Sorry guys, Title said fourth gen... it's a 5th...

Hey guys. My FIFTH gen LS is acting up. Sometimes while accelerating (either from a stop or while readily traveling) it seems to plateau. The revs drop down slowly to idle and it stops producing any power at all. I can't seem to make it get out of it's own way sometimes. It works great other times, but this has me flustered.

It's been doing this for about two weeks. Other problems with the car are a loud ticking noise from the top end that I can't seem to quiet, occasionally the Check Engine Light blinks for a misfire, and I've got a constant CEL for something having to do with EVAP (even the mechanic who ran the OBD-II scan couldn't tell me what it needed).

I've replaced the fuel pump yesterday hoping it was just a fuel starvation issue, but I didn't have a few dollars for a new fuel filter (so that's on my "need to order list"). I also have swapped the MAF, EGR valve, and ignition coils/wires/plugs. Nothing is making a difference. I just thought as I was typing this that I should check my TPS. Does anyone have any other recommendations?

Thanks in advance guys!

 

well, the loud ticking's gotta be the lifters, my car does it too. sounds like its a small diesel, haha. but noisy lifters wouldint cause the problems your having.

other than the TPS, i would say put a new fuel filter in it and perhaps it could be the upstream 02 sensor has gone bad ( would throw the service engine light) but it could also be the trans... does it seem like the car is kinda stumbeling pulling away from a light or under mild acceleration?

 

Mine does the exact same thing around 2100 rpm when driving at 60mph. If i dont push the pedal to the max, i can hear the rpm going up, but the car isnt following. Like if there was a gap where even if you add gas... rpm stay there.
Honestly, it didnt bothered me that much... I use it as an excuse to push it to the floor when i need more rpms.

I dunno if it is related, but my pedal is loose. I can jiggle with the pedal from right to left for less than half an inch, and i can lift it(up and down) for maybe half an inch before it gives gas.

 

You need to have the mechanic with the scan tool take it for a drive and log the major sensors. IMO just shotgun replacing parts until something fixes it is a bad idea- you could be replacing perfectly fine parts (ie the MAF, fuel pump, EGR, and coils). Someone who is good at reading scan tool data (ie a mechanic) could tell you right away what is going wrong by just looking at the feedback from the sensors.

 

not just that when was the last time you did a tune up as in replace the plugs and if it did the same thing have the computer read at a shop to see whats going on

 

Thanks for all of your responses!

Skylark, 02's aren't throwing codes so I ruled that out. I thought about the tranny too, but it doesn't matter what gear you're in. I see it happen most of the time at 20, 35, and 65mph.

Monte quebec, yours sounds a little different to me. Your issue is similar to a torque converter issue I once had with a Celebrity.

Bumpin96monte, good recommendation but the scan tool doesn't have those features. I'd have to go to a mechanic that I would have to pay... and that; I cannot do. I'm not out any money yet. I've been swapping parts off my original motor onto it (parts that worked and didn't throw codes a few months ago). After I swapped out the fuel pump and sending unit my gas gauge started working so I'm not lost of time or effort from that swap.

Monte07
Plugs, coils and wires were installed in November.

I think I'm gonna try swapping my TPS and try to snag a fuel filter just for good measure (I have only owned the car since Nov. (I see a few familiar names in here from my motor swap thread back when I bought the car) So I'm still cleaning up other peoples problems).

 

You have a bad/clogged catalytic converter. That's what's causing the loss of power. It MIGHT be causing the CEL code to be thrown but that's unusual. Also, you didn't say what the CEL code was, so we can't do anything but guess at that. Any GOOD tech could tell you exactly what the code was for.
Start by having a pressure check done on the cat' and go from there. We've seen it WAY too many times around here, and you have all the symptoms, with severe power loss being top of the list.

 

Thanks, Rockn! That's a logical quote. I hardly remember that occasionally I smell an "eggy" exhaust scent, and the exhaust has recently gotten a little louder. I'm kind of afraid of exhaust work on this car though. It's a very rusty connection to the cat' from both ends and I'd rather not open a can of worms I can't close without hittin' rock bottom.

I'll see if I can get the car on another scanner and find out what exact engine code being thrown.

 

Ok... I got a few minutes today to check my TPS, IAC, and EGR...
TPS was filled with oil (I found this odd) so I replaced it. Didn't make a difference. IAC is dry as a bone. EGR was filled with a smooth peanut butter colored paste. I'm flabbergasted by what this could be. I cleaned out the paste I could see and swapped EGR's and it runs mint now. Any ideas on what this paste-like substance is? It doesn't smell like oil, it just smells like exhaust gas. Could it be a mixture of oil and antifreeze frothed up or something?

 

from what I've heard your LIM(lower intake manifold) gasket is bad, I'm sure you will get more people here pretty much saying the same thing!

I'm no expert, but I have a ton of time logged on the forum, goodluck, wish I had better news.