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truck is stuck... again... need help!

FlatBlackBurb

FlatBlackBurb

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okay here's what i've got. 1987 suburban with a 5.7 TBI motor.

i got an exhaust violation (open after y pipe), and after welding up muffler and cat (that i believe to be clogged) i was driving it and it was fine. but then i took it about 2 miles to the local CHP station so he could write it off. successful. on the way back, my engine started to hesitate a little bit. i thought it was just because of the stupid cat but just to be safe (because my gas gauge is broken) i flipped a U and got 25 bucks of gas. headed home truck hesitated pretty bad and then died. i started it and tried to drive but it acted like it was flodded. no throttle response barely.

so i pulled over in a parking lot and my friend thought it could be the MAP sensor. a quick trip to autozone and a couple minutes later we figured out it wasnt the MAP sensor. it's getting fuel just fine. what could be the problem here? any other sensors on this TBI bulls***? it started and idles fine for a half second and then immediately dies. i got it to drive in reverse for about 20 feet and now it wont drive anymore it dies immediately.

took the air filter off and ran it same thing happened and both injectors were spraying fuel just fine. disconnected fuel lines after the fuel pump and fuel is coming out at a fine rate. when i start it and push the throttle down half way it sputters and acts like it wants to die and when i let up it idles at a higher rate just fine and then dies. i know it can idle fine so i dont think its a spark plug problem. any suggestions???? my trucks stranded in a parking lot in town. it sucks.
 
Check your battery and terminals and connectors. TBI and computer controlled vehicles need a good battery to run. Its not like the old days where the batt was just for starting, modern cars and electronics need the batt to run.

*ah, since you say it idles fine. hmmm. that could rule out batt. issue.
 
If the cat was truely clogged, it would stall out like that. It would probably barely run at all. And, the cat would probably be glowing red too.
 
yeah i dont think the cat is really clogged there's like noticeable hesitation now that its welded back on. and no it's not glowing red. any other sensors, or things i should check for?
 
I'm going to vote for a possible bad fuel pump. When they go bad sometimes (in my case) they will idle perfect but once you start to put a load on the engine the pump can't handle the request and it stumbles or dies.

The TPS could give you some problems but usually the truck will still drive without dying.

Did you check for any codes yet? If not i suggest you do that before going any further. If there are any codes present at least you have a starting point to go from.
 
sounds like what mine did when the dizzy went. truck ran for maybe 30 secs to a minute, minute and half then would just die. i replaced the fuel pump and same thing. replaced the dizzy and she was good to go
 
I remember my TBI camaro doing something similar. Turned out to be a loose connection on one of the connectors ontop of the injector. Just a thought.

If it starts up and dies maybe its a bad oil pressure sensor switch? Suppose to be an emergency shut off when no oil pressure is detected.
 
Stomis said:
I remember my TBI camaro doing something similar. Turned out to be a loose connection on one of the connectors ontop of the injector. Just a thought.

If it starts up and dies maybe its a bad oil pressure sensor switch? Suppose to be an emergency shut off when no oil pressure is detected.
Click to expand...

When are we going to get this straight. :wink1: The oil pressure switch allows the fuel pump to continue running if there is at least 5 psi of oil pressure and the fuel pump relay fails. It IS NOT an emergency shut off switch.
 
drill two holes in you exhaust pipe, one immediately in front of and immediately behind you catalytic converter. measure the pressure with a hand held fuel pressure gauge, while running. Pressure in front of the cat should never exceed about two pounds, even with high engine speed.
You should see maybe a 1/2 pound difference pressure reading from in front and behind the cat.

When done, either drop a quick weld glob back over the holes, or, run a sheet metal screw of equal diameter into the holes. done!
 
i think i'm going to try seeing if it comes up with any codes. it threw a code right before this whole thing happened. can anyone link me to a page with information on how to get codes out? i know you can jump like two pins with a paper clip or something and then it blinks right?

fuel pump eh? i just replaced that probably like 3,000 miles ago but hey you never know. how do i know if the TPS is bad?
 
4X4HIGH said:
When are we going to get this straight. :wink1: The oil pressure switch allows the fuel pump to continue running if there is at least 5 psi of oil pressure and the fuel pump relay fails. It IS NOT an emergency shut off switch.
Click to expand...

O alright I couldnt tell you I dont know from experience. A co-worker had just told me that theres a sender on the passenger side that does what I said. Guess hes wrong then.

And I guess my switch doesnt work since my truck completely dies when I blow my pump fuse.
 
Go to discount auto or auto zone and they will read your codes for free. The pin deal is a pain and only shows like 10% of the available ones.
Bailey
 
yeah the paper clip method only showed "12" so i got over it real quick. i called up my insurance people and just had it towed to my house (which was luckily like 5 minutes away) so now the fun begins. at least it's home and in a place where i can work on it better. i'm going to replace the TPS probably tomorrow or whenever i get the chance and see if that makes a difference
 
maybe it is the fuel pump? when i turned the key on i heard the pump but it wasnt as loud as i remember it being. i cranked it and it took extra long to turn over. ran fine for about a second then sputtered and died. shut the truck off and then turned the key on and heard nothing from the fuel pump. maybe it's a bad connection. i'm going to check for pinched wires and see if i can't get a decent response out of the throttle later this week.
 
Fuel pump won't prime every time you turn the engine on/off...but it should turn on as soon as the engine starts to rotate, assuming the fuel pump relay is ok.

If you suspect fuel pressure, testing it using a gauge isn't a bad idea.

But first do a good visual inspection of all your wiring, plug wires, etc.
 
it may not be recommended but a squirt or two of starting fluid sometimes help you do diagnostics.. namely, if its ignition related or not. (spark, etc)
 
If you are just getting a code 12 and no other codes try replaceing the distributor module before you do anything else.
The pin deal is a pain and only shows like 10% of the available ones
Click to expand...

That is not true. Jumping A & B pins on the ALDL connector will show ALL of the Hard and soft trouble codes stored in the ECM's Memory.
 
That is not true. Jumping A & B pins on the ALDL connector will show ALL of the Hard and soft trouble codes stored in the ECM's Memory.
Click to expand...

x2. that's how i check for codes. it works fine for me.

my truck did almost the exact same thing when my ignition coil died. one day after work, it idled fine, but when i hit the highway, i couldn't maintain speed and within a few minutes it was dead on the shoulder.
 
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