Strange highway misfire on a 97 LR Discovery

[Alex Fry]

Hey all. I was having an issue with my Discovery. I was having a bit of spirited driving, racing my buddy in a bmw. I was running 5000 rpm+ for about a mile, and basically topped out my LR while going up a hill. (I hit 120 btw )

All was well as we slowed down before we saw any cars and we were laughing about it. About 10 minutes later I was cruising at 80 and went to accelerate a bit, and it seemed almost like it wasn't getting any fuel. It sputtered and choked. I let off quickly and thought "Oh shit" then when I went to hit it again it ran just fine. No noticeable noises afterwards, no funny smells, ran just fine all the way home.

My question is what could have caused this? I have a sneaking suspicion its my fuel pump, as I was low on gas while thrashing it wide open for several miles. Should I replace that or wait until I either figure it its good or it strands me?

It almost seemed like the damn MAF sensor came unplugged, but I dunno.

 

[Alex Fry]

Were you still low on fuel when the loss of power happened? Were you going up-hill or down-hill? Could have been any number of things even the transmission.

I wasn't really low on gas, a little less than 1/4. The power loss occurred on flat ground.
What would cause power loss coming from the transmission? it never seemed like it was slipping. Just felt like I let off the gas and when I tried to fuel it, it sucked air and the revs continued to drop. Then after 4 seconds all was well in the little land rover.

 

[Alex Fry]

Were you still low on fuel when the loss of power happened? Were you going up-hill or down-hill? Could have been any number of things even the transmission.

Maybe a clog in my catalytic converter? It does make a bit of rattling and is a bit dodgy. Would that cause the same sort of deal? It mostly sputtered but maybe it was getting fuel.

Again the sound was so brief, I couldn't get a good listen. Sounded like it was no gas, but it also sounded a little like a clogged exhaust, too.

 

[Alex Fry]

I wasn't really low on gas, a little less than 1/4. The power loss occurred on flat ground.
What would cause power loss coming from the transmission? it never seemed like it was slipping. Just felt like I let off the gas and when I tried to fuel it, it sucked air and the revs continued to drop. Then after 4 seconds all was well in the little land rover.

It could have been momentarily stuck in high gear/over-drive when you floored it while cruising which would account for a bogged down/very low RPM feel. Technically, you didn't lose power if this was the case your transmission just didn't downshift fast enough. Once you let off the gas, it properly shifts down and everything feels normal and responsive again. A torque converter slip would actually be the opposite and would probably redline the motor as it would be like if the motor was in neutral much like a slipping clutch would do.

Also, is your model a 4x4? If so, which mode were you in?

Maybe a clog in my catalytic converter? It does make a bit of rattling and is a bit dodgy. Would that cause the same sort of deal? It mostly sputtered but maybe it was getting fuel.

Again the sound was so brief, I couldn't get a good listen. Sounded like it was no gas, but it also sounded a little like a clogged exhaust, too.

A clogged cat could very well have caused it. The ceramic honeycomb structure inside the cat could have been broken already but only came loose and blocked your exhaust flow when you went wide open throttle for a mile. I have seen many cases of clogged cats caused by broken ceramic honeycombs which block the exhaust flow. Typically, the loss of power is pretty permanent though. Very rarely is it intermittent. Once the blockage occurs, it stays that way until repaired. But, you could have knocked a small piece into a position where it blocked the flow of exhaust and then knocked it out of the way again but I find it unlikely. That doesn't mean that you shouldn't have the exhaust checked. Are you getting any check engine lights on the dash? A bad cat will sometimes throw at least one O2 sensor code, the post-cat one. I am not familiar with The LR Discovery motor but I would assume that if it is the V8 model you most likely have dual catalytic converters, one on each bank with at least 4x oxygen sensors. But, sometimes, it is difficult to diagnose since physically damaged cats could still function in burning the proper amount of excess fuel which will not throw any O2 sensor codes. In that case, the easiest way to diagnose it is to take a long pry bar and tap the cat. If it rattles like a big metal baby rattle then you got a broken honeycomb. You could also simply unbolt it and give it a shake. If it turns out it does have a blockage and you live in an area where they are required, the best option is to buy a new one since used cats won't last very long. If you live anywhere that doesn't require them, replace them with a straight pipes and you will do much better against your friend's Beemer next time.

Thanks so much! I tapped the cat with a really long stick and the one on the left sounded like a nearly empty paint can.

Awesome excuse to get a new set of pipes for the rover. Thanks again!