Engine hesitation, low RPM's

[Dre]

What could it be? It happened before but since it went away I didn't really check it. I get "Check Engine" light on from the moment I start the engine then I get very low RPM's idle, looks like slightly above 500 mark and every time I touch the accelerator to move my rig it hesitates for a moment and then "jumps" forward. Did we talk about it before?

Need help,

 

[BExplorer]

Similar...

I have a similar problem on my 94, since it's manual I just give it gas to UNSTUCK if I may say so the engine and then I release the clutch. It does not solve the problem but no jumps for me. If you look at voltage gauge, it should take a drop, try the test in neutral. I to would like to get some answer, else I can live with it.

 

[Triton46]

Check Engine usually means some sort of emissions. How is your MPG? How many miles do you have on it? When it does drive without bucking, do you have decent performance?

 

[Anime]

geh

I would guess ignition, air or fuel ...there is the possiblity of an exhaust/emissions prob if you have an old rig with the stock exhaust.

If you havent already replaced spark plugs, wires, air filter, etc etc...do so. You also might have some dirty injectors..try high octane gas and some redline or STP fuel injector cleaner too. Also do the MAS cleaning..
Check your throttle lines and clean em thoroughly...theres a little hole where the spring is at the throttle body..if that hole is blocked problems occur.
If you have all this done and still its a prob. maybe check your vacuum lines for a leak..other than that it might be the exhaust..and maybe fuel pump too.

 

[Dre]

It's pretty much there. New wires, plugs, open K&N filter. Only thing now might MAS or exhaust. Anybody else?

 

[Triton46]

You haven't provided enough info (mileage, power, etc). It could be alot of things but these will help narrow it down (FPR, Filter, MAF, O2, etc).

 

[Dre]

OK, so:
1994 Limited, 99K miles, engine with no mods except for open K&N filter and Split Fire plugs and wires. I cleaned MAS not too long ago. Fuel consumption seems to be getting back to normal at about 10-11 mpg. It was worse just a few weeks ago but that could be associated to cold weather. Although I have 3.73 gears and I'm currently running 31 inch tires. Power is still OK, no significant differance here.

Later,

 

[Triton46]

10 to 11 ain't normal friend. I'm thinking with your mileage it is probably the FPR. Some have said that decreased performance is also a sign, but mine never had bad performance during this time. This little bugger goes out about 100k...on mine it went bad at 96k. If you're not getting check engine lights, you probably will soon. The FPR looses its ablity to pressurize fuel so you start running rich. The rich fuel fouls the O2 sensors triggering a CHECK ENGINE (computer thinking you have an emission problem). If you change the O2, things go back to normal but only until the FPR has sent enough rich fuel to foul the O2 again.

You should probably be getting closer to 15mpg with your 3.73 and 31 inch tires. I have a stock 91 Sport that went from 10mpg to 18/20 (city/highway) by fixing the FPR.

 

[Dre]

thanks, I should look into this baby soon. (and what would I do without you guys???????????)

Does that mean that I'll have to replace my O2 sensors now too?

 

[Triton46]

If you're not getting a check engine light, I wouldn't worry about it at this point. But just be aware it might popup soon after the change or before the change (depending on when you do this).

 

[Rhett]

I am not sure about this, but I think a stuck EGR valve can cause hesitation and jerkiness in the engine.

1994 was the first year for EGR on the Explorer.

 

[Raasch09]

Where is the fpr valve located and what does this part usually cost