ENGINE VIBRATES WHEN IDLING, AND SURGES AT ANY SPEED

Ford Explorer

Tiny

jay-son

June, 5, 2007 AT 5:12 PM

Hello;
I have a 96 ford explorer xlt 4wd with 300k v6 4.0L pushrod
and automatic transmission.

What It’s doing is: vibrate when idling, and surge at any speed.
When engine is warm or cold. The problem has gotten more noticeable over time.
I have changed plugs, wires, fuel filter and air filter. This has made absolutely no change.
The shop found no error codes or leeks on the intake manifold.

I know it could be a lot of things, what I’m hoping makes my problem unique
Is when I first start the engine (warm or cold) it runs at 1500rpm for 30 seconds
When it drops down then the idle gets rough. If I bring the idle back up to1500 manually
It’s still rough. I think it’s something electronic or the EGR system but don’t know where to start. Any pointers would be appreciated.
Thanks.

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3 Answers

Tiny

Rudpro

June, 5, 2007 AT 5:33 PM

If your sure there are no leaks on the intake manifold, vacuum lines and throttle body, my first guess would be the Mass Air Flow Sensor. It can become contaminated where it's not working right but it's not enough to set a trouble code. It can be checked with a digital multimeter. A shop should also be able to check it with a scan tool that reads live data. Let me know if you want the procedure for checking it with a digital multimeter.

Tiny

jay-son

June, 6, 2007 AT 8:46 AM

Hi thanks for your response. I just bought a millimeter I know works.
I get no resistance off the (GND) and (PCM POWER GND)
and absolutely no reading on the other of the connections. What I can t get from
my Haynes manual is if this is good or bad.
The sensor itself looks good.

Tiny

Rudpro

June, 6, 2007 AT 10:33 AM

If you private message me with your e-mail address I can send you a picture of the plug and what reading you should get. If I post the picture here, it will be too small and hard to see. You need to backprobe the connector with the engine idling, verify the reference voltage and ground, and take a reading on the signal wires.

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