87 s-10 Blazer 2.8L nead HELP (Computer Problems?)

[pilfit]

I have an 1987 s-10 Blazer 2.8L TBI. Runs bad and stalls. When I start to push the gas in it loses power and starts to stall if I push it a bit more it comes back. I have replaced the TPS senser, MAP, Full filter, Idle Air control valve, cap and roter, and O2 senser. If I unplug the MAP it will run ok but not good. any help?

ps. there are no trouble codes.

[Code Red Monte]

just flash the comp. that can sometimes do the trick or you might of pinched a vacuam line. my 89 k5 ran like shit cause i creased a vacuam line in the back of the motor

[pilfit]

How would I do that with the computer? and I'v checked all the vac lines

[mikedesc]

Pilfit:

I have a similar problem, see my message next to yours. Tonight, I finally got the beast to keep stalling until I got home to my garage. Just on a whim, I decided to check the injector spray patterns and there it was, only one injector was working. I swapped the leads and the off injector came alive. This greatly narrows down the problem. It is now either a wiring problem or a computer problem. Btw, the problem goes away when everything cools down in the engine compartment. From the schematic, I see that the computer switches the lows. If so, it should be fairly easy to find the problem. If the 12v is at the connector, it is the low line or the computer, if not the problem is in the 12v line.

I think flashing the computer is removing the negative battery terminal for a few minutes and then re-connecting the same. This clears the computer.

Mike

[tom3]

Also a common symptom of a failing fuel pump. Hard to get a fuel pressure check on these TBI engines, have to cut fuel line or buy special gauge connector. How old is the pump? If nearing 100K miles on it, could be the problem.

[pilfit]

I'v checked the injectors they spray fine and it runs ok when in limp home mode thats why I have the MAP seneor unpluged. so it cant be the fuel pump i'v narowed it down to a problem in the fuel control system

[thepolishmafia1337]

a couple things when you replace a sensor it is still possible that the new one is bad to. you can test them with a dvom but the refreash rate on the dvom is too slow to catch glitches. the best way is an ossilliscope. another thing, dont rule out the coolant temp sender. if it is reading -40 your going to have a fuel problem. also your new o2 sensor could be biased lean. any large exhaust leaks?

[pilfit]

the temp sensors are the only thing I havent replaced and thats what i'm doing today. no exhaust leaks, new cat back last summer. any one know wich one I should try first the coolant temp sensor or the air temp?

[mikedesc]

One last thought before I go and chase my injector wiring demons. Are you sure you are in closed loop vs open loop? I had to change out the thermostat and temp sensor before the computer would close the loop. Easy to to verify is with small plug in code checker during engine warm up. Other way is to see if you are is when you are driving. Does the car seem to surge slightly as you are moving? If so, it is open looped.

[mikedesc]

I changed the coolant temp sensor. The engine temp indicator was running on the low side.

[thepolishmafia1337]

what is the low side??? if im not mistaken blazers have a temp gauge goes like 100-160-210-250 instead of L and H. you already know that you are running in closed loop because you said if you unplug the map then it runs ok. when you do that it runs in open loop mode(substitutes known good values for fuel and timing curve) just curious how does it run at cruise, wide open throttle, and decel??

[pilfit]

with the map unpluged is the only way it can be driven At cruise and decel it surges, at open trottle its just fine but less power then it should have

[thepolishmafia1337]

just on a whim i think you should check the egr for fuctionality. blazers are real bad about getting carbon built up and making the egr stick open. an open egr can cause similar problems.

[swgeno]

I am having similiar problems with a 87 s-10 with a 2.8. It "hiccups" when accelerating or climbing one of the many hills in seattle to get home. I have replaced the o2, a tps with holes in the voltage. It gave me a lean exhaust code. Every once in a while it will pop back through the TBI. a full tank of fuel only goes about 175 miles. Im going to put a new fuel filter, cap and rotor this weekend. Anything else come to mind that I should look at??

Thanx

[maxwedge]

Way too old a thread here start a new one!