nissan sentra no power

[blazered]

I have a 2001 nissan sentra automatic with the 1.8 liter engine, dual overhead cam, with variable cam timing in the admission side. The engine does not have power. Fuel pump pressure ok, we noticed low vacum (about 10 psi from an expected 17 psi) but the engine idles fine. We checked the exhaust for obstructions, none find, no clogged catalitic or anything. The variable timing oil valve works ok. The compression on pistons from 1 to 4 is 120psi, 100psi, 100psi, 120psi. The timing chains were checked and also the timing marks are ok. We removed the head to look for a problem with the valves, did not find anything wrong there, and pistons look ok too. A guess is that the timing mechanism in the admission cam could be wrong, and that could explain the low compression and the lack of vacum. Does anyone know how could we test it? Anyone with a similar problem?

[Psychobob_007]

is the lack of power through the entire powerband? if so it could be your injectors of spark plugs. miss gapped plugs can cause this problem so you may need to gap them or replace them. also you may try cleaning your MAF sensor with good MAF cleaner. it helped my car gain some power. did you check your Camshaft when you had the heads off? they could be worn. hmmmm. can't think of anything else that may be the problem. good luck.

[blazered]

Hello psychobob. Yes, the lack of power is there, whenever you push the accelerator, it does not respond. If you push it slowly, it gains speed slowly. The camshaft are ok.. The main thing is to find why there is so litle vacuum, and low compression, on an engine that was working fine. What happened? Any ideas whom or were to ask for help on this?

[Twilight sentra tuner]

well there's a problem. try checking the manifold runners leading to intake ports of the motor. look for cracks or any leaks. a good ear is helpful.

it could also be your compression and oil rings on your pistons. too much blow-by. check your oil and see how dirty it is. then change your oil and keep a tab how long your oil can stay clean.

is your check engine light on? if so it sounds like it could be MAF

[Buzzman]

The main thing is to find why there is so little vacuum, and low compression, on an engine that was working fine. What happened? Any ideas whom or where to ask for help on this?

Ok, first a disclaimer: If you blow yourself up, don't sue me.Now, I've used this little trick in the past to find a vacuum leak, but you need to be careful, and you need to do this outside where there is PLENTY of ventilation.Here goes: If you don't have one already, get your hands on a plumbers propane canister and nozzle, the kind they use to solder copper water pipe. (Runs about $10.00-$15.00 in a hardware store.)With the engine running (idling), open the valve on the propane nozzle, but DON'T light it. Aim the nozzle at various areas around the engine where you think there may be a vacuum leak. If there is a leak, the engine will suck in the propane gas, and the engine will change RPM's. I've been able to find leaks using this method quite successfully.Be careful, and good luck.