[font size="1" color="#FF0000"]LAST EDITED ON 05-Mar-01 AT 10:01 PM (EST)[/font][p]I don't know why, but my check engine light on my 88 F-150 4.9 liter 4x2 just sort of flickers on when the engine is under a load(i.e. in gear and with my foot on the gas) It never stays on. However it doesn't do it when i simply rev the engine or I'm coasting down hill.

Another flickering problem is that my signal lights don't blink, they also just flicker at random, though I don't think the two are related.

Any advice or suggestions would be great.

~eriC

 

I had a check engine lite do that also and I replaced the electronic solenoid for the egr valve.It would only come on under load and in the a.m.when it was relatively cold outside and had no problems since.As for your t/s lights have you replaced your t/s flasher?? I'd start there,good luck

 

My '88 4.9 did the same thing, although it wasn't exactly flickering. Rather, the check eng. light came on and off rapidly, in one, twos and threes, if memory serves. If you don't have a scanner or want to use the check eng. light to pull codes, a quick test is to put a vacuum on the EGR w/ a hand pump, and see if it holds. If not, that's definitely a bad EGR valve. You may or may not have a bad EGR positioning sensor as well, but the vacuum test shows nothing re: the sensor. It's just a quick test of the mech. integrity of the EGR.

 

ok, i hate to sound dumb, but where's the EGR valve?

~eriC

 

When the light started flashing on my 88 F150 5.0L I took out the EGR valve position sensor, measured resistance at open/close position, put it back in and the flicker was gone <shrug>

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1988 F-150, 5.0L 302ci, 5spd, SuperCab. Shorty headers, K&N filter, Accell 300 8.8mm race wires, Accell supercoil, Accell rotor+cap, Bosch +4 Platinum plugs, RanchHand bumper. Soon: MSD 6a ignition and dual exhaust.

 

EGR Valve, it's located on the back of the Intake. Right up top, next to the firewall. It should have a White sensor and a Green vacuum line running to it.

 

Danke

~eriC

 

[font size="1" color="#FF0000"]LAST EDITED ON 07-Mar-01 AT 03:45&nbsp;AM (EST)[/font][p]Might b Giant (And Jake, from like 3 weeks ago!)

On the EGR valve, I thought my junkyard EGR valve had failed after 4 months, as I was getting bursts of "check eng." in like twos and threes, on heavy accel., and I was getting the bucking/chucking (Jake and I talked about) at b/w 1,600 and 2,100 RPM.

Well, when I went to put on yet another junkyard EGR valve, and I did my (home made) vacuum pump diagnostic test I mentioned, BOTH the old and new EGR valves were good. This was after the green vacuum line the fellow mentioned BROKE OFF in my hand, right below the black rubber fitting that slips onto the EGR valve, when I tried to slip it off the valve.

Okay, gals, (if there ARE any on this website???) this one's for you! While I was bemoaning the fact that this line broke and the replacement I had was wrong, MY GIRLFRIEND says "Maybe the only thing wrong was the vacuum line--maybe it was CRACKED prior to it breaking when you removed it, and you had a VACUUM LEAK, and THAT'S WHY YOUR CHECK ENGINE LIGHT WAS ON. Smart girl.

Jake: did you ever find out if you had vacuum leak, like you suspected, as opposed to a bad EGR, which I thought your symptoms were consistent with? Yes I did think of you after my girlfriend's correct diagnosis.

So I made up a vacuum line end using two different sized, snug-fitting pieces of vacuum line, reattached and all is good.

My girlfriend has an Art History undergrad degree, w/ an MBA on top of that. No, no formal technical experience, thank you. Yes, I am humbled....

 

 

Yep, my '88 F150 check engine light is doing the same thing.........flashes when its cold or under a load. Been doing it for about 2 weeks......while in the meantime I'ver replaced a headlight and a brake light........well, maybe there IS some connection between the check engine light and some electrical "short curcuit". Ya neva know.