Hey i'm new here and i'm hoping someone can give me the benefit of their experience . I've got a 90 Bronco, 351 and E40D transmission, 120,000 miles on it. I've owned it for a year and only put 6000 miles on it in that time, since i live 1.5 miles from work. when I got it i did a complete tune up (plugs, cap, rotor, wires, pcv valve, fuel filter, air filter, crankcase breather filter) and fuel pump (would not hold pressure as soon as pump quit running) The fuel pressure regulator checked out fine and now i dont have any fuel pressure problems. Then it started smoking black and was really hard to start, and erratic idle.....cleaned and then replaced the Idle Air Control valve but that didnt fix it...actually made it worse. Problem turned out to be Coolant Temp Sensor...... Ok so this was all last spring, over the summer in local (short trip) driving, or towing my boat to the lake, i was getting 11mpg....... not great but that's about all i expected due to my type of driving. I did replace the O2 sensor a few months ago , just because i didnt do it when i got the truck and it looked like the original one. Anyway now it seems to run fine BUT i'm down to 7.8 to 8.2 miles per gallon! filled up yesterday, 23.7 gallons to go 182 miles! the idle is still just SLIGHTLY erratic when she's warmed up...so slight that it's hard to notice..... anyway i was gonna check the timing and check for vacuum leaks this morning but i was wonderin' if anyone had any similar problems and what i should look for. There is no check engine light being set, BTW. i do have access to a snap on scanner if necessary but i'm not expert at this and my buddy that has the scanner is a transmission mechanic so he's not a driveablity expert either.... Thanks in advance, sorry this is so damn long!

 

Definitely check for codes. It will store them whether or not the MIL lights up. Then you can run a KOER test, and the ECM will check everything for you while the engine is running. If it finds anything wrong, it will let you know.



http://www.autoemf.com.au/eec4test.htm

Take care,
~Chris

 

ok i checked my timing and it was right at 10 degrees BTDC, and i checked for vacuum leaks with carb spray while the engine was running, everthing seemed ok. So i went to my friend's shop and we put the Snap-On scanner on it. It had a 'memory code' saying 'low EGR signal' . He pulled vacuum on the egr valve and checked the voltage with his meter and it was in spec. checked to make sure it's getting vacuum and it is. also check the MAP sensor and TPS while the scanner was hooked up. Both within specs. My friend (Who's a tranny man , not a drivability guy) said it's possible that the EGR valve or EGR position sensor is sticking intermittently, but everything checked out ok while we were working on it. Would an EGR valve or sensor that sticks only occasionally cause that much of a drop in gas mileage? (from 11 to under 8 ? ) ..... Also the tailpipe is not black or sooty at all, like you'd expect if it was using that much excess fuel.... I'm wondering if maybe i have not been supplying gas to one of the neighborhood kids while i'm sleeping or something, but i've never noticed the gauge to be lower than it was when i parked the night before........anyway i put a locking gas cap on so we'll see if that's the case.. Just seems to me that it would be running really bad and smoking black if it is really using that much gas!...... anyone have anymore ideas??

 

I say investigate that EGR a bit more. PKRWUD might have some more ideas on what could be wrong, but i had a similar thing happen with a thunderbird i used to have, i ended up just replacing the whole EGR valve.

its good to see another member from Idaho!

 

Sometimes when the code reports a EGR value, the problem is usually something that is connected to the EGR value, and not the EGR value itself. But a new EGR value is like $60 anyway.

There is a sensor next to the EGR value called a DPFE. It breaks often.

 

When testing the egr, one of the things you have to do is apply vacuum to it at idle, and see if the engine stumbles or stalls. Did your friend do that?

 

No it was not running when he put vaccum to it. he probed one of the wires going to the EGR position sensor and then applied vacuum to the EGR valve, and the voltage went up to 4.2 volts, which is what the manual said it should be. but i've got a vacuum pump so i can apply vacuum to it while running and see if it stumbles, i just don't have a multimeter to check the voltage. I'll try that tonight, but the engine never seems to stumble when i'm driving it. Anything else i should do besides just see if it stumbles? and if it does , does that mean bad EGR valve, or bad EGR position sensor? Thanks for all the info!

 

Hi K

You didnt say, but is it fuel inj? If orig. inj. thats alot of mileage. Wear/tear = less mpg.

Just a thought. Good luck on the fix.

OT....

 

What you are doing is confirming that the egr valve works, and that the passage is not clogged. If, at idle, you apply vacuum to the egr valve, you arfe essentially leaning out the mixture. You are allowing unmetered air into the engine, and the result will be a stumble, or even a stall. If it does that, the valve and passage beyond it are good. If the engine doesn't react to the vacuum pump, either the egr valve diaphram is bad, or the passage is clogged.

 

ok i applied vacuum to the EGR valve with the engine idling, and it did stumble .....if i hold vacuum on the valve it will actually stall. So i'm Assuming that the EGR valve and the EGR position sensor are both working fine. the EGR gets it's vacuum supply from a solenoid located next to the ignition coil, is there a way to test this solenoid? The code that was stored was "low EGR signal", but it was a memory code. We could not get it to set any code while we had the scan tool on it. I'm beginning to think there's nothing wrong with it, that it's just a gas hog......hopefully when the weather warms up i'll be back up at least over 10mpg. anyway thanks for all the info, if there's anything i've overlooked besides that solenoid i'm still open to suggestions.....

 

Short driving is not good could it be that the engine is all-carbened up dirty injectors could a simple bodle of fuel injector cleaner help? get that thing on the high way get it nice and hot.

ps i have a 1990 Ford Bronco ED 351w E4OD https://www.f150online.com/galleries....cfm?gnum=2884

 

i've run fuel injector cleaner thru it every so often ever since i've owned it, so if the injectors are clogged they are worse than what the stuff you pour in the tank will fix...there's a shop here that has an injector flow bench and he can test and recondition them but i think it's running too well to have an injector problem. After checking everything i can think of and finding nothing wrong i'm thinking it's a combination of (1) my type of driving--i drive 1.5 miles to work, shut it off....drive 1.5 miles home for lunch, shut it off.....drive back to work.......well you get the idea... and (2) the colder weather.... not only does it take longer to go into closed loop but also maybe i'm letting it idle a bit longer to get the heater working... and (3) there's a possibility that on that last tankful i was supplying gas to another car without my knowledge. I put a locking cap on it , plus i actually did some highway driving the other day , and i can tell by the gauge that it's doing better than last tankful.... I do eventually want to put better (free flowing ) exhaust on it, but i dont think that's really a factor around town......the other thing i'm thinking of is calling up Comp Cam's tech line to see about changing the cam to something that might be a little more fuel efficient....they've never steered me wrong in the past... Thank you all for your responses...

 

Reset your ECM, and see if the code comes back.