you nailed it. I think your problem is gone for good.... until the other 25 year old injector goes bad.

I think that injector was getting flaky on you well before it turned it's toes up and completely stopped spraying, if I had to guess.

Actually, those TBI injectors are normally fairly bulletproof. They're "over-built" by GM. There's guys running them on this board with more than double the factory 12 PSI they run at in a stock application and they don't have issues. But, like all things mechanical, they can break and fail eventually. In this case, eventually = 25 years.

Now get out there with your new-found power and stomp that LS1 into the dirt! (In fantasy-world you'll beat him, just don't try it in reality.)

TRANSSPORT

i actually would have preferred to change both but could only find one in stock. i will order another and keep it on hand. I did notice how smooth the engine is running now. 180,000 + MILES and I could set a full cup of water on the air cleaner and not spill a drop. Love Chevy smallblocks man. Speaking of, that Ls1 was a joy to drive! I only got on it a few times as it was not my car, but i passed a big rig in the blink of an eye! Amazing power!