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91 TBI bad gas/stuck injector HELP?

4920 Views 5 Replies 3 Participants Last post by  Fred Kiehl
1991 caprice with 305 throttle body, bit of a unique help request because i'm disabled, lack the money for a mechanic, and have to get to medical treatment so need hopefully something simple within my abilities to get running again. :( My mechanical knowledge is splotchy/self taught only and my confidence low - I successfully swapped a clutch on a saturn SL, but failed rebuilding a carburetor for a lawnmower which never ran again, so apologies if i'm slow or unexperienced at knowing what to do or how properly.

Had to have this parked (due to low mpg) for the last year or plus, I put Pri-G in the tank so wasn't too concerned, had a half or 3/4 tank (not sure how accurate gauge is) or so when I did.

Had my saturn car break down so suddenly needed to use this/the backup. Didn't start instantly due to sticky residue in TBI, I sprayed carb cleaner (yes carb cleaner, only thing I had handy and couldn't get proper TBI cleaner without a running car) onto it which both cleaned up the spray near instantly and worked as starting ether - idled perfectly smooth with no misses or problems. Drove to the gas station and put on 3 gallons gas to mix out some of whats already in there.

Drove 60 miles around town with absolutely no trouble the last two days, have been expecting no trouble.

Suddenly went to crap out of the blue when pulling into a parking lot - died on me, on restart it ran HORRIBLE, missing so bad I could barely keep it running no matter what I did with the throttle, accelerating any near impossible, but would maintain jerky speed once I was there. Stopping at a stop sign or light would have it die every time.

I immediately filled the tank at the nearest gas station to dillute out what was left, putting in about 7 gallons, then struggled to start the car and limp it home which was 5 miles away.

I put 2/3 of a container of fuel injector cleaner into the tank (all I had left) and probably a triple dose of Pri-G (which unlike Stabil can be used to revitalize old gas, and yes it works, quite amazingly even) into the tank, but could only stick about a liter of additional gas into the tank to try mix any of it. If i'd had the Pri-G with when filling at the gas station it would work better i'm sure.

Tried to start it again today, it will start but immediately dies without abusing the throttle. Tried to run a few minutes to get what I thought was bad gas through it but it still runs bad. Worked the throttle body with some carb cleaner on a toothbrush assuming maybe the spray was just cloggy like when it first started - this noticibly improved the spray pattern but it runs just as bad so maybe it's the gas..?

I'm aware I need to give the Pri-G 24 hours or so usually and don't know how well it will be mixed under the circumstances, but other than sitting and waiting (as i'm needing to get to medical treatment 250 miles from here as soon as possible) and hoping it starts better later I need to look at other strategies...

Not sure how hard it is to replace a TBI but that assumes that's even the problem and dunno if a junkyard part run any better from sitting, A-graded or not. I'm hoping the mix of Pri-G and 11 gallons fresh gas by now (which should have mixed with what was maybe 15 gallons older gas) will take effect, and i'd assume anything nasty would have been caught by the fuel filter... and if that were clogged i'd assume it might idle okay but have problems maintaining a higher rpm, when it's more the opposite. Obviously pretty sure my ignition is fine when it ran the first 60 miles fine.

Open to suggestions. :(
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when you stop using a vehicle you have to put gas STABILIZER AT THE double dose when for a 1 year sleep. also you must put a few miles on it with this in the fuel before shutdown.

crap grows in the tank ..I suspect a plugged up filter.. with alcohol the less you use the vehicle the fuel filters require more frequent replacing.. cut open the old one hopefully it did not blow and get crap in your TB,..
First put a fuel filter on it. There is no such thing as bad gas. The octane rating goes down as time passes, but the gas will still run the car. The alcohol in the gas may have damaged the fuel pump or rubber hose in the tank.

Does the car act differently after running for over 5 minutes (closed loop operation)?

If so, check the ground a the passenger's side of the thermostat housing. Remove the nut, and the lugs, and remove the stud (when the engine is cold). Clean the stud threads, and the threads in the hole. GM thought it was a good idea to put two dissimilar metals together near water.

Then if it still does not run properly, you may have an errant fuel pump or the soft line inside of the tank may be cracked. If the line in the tank is cracked, it will pump the fuel into the tank instead of the TBI. Pressure will be low, and the flow pattern may suffer because of it. Adding "fixes" to the gas tends to cause degradation of the hose. If you pull the tank, put a new AC Delco, or Delphi pump in. Do not use any other brand. It is difficult to get the fuel pressure checked, because the wonderful engineers at GM deleted the Schrader valve on the pressure line for the B bodies.

It could also be your plug wires, or cap and rotor, depending on how old they are. I think it is something else, but there is the possibility of the wires being bad.

If it is acting up more after 5 minutes, it could also be the O2 sensor.

Since it idles OK, you know you do not have a vacuum leak.

Check your EGR valve, and the solenoid that controls it.

Another easy parts swap is the MAP sensor on the firewall. They are known to cause similar issues, but are usually not a problem. Make sure the hose between it and the back of the TBI is connected.

Do not replace the TBI, it is not the issue.

Try turning the ignition switch on with out starting the engine, and listen to the fuel pump whir. Try recycling the switch after a few seconds, and listen to it again. If it runs about the same every time, you may have a fuel pressure issue. It should run less on the second and successive try.

Did you check for any codes? If you cross the A and B pins on the ADL connector under the dash to the right of the steering column, the service engine light will blink for the two digit codes. You must put the key in the run position, and have the engine off. It will flash a number of times and then once and twice for 12. 12 lets you know the computer is operating. It will show 12 three times, then any other codes in the same manner. If it has codes, let us know.

If there are no codes, you can probably assume it is fuel or spark, because they do not throw codes.
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NOTE for some reason it's refusing to let me post for a reason I cant discern, telling me "must be at least 5 characters" when i'm trying to post the below block of text. Just in case it takes awhile to follow up again. (EDIT: a block of text it has deleted for the FOURTH TIME now)

I'm going to have to rewrite entirely a few lines at a time using Edit or it seems to eat my post not letting me put up anything. Hope it doesn't annoy mods with endless message change messages. (edit: ok I think this is my last addition for now)

I replaced the fuel filter. Nothing is running any better. I didn't cut open the old one, not sure i'd know what i'm looking for anyway or if it will tell me anything when the new one works no better...

I cannot idle the vehicle for even 1 minute - it instantly dies if it starts at all. Only violent throttle manipulation will sometimes (like 1 in 20 "starts") keep it running for a few seconds. Which if I slammed it roughly into gear (this is how I got home) would jerk the vehicle forward, long enough for momentum to keep the engine turning, so it catches again until it finally gets up to 25mph in 1st where it's still obviously missing about 3 cylinders but at least stays running if I never stop for a moment. Getting home involved running red lights.

Multiple cylinders are missing, probably the entire right bank.

The one drive I took in it after it ran bad (a few days ago when it was half running) it got fully up to warm temperature - once stopped it would NOT restart when hot. No change of behavior vs cold - after sitting it wouldn't start any better while cold.

Could a fuel pump make it idle terribly yet run at 40mph much better? I'm confused how this would work. :-/ I would think it would be the exact opposite?

What would be the best way to test the fuel pump to rule it in or rule it out, put a tee behind the fuel filter or something and try to read a pressure with... i dont know what you'd even use? I assume a fuel pump would show no code. I also assume a fuel pump might randomly die maybe... FWIW when I put in the new fuel filter it seemed to take longer than i'd expect to get fuel to the TBI, like 45 seconds of cranking it seemed. Unless the introduction of air from swapping it creates a problem.

Remember RAN PERFECT on same tank of (old) gas no changes one week ago. Only thing I touched was removing the air cleaner assembly to spray the throttle body to get rid of some varnish on first start.

I'm very confused because it was a sudden out of the blue change, not some slow or constant degradation. Was running perfectly until someone 'threw a switch' and now I can't even start and idle. It's also showing no codes (although it showed a lean engine code when I limped it out a few days ago, nothing after reset, yet ran even worse after resetting). So it has to be something which could crap out, without the computer knowing there is a problem.

Battery out resetting of the auto-learning whatever makes no change - batt has been out hours at a time to see if that had anything to do with it.

I may not have the skills or tools for advanced work either, i'm going to try a few more things and if it doesn't work it's probably staying parked possibly permanently despite being a nice car that I like because I don't have money to fix. :(
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I know I am assuming a lot with what you may know about these things.

since I really have no idea of your abilities or knowledge.
The reason I stated to cut open the fuel filter was for YOU to see if this filter is dirty. you ever see filters like for a furnace air filters. or even the air filter in the air box of a vehicle . well this is the same in the fuel filter. the filter media has pleats . these should look clean and not be filled with debris [DIRT]. Also the pleats should not be fractured because if the filter is with debris , the restriction can cause this filter to blow out and then the debris will foul the injector.

next is the injector connection maybe damaged or disturbed when you cleaned/sprayed it. the electrical connection may need some work.

the TB has a fuel regulator and this may also be damaged. being this old good chance these things need some work.

find someone that has some knowledge about this stuff and see if they can see whats the issue.
Since it is nearly impossible to check the fuel pressure, put a pump in it. Use only AC Delco or Delphi (Delphi makes AC Delco). If the pump does not fix it, it could be the ignition wires, but I would go for the pump first. The rubber connector in the tank is notorious for cracking, and then you have no fuel pressure, because it pumps it back into the tank through the crack.
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