Idle loping
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Joined: Sep 2003
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Idle loping
I have a 1988 ford 150 4.9L inline six engine that starts fine. After warming up, the idle ranges from 200-500 rpm and sometimes dies. Power is reduced dramatically. I went and bought a scan tool($25.00)at Autozone but the tool isnt reading any codes and my "check Engine Light" is on all the time now. The scan tool just shows a constant light. Does that mean that the computer is dead? I have read about a power realy for the computer may be the problem. My gas mileage has dropped approx. 30%. NOTE: When I uplug the water temperature sensor when the engine hot, it helps the idle somewhat. Any ideas that could be the problem would be greatly appreciated!
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Joined: Aug 2003
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From: kansas
Idle loping
Sounds like more than one problem. Test fuel pressure, and fuel filter, however, this wont make lite come on immediately. Check EEC relay for battery voltage to engine computer. Check computer ground near battery. This is a single black wire with a pull apart connector. Check computer full time power feed. Ign switch may not be powering up EEC relay when key turned to run or start. Could be ign module problem. Unplugging temp sensor make computer think engine is cold so it richens the fuel. Computer has to be partially alive or engine wouldnt even run. Computer needs both ign on power and full time power to funtion properly. An IAC(idle air motor) with insufficient electrical resistance will cause the computer to not even try to contol idle. As you can see there are a lot of possiblities. Problem is, pre 91 fords have no data read out , only codes. Oh, bye the way, MAP (manifold vacumn sensor) could be goofy. Good luck . I,ll check back with fte to see if I.ve been helpful. Signed circledirt, ASE master, 408W ,550 horses roundyrounder.
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Idle loping
I tightened a wire-nutted black ground coming from the ECC relay. That solved the problem of the "Check Engine Light" from coming on. But on the first WOT test drive, the light came back on. Looks like someone has done some splicing of wires near the EEC relay. Gonna take the IGN module to Autozone for testing. Already replaced the TPS.
I found a clean '91 inline six engine and took the MAP,IAC. No change.
I found a clean '91 inline six engine and took the MAP,IAC. No change.
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Joined: Aug 2003
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From: kansas
Idle loping
Now you should be able to pull a code for the lite. Still idles too low? Maybe clean throttle plate and bore. Sometimes I cheat a little and adjust the throttle stop screw. Do this without the engine running or EEC will not know what minimum TPS is for a while. Runs alright other than idle problem now? I,ll check back,let me know.
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Joined: Aug 2003
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From: kansas
Idle loping
Not familiar with autozone code checker. How does it hook up? I,m used to snap-on or tech one. There is an IAT (intake air temp sensor) located on intake manifold. Wonder if its shorted or open? I couldn,t possibly walk you thru all the testing that may be necessary to fix problem on line. Does lite come on immediately at start up?Will your code checker run both key on engine off and key on engine running test? Is your checker just supposed to make lite flash for code(s)? Awaiting reply.
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