This car has 210k miles with very minimal problems. I’m the original owner and have always done my own repair work. For the last two years the car has been surging on acceleration. It is fairly rapid surging and it is intermittent. When it is especially bad I can let up on the throttle, press again and it may be OK…until the next time I accelerate. I have replaced a lot of parts, there are no trouble codes and nothing noticed in the data streams. I’ve tried four throttle position sensors (second one failed and set a code) and nothing makes any difference. Here is a list of other parts I’ve replaced since this problem started, again nothing changes the surging, fuel pump (failed level sensor), fuel pressure regulator (pressure was on low side of range), idle air motor, map sensor, mass air flow sensor (swapped with my S10 pickup). I’m planning to donate the car to an organization after I get this problem fixed (my wife won’t let me donate it with the surging problem since it could be safety issue if the car doesn’t accelerate when its needed).
Another Saturday and another part replaced, the EGR valve and the problem still continues unchanged. The only other sensors I can think of are camshaft position, crankshaft position, AC pressure. I’m pretty sure the O2 sensors would set a code if they were a problem.
I noticed you didn’t mention the fuel filter in your list of replaced parts. It could be that simple. A clogged fuel filter can cause surging on acceleration.
I just forgot to mention the filter. It was replaced too. I’ve also replaced spark plugs and wires.
I had a feeling it was just an oversight.
At first I thought it was the locking torque converter and it still might be. Two years ago the transmission got hot in Colorado, I added some Lucas product and got home fine. Soon after I got home the surging started. I change the transmission oil and then a few months later took it to a transmission shop. They couldn’t find anything wrong, a few months after that I took it in again and they still couldn’t find a transmission problem but they flushed the oil that time. None of that changed the symptoms at all.
Sometimes I step on the gas and it doesn’t seem to have any power, let up and step on it again and it is fine. Going down the highway and come to an uphill grade, open the throttle a bit and it starts surging. Let up on the gas and step down again and it is usually fine till I come to the next hill.
Doing an oil flush only flushed some extra dollars out of your wallet.
They knew it was not going to clear up your problem, but they wanted to make sure to get into your wallet deep enough.
Never do an engine oil flush, or a tranny fluid flush. All it does is loosen up deposits that are sitting quietly in the nooks and crannies and mixes them into the fresh oil or fluid. You could flush an engine for hours and not get 50% of the sludge out, and the other 50% is loosened up to mix with the new oil or tranny fluid.
What about the air filter and have you cleaned the throttle body.
Also check the air intake duct to be sure that there are no tears in it. There can be small tears in the ribs that are hard to locate, and make sure both ends are on …clamped down snug and there are no leaks…
Looked at both filter and air intake duct today while replacing the EGR valve. Both are fine. I cleaned the throttle body with some spray cleaner a while ago. The throttle body shaft seems to be fine without excessive play.
Is the frequency of the surging always the same? Is it more like once/second? Five times/second?
Maybe that MAF sensor off the S10 was no good.
The MAF sensor on the S10 worked fine on the S10 and the Venture’s MAF sensor is fine on the S10. I’ve been swapping whatever parts I can across the two vehicles thinking that some day the problem will show up on the other vehicle.
The surging isn’t severe but it is more than once/second. Most passengers don’t notice it. I’d guess something like 2 to 3 times per second. If I let up on the throttle just slightly it immediately quits surging. Its not like an engine misfire.
It does sound like a clutch misbehaving in the transmission.
Is there a simple way to disable the clutch? I looked at the wiring diagram and thought about pulling one pin on the transmission connector but it sure is hard to reach. I suppose I could cut the wire elsewhere in a way I could splice it again if that isn’t it. When I took it to the transmission shop I suggested it might be the clutch but they said everything checked out OK both times they had it in the shop. The transmission getting hot in the mountains and then this problem very soon after makes me think that’s what it could be. Are there diagnostic tools that can command it to lock or unlock? As much trouble as I’ve had, if its an engine problem, you would think it would have set a code. My transmission expert friend passed away recently so I don’t have his help anymore.
Yes, a factory level scan tool will command the transmission to do various things, such as shift gears, lock/unlock the clutch, etc.
This doesn’t necessarily have to be at a dealer
There are aftermarket scan tools which have high capabilities, which a well stocked shop might have
Well my problem is the locking torque converter. I found the TCC wire at the transmission connector and cut it. The car runs better than it has for over two years. I also discovered I could have diagnosed the problem by pressing the brake pedal enough to turn on the brake light. The brake light switch contains contacts to unlock the TCC. Sure would have been easier.
Thanks for the fix @DustyB. I take it you’re not replacing the torque converter?
No, I’m not replacing the torque converter on a car this old. Its been reliable even with it surging for over two years. Now I know what the problem is and I’m not spending any more money on it. The TCC hasn’t been working properly for so long I no longer need it and it doesn’t surge anymore. I did splice the TCC wire, unplugged its wires from the stop light switch and turned off the SES light. We’ll see how long the SES light stays out.