Wherer did my POWER go!?...AGAIN

[gm29chev]

Hey so I had some great things to try from my post the other day.

My origional post was this: I have a 86 Blazer and it has pretty much stock everything at the moment. The only real change that has been made prior to me owning it was an electic fuel pump. Anyways, I hoped in the truck the other day and after letting it warm up I took off. The engine runs great going down the road but when I really hit the gas the truck lags bad. It even died on me a few times. After a long trip the other day, about 50 miles, I checked my engine temp and it only read 120F. And even after 50 miles of interstate driving the engine still lagged at about 70%+ peddle to the floor. This problem started rather suddenly as the day before when I drove it it was fine.

Everyone was really helpfull and it was determined that it was probably my thermostate being stuck open not letting the engine heat up.

My current problem: I changed out the thermostat and it definately fixed my heating issue. The problem now is that I STILL have that lack of power. It really didnt touch the issue at all. Am I looking at a vacuum issue now that the thermostat is fixed? Am I really going to have to go through the vacuum issue? If so does anyone have any ideas on how to make that as painless as possible?

 

[Duntz00]

You can take some starting fluid and spray around the vacuum lines and if it idles up you found your leak.

 

[gotblazers]

A video would be really helpful. Is it getting too much gas and not igniting or is the gas not getting there fast enough in the first place?

 

[blazinzuk]

I bet money your electric fuel pump is failing, at idle and lighter load it is still pushing enough fuel to supply demand. When under a load it cannot supply enough fuel, hence no power it is still supplying only enough fuel to idle or under light throttle.

I don't care how new it is BTW, I have seen all sorts of different brands of fuel pumps go out within a couple days.

I am pretty sure you have some sort of fuel delivery problem.

When you rev it not under load does it rev just fine?

How is acceleration?

 

[Blue85]

Did you verify that the choke is opening all the way?

I think the problem could be spark or fuel related. Vacuum seems less likely because typically that causes the most problems at idle (or even light cruise in the case of EGR). Since you describe it as a "bog" I think that makes fuel the most likely culprit.

 

[diesel4me]

Do you have a Holley carb??..might have a bad power valve ...Q-jets have a power piston inside that can stick or be inoperative due to clogged passages in the carb too..

is your vacuum advance working,if it has one?..distributor weights seized in the retarted spark position?...EGR valve sticking open,or opening too soon?...exhaust heat riser butterfly stuck closed,if it has one?...muffler or catalitic converter clogged up??..(A vacuum gauge can help diagnose that)....

The easiest way to pinpoint vacuum leaks is to spray carb cleaner at suspected areas where a hose might be split or rubbed thru,et,the engine will change speeds if carb cleaner gets inhaled by a vacuum leak...I'd definately check fuel pump pressure and volume also..

One engine in a friends car developed a sudden power loss,and it took us about two hours to figure out why--it ran great with the air cleaner off,but with it on the engine ran way rich and blew black smoke..when we took off the air cleaner,we found it was filled to the max with acorns,mouse nest and a zillion nut shells,the thing was so clogged hardly any air could go thru the filter!...we also found dead ice in the sorkel leading to the air cleaner and more nest material ....

 

[gm29chev]

I bet money your electric fuel pump is failing, at idle and lighter load it is still pushing enough fuel to supply demand. When under a load it cannot supply enough fuel, hence no power it is still supplying only enough fuel to idle or under light throttle.

I don't care how new it is BTW, I have seen all sorts of different brands of fuel pumps go out within a couple days.

I am pretty sure you have some sort of fuel delivery problem.

When you rev it not under load does it rev just fine?

How is acceleration?

Now could it also be that something is not hooked up right and it is supplyin too much fuel? And yes when I rev motor not under load it revs just fine. Only when I go to punch it does it completely fail me.

 

[gm29chev]

Did you verify that the choke is opening all the way?

I think the problem could be spark or fuel related. Vacuum seems less likely because typically that causes the most problems at idle (or even light cruise in the case of EGR). Since you describe it as a "bog" I think that makes fuel the most likely culprit.

You know we replaced the thermostat and we didnt even bother to check that. It very well could still be a choke issue. I will check that.

 

[gm29chev]

You can take some starting fluid and spray around the vacuum lines and if it idles up you found your leak.

Now when Im looking for a vacuum leak am I looking more at hoses or are there other places that I can have a leak? If I replace just my hoses could I be missing something?

 

[diesel4me]

You could have a vacuum leak at the base gasket of the carb,intake gaskets,the power brake booster (unlikely as you'd have noticed a lack of power assist most likely),and the EGR valve can recirculate exhaust into the intake if it sticks open or opens too soon,which is the same as a vacuum leak as far as the engine is concerned,maybe worse becaue its sucking exhaust in,instead of fresh air...
Something as simple as a plugged PCV valve can throw off the carb mixture enough to cause a big drop in performance..

You say it shows up mostly under acceleration,that could be a bad accelerator pump in the carb ,a bad vacuum advance unit if you have one,or a vacuuum leak..