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prestoh
Novice
Jun 1, 2005, 9:08 PM
Post #1 of 2
(5201 views)
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Hi I am a newbee to this I hope I can find the answer I spent all my fishing money on. I have a 1994 aerostar 2wd with 4liter auto. I get a carbon knock when under load but it will stop when I put the gas to it. I had all the tests done and canged plugs,MAS,and did all the decarbon things Ford said would work.The next step is to change the ECM. If you can help befor I spend next years fishing money I would be greatfull. Thanks Prestoh
one more eh
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 2, 2005, 6:59 AM
Post #2 of 2
(5194 views)
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Are you sure this is true carbon knock? The old spark plugs would have been a good indicator. That's usually caused by a lot of very slow driving over a long time, and the knock generally gets worse with increased load on engine. More common is spark knock, caused mostly by overadvanced timing. Timing gets automatically adjusted in your car from information from a few items.
For free - you should inspect all wiring (under hood) is securely plugged in. Also check hard for all the vacuum lines, elbows and connections. Listen for leaks too and if they shut up when moved or get worse you found one. Hose is cheap but use automotive hose if needed. Many vac lines go onto plastic lines that get brittle or burnt on things. you can just splice over any you may find.
One more for free - if you normally drive right about where overdrive kicks in (about 35-45mph) use the regular "D" unless you are going to drive faster. Overdrive will kick out and should under a fairly hard load which puts less load on engine, like downshifting reducing the chance for knock and gives you more power like to pass a car, or going up a steep hill. It you don't notice it kicking out it's not working right.
OK - that gives you some things to check out. Check back to say whether you found anything. If the problem is still there hit back and we can go on to some things that will cost some $. Good luck,
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