Engine acting funny

These past two days I've been experiencing a weird problem: when I'm at slow speed and starting to apply the break, the engine races and the car surges forward. The tachometer goes from about 1k to 2k, I also notice the TOD trying to engage. Everything goes back to normal after a short time.

What could it be? Is it a senor or something?

The only thing I can think of is that I put some cheap gasoline in the tank (i.e. not Mobil, Shell, etc...) About 15 gallons. Could this have something to do with it?

as always, thanks in advance.

I've been getting something like that too. I'll start and it'll immediately die. Then restart, I have to give it some gas to keep the rpms up or it'll die again. After I goose it a bit it'll keep idling, but at low rpm, almost to the point of stalling. If I put it into drive, it drives fine. After stopping, killing the engine to go into a store, then restarting, it revs high, like 2,000 rpms and won't fall off. After I get it into drive it drives normally. Did that for two days, then cleared up today.

It's like the MAS/MAF combo is reporting the wrong combination, producing a weird mix. The odd thing is that it goes the the opposite extreme every time I start the truck. I'm not detecting any leaks in the intake or intake gasket. Very odd behavior.

I'm not sure if it's bad gas or what (filled up with some super cheap gas in South Carolina - very different mix from what the VX is used to in Atlanta). I'm replacing the gas filter this week to see if the problem fixes itself. I'll keep you posted.

-- John

Ive been having this problem as well. I have noticed that if I open the airbox, and let a little more air in, the idle speed returnes to normal a little quicker. In my circumstance it feels like a problem I had fixed once. I had a cone filter on the end of the MAF, and when I left humble Utah for Las Vegas, the change in ambient air temperature caused the engine bay to get extremely hot. In turn the engine was sucking very hot air (Due in part to the way the engine fan forces all the hot air right into that corner!!) and was telling the computer to "lean under power" and shut off the fuel supply. So then it would start to jerk, and stall out since it was receiving no gas. I am having this problem now, as well as the start and die, start and die and barely keep running, and the engine revving at 2K or so problem...... very frustrating. I think its a sensor though, maybe the MAF? Or perhaps the Throttle Position Sensor, or Intake Air Temp???

Don't know if this will apply or not. But, if you have aftermarket pedals (gas and brake) attached, it could be possible that the pedals may be positioned a bit too close together. If this is the case, when you apply the brake for a stop, sometimes the edge of your shoe can catch the edge of the accelerator pedal and thus apply gas to the engine while trying to stop. The symptoms are very similar to what you've described.

Happened to me a couple of times and caught me off guard especially coming to a stop. I realized what was happening when I noticed how close my aftermarket pedals were to each other. And that the edge of my shoe would periodically catch the accelerator depending on the angle of my foot and location on the brake pedal.

However, if you don't have the aftermarket pedals, examine where you place your foot on the brake to see if it's anywhere catching the accelerator pedal. Remember, that it won't happen to all shoe types. Just certain ones with a slightly wider edge lip around the ball of your foot area of the shoe.

And if that's not the issue, disregard this message. :mbrasd:

Same problem. Seem worse at home -5500 ft vs. sea level.
Roy

No aftermarket pedals here, this problem will happen with the trans. in park as well as drive. I have noticed a difference with elevation as well perhaps a Barometric Pressure Sens.?

HAHA Ron that has happen to me too...

I think we have the same razos.

I had the same problem....always on wierd hot days ..when the weather is one extreme (hot) or muggy....I think I read once on this site, where if this happens just open up the gas cap, it supposedly eliminates the vacum or pressure caused by the heat...it worked for me all the time...it's a bit annoying but it sounds like a little glitch from the engineers from Isuzu...

You guys got big feet....;pg;

I'm in Phoenix where it is REALLY HOT and have NEVER had this problem... maybe it has to do more with humidity?

Very humid here, especially with the cone filter.

About the pedal thing, I've had a reving issue with the mat riding up on the gas pedal - first thing I looked for.

-- John

I tried cleaning the MAF today. So far it feels like it has helped all around.... acceleration seems smoother and the idle speed stays far more level than before. Cleaning was really easy, the thing just comes apart into 3 pieces and i just sprayed it off with electrical cleaner. The 5 wires inside mine were black when I opened it up, and silver when I was finished. I really hope this helps somewhat.

...it finally threw a code about 2 weeks ago so I took it in for service. It was a faulty intake manifold gasket, and a few other things as well that were all taken care of under warranty. I'll have to check my invoice for the details, issue was our onboard computer compensates for these malfunctions on the fly and will not post a code until their is NO solution or something fails, so I drove all summer with intermitent problems. My VX is fine now, runs like new.

Funny how? Funny like a clown? ;)

Still having problems today. I replaced both the Intake Manifold Gaskets at about 80,000K, Im not sure what to try next.... I hate it when I dont have all that power! I threw another check engine light today so I'll get it scanned tommorrow. Looking forward to hearing what else they did for you Navigator.