Most puzzling (and wastefully expensive) car problem ever.

[cotjones 10+ year member]

Ba ha ha, I mean honestly its just transportation and for this to be the first time its had out of ordinary maintenance in like 25 years, I think I like it. not to mention every normal part for it is cheap and easy to fix. Even the one of the most specialized parts on the thing (the TBI FPR) is a cool 35 bucks at autozone. parts for this thing are CHEAP it doesnt even have an expensive *** prone to failure Mass Airflow sensor. those things have Plagued my entire life.

Please point me to where you said that.

there... Tho i'll admit, punctuation wasn't my friend.

 

[thevic24 5,000+ posts]

My thought too, but the pressure goes up actually. sprays like a super soaker! For some reason it DUMPS fuel (figuratively) It atomizes well enough, just way too much of it. Causing flooding.

Need to check the throttle position sensor, if its sending a bad signal( throttle plate angle vs actual angle) to the ecu, the ecu will just think

it needs more fuel than it really dose for any given position.(if its reading too high. also, )

You would need a crap tone of fuel psi to have an injector "spray too much", more than most pumps could produce.

What is probably happening is the ecu is holding the injectors open too long.

And I was going to say that year/motor did not have a MAFM system.

Let me look up what the TP sensor idle voltage is and that way you can check it and see if its that or not.

 

[thevic24 5,000+ posts]

ok, with the ign on and engine off, the voltage at terminals a and (cneter) b should be between .42 and .45v dc.

If its not in that range you can try to adjust it or replace it.

to adjust it, loosen the 2 screws slightly. Leave the key on , motor off and slightly twist the sensor in either direction and see if you

can hit the voltages above.

If you replace it, you will need to do the inital adjustments above

 

[cotjones 10+ year member]

Ba ha ha, I mean honestly its just transportation and for this to be the first time its had out of ordinary maintenance in like 25 years, I think I like it. not to mention every normal part for it is cheap and easy to fix. Even the one of the most specialized parts on the thing (the TBI FPR) is a cool 35 bucks at autozone. parts for this thing are CHEAP it doesnt even have an expensive *** prone to failure Mass Airflow sensor. those things have Plagued my entire life.

ok, with the ign on and engine off, the voltage at terminals a and (cneter) b should be between .42 and .45v dc.If its not in that range you can try to adjust it or replace it.

to adjust it, loosen the 2 screws slightly. Leave the key on , motor off and slightly twist the sensor in either direction and see if you

can hit the voltages above.

If you replace it, you will need to do the inital adjustments above

Thx, i'll try when I get off work... tho I BELIEVE the mechanic would've tested it when I had it there, but no harm double checking.

I am beginning to suspect some kind of sensor problem though because like I said, with the MAP sensor unplugged, there is a positive change in performance. Unplugging the O2 sensor has minimal effects. Haven't focused on TPS too much personally.

Also need to locate a hissing sound I recently noted after turning the engine off. Starts loud and then sounds like it looses pressure, Probably a missed leaky vacuum hose, or possibly crack in the canister, but ironically most of the critical vacuum hoses did check out to be OK on pressure.

 

[Big GeRm 10+ year member]

My thought too, but the pressure goes up actually. sprays like a super soaker! For some reason it DUMPS fuel (figuratively) It atomizes well enough, just way too much of it. Causing flooding.

But do you actually have a gauge on the schrader?...I still think its a fuel issue

 

[Wingsfreak9 10+ year member]

OK so some of you car geniuses please give me some ideas. I'm completely burnt out on this.
So basically the car isn't working correctly and no one seems to know why.

K the type of car is 1986 S-10 Blazer. It is 4WD and has a 2.8L V6.

Briefly, the symptoms and problems it has are as follows:

1. At times the car won't accelerate when you give it steady gas, if you feather or "pump" the accelerator, it will progressively rev up, but never really wants to go more than about 45MPH. Steady pressure on the accelerator causes the RPM level to drop to the point of stalling out.

2. While engine is revving, stays running fine, when you come to a stop light or stop revving it, it will idle fine for a little while (about 20-30 seconds), then RPMs rise by about 200, then drop back down and the car dies.

3. The above conditions exist with the MAP sensor Vacuum supply disconnected. When it is connected, the car will not idle enough to remain running. It turns over fine, but won't stay running for any period of time (unless the car is VERY warmed up "has been running for at least 30 min") then with the sensor connected, the car idles more steadily and doesn't die.

4. As a side note, there is an exhaust leak at the donut which connects the manifold to the pipe, but this leak has plagued this truck forever.

5. Diagnostic codes popping up are 33 and 34 which are low and high vacuum pressure to the map sensor. and 44 and 45, which are rich and lean exhaust detected.

6. visually, and from the smell, the injectors are dumping far too much fuel.

I've had TONS of people give me second opinions and advice and i've done alot of work which has gotten me nowhere.

Attempted repairs are as follows:

Replaced Map sensor, O2 sensor, several leaky vacuum hoses, Sparkplugs and wires.

Checked vacuum levels (ok), EGR valve function (ok), dealership ran computer tests (ok), timing seems ok.

after 300$ in diagnostics, the dealer tells me that the exhaust leak is causing the O2 sensor to detect lean and dump more fuel, flooding and causing misfires. I personally think that sounds like crap.

My next plan of attack is to try replacing the fuel pressure regulator diaphragm.

Any thoughts geniuses?

Or know of the best forum to post this question to?

found your issue

 

[cotjones 10+ year member]

But do you actually have a gauge on the schrader?...I still think its a fuel issue

No, but I mean, visually, you can see it spray HEAVY, you can hear it, IT's so rich it burns your eyes and you can smell it strong. Its DEFINITELY too rich. Haven't personally checked fuel pressure, but again I would hope the mechanic would've checked it for the 300 bucks they soaked me for.

Don't have a gauge so I can't really check it without borrowing from someone (maybe Autozone has a loaner?).

 

[xX J Brutal Xx 10+ year member]

catalytic converter plugged?

 

[Imtjnotu 5,000+ posts]

holy shiit i havent seen cotjones for ages....grab a can of wd40 or some sort of carb or tb cleaner and spray all over checking for leaks(car will rev high when u spray into a leak)...have u checked the o2?...sounds like u are having an air leak of some sort somewhere...take off the line that goes from the FPR to the Manifold and see if u smell gas? what about cleaning out ur manifold or TB plate?

 

---------- Post added at 02:30 PM ---------- Previous post was at 02:28 PM ----------

 

 

[cotjones 10+ year member]

catalytic converter plugged?

IDK i kinda doubt it on an 86, plus theres a gaping hole at the donut, so i don't see it building too much back pressure.

 

[Big GeRm 10+ year member]

Have you check the IAC valve?

 

[cotjones 10+ year member]

holy shiit i havent seen cotjones for ages....grab a can of wd40 or some sort of carb or tb cleaner and spray all over checking for leaks(car will rev high when u spray into a leak)...have u checked the o2?...sounds like u are having an air leak of some sort somewhere...take off the line that goes from the FPR to the Manifold and see if u smell gas? what about cleaning out ur manifold or TB plate?

 

See i'm kinda with you here, the problem is, on this TBI, the FPR and lines too it are internal so the vacuum line can't just be pulled off like the one in the vid.

I replaced O2 sensor (no change) Manifold is fairly clean. I definitely think I need to search more for vacuum leaks, but i have a feeling I have a bad FPR. I actually hope i do, because the rebuild kit for the TBI includes one, and only costs like 30 bucks, not to mention it looks like fun to rebuild.

 

I'm also chalking in the TPS votage on my check list.

 

I

 

[cotjones 10+ year member]

Now that you mention it, that could be a good place to look for the stalling problem at idle, but I don't necessarily see it causing the acceleration problems. I think though that it may be a compounding issue. Can I check the IAC by unplugging it?

 

[cotjones 10+ year member]

i'm really appreciating all the ideas guys. thanks alot! I'll get it eventually.

 

[Imtjnotu 5,000+ posts]

unplug it and then check if there is any major changes but i think u should look for leaks first...also go to autozone and ask them to check ur fuel pressure or borrow the meter to check it