Photon440

So, recently my engine has been giving me problems. 2001 Venture, around 125,000 miles (200,000 km for me) runs fine when cold, but once warmed up it starts missing severely, especially under more throttle and lower rpm. It's not like an individual plug misfire, more like the engine shuts of and starts, as if I was taking off from a stop sign while turning the key off and on two or three times per second. Any ideas? Two different OBDII readers assure me that there are no codes.

At first, the problem wasn't as bad, and once up to cruising speed it smoothed right out. But the past couple of days it not only got worse, but also continued to happen under light throttle at highway speed. I can't even climb a hill any more.

kevinkpk

Have you changed the fuel filter?

Photon440

Thanks for the quick reply. No, I had not changed the filter, simply because there were no low fuel pressure codes showing. However, it is a good idea and easy to do so I'll give it a try and report back.

Photon440

Okay, now I have changed the fuel filter. It wasn't particularly plugged - I could blow through it. Anyway, the problem is still there.

oldchevy

When was the last time a tune up was done it? You don't state what year it is or which engine it has. Running some Sea Foam through could also help along with cleaning the throttle body..

Photon440

Sorry, I thought all those Ventures had the 3.4 engine, I did mention 2001 in the first post. Last tune-up was about 14,000 miles ago. Thanks for the input!

Photon440

I put a fuel pressure test kit on the van and found the pressure dropping after running for a couple of minutes. Initially a little over 50 psi. it suddenly started to drop until it was nearly zero when the engine became a lot rougher at idle. When the pressure was high, unplugging the vacuum on the pressure regulator caused a jump (about 5 pounds) in pressure but it did nothing when the pressure was low. Since the pump appears to be on the way out, another one is now on order. I'll let you know if the problem was solved when it's installed.

Photon440

Just an update - with a new fuel pump installed, it seems to be running okay. I haven't tested the fuel pressure again, but so far it's running smoothly. So much for my earlier post when I mentioned that the OBDII had no Low Fuel Pressure codes showing. I would have thought they'd be there.

Photon440

Going backwards, I hadn't had the van licensed for a few months, I put it back on the road this week and it seems that the problem is still there, engine running jerky under load after it warms up. I guess the faulty fuel pump wasn't the cause of that. I'm wondering about the egr, I'll check that next.

Photon440

Rather than go through circuit testing on the EGR valve, I just replaced it. Well, it didn't change the problem. So I'm still looking for a solution to the problem of an engine that runs well when cold but jerks on any sort of mild acceleration after it's warmed up for more than five minutes.