KA24DE w/ 62,000 miles loss of power above 4000rpm

[brage]

The following is referring to a 1996 KA24DE in a 1995 S14 240SX.

Just looking to get some quick opinions on the most likely cause of a power loss above 4000 RPMS...

Here are the symptoms:When under load the car will accelerate normally to about 4,000 rpm, after 4000RPM the car just seems unresponsive if I go WOT it almost feels like it is hitting the rev limiter. Also, starting at 4,000 RPM the engine starts to get very loud and sounds "cammy". This sound is only heard under load. When the engine is revved in neutral it sounds normal.

The fuel injectors are from my old motor which had approximately 106,000 miles on it. Everything else came with this engine and has ~60,000 miles on it.

The problems came up after I tested the compression and installed new spark plugs. The compressesion checked out at ~195psi on all 4 cylinders. The timing is set at 17 degrees BTDC.

After I started experiencing this problem, I thought I would try checking the compression again and switching back to the originial plugs (I had switched from OEM to Bosch platinum +4s).

The compression once again checked out at 195psi on all four cylinders. After the orginal spark plugs were installed, the problem did not dissapate.

Looking for some insight, information on where I should start debugging this problem, perhaps whether I should bring it to a mechanic, although I haven't found a mechanic around here i trust. I was just about to install the F-Max stage II turbo kit on this car and I need to get this resolved first.

I have new injectors, MAF, ECU that will be going into the car along with a new walbro 255lph HP fuel pump w/ S14 compatible sock. The turbo kit is sitting in my garage awaiting the resolution of this problem

[NISTECH]

you say the car ran fine before you put plugs in it? is that all you did to the car(comp test and threw plugs in)? if so i would say possibly you got some wires crossed.

[brage]

only other thing that changed was I filled up with 87 octane, when I have always used 91... Also I followed the FSM procedures for compression testing, including the fuel presure release method as well as disconnecting the distributor harnesses. (perhaps I am getting bad contact there?)

-jeff

[NISTECH]

thats a good possibility. check the connector terminals for excessive opening too. If they are to wide you can slightly bend then in with a scribe,or some other sharp pointed object. also check the connection for corrosion.

[brage]

thats a good possibility. check the connector terminals for excessive opening too. If they are to wide you can slightly bend then in with a scribe,or some other sharp pointed object. also check the connection for corrosion.

thanks, any other suggestions on what I should pay specific attention to (problems you have seen as common that would cause this etc?)

[NISTECH]

since you didnt have a problem before i wouldnt think it could be a common prob. but some of the things i se on those engines is egr problems, vac lines disconnected, air flow meter harness problems.

[brage]

since you didnt have a problem before i wouldnt think it could be a common prob. but some of the things i se on those engines is egr problems, vac lines disconnected, air flow meter harness problems.

Thanks a lot, I appreciate it. I'll give some attention to those items and see how it goes...

Thanks,Jeff

[brage]

Well I just tried checking all of the connections in the area where I was working ... both harnesses on the distributor as well as the MAF and AIT sensor harnesses... I cleaned them and applied dielectric grease to the contacts. No luck Still losing power @ 4000rpm with A/C off and 3500RPM w/ AC on. 1st and 2nd gear seem to rev fine, but at higher loads - 3rd and 4th gear are just **** after 4000

-jeff

PS- is there a chance that filling up w/ 87 octane had anything to do with it?

[D-UNIT]

I think so. 195 c.r. is kinda high for 87 gas i.m.o. Before you start getting all crazy. You should do what you know works. (91 oct.) My car runs really bad without it.

[brage]

I think so. 195 c.r. is kinda high for 87 gas i.m.o. Before you start getting all crazy. You should do what you know works. (91 oct.) My car runs really bad without it.

195 isn't the compression ratio it is the cylinder compression. very different things

[D-UNIT]

Thats what I meant. Jeez!! Is your engine rebuilt? Did you cut the head? Because your CYLINDER COMPRESSION( must think when tying) is higher than normal imo. Sorry bout that, btw. where I'm from we have 92 oct.

[bruinbear714]

Your compression looks good... but your timing + 87 octane could be the culprit.

Try running 91+ octane, and set your timing to the factory setting of 20d btdc. Look on the 240sx faq section under Timing Change on how to do this.

Also, run an ecu diag code check and see if any codes pop up.

Start there, and report back on how it runs and if any codes show.

We once bought an 89 240SX with an sohc engine that wouldn't rev past 3500rpm and it turned to be faulty injectors.

[Thee 240sx Owner]

Ya faulty injectors and fuel pump/filter can be a problem... My 89 started to go past 4000rpm when it was in 3rd 4th and 5th. I thought maybe it could be the fuel regulator but it wasn't Ended up being that my fuel pump was slowing dying and wasn't providing enough fuel for the rest of the gears... You may want to check that...

[brage]

Ya faulty injectors and fuel pump/filter can be a problem... My 89 started to go past 4000rpm when it was in 3rd 4th and 5th. I thought maybe it could be the fuel regulator but it wasn't Ended up being that my fuel pump was slowing dying and wasn't providing enough fuel for the rest of the gears... You may want to check that...

what did it sound like when this happened ? I am seriously thinking that the fuel system is the culprit here.

-jeff

[Thee 240sx Owner]

Felt like umm like it was stalling out when it hit 4k... When it did that unless i took my foot off the gas.. Its would put and choke and felt like it was bout to die.. One time i could only do 55 in 5th on a major highway.. Really bad.. The next day is when the pumped died...

[brage]

Felt like umm like it was stalling out when it hit 4k... When it did that unless i took my foot off the gas.. Its would put and choke and felt like it was bout to die.. One time i could only do 55 in 5th on a major highway.. Really bad.. The next day is when the pumped died...

any mechanical noise at all or just bogged down?

-jeff

[Thee 240sx Owner]

No noise except for my motor moving back and forth from the putting from lack of gas.. but thats bout it

[p00t]

make sure your not running boshe, make sure your "oem" ones are ngk. coulda been switched before during a previous tuneup.

your gonna have to test fuel pressure and MAS voltages.

[brage]

I solved the problem long asgo, thought i'd post it in case any one else experiences this. The problem was the last place I decided to look. The catalytic converter was all broken up and was restricting exhaust flow.

-jeff