1991 sonoma/s10 4.3 tbi running rich nightmare

[goomes711]

Hi, my 1991 Sonoma 4.3 TBI started giving me code 45 (rich), idles rough, stalls, black smoke.
Everything listed here has been done by me or my mechanic, who says he is stumped at this point.
I need some suggestions that are not on my list. Any crazy idea would be considered at this point, THANKS>>>>

New egr valve
New idle air control solenoid
New Iac motor
New map sensor
New tps
New o2 sensor
New knock sensor
New coolant temp sensor
New distributor
New coil
New wires
New plugs gapped to .035
New tbi rebuild rings/gaskets
New fuel pressure reg
New fuel pump
New fuel pump sending unit
New spark control mod
Replaced computer ecm
New exhaust/cat



Timing done
Fuel pressure tested at 13 psi
Fuel return line blown out/ no kink
Injector pattern fine
compression test fine 100-110 all

[jasoninnorman]

well i got a 89 s10 tahoe it has the 4.3l tbi with 700r tranny. i have same prob and replaced almost all the things u have and well, im past stumped myself. the odd part is im gettin little over 20mpg with it running like this. the people i got it from took to shop and they said return line on fuel pump blew well i put new pump in it, and well it wasnt. i cant find anything else. one i get it over the idle it seem to run fine. this will intreast u, i tryed to replace o2 senser and well it rusted in place so i had it unpluged and took it to muffler shop so they could heat old one with torch and well with it unpluged it run almost perfect. that has me boggled totally. i did have the ign control modual was bad but it didnt make a differnce other then cruise ctrl works now, well trys to work. so if u have come up with anything yet plz let me know. if i find anything ill let u know also.

[jasoninnorman]

oh i forgot to mention, the truck hasnt yet to through a code/light.

[Schrade]

Vacuum leak will show no codes.

Loping idle is vacuum leak. 30 year old lawnmower, or a new car on the lot. If it sucks air where it ain't supposed to, it lopes.

Brick on pedal, block TB arm, anything to get a STEADY idle. 1200rpms or so... Feed starting fluid spray, A LITTLE AT A TIME, EVERYWHERE. Rev increase is the leak.

In a tough spot to pinpoint? Light a book of matches, blow it out while the heads are burnin', and feed the smoke to the leak.

Check fuel pressure too; see youtube 'fuel pressure test'...

Problems with both could cause a rich condition...

NEVER, EVER listen to a mechanic who is working on a car, and says it COULD be something. If a part is broken, it shows. If current is not where it is supposed to be, it shows.

COULD??? Tell him to grab a shovel, and put down the wrench.

[jasoninnorman]

well i tryed the deal with starting fluid didnt work, no leaks. the injectors are flooding truck with gas. it puddles in the tbi butter fly valves. i tryed everything, it all seems good with all parts replaced even. nothing makes a differnce. fuel presure is good, i also just put new pump in it last weekend. old one was week. only thing not done was rebuild fuel pressure regulator. the old pump was week. suprized it could run honestly. if anyone has other ideas let me know, thanks

Originally Posted by cbec1999

Vacuum leak will show no codes.


Check fuel pressure too; see youtube 'fuel pressure test'...

Problems with both could cause a rich condition...

[Schrade]

Originally Posted by jasoninnorman

well i tryed the deal with starting fluid didnt work, no leaks. the injectors are flooding truck with gas. it puddles in the tbi butter fly valves. i tryed everything, it all seems good with all parts replaced even. nothing makes a differnce. fuel presure is good, i also just put new pump in it last weekend. old one was week. only thing not done was rebuild fuel pressure regulator. the old pump was week. suprized it could run honestly. if anyone has other ideas let me know, thanks

Test the resistance of the injectors, cold and hot. Got multimeter?

[jasoninnorman]

yes i got one. volt/ohm meter. i didnt know u can test the injectors at all. let me know how to do that one. jason

Originally Posted by cbec1999

Test the resistance of the injectors, cold and hot. Got multimeter?

[jasoninnorman]

ok well i looked online and talked to auto parts store about checkin resistence of injectors. about a 1.5 is wat both showed. the auto parts store checked there new ones and they said there holdin at 1.5 ohms. so that part of my injectors seem to be fine, but the people i got the truck from were not rich and im more then sure they run the cheapest gas money could buy, sad to say. so if u got a idea let me know. a buddy of mine has a auto shop and he got a 89 4.3 with same tbi. more mls then i have but he said motor runs great but parts truck, so he told me $10 on whole throttle body off it. but anyways if got anything else let me know asap. thanks

[Schrade]

Originally Posted by jasoninnorman

ok well i looked online and talked to auto parts store about checkin resistence of injectors. about a 1.5 is wat both showed. the auto parts store checked there new ones and they said there holdin at 1.5 ohms. so that part of my injectors seem to be fine, but the people i got the truck from were not rich and im more then sure they run the cheapest gas money could buy, sad to say. so if u got a idea let me know. a buddy of mine has a auto shop and he got a 89 4.3 with same tbi. more mls then i have but he said motor runs great but parts truck, so he told me $10 on whole throttle body off it. but anyways if got anything else let me know asap. thanks

Does the Check Engine Light come on when you turn the key on? BEFORE starting the truck???

1.5 ohms don't sound right there mr J... 15 ohms sounds right. Did you test them cold and hot?

Exactly what is your static (motor off) fuel pressure?

I'm kinda' not convinced about the vac leak test... Can you describe what you did?

Only fuel pressure problems or a vacuum leak can cause problems, WITHOUT lightin' up the CEL light, that I know of...

[jasoninnorman]

well check light comes on wen key is on and motor off. but no ever come on for a engine error. i dont remember the fuel pressure off top my head now. but it does have brand new pump in it. but the 1.5 ohms might been 15 could read it wrong so. but the new one at auto parts shop read the same thing. i tested them both cold and hot and was the same reading. the leak check. i took startin fluid- and sprayed it all around intake-tbi and lines with motor running to see if it changed engine rpm. didnt do anything but waist startin fluid. but i did go get throttle body from a buddys junk truck that runs just fine and put oin this truck. it didnt fix the prob either. but it did make it run stronger. wen it trys to choke out its not as bad. it only does it at a idle. wen i had throttle body off i pulled egr valve and checked it all out. its very clean, i was suprized to see it so clean. also the only things i havent replaced is knock sensor-oil sending unit. everything now is new parts. so let me know wat u think. thanks jason

Originally Posted by cbec1999

Does the Check Engine Light come on when you turn the key on? BEFORE starting the truck???

1.5 ohms don't sound right there mr J... 15 ohms sounds right. Did you test them cold and hot?

Exactly what is your static (motor off) fuel pressure?

I'm kinda' not convinced about the vac leak test... Can you describe what you did?

Only fuel pressure problems or a vacuum leak can cause problems, WITHOUT lightin' up the CEL light, that I know of...

[Schrade]

Originally Posted by jasoninnorman

wen it trys to choke out its not as bad. it only does it at a idle.

Choke out at idle??? Does the revs go up and down by itself?

What does the temperature gauge say when warmed up? If it says 190 - 200, or within a few degrees of that, you're gonna' have to get scanned, to see if it is going to CLOSED LOOP.

If is says anything low, like cold, that is probably the problem.

[jasoninnorman]

yeah it trys to choke at idle now after replaced all them things in it. but yeah it does it sometimes the rev up and down just a little. it tryed to rev up wen it starts to choke out. at its norm operating temp is 190-200. its got a 190* thermostat in it. but yeah im thinkin i was goin to have to have it hooked to computer to see wat its doin. iv done everything i can. so i guess it next thing to do there. but ill write u wen i get money now to get it check at shop and let u know wat they come up with, hopefully they find something. im stummped on it now. thanks for your help man, ill let u know like i said, asap. jason

Originally Posted by cbec1999

Choke out at idle??? Does the revs go up and down by itself?

What does the temperature gauge say when warmed up? If it says 190 - 200, or within a few degrees of that, you're gonna' have to get scanned, to see if it is going to CLOSED LOOP.

If is says anything low, like cold, that is probably the problem.

[tesney]

Originally Posted by jasoninnorman

yeah it trys to choke at idle now after replaced all them things in it. but yeah it does it sometimes the rev up and down just a little. it tryed to rev up wen it starts to choke out. at its norm operating temp is 190-200. its got a 190* thermostat in it. but yeah im thinkin i was goin to have to have it hooked to computer to see wat its doin. iv done everything i can. so i guess it next thing to do there. but ill write u wen i get money now to get it check at shop and let u know wat they come up with, hopefully they find something. im stummped on it now. thanks for your help man, ill let u know like i said, asap. jason

Jason - how did this all end up -- ever find the problem?

I have the same issue as you with a 91 S10 Tahoe and would like to know the answer!

[mr.gyro]

i have a 92 s 10 and i have replaced all the same parts and no change i can unplug the iac valve and the tp sensor and it dont change anything have you fixed your truck or did you give up on it i can unplug one injector and it runs ok

[mcbee]

Heres my problum .... Its the same as the one above BUT it is at 2500 and up rpm. Iv dun all the parts changeing map, cooling sencer, tps, injectors,o2 even the ecm.... Idles great a little rich at cruze but stick ur foot on the floor and it will drain the tank. I have a snap-on scaner and all readings are good. No vac leaks no fule leaks. Been thro all grounds and there good. V-ref is dead on. This is not the first time iv seen this but don't know if it got fixed on there truck .... Im at a wall here eney help would be nice