No power above 2k rpm, idle is low, engine kicks and sputters wile driving

[Sijonda]

I have a 1991 240sx that has 220k miles on the car and 88k miles on the engine since the previous owner said he swapped the engine. I had a mechanic replace the head gasket, timing chains, both tensioners, and guides. this was done around a month prior to the breakdown. the car was rattling inconsistently also prior to the breakdown (yea thats me enjoying the car too much to park it) Wile driving I was listening to music rather loud and I felt a slight loss of power which increased as I drove home. Now I have no torque and it sputters over 2k rpm. I'm at a complete loss since it idles lower then it used to which was at 1k-1.2k now it idles around 500 or 700, but it idles smoothly. I now have it up on jack stands with the cam cover and upper timing chain cover off to see if I could find anything broken. so everything looks fine except the for the valve lash on 6 of the valves. the one thats farthest out is .011mm on the intake side, which is suppose to be between .012-.015 that would explain the rattling sound from the top of the engine but the second rattle is still a mystery since the tensioners and guide are still in fairly new condition (I tossed the upper chain guide since people seem to do it) I don't think I have a clogged catalytic converter since I still have power below 2k rpm and I don't think I have a bad fuel injector since it idles smoothly when its not under load.

Anybody have any idea of what could be causing this?

[onosqv]

2k issues sound like unplugged / bad maf.

turn off carunplug the mafturn on car

does it behave exactly the same w/o the maf? if so, it's your maf and/or maf wiring.

all the other stuff you wrote about, I didn't look at (rather deal w/ the simple issue first).

[Sijonda]

I'll try that next, now I just gota put it back together.Thanks for the quick response

[Sijonda]

I put the engine back together and I have the engine idling smoothly. I started it up, let it idle for a bit then unplugged the MAF sensor. idle went down a little bit and got a "little" rough but nothing much. I'm not sure if its bad or not since it didn't exactly do nothing.

[onosqv]

No, no, this is how you test it:

- with everything normal & plugged in, drive around, if you have ur problem w/ above 2k, okay.

- now TURN OFF the car, unplug the maf, turn it on, drive around - if it feels exactly the same as before, then you have found ur problem - bad maf or bad maf wiring.

[Sijonda]

OH.. OK, well today I checked the error codes and got a code 34 - detonation sensor/knock sensor. I really don't want to drive this thing around with all this noise. I'm not sure if something will get worse the more I run the engine since these noises are REALLY loud, I also don't want to break something else wile driving it around. The car now idles at 1,100 rpm not 500-700. So according to you I didn't check the MAF right so I'll write it off for now as a possibility for the power loss, but not the noise. If a bad MAF is whats causing all the loud rattling and knocking then I'll replace it right now, but I don't know that. I feel like if I don't fix the noise it could end the life of this engine. I can deal with the power loss later. I also understand that figuring out what a sound is being caused from without being there to hear it is next to impossible so, unless anybody knows a trusted mechanic in the Bucks County area I might be SOL on finding whats causing the rattling. I'm going to do a compression test in the morning next since I'm zeroing down the noise in the top to somewhere around the valves. it also sounds like one of the chains is hitting the covers but everything is still tight and working as it should, just wish I could turn the engine over really fast to see what everything is doing.
Modified by Sijonda at 9:32 PM 8/8/2008

[onosqv]

i didn't read anything in your previous posts about any noise - i give advice based on what you write - you may have made things worse trying to fix this yourself... perhaps it's time for a mechanic or someone more experienced to look @ it for you in person. gl.