97 d1 rpm fluxuation

[pdXDisco97]

New issue popped up last night. When traveling around 30-35 mph, letting my foot off the gas and coasting caused the rpms to drop and "bounce" from 1000-1500 in rapid succession. Sometimes as many as 10 times, sometimes only 2 or 3 times.

97 d1, 154000 miles

 

[robertf]

time travel?

 

[d1driver]

Did the actual engine RPM change or was it just the gauge?

 

[pdXDisco97]

robertf, I checked the flux capacitor, it was working fine. that's what I get for posting before coffee.

Yes, the engine was revving in relation to the tach. But the truck wasn't lurching or anything, just revving. It didn't do it today on any trip.

 

[96discoI]

Could be the MAF. Mine fluctuated like that intermittently until it did it all the time.

 

[singingcamel]

I'd say you have a vaccum leak , check all your vaccum hoses for cracks .

 

[96discoI]

X2 on the vac leak. many places to check but the one I missed and the one a lot of people miss is the little one on the back of the fuel pressure regulator. while you are at it, check the schrader valve on the fuel rail. My valve was old and leaking. it is a cheap fix but if your valve cap breaks, it will spray fuel all over the top of the engine and that will not be cheap. luckily my cap was good and I only found it because I tried to test my fuel pressure and it sprayed me in the face...

 

[apg]

Could be the idle air control valve. Symptoms are the revs 'hunting' - going up and down between almost stalling out and 1500 or so. Simple, no bux fix: remove and clean both the unit and its port.

 

[pdXDisco97]

Thanks guys. I actually sold this disco (I still have my XD) to my brother-in-law, so I will pass this information on to him.

 

[singingcamel]

So , couldn't fix it so you sold it .

 

[pdXDisco97]

Actually, he had already committed to buying it, the fluctuation happened while I was driving it the day before we drove it up to Seattle to deliver it. The hesitation never happened on the trip, and I told him about it when he took the keys.

What I didn't tell him about was the dead mouse in the passenger seat. My sister in law is going to love finding that!

 

[discostew]

So , couldn't fix it so you sold it .

I couldnt fix a diesel oldsmobile one time so I bought it.

 

[discostew]

Is the trans looking for the right gear ? See if it happens on decel in nuetral