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Topic: never had this problem before (bucking in curves only) SOLVED (Read 2372 times) previous topic - next topic

never had this problem before (bucking in curves only) SOLVED

http://p089.ezboard.com/ffoxthunderbirdsenginetech.showMessage?topicID=2144.topic

well, per the above link, i have chased this problem for several months now and its fixed thank goodness :)

my egr base plate gasket was ,i guess, all fuggerd up. It was new from my rebuild but upon separation, the paper gasket supplied by the kit just fell apart.

mystery to consider
i sprayed carb cleaner along the seems of my cfi to detect a vac leak and no change in engine rpm.

i hooked a vac guage up to the car and had a solid 17 or so psi.  WOT dropped it to zero but i shot right back up to 17 there abouts.

I checked the tps several times but this last time i checked it with a light bulb which was kind of neat.  you could see the light getting brighter and brighter ect.

i check my fuel pump presure and wiring

i checked my engine bay harness

i checked my alternator

i checked my rear differential a while back

i checked the HVAC system in the dash

i check and checked and checked then yesterday i said screw it and did a tune up.

as i stared at the cfi, i decided to pull it off so i could determine my options for deleting the CFI EGR aluminum base plate.

i found a couple britttle pieces of the paper gasket separated and cracked so i replaced it and all is well. 

Car now is back to liking 38psi fuel presure exactly and pulls constantly in passing gear like its suppose to do.

MY THEORY on why i could not detect a vac leak
the vac leak was small enough that carb cleaner would not make it stand out.

the vac leak was large enough that when i put the added load on the engine by calling on the power steering pump that it would stumble like a sommmbeyyyoch.

Re: never had this problem before (bucking in curves only) SOLVED

Reply #1 –
I have almost this same problem with my 87 3.8. Mine doesn't buck in turns but it will buck once in a while when I am just going straight. When I pulled the codes I got 84 and 31 which were EGR vacuum solenoid failure and EGR position sensor failure. Hopefully when I replace these my problem will be solved.

Re: never had this problem before (bucking in curves only) SOLVED

Reply #2 –
Greetings, I have an '88 5.0, I have been working on it for about 2 years now. Just to keep it running that is. I have a small issuee that I want to stiop before it becomes a big one. My car will start jumping or bucking when I level off at 45-50 mph. I am not sure what, how, or why this is happening. HELP.
On another note I am also hearing a very high pitch sound when I let off the gas, but don't hear it when I am speeding up.

Re: never had this problem before (bucking in curves only) SOLVED

Reply #3 –
high pitched sound might be vac leak?

Re: never had this problem before (bucking in curves only) SOLVED

Reply #4 –
Hey JCassity can you describe the technique of using the carb leaner to detect vacuum leaks a little more?

I’m pretty sure I have a leak somewhere, but I’m guessing it’s in one of the lines.

I’m guessing the carb cleaner causes the engine to increase rpms if there is a leak, but I’ve never heard of checking for leaks this way before (not surprising since I’m new to all of this.)


Thanks.

Re: never had this problem before (bucking in curves only) SOLVED

Reply #5 –
Carb cleaner (or anything along those lines) to check vac leaks
point spray along seems/hoses/fittings that are involved with vac presure.  the engine will usually sputter or change in rpm. 


to check for a intermittant wire or plug wire sparking to ground
wait till its dark out
spary water on plug wires and elec connections.  the spark will be assisted by the water by jumping thru it to ground.  You will see the physical spark easily if done at night or in the dark.


The end result of my not finding this problem for several months was a totally broken alternator/smog pump mounting bracket.  The missing that i expierienced while in a cure was so violent at times that i guess something had to give.  Ill be shopping around for that part unless someone can hook me up :grinno:

Re: never had this problem before (bucking in curves only) SOLVED

Reply #6 –
Quote from: workINprogress
Greetings, I have an '88 5.0, I have been working on it for about 2 years now. Just to keep it running that is. I have a small issuee that I want to stiop before it becomes a big one. My car will start jumping or bucking when I level off at 45-50 mph. I am not sure what, how, or why this is happening. HELP.
On another note I am also hearing a very high pitch sound when I let off the gas, but don't hear it when I am speeding up.


that does not sound like a symptom ive often heard of on the SEFI engines.  It sounds more like a symptom related to the idle control motor assy on a CFI (carb type) engine on the 3.8 where its just out of adjustment.

your IAC is suppose to extend a plunger out when gas is applied.  when you let off the gas, the plunger on the iac remains extended but instantly starts to  retract the trottle plate for you so you dont feel that bump bump bump or bounce bounce bounce feeling like its coming from the rear differential. While its doing its job properly, its sending out different voltages to the computer which end up talking to the trottle position sensor and the injectors in control of the pulse with modulation of the fuel supply.  If its sending wrong voltages cause its retracting too slow/getting stuck or not at all, the computer has to compensate for the lost family memeber by doing what it thinks is best.  I know that feeling all too well and know exactly where your coming from.  If you did not have this device, when you let off the gas,, you would have no choice but to feel an instant head to the windshield slow down effect (ie-head bobbing forward and back as you give and let off the gas. Its kind of like driving in first gear at 4 grand then let off the gas, then step on it again the let off.  Ive seen versions of this device in a spring loaded vac form mounted inline with the throttle cable but they all pretty much achieve the same thing.,, smooth out the effect of letting off the gas.  You probably feel a clunk in the rear end as well?  welcome to the world of fords :grinno:


start you own thread about this and well see what we come up with but id say,, pull the IAC and clean out the carbon buildup.

plug the IAC back in but dont install it.
turn the key forward only***no start
does the plunger extend out? if not , its broke or not getting a signal from somewhere land.
If it does extend, install and taker er for a spin.