Hi I'm new to the forum. I've been searching around the internet but I haven't found any concrete answers. I'm not too car savvy, so I thought I might ask some people that know a bit more about cars.

I drive a '91 Montero 3L V6. When I try accelerating the car, it bogs down to nearly stalling out, then suddenly jumps rpms and accelerates normally for awhile. Then the process repeats if I let the gas off whatsoever (slowing down, coming to a stop etc) and then trying to speed up again. Getting on the freeway was a pain as it wouldn't accelerate past 35mph for about 45 seconds. The car idles fine when it's in neutral or park.
It can't be bad gas since I drove fine over the weekend. I can't tell if the engine is running rich or not. I burn oil and top it off every few weeks, so I'm not sure how to tell if I'm running rich or not.

Could I need a new fuel/air filter? Or clean the spark plugs? Sensor perhaps? Or even just add some fuel injector cleaner haha. Any help would be great. I'm a bit broke for the next 10 days till I get paid. Thanks ahead of time.

 

How many miles do you have on the Monty? Have you had the timing belt changed? I had a similar problem and had the timing belt changed and that fixed the problem.

 

It has about 185k. I recently bought the car about 6 weeks ago from a family friend. I could always ask him the last time he had it changed.
Also, I added more oil and poured in a fuel injector/carb cleaner, and nothing has changed.

Thanks for the help! If anybody else has had issues please let me know so I know what I can look forward to spending.

 

Doesn't sound like a timing belt problem to me. IMO, TB problems fall into three categories:

1) Belt is fine and the truck runs fine.
2) Belt somehow slips a cog or two on the cam gear and the timing is off making it run badly all the time, not intermittently.
3) Belt breaks and you have complete engine failure.

However - definietly do find out when the belt was last changed. If more than 80K miles ago you're pushing your luck and your "friend" is to blame.

Also find out when the spark plugs were last changed. 100K miles is about max for them.

After finding out whether or not your family friend took good care of these things you might want to go to a parts store like AutoZone or PepBoys and get a free scan for any error codes. Let us know if there are any and what they are.

Ron

 

Ron is right to start you off on a code quest; so many things could be causing the symptoms you're experiencing that you'll want to start there as a baseline on your vehicle's condition, especially since it's completely new to you and you are not, as you say, car savvy.

If I had a dollar I might be tempted to place it on the Thottle Position Sensor being bad, but we'll just wait and see what your trouble codes show...

 

i had the same issue with mine, new timing belt i put on skipped a cog and bogged down, also try and disconnect the harness going to your MAF sensor behind your airbox, may have a dead circuit in it as well. I run NGK plugs for 2-3$ a pop so they are cheap enough to replace every other oil change. if its a TPS, make sure it is set to approx .5v that could throw this off as well. without being able to hear it or see it its a litte hard to tell you exactly what it is but i dont believe its a fuel issure, more or less a timing issue. believe me, i have 196k on mine and i was troubleshooting an issue where once i hit 4k rpm felt like a rev limiter until you powered past it. changed oil, fuel filter, fuel pump, replaced o ring on injectors (possibility as well, the little donut that meets the manifold, had one cracked, shoot it with tb cleaner and tap throttle see if she evens out as well) replaced a bad injector that was weak but still spraying, and in the end, it was a bad MAF, 70$ used on ebay. check your plug wires if its a distributor system as well, not very familiar with the 3.0 or 3.5l just know my way around the 2.4l for now.

 

Thanks for all the help guys. I've been told that it might be the TPS or the fuel pump, as well as timing belt and half a dozen other things. I'm working on getting codes, but autozone didn't have the right hookup for it, so I took it into a shop, and he was baffled that I even made it there. He also, didn't have the right diagnostics equipment.
So today, I attempted to drive it from one shop, to a guy that's known for great work here. And the car stalled out (many times) and couldn't stay above 300rpms. So I coasted most of the way, but on the 20th or so stall, it decided not to start again. I got it towed to the shop and I'll find out in a day or two what the issue is.

Thanks again for all the input. It gives me a chance to give myself an estimate on what I could look forward to paying prior to diagnosis.