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TBI help needed

A

angrysnowplow

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1990 k5, stock tbi 350

The truck will not stay running. It has 10 psi of fuel pressure at the filter, the egr is fairly new and doesn't seem to be sticking, I tried a replacement module under the distributor cap, cleaned the IAC with carb cleaner, and tried a replacement TPS.
It cranks much longer before firing before all this started. When it does fire, it stumbles and dies. If I give it some gas, it will load up, bog down, and die.
I unplugged the map sensor, and now the truck still cranks for a long time, but idles smoothly, at a high rpm. If I put it into gear, it dies immediately. Also, if I blip the throttle, the rpm's come down slowly. New map sensor did not help.

throws codes 33 and 34...

New fuel filter as I just replaced some fuel line, maybe I'll try running it wothout one for a minute. :confused:

I'm at a loss here...

and should I be able to move the plunger on the IAC by hand?
 
Last edited:
angrysnowplow said:
1990 k5, stock tbi 350

The truck will not stay running. It has 10 psi of fuel pressure at the filter, the egr is fairly new and doesn't seem to be sticking, I tried a replacement module under the distributor cap, cleaned the IAC with carb cleaner, and tried a replacement TPS.
It cranks much longer before firing before all this started. When it does fire, it stumbles and dies. If I give it some gas, it will load up, bog down, and die.
I unplugged the map sensor, and now the truck still cranks for a long time, but idles smoothly, at a high rpm. If I put it into gear, it dies immediately. Also, if I blip the throttle, the rpm's come down slowly. New map sensor did not help.

throws codes 33 and 34...

New fuel filter as I just replaced some fuel line, maybe I'll try running it wothout one for a minute. :confused:

I'm at a loss here...

and should I be able to move the plunger on the IAC by hand?
Click to expand...

Does your EGR have a wiring harness? Or does it have a vacuum line to the MAP sensor? My EGR was BRAND NEW and it didn't work. Betcha it's bad. Is it an aftermarket one? If so, they are POS's. I got tired of replacing htem and finally bought an OEM unit from the dealer.
 
I've been searching for the past couple days...I think I remember a post of yours saying that.
Yep, it's aftermarket.
I've also read that a bad egr can cause the map sensor code to be thrown...that does make sense.
There are no electrical connections, just one vacuum line going from it to another sensor, not the map, ( :confused: ) and then a line going from there to the front of the throttle body.

Imma go outside and try the fuel filter once more, and maybe get a pic of what I was just talking about.
 
If you want the entire TBI troubleshooting code list (which I haven't looked at entirely) in .pdf format, PM me, I can email it to you. These are the flowcharts that take you through the procedures step by step.

They are for '88 TBI in a Firebird, but air temp sensor is the only difference AFAIK.

If anyone is willing to host these for the good of everyone, PM me and I'll send you the same +TPI.
 
4118Picture.jpg
map sensor on the left with the green connector. :thinking:

And I will try plugging the egr lines now. I thought I needed to just unplug them to test the egr, not block them.

Maybe my damage is brained too. :D

So, is the egr valve solenoid what is on the other end of that vacuum hose from the egr?
 
Plugging egr line made no difference.

Hard start, fires for about 1 second, dies.

If I give it gas, it loads up and dies.



dyeager, you have a pm.
 
angrysnowplow said:
and should I be able to move the plunger on the IAC by hand?
Click to expand...

No. It's a stepper motor and won't work like that.
 
Am I seeing things??

angrysnowplow said:
4118Picture.jpg
map sensor on the left with the green connector. :thinking:

And I will try plugging the egr lines now. I thought I needed to just unplug them to test the egr, not block them.

Maybe my damage is brained too. :D

So, is the egr valve solenoid what is on the other end of that vacuum hose from the egr?
Click to expand...

Is that a crack in the intake under the EGR valve??--sure looks like one in the picture,but it might just be dirt....

I dont know much about EFI,but I have a friend who fixes a lot of the newer 90-up trucks--he lacks a lot of the computer diagnostics stuff,he usually just tries used parts saved off a parts truck to diagnose most of them...first thing he tries is a module,then a crank sensor...if that does not cure it,he usually sends it to another shop that has all the computer diagnosis stuff--90% of the time it turns out to be a bad wire somewhere if the module and crank sensor didn't fix it.. :crazy:
 
development-

reading codes again for the hell of it...
nothing but 12, but a peculiar noise coming from the throttle body. It is the IAC (which my damn voltmeter said was ok) and it's little motor is running constantly. I pulled it out, plugged it back in, and it will push the plunger and pop it out, everytime.

:what:
 
who needs emissions anyways? took my AIR out, left the controller thing plugged in, and stuffed it over behind some leftover AC crap on the firewall :)
 
you mean the air pump?

my truck was never equipped with one of those...

and if you meant the IAC, I did try to run it not plugged in, taken out and still plugged in...

you get the idea. If this pos ever runs again I will be suprised. :(
 
Might check thirdgen.org to see if there is any IAC diagnostic info over there. I know there is a minimum air setting procedure, but I'd want to know what the "correct" procedure for testing is.
 
I did some reading on thirdgen.org...

"I have to adjust/reset my IAC, how can I do this?

The IAC is not adjustable. The IAC is reset upon each shutdown of the ecm so it can ensure that the IAC will be at a known location. After which, the ecm parks the TBI. "



"...reconnect the IAC connector and place a bag or towel around the IAC so the pintle doest go flying off. Once this is done, jumper pins 'A' + 'B' in the ALDL connector. Once jumpered, turn the key to the ON position, but dont start the car. The ecm will eject the IAC pintle." So that IS supposed to happen.

I'm back to square one now. I thought 9-15 psi fuel pressure was acceptable, was the 10 psi I posted earlier enough?
 
I can vouch for this thing being a pain! It seems to be acting like the timing is off, but we are 99% sure it is where it was when the distributor was removed earlier today...

Now it won't catch and just spits back out the throttle body :confused:
 
funny cause my truck is doing the same thing, i sprayed some carb cleaner by egr and along intake next to head and sat there and sprayed and my truck idled perfectly no missfire or anything, so im assuming the intake is sucking in air causing a lean condition which also runs horrible when cold out
im going to replace my intake,egr,throttle body gaskets and let you know...
 
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