Most puzzling (and wastefully expensive) car problem ever.

[cotjones 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?

Click to read more...

 

[Mitch86 5,000+ posts]

s10forum.com or s10forums.com //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[retrojordans 10+ year member]

Ford

 

[thevic24 5,000+ posts]

Here are a few things I found on ALLDATA for your symptoms

Links failed....sorry.

I cant seem to post the links but I may be able to post the testing procedures for the codes that you pulled.

PM me if you want them

With my experience with these, If you have TB injection, I would check the injectors. They were known for leaking.

One other thing to check is the TP sensor.(Throttle position)

 

[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.

 

[cotjones 10+ year member]

Here are a few things I found on ALLDATA for your symptoms Links failed....sorry.

I cant seem to post the links but I may be able to post the testing procedures for the codes that you pulled.

PM me if you want them

With my experience with these, If you have TB injection, I would check the injectors. They were known for leaking.

One other thing to check is the TP sensor.(Throttle position)

That was one of my first thoughts, However the injectors do have sensors on both of them, no codes are popping up on them, and the fuel flow from them looks identical. seems unlikely that they are bad, thats why i was thinkin FPR. It wouldn't show a trouble code cause it has no sensor and supplies the fuel to both injectors. what i do not know, is if they normally fail open (too much fuel flow) or fail closed (weak fuel flow.)

Anyone experienced with these TBI fuel pressure regulators?

 

[thevic24 5,000+ posts]

IDK why I cant post the links but it dose say in alldata that a bad or misreading 02 sensor can cause a rich/lean condition.

IIRC, with OBD1, I do not think that there is a specific code for just the injectors.

I would not think that both injectors would fup at the same time but who knows..

Check the throttle position sensor, it will be attached where the throttle plates pivot at. If that is going bad, it will mess up the whole system.

 

[Big GeRm 10+ year member]

I had a similar issue...I had a faulty Fuel Pump...It would start and run...if i feather the throttle it will run no problem...but if i punched it..the whole car would surge.

I would check the fuel pressure at the shrader valve and see if the pressure drops off while the car is running.

 

[whitedragon551 5,000+ posts]

Check the mass air flow sensor. Same exact thing happened to my Grand Prix.

 

[Slayerx 10+ year member]

This is why I miss carbed cars lol. I had a similar problem, went through and cleaned all my electrical connections/plugs and that fixed it. Sometimes its not the part itself, but the communications between them.

Goodluck

 

[wickedwitt 10+ year member]

MAFS or your cat. converter(s) are stopped up. Run a back pressure test at a trusted shop. Should be no more than 5-6 PSI. My truck started acting retarded a couple years ago, had 36PSI back pressure. Mass Airflow Sensor can cause some of the probs as well.

 

[thevic24 5,000+ posts]

This is why I miss carbed cars lol. I had a similar problem, went through and cleaned all my electrical connections/plugs and that fixed it. Sometimes its not the part itself, but the communications between them. Goodluck

Very true..

I spent about 6 hours tracing a knock sensor code in a GX460 a few weeks back.(Brand new..3 miles)

Turned out to be a crimped terminal, the wire was never stripped out....a connection in the sensor circuit that was behind the dash.

(Yes I took the complete dash/crash bar/ harness out of the car)lol

 

[cotjones 10+ year member]

Check the mass air flow sensor. Same exact thing happened to my Grand Prix.

HAHa there is no mass airflow sensor, i just said that.

 

[whitedragon551 5,000+ posts]

HAHa there is no mass airflow sensor, i just said that.

Please point me to where you said that.

 

[cotjones 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.