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1990 chevy 350

  
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1990 chevy 350

 
ddaygi ddaygi
New User | Posts: 1 | Joined: 10/13
Posted: 10/12/13
02:01 PM

I've got a tbi 350 in my 90 suburban. Fuel pump locked up so i changed it, cleaned the tank, new fuel filter. the truck will crank and run but has no power when under load and has caught on fire 3 time now while trying to find problem. I've rebuilt the throttle body, cant find a fuel leak anywhere, have right at 15psi pressure and cant figure this out. I bought it with the bad pump so I have no info on how it ran before and from the look of the tank it had been sitting for a while.  Any help would be appreciated.  

wayne712222 wayne712222
User | Posts: 205 | Joined: 10/13
Posted: 10/13/13
12:27 AM

i will have some stuff for you by sunday morning.. its a lot of typing..

did you also change the fuel filter inline...?? somewhere usually inside the frame rail???  please be careful there are Orings on the end of the filter tubes that also need to be replaced.. and they don't come with the filters usually..

when you say.. you rebuilt the throttle body..

i am taking that you replaced the Orings, filters around the injector ends and replaced the fuel pressure regulator diaphragm..

did you find any PLAY in the throttle shaft??? when you held the throttle part way open...

how did you adjust the TPS on the end of the throttle shaft.. Throttle position sensor...


there are a pair of wires that come out of the fuel injection harness that are bolted down to the intake.. these are the only ground wires the computer has..

and must be properly attached..  

wayne712222 wayne712222
User | Posts: 205 | Joined: 10/13
Posted: 10/13/13
04:36 PM

there is a bunch of stuff to verify...


pull the cap off the distributor...

grab the rotor.. shake the shaft.. is it loose... then you might have an issue..

pull the rotor off.. take a bright flashlight and look straight down the top of the shaft.. look at the second layer under the riveted down part.. its a dark grey color. if you can see cracks.. you must replace the distributor..

Untitled27 Zpsf08c7b4c

remans that have this shape of pickup coil and reluctor are far superior to the oem design.

Untitled23 Zpsfded343c


please.. check the sides of your ignition coil for signs of high voltage leaks...

Untitled24 Zpsddcbb213

more to come..  

wayne712222 wayne712222
User | Posts: 205 | Joined: 10/13
Posted: 10/13/13
05:34 PM

lets dive back into the fuel injection system...

you mentioned you rebuilt the throttle body...

play in the throttle shaft is bad....

open the throttle slightly.. engine off. and then see if you get slack forward and backward when its part way open...

what..

(O)  good.. no movement or very very little..

( O)  (O ) bad..

what happens is this slop in the throttle bore allows the throttle to close to different angles each time..  this effects the fuel injection system in several different ways...

first.. the Throttle position sensor is on the end of the shaft.. when the throttle is closed.. it should go back to the exact same fraction of a volt each time..

0.52 volts to 0.90 volts.. but it has to be PERFECT..or the computer will think that you have your foot on the gas pedal part way and keep the fuel system in the RUN mode instead of dropping it back into the idle mode.. so its just pouring on the fuel ..

this can also cause stalling issues.. as there are several things going on at the same time.. the big hex shaped device on the side of the throttle body is the IDLE air control valve...  its a stepper motor.. so it can be controlled by the computer..  

at idle, computer measured engine coolant temp reading above 185F, TPS below 0.98 volts .. the ECM should have the idle air motor somewhere between 20 and 50 idle air counts..

if the IAC is higher than 50.. you need to open the idle stop screw slightly..
if the IAC is lower.. you need to open the idle stop screw slightly

this brings you back into a controlled area.. sorry IAC can only be viewed with a scan tool that works with these OBD1 GM systems and shows live data stream.


you can also tap into the throttle position sensor wiring..

Adjustment & Testing

The TP sensor wiring should consist of a 3-wire harness connector. The gray wire is normally the 5 volt reference signal from the computer control module. The dark blue wire should be the TP signal and the black wire is ground.

probe the black and the blue wire to measure the TPS voltage..

0.52 to 0.98 closer to 0.75 is better..  this is with the throttle closed..

you can set minimum idle speed. in a different way to attack this issue.

you will feel a big vacuum leak next to one of the Throttle body hold down bolts..

you can take a screw driver and stuff a CLOTH shop rag down the cavity.. to shut off the additional air.. at this point.. you can adjust the Torx15 idle stop screw so the engine JUST BARELY idles..  this is with clean bores...

the adjustment should NOT cause the blades to hang up or bind down in the bores.. so a fraction of a turn above that point with the engine idling..

you can now pull the shop towel out.. reset the TPS voltage by loosening the screws and moving it slightly to get the black wire to blue wire voltage below 1.0 volts.  again right around 0.75.. but somewhere between 0.53 and 0.98..


~~~~~~~~~~~~~~~~~~~~


while you are in there.. please verify that you have connected the vacuum hose to the domino shaped device called the MAP Sensor.. it needs to see MANIFOLD VACUUM..



please get under the dashboard... find the ALDL connector ..

Aldl

use a short piece of wire to jump the A and B terminals..  at this point when you turn the ignition key on.. the check engine light should start flashing codes at you..

ON________________ON___ON________________________________ON________________ON___ON________________________________ON________________ON___ON________________________________

is a code 12..  see the pattern..



88 92 GM DTC TBI Zpsac582fe6






if you have access to a scan tool... that displays live data.. this is what the data should look like

Scandatagm  

wayne712222 wayne712222
User | Posts: 205 | Joined: 10/13
Posted: 10/13/13
05:35 PM

i don't expect you or anybody to understand any of this...

it took me a long time to get this much info...

ask questions..

post any codes you get...


almost everything above has been a CHECK or ADJUSTMENT..

there is one part that should probably be changed..

the engine coolant temp sensor.. its on the top of the front of the intake manifold.. has a black and a yellow wire on it..  its part number SU102 at AZ Stores and that number comes with a pigtail connector for under 20 buck..

these fail.. will limit power.. will set either a code 14 or 15.

Su102  

wayne712222 wayne712222
User | Posts: 205 | Joined: 10/13
Posted: 10/13/13
05:38 PM

if you find play in the throttle shaft..

there are several ways to go..

find a good throttle body..

be sure to verify the injector numbers match..  4.3 V6, 5.0 5.7 and 5.7 police 9C1 throttle bodies are mostly identical except for flow rates of the injectors..

there are NEW holley throttle bodies available..

some carb shops and several places online rebush the shafts...

i have a valve guide reamer in 0.375... and i use a Letter Y drill 0.404" to drill the shaft bore... i use a K line thin wall valve guide liner that is for .375..so i get a nice fit.. the hard part are the replacement screws.. one has to grind the exposed threads off or the screws will snap off when you try to remove them.. and replacements in that size are hard to find.. 2.5MM x .60 x 10mm long pan head..
with a large head.. they are specials..

one can be careful not grind the screw threads flush to there is some to distort when locking them in place..  

skyeking skyeking
Addict | Posts: 2738 | Joined: 08/09
Posted: 10/15/13
06:46 PM

Hi Wayne,
And a Happy peanut butter day to you...Noel in OZ.
Check your mail.  
skyeking

Dave632 Dave632
Addict | Posts: 2225 | Joined: 07/08
Posted: 10/15/13
09:16 PM

Icon Quotewayne712222:
i don't expect you or anybody to understand any of this...

it took me a long time to get this much info...

ask questions..

post any codes you get...


almost everything above has been a CHECK or ADJUSTMENT..

there is one part that should probably be changed..

the engine coolant temp sensor.. its on the top of the front of the intake manifold.. has a black and a yellow wire on it..  its part number SU102 at AZ Stores and that number comes with a pigtail connector for under 20 buck..

these fail.. will limit power.. will set either a code 14 or 15.

Su102


Had one of those go bad in a 93 Chevy truck. It caused the engine to run OK when cold but as soon as it warmed up even a little it would hardly run if at all.
It was running super rich as the temp sensor was indicating that the motor was dead cold so the computer sent a signal for a rich mixture.  
[[SUPPORT AMERICAN CARS, STOMP A RICE CAR TODAY.]]

wayne712222 wayne712222
User | Posts: 205 | Joined: 10/13
Posted: 10/15/13
11:03 PM

skyking.. resend the message.. forum updates required a different log on and i no longer have access to earlier emails..  

skyeking skyeking
Addict | Posts: 2738 | Joined: 08/09
Posted: 10/16/13
03:50 PM

Laugh Hi Wayne,
 a web site says that [with lots of testing of each item]
 that we can use [believe it or not]
 for an emergency usage for a short time that in place of
 heat sink greases,  toothpaste,/ Vegemite/marmite beef extracts
 and super best Wink   PEANUT BUTTER!! Shocked  Shocked
   All average the potential of Hi Ho Silver for a while. Cool
 
 All the best to all the People Smile  Smile  
skyeking