1992 Cadillac Deville the IAC

Tiny
REARDRIVE
  • MEMBER
  • 1992 CADILLAC DEVILLE
  • 4.9L
  • V8
  • 2WD
  • AUTOMATIC
Before I put on a new IAC there wa no service soon light on, but when I put the new IAC on, now the service engine soon is on. The engine is running high, so I took the shorter screw from the old IAC and put it on the new IAC that made the engine runlower but it still to high. Now there is three codes, E30, E98 and E52 what they mean and how fix the problems p/s can I put a shorter screw in the IAC to make the engine run lower
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Tuesday, May 27th, 2014 AT 5:57 PM

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Tiny
JACOBANDNICKOLAS
  • EXPERT
E30 - ISC RPM Out Of Range

E52 - PCM/ECM Memory Reset

E98 - P/N To D/R ISC Engaged Problem

Where I feel the problem is coming from is the E30. Basically, it means the PCM/ECM which controls engine idle by increasing or decreasing the throttle opening using the idle speed control motor (ISC) has failed or is not within the tolerance programmed from the factory. Code E30 sets because the actual engine speed never reaches correct RPM which indicates a slow or bad ISC motor. The ISC motor connector is located behind the alternator. Is that what you replaced?

As far as the other codes, E52 means there was a loss of power to the ECM/PCM. You may have disconnected the battery, ECM. You should just clear that code once power is replaced. This isn't the cause of the problem.

The E98 basically is part of the system that monitors the idle speed when the engine is in park or neutral. If the speed it too high, it will actually retard the ignition timing to slow the engine and prevent a harsh shift to drive or reverse. Again, that isn't the problem.

If it is the ISC you replaced, try this. Press on the ISC plunger. It should retract. When it bottoms out, unplug it. RPM should be around 400. Now adjust the plunger to throttle hammer gap to about.030". Once you reconnect the ISC, it should be good to go.

Let me know what you find.
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Tuesday, May 27th, 2014 AT 6:32 PM

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