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Matt
Matt, Engineer
Category: Nissan
Satisfied Customers: 20607
Experience:  BEng hons Mech engineering, worked in auto industry for 22 years on engine, transmission and suspension design
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I have a 2002 Sentra. Customer said a head job was done

Customer Question

I have a 2002 Sentra . Customer said a head job was done couple months ago. The problem started after the head job. Car feels like its holding back when accelerating down a straight road. Plus car sometimes cuts off when slowing down to go over a speed bump. I noticed when car is in drive (D) or reverse (R) and you pump the brakes it cuts off.!

Submitted: 1 year ago.
Category: Nissan
Expert:  Matt replied 1 year ago.

Hello

there's a couple of possibilites here

1st I'd consider doing a compression test across all cylinders as they should be within 10-15 psi of each other

as this will show if the cam timing is correct

and if this is OK then I'd check for an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

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