No Power Please Help

[kyleamiller]

I recently bought a 1990 300zx NA and it runs decent but there seems like there is no power. The previous owner did a motor swap so there are cables/vacuum lines that dont go anywhere, EGR valve deleted ect.

Things done so far:
Sparkplugs
fuel injectors
water pump
MAF
throttle postion sensor

Symptoms:

ECU is throwing the det sensor code

I tried to check the timing with an inductive type light but when I put it on the #1 coil the signal was barely there. If I disconnect the plug the engine dies. The signal on the other coils is erratic at times. When I remove the other cables one at a time the engine comes close to stalling.


Also if I turn the throttle position sensor all the way clockwise it runs ok but if i turn it all the way counterclockise then it is extremely bogged down, I cant rev past about 2k.

This is my first project car and I would really appreciate help/suggestions.

[t.mcginley.jr]

Vacuum leak is usually the cause of lack of power. What do you mean vacuum lines that don't go anywhere? Like they are capped or just open?

The det code could be a bad knock sensor. They tend to go after so many years. Its a b**** to get to though, located under the lower intake.

[kyleamiller]

sorry yes the vacuum lines are capped and Ive spayed starter fluid around the intake and chouldnt find any leaks. Im not too concerned about the det sensor at the moment though

[KornFlakeZ]

do a power balance test to check if any coilpacks have gone bad. coilpacks on the z are known for failing.

[t.mcginley.jr]

All hose clamps are tight? It still sounds like a vacuum leak to me. Did the PO correctly block the EGR ports on either side of the intake plenum (underneath)?

[kyleamiller]

update:

I cleaned the PTU and CAS conectors then cleaned the injector and coil connectors, all the injectors had a resistance reading of 12.3-12.5 and coils packs were all good. After all that the car is running much better but still not alot of power in low rpms like under 2K. Also noticed some smoking at start up in the engine bay by the firewall.

Yes clamps are tight and im not too familiar with the egr bc I never saw it but could the smoking by the fire wall be a leak from where it was deleted??

[t.mcginley.jr]

I did a quick search on this issue and it seems like the fuel dampener could be the culprit. It seems that after time the diaphragm inside could go, resulting in poor low end power but plenty of power after 3k rpms. This is the fuel dampener:

http://www.z32photoguide.com/images/fdfpr.jpg


Maybe grab a working used one and see if that clears up the issue then get a good new one after.


If it isn't that then possibly a bad TPS.

[kyleamiller]

That will be the very next thing I do thank you for the help I will update once I've tried it

[t.mcginley.jr]

Good luck! Hopefully that's your issue after all

[kyleamiller]

So I replaced the fuel dampener and the fuel regulator, but still no change. Low power. Still looking for suggestions on what to try. My next step will probably be to take off the intake manifold again and see if there's some sort of massive vacuum leak that I missed...

[t.mcginley.jr]

Does it idle rough or just have lack of power at low rpms? If it idle's rough too then you could have pinched an O-ring when you were putting the injectors in which causes a vacuum leak.

Another thing I was thinking could be an exhaust leak somewhere. Do you have a stock exhaust setup? See with an NA when your exhaust is too big (like 3") then you lose alot of low end torque and power. The same thing happens if you have a bad exhaust leak somewhere because it messes up the pressure in the pipes.

[kyleamiller]

It doesn't idle rough I did pinch an o ring tho when I did them and had to replace it. It was actually leaking fuel.

There is some smoking at start up behind the engine near the fire wall that could be exhaust... I will look into that but no the PO did headers and mufflers but the rest is stock

[t.mcginley.jr]

Have you done a simple compression test yet?

[kyleamiller]

No I have the pressure gauge and adapter but haven't had a chance to yet. Is there a certain pressure it should be or should they all just be the about the same?

[GerryO]

Automatic or manual transmission?

The KS code will significantly affect engine timing and performance.

Proper TPS adjustment is especially critical with an automatic transmission.

Pulling the plenum, cleaning the IAA/AAC/FICD/Air Regulator and MAF, replacing PCV valves, spark plugs, old hoses and gaskets would all be good things to do.

http://www.google.com/url?sa=t&rct=j&q= ... IyQqVvpyeQ

[t.mcginley.jr]

Compression test results:

NA: 186psi is 'perfect', minimum of 136psi.
TT: 174psi is 'perfect', minimum of 121psi.

What GerryO said is very valid also

[kyleamiller]

Great link! Its a manual transmission I'm not familiar with a ks code but I will be doing all of those things. Now it's just a problem of finding time to lol thank you all for pointing me in the right direction I will update once I figure it out

Thanks again