1997 4.6 dead spot off idle

Jmc6000

New Member
Sep 25, 2019
1
0
1
38
Lebanon, OR
Just bought a 97 Automatic with 180,000 miles on her and she runs great. Nice and smooth no no CEL on or any other warning lights for that matter. Before I picked it up the car was sitting for about 9 months that was started occasionally throughout that time. So there is at least a 2 second delay by the time I mash the throttle while in park to the the time the engine actually revs up. In drive there is a 3 to 4 second delay when I mash the throttle off idle to where the engine starts to finally catch up to itself. Any help or ideas would be great. Maybe seafoam in the tank might be what it needs?
 
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wmburns

SN Certified Technician
Aug 14, 2009
5,842
505
194
Houston Texas
+1 on above. Also double check that the fuel pressure regulator intake vacuum reference line is connected and leak free. Verify that the fuel pressure is correctly intake vacuum referenced. That is the fuel pressure as measured via an external gauge jumps to 40 PSI when the intake vacuum reference line is disconnected.

I would be interest in knowing the intake vacuum at idle and under a load.

Have you cleaned the MAF? Have you looked for excessive carbon deposits inside the throttle body?

What have you done to rule out an intake vacuum leak?

What have you done to rule out a clogged exhaust?

What have you done to rule out clogged fuel injectors? Consider an injector cleaning and flow test service such as InjectorRX.com.

Do you have an ODB2 scanner? Do you know what the long term fuel trim (LTFT) is at idle and under load? Being able to view various PID's might make short work of your issue.

ForScan ODB2 scanner w ELM327 USB
 
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