well i went to look at an s5 today because the guy that is selling it is selling it for cheap because it has an engine problem. i go there and talk to him and he claims that last week he felt a sudden loss in power. when i test drive the car, its starts up but its idle is erratic, engine response is slow, and its just fucked up. so after i went around the block, i check if he has blown coolant seals by checking if the exhaust is pushing the coolant out, and noting, coolant seals are fine. i check to see if tps is plug in all the way and its, i did the same thing with the maf. so i suspect its fuel related. the best way i can describe it is that when you rev it, it feels as though something is holding it back. like its not free reving. it does not backfire, no smokes, i just really want it so i can have 2 fcs. lol. idk. maybe it could be a clogged cat. lol. so wat do you guys think?

 

Could be a sudden vac leak, could be the CAS failed or came loose, could be TPS. Seriously though it could be a hundred different things. Is this a TII or NA? Any smoke? Hard start?

 

Clogged cat I would think is a possibility. Mine would start & idle fine but had no power & would only run at about 2800 rpm's, wouldn't hardly go uphill. I was about to panic. I came on this forum back in 2002 and figured out it was a clogged cat. If its the original setup I would guess its probably KAPUT!! you could buy or make a test pipe & remove the cats to know for sure also is possible to gut the insides of the cats.

Ramses666

 

How's the compression? Bad idle and sudden loss of power is what you get when an apex seal goes on you.

 

Yeah a compression test is a good idea. The thing about these symptoms is that many things can cause them, so start with the most likely/easiest/cheapest things to test first.

 

I would suspect that a compression test with clogged cats would read strangely but would indicate the difference in pressure of a blown apex seal. It would be easier than putting in a test pipe instead of cats. My bad cats came on pretty suddenly - it went from hero to zero in a few miles.

Ramses666

 

its an 88 na. it starts fine but it idles bad for a few minutes. like you have to hold the gas down to keep it alive. but then it'll idle fine. so far if i do get it, im already expecting a rebuild. it does already have 170XXX miles on it. so yea. thanks for the replys.

 

Clogged cats probably aren't going to inhibit flow much during startup. Some, but I bet not enough to knock a compression test down 10% or more. There really isn't much air flowing during cranking, and while significantly more at idle, it's still not a lot flowing. Ever watch the air flow signal at idle? IIRC it's only around 2-4% of the full range. Cranking would be much less than even that, the volume of gases out during runtime is much greater than the volume of gases put in, because the gasoline vaporizes, ignites, then expands (a lot) during combustion.



170k miles is quite a bit, you'd do well to take a compression test.