TBI sensors

[blazerboy_4life]

Does anybody have a list of all the sensors on a 350 TBI and possibly what happens when to the engine when they arent running properly? I just bought a 90' ex cab long box 4x4 and it backfires out the tb and misses at speed. It happens less when i keep it in 3rd but still happens. I have already replaced the fuel filter and TPS and that made a difference in running and idleing but not at speed. I just bought plugs and wires last night and I know I should check the timing too. Should be set at 0 degrees right? This is my first time working on a fuel injected engine so I know I have a lot to learn but I pick it up fast.

Also what are the simplest and cheapest things to do for hp and mpg gain?

Heres what Im working with. 90' 5.7 TBI, 700r4, 265/75/16 tires. Currently has manifolds into single exhaust. Not sure about rear end.

Thanks in advance for all the help everyone.

[rfmaster]

You can pull trouble codes by installing jumper wire between Pins A & B of ALDL connector. Use search for procedure detail. Once you know what trouble codes are set (if any) you can address them.

Allow engine to warm up fully before setting base timing. Timing, with EST connector open, should be 0 deg. Once timing is set reconnect set EST connector, shut engine down, disconnect battery to clear code 43 (results from EST connector being open). This will also clear all other DTC codes that may be present.

Most common problem that these old TBI trucks have is a worn fuel pump - low fuel pressure. Stock FP is between 9 to 13 PSI, but I have seen TBI idle with 6 PSI, but it would back fire once throttle was moved of idle. Too lean.

So do basic ALDL check and report .

Also note that distributor is a known failure point due to water condensation under distributor hat. If inside is very rusty looking expect to replace dizzy with a rebuild unit.

//RF

[blazerboy_4life]

Ok I already purchased the fuel pump assuming it was a weak link. I dont have a way to check the fuel pressure at home without taking it in somewhere. Im trying to avoid that because I like to learn what to do on my own. The check engine light comes on and off and I pulled the codes the other day with no results. It said there were no codes stored. Any ideas what would cause the light to pop on and off like that?

[rfmaster]

It is normal for SES light to be on when engine is OFF - ignition ON (run position).

ECM goes through power on self test (POST) when you move ignition key from off into run position. SES should go from solid ON blink off and turn solid ON through initial engine cranking. At the same time fuel pump is powered up for about 2 - 3 sec.

Make sure that you're connecting correct two pins on ALDL connector -> A & B. SES light will blink code 12 three times followed by other DTC codes (if any), but it must blink Code 12 first! This tells you positively that ECM is in diagnostic mode.

Once engine starts running (400+ RPM) SES should go OFF and stay off until engine is shut down. If you are getting engine stall (i.e engine RPM falls below 400RPM) you may see SES come on or blink. This usually happens when ECM looses DRP signal from dizzy. TBI ECM must have DRP signal from dizzy to fire injectors! This is why malfunctioning dizzy will create havoc.

Checking fuel pressure is not that difficult, but you'll need to have FP gauge with TBI specific adapter. You can find inexpensive reasonably priced, decent units on ebay ( 230776223174 ). Factory spec is 9 to 13 PSI.

//RF