t.b.i. problems

i've been having problems with my small block on my truck.when you floor the gas pedal it starts to go very slow it does not get the passing gear and when its at high rpm the truck starts to studder it starts cutting of like it needs more fuel or spark its really slow. I've replace the transmission, fuel pump and filter, did a t.b.i. rebuilt, distributer rebuilt, new plugs and wires, new coil replace air filter. i dont know what to do with the system im planning in making it a carburetor but thats one of the reasons i fix up this truck because of the t.b.i. no mecanice where i live has found anything wronge with it o and also replaced the computer with a brand new one please help me with the problem i have.:(
its a 1987 chevy 350 with a tbi and a 700r4 and sometimes it feels like if the clutches on the trans are slipping you floor it and it just revs up

If it is a factory rochester dual injector TBI, that is usually a fairly reliable system. I can tell you this much for sure though. 1)You wasted your money on the computer. If a TBI runs, it has a good computer. 2) The first thing you should check is your CKP. Crankshaft positioning sensor. It tells this motor how many RPMs it is running at, and as such is a referance for injection speed. A good way to verify this is to have someone hit the gas and bring it up through the R's while you watch. If you get a steady spray of fuel, chances are its not the CKP. if you have fluctuations, thats a common target. Also, use the Pin(paper-clip) method of computer scanning to see if its the O2 sensor. If your truck is saying its running too rich or lean, it will try and compensate, causing the condition you speak of. If it is the O2 sensor, spend the $10 and get the socket. it Really helps.

Catalytic converter is probably original and clogged, restricting exhaust flow. Replace with high flow converter, about $60 fm Auto Zone, weld-on or clamp-on. Your spark, gas, intake air is normal but engine cannot exhaust burned gas fast enough when you accelerate, Been there...

One cheap thing you might try.....worked for me once......get under the truck while it is idling and pound on the converter with a hammer. If the thing is clogged, you might hear an rpm change with the jolts.....have someone you trust keep their foot on the brake.

Clogged converter symptoms are a slow reving motor under load.

Also, doesnt the TBI run 12 psi fuel pressure.....more than a carb fuel pump.....

hi guys, i posted a message a week ago about my 87 chevy with tbi ive been having problems with it it just dosnt pick up when you floor it it feels like if my transmission is sliping when its going to shift but i just put a new tranny on it its been doing that before the tranny change also when you start the truck cold its starts worse than a carbureted one some guy replied with my other post to change the o2 censor and the camchaft censore and i did but same thing still happens please help me out with these problem as sson as possible. ive replaced fuel pump fuel filter, t.b.i. overhaul, distributor rebuilt new plugs and wires new coil, when the truck is on park and its on if you floor it you can see the spray on the injector evenly. Please help me aout guys i will really appreciate it

Have you checked the EGR valve? could have carbon buildup which is keeping it open. Is the car idling rough?

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Originally posted by tellezj
hi guys, i posted a message a week ago about my 87 chevy with tbi ive been having problems with it it just dosnt pick up when you floor it it feels like if my transmission is sliping when its going to shift but i just put a new tranny on it its been doing that before the tranny change also when you start the truck cold its starts worse than a carbureted one some guy replied with my other post to change the o2 censor and the camchaft censore and i did but same thing still happens please help me out with these problem as sson as possible. ive replaced fuel pump fuel filter, t.b.i. overhaul, distributor rebuilt new plugs and wires new coil, when the truck is on park and its on if you floor it you can see the spray on the injector evenly. Please help me aout guys i will really appreciate it

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if you got a ign. problem you should show a code, jump the plug and check for codes the plug is under dash, driver side.. count the check engine light flashing:D

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Originally posted by DennyW
Absolutely, check codes first thing. If you have already changed the 02 sensor, and checked the egr, and it's a vortec motor, and cleared the codes, but they return after a short run, most likely the injectors are bad, leaking. :) Especially if you get an 02 sensor right or left bank code, or egr code. Because it causes the system to run rich, and gives you a false code for them being bad. The computer is trying to correct the rich mixture, and goes out of limits.

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I agree if its a vortec its leaking down, when did they come out with the vortec.? I fixed a 3.8 the other day on here with a temp. sensor code. no comment on my drawing?

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Originally posted by lt1s10
I agree if its a vortec its leaking down, when did they come out with the vortec.? I fixed a 3.8 the other day on here with a temp. sensor code. no comment on my drawing?

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Nope, We went through that B-4. The drawing worked the last time so it must B O.K. ....... HEHEHE:)

Arrows still need some work tho. :LOL: :LOL: :LOL:

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Originally posted by pro70z28
Nope, We went through that B-4. The drawing worked the last time so it must B O.K. ....... HEHEHE:)

Arrows still need some work tho. :LOL: :LOL: :LOL:

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I almost fell mechanical drawing(in school) because of my arrows, now you can see why:LOL: :LOL: :LOL:

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Originally posted by DennyW
:D , hahaha, no. I'm not sure on the year. I'm thinking 96-98. I'm joking with you on the drawing, hahaha:)

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trying to show me up.....well shame on you.
:LOL: :LOL: :LOL:


that plug is pre 95, the obd2 is dif, and you cant jump them. :p :LOL: :LOL:

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Originally posted by DennyW
:D , hahaha, no. I'm not sure on the year. I'm thinking 96-98. I'm joking with you on the drawing, hahaha:)

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i dont see the problem, mine looks that good.:LOL: :LOL:

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Originally posted by lt1s10
i dont see the problem, mine looks that good.:LOL: :LOL:

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Originally posted by DennyW
Yes, that's true. There is a few places like auto zone that will check your codes for free. If he can't afford a small scanner, or to take it to a garage.:)

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true but with that 1987 maybe he can retrive te codes. i think we have lost him anyway.:LOL: :LOL:

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Originally posted by DennyW
Kinda looks like it. Maybe he will be on a little later to check.

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i hope so. :rolleyes:

sorry i didnt reply its because im at work. the truck when you start it cold it starts like a carburated one it studders when you try to pick up speed you cant floor the gas because it wont go it feels like the trans is slipping im having allot of problems with it when truck is at park and you floor it pops at high rpms.

i dont have no catalic converters and i have a brand new tci converter

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Originally posted by tellezj
i dont have no catalic converters and i have a brand new tci converter

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you still need to check for codes. that could eliminate a lot of things. if you had checked the codes first, it would have told you, that you didnt need all of that stuff youve already replaced. it could be most anything, check the codes. :HMMM: :D

ive already checked for codes thats the first thing i did

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Originally posted by tellezj
ive already checked for codes thats the first thing i did

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Are you driving the truck? How does it run hot. if you dont have codes then you need to look at some things that dont give codes. vac. leak, fuel presser, fuel filter, timing, plugs rotor cap and wires, if its a vac. leak or egr valve it should run good above idle. let me know if it runs good hot.

:confused:

I read lots of good advice on this one,But have not seen any suggestions about the basics.......Fuel preasure..... I know at the start it says its got a new fuel pump but nowhere have I seen the fuel preasure & volume readings... Those TBI's are pretty reliable,but I have seen the preasure regulators go bad pretty often.. and when ya say she backfires on accel that tells me she's goin lean....
Try this ... find the smaller of the 2 fuel lines off the TBI follow it down till ya find some neoprene hose and crimp that bugger shut.. now go drive it and if it runs o.k. I would then start looking at fuel preasure it should be 9-13 lbs (hafta have the proper tester and ya hook it up at the fuel filter) no specs on dead head preasure ( return line blocked) but I would expect to see 25-30 lbs If the pumps capable of that,and she runs good with the return line blocked,put a new filter and preasure regulator on it,I would also put a new (Bosch or ACDelco)oxygen sensor on it if yours has over 30,000 miles on it..... Hope this helps

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Originally posted by HWORRELL
I read lots of good advice on this one,But have not seen any suggestions about the basics.......Fuel preasure..... I know at the start it says its got a new fuel pump but nowhere have I seen the fuel preasure & volume readings... Those TBI's are pretty reliable,but I have seen the preasure regulators go bad pretty often.. and when ya say she backfires on accel that tells me she's goin lean....
Try this ... find the smaller of the 2 fuel lines off the TBI follow it down till ya find some neoprene hose and crimp that bugger shut.. now go drive it and if it runs o.k. I would then start looking at fuel preasure it should be 9-13 lbs (hafta have the proper tester and ya hook it up at the fuel filter) no specs on dead head preasure ( return line blocked) but I would expect to see 25-30 lbs If the pumps capable of that,and she runs good with the return line blocked,put a new filter and preasure regulator on it,I would also put a new (Bosch or ACDelco)oxygen sensor on it if yours has over 30,000 miles on it..... Hope this helps

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you must have jumped right over my last post HWORRELL. :LOL: :LOL: