2002 GMC Savana 3500 cargo van with the 6.5 diesel, has ~185k miles on it. No mechanical failures so far.


The other day while climbing up a hill on cruise control, at 65mph (same route I do every day, same hill I climb every day at same speed) the van lost power. It kicked down out of overdrive, and slowed all the way down to almost 50mph. No smoke coming out of the exhaust. It was hot out but engine temps weren't too hot, below the half-mark on the gauge.


The van felt like it had suddenly lost half of its horsepower. I drove it another 20 minutes and it felt weak the whole time. I finished work and shut it off, hoping it would re-start in the morning!


Next morning it started and ran fine. It's been running normal ever since.


Any ideas what this might have been? It really had me worried, it sure was a relief to discover that the problem went away but I'd sure like to know what it was.


No SES light or anything like that, BTW.

TDG or gmctd have good working knowledge on the PCM/pump operation and could probably speculate as to the hiccup as it were.


I wonder if you saw the MIL lamp while it lost power? If not I would think fuel. Either the quality or If you had water in your tank and passed some going up and down hills or even what the filter looked like.

What is the MIL lamp?

Malfunction Indicator Lite same as SES service engine soon, when was last fuel filt change, and have you looked at lift pump recently possibly early indication of problem there or power to it would be my 1st guess since it did not shut down all the way, an IP with out lift will run but stumbles under load as it has to pull from the tank with no assist.

The last fuel filter change was about 30k miles ago. I had the lift pump go out on me about 6 months ago, had no symptoms at all, I don't know how long it was out for but I found out the hard way when I changed my fuel filter and it wouldn't prime. This one's fine, I can hear it when I turn the ignition on.

Couldn't hurt to change a fuel filter with 30,000. I change mine at 10,000 intervals.

Actually I was planning on changing it anyways, bought one at the dealer yesterday and brought the van in for an oil change today with the new fuel filter. What do you know, the parts guy gave me the wrong filter, so it'll have to wait till next time.


I change the one in my dmax every 10k miles but I put way too many miles on the van for it to be economically feasible. I just run a steady trickle of Stanadyne in the fuel and change the filter every 6 months (~50k miles)

put way too many miles on the van for it to be economically feasible. I just run a steady trickle of Stanadyne in the fuel and change the filter every 6 months (~50k miles)


What did you pay? They are only about $12 at the parts stores around here.


On edit: Are they different than on a pickup?Edited by: whatnot

get codes scanned sounds like you kicked into "limp" mode usually electrical problem esp. if it ran fine the next day. check codes and look for crapped out sensor, sol., ect., ect. 185K? about time for every replacable electronic device to start dropping off about one every two months. it's a shame that any of these $30 parts can make a $30,000 vehicle run like s**t. thats the only reason i'm working up a conversion to mech. pump. i want an engine that will run under water and do it reliably on just one wire to keep the main fuel on.Edited by: lupey6.5

I didn't know the 6.5 even had a limp mode. I'll have to take it to the dealer. They told me that if no warning lights came on they probably wouldn't find anything, but maybe they're just being lazy or the guys who answer the phones are answering phones instead of working on trucks for a reason, lol..


I think the filter is different for the van, I recall paying around $50 for it last time, so they would probably be $30-40 in US funds.

I too have a van, and the filter IS different than that in the truck. NAPA was the only one that came through and had the right one. Autozone gave me the wrong one, called them, and they said, it was right according to computer.


As for the problem, no SES light, a few things to try: Check your fuel cap and see if there is a vacuum in tank. Maybe your IAT sensor is getting weird. Hot day, it thinks your intake temp is getting too high, and cuts fuel back. Just a theory. Any takers on that theory?


You can have some local stores like Azone read your codes for you without the $100 computer hookup fee from a dealer.Edited by: knkreb

iat sensor is a definite possibility. but get codes read, start there. get back wih us. guuuuud luk!

Do you have vacuum in the tank when you remove the cap?


I just remembered reading a long time ago on the diesel page about someone with a motorhome that couldn't get up a hill till he loosened the cap to relieve the vacuum.


Might be worth a try if it happens again.

It should have a slight vacuum just not a whoosh! of air sucking in. Try it right after a drive.

It should have a little pressure, not vacuum. Even a little vacuum will make the fuel pump work harder. They make the caps hold pressure too keep fuel fumes from escaping. (emmisions stuff)

There's always been a bit of vacuum when I pull the cap off, definitely not excessive.


Thanks for the tips guys, I'm just going to keep on running it and if it does it again I'll wheel it into the stealer. I don't know of any auto parts retailers here that have the equipment to plug the van into, but thanks for the idea.

How much fuel was in the tank, possibly a leak in the tank pickup allowing the fuel system to temporarily draw air into the fuel system.

Tank was probably 3/4 full.

There is a limited number of things that could have caused the 'hiccup' you describe. You said it continued to have low power the rest of the way home points to a sensor problem, air would have cleared when you crested the hill, boost problem would create lots of black smoke. It is possible you have a PMD problem on the horizon, but I would reccommend changing the fuel filter as good measure, and cut the old one open to have a look at the filter media inside. EVERY van we get in we do this to show the customer because they're all black and filthy, and its because its harder to get to under the chassis and its more expensive than the truck filters. Inconvenience is no excuse for neglect. Your truck is an '02, but 185k is 185k no matter how you look at it your maintaining a vehicle thats getting close to the 200k mark.