sudden loss of power (92 240, ka24de)

[aradapilot]

I drive a 1992 240 with a ka24de bone stock, save for high-flow injectors. 120k on the block and 20k on the head. she ran absolutely flawlessly until monday, when on the way home from work (~80mph on highway) I noticed a significant loss of power and more irregular engine noise, chugging, like a misfire. When I got down to normal road speeds there was significant shaking, and my idle bounces between 500-1000 where before it held a perfect 750. Stalled once at idle. The motor shakes like a bastard at idle. Also there is now a distinct rattle coming from the motor, especially from 1000-2000 rpm

Also, when holding a steady throttle under no load...i.e. in neutral revving to 3500, it will not stay there...drops to 3000 or even 2500 with no change in throttle, then comes back up to 3500.

ECU throws no codes. plugs, wires, injectors, fuel filter I've changed recently. O2 sensor went a while back and was an easy fix, but it shouldn't have gone already. ECU test on the O2 sensor gives only 2-3 blinks per 10 secs as opposed to the 5 that are expected.

One thing I noted is that this started about 30 miles into a new tank of gas from a no-name station I stopped at when almost empty the night before. Am I just running on bad gas? I threw 2 cans of drygas into the tank, but I've only burned about a quarter of it so far as I haven't driven much since this started...but I've never had contaminated gas before and don't know the signs aside from what I've seen posted here which looks similar. If so, what sort of damage am I looking at? will that o2 sensor need replacing? new tune up? or is there another thing that might be wrong? Just surprised that this came about all of a sudden after thousands of miles of perfect running.

here is a (bad quality) recording of the rattle noise: http://www.zeropride.com/0618081823.wav

thanks for your input...

[SomedaySoon]

Honestly, I'd check to make your you don't have an injector unplugged, considering running on three cylinders have all those signs you pointed out.

Just a thought.

[aradapilot]

the injectors are all connected and getting in spec voltage. perhaps one is clogged though...the intermittance of the issue, i.e. running fine at 3500 then dropping to 3k and back up and down randomly...would lead me to believe that it's not misfiring on every rotation.

[Vegascorbin]

I would drain the tank and put in known good gas from a known station. YOu know where in your area. Try that for a while to burn the fuel in the lines.

After you put good gas in pull the plugs and clean or replace them as they may be messed up.

Sorry to say but what little I could hear on the recording sounded just like our engine just before we threw a rod through the side of the block. How is the oil and coolent? Any Smoke?

Hope it is just bad gas but could be more.

[danielsan]

sounds like a bad injector. check the resistance of each one. hell even easier with the engine idling unplug each injector one by one and take notice of which one does not cause a change in idle. the one that doesnt cause a change is the bad one.

[aradapilot]

so i drained the tank (hotwired fuel pump, hooray) and put in 10 gals of premium. should offset what was left in there. swapped in a new fuel filter and new plugs, the old plugs were (suddenly) dirty as hell but they fired when i tested them. also compression gauge showed ~175psi in all cyls. didn't have time to put any miles on it last night after this, but this morning i took her to work (30mi?)...marked improvement, but still not perfect. seems like that 4th cyl kicks in at higher rpms, then will stay going for a while when i drop them, then after a bit it goes back to how it was, then back to good, etc.

the rattly noise is worrying me...though i'm thinking it could be the timing chain guides? wasn't that a common issue in ka24de's? is this possible and if so is it a case of 'fix this or the chain breaks' or is it just an annoyance?

so what could be left wrong with this...maybe a bad O2 sensor? could that cause an issue like this? it looks like an easy replacement, right out in the open.

danielsan: injectors are all getting voltage, didnt think to just unplug them and see what happens, will try that.

vegas: what was wrong with yer motor that you threw a rod? nothing i've seen through working on this has led me to that thought, but if theres a problem with the de i dont know about, tell me.

[Vegascorbin]

Sorry for the confusen but mine WAS a SOHC. We have not taken apart the motor yet to figure out just waht went wrong. Anything can happen with a race car

If you can, try to isolate the location of the rattle. Timing chain guides will be in a differant location from any lower end noise. (We suspect we lost a berring and then self distruct sequence started.)

[atl92sx]

i have a similar problem, twice now, one with a 89, and now a 92, im not sure why but seems like 240s have this problem of spuddering...

some help would be greatly appreciated

[240vertkid]

the rattling sound is probably your timing chain hitting the side of the caseing..which is a timing chain tensioner..which usually starts loosening around 100 to 150 thousand miles..

and my 240sx is having the same problem where it runs like a champ, but then a cylinder will go out for a couple minutes..

but the tensioner isnt really a biggie..i mean you need to take care of it, or the rattling will get worse..and a matter of fact, i just bought a new one and it was $75 for the right and $12 for the left.

hope this helped ya lil bit..