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Ok so recently i picked up an old car to fix up as a project car – a 2000 Nissan Pulsar (Almera) N16 1.8L (QG18DE engine) but the problem i am seeing has got me stumped
On a cold start the car will start easily, but moments later its running a little rough, if rev the engine it nearly dies, as the car warms up this symptom almost clears up but the engine remains down on power and at about ~2000rpm it struggles to gain more revs and finally will make it up through the rev range
While the car is running if i clamp the return fuel line (it works on a loop system with a regulator on the fuel rail) the revs will raise up to normal and the problem simply disappears – engine idle is smooth, revs pick up rapidly on demand throughout the rev range, but as i remove the clamp it goes back to bad
I assumed this was a fuel regulator issue and replaced the regulator – no change, i then replaced the entire fuel pump assembly (pump, filter etc) with one from a wreckers – no change, i then took apart the old pump and inspected the filter (in case both mine and the replacement ones were both blocked) – although dirty it was not blocked or restricted, i blasted both fuel and compressed air backward through the filter to clean out any junk and then re-fitted the old fuel pump assembly back in with still no change
Any suggestions on what could cause these symptoms and what to check next?
This is an Australian vehicle so no guarantee the OBD scanner port is wired and working (standard wasnt required when the vehicle was made) – i might buy a scanner if i cant find a solution and try my luck and hope the port works
I do not get a check engine light (unless im messing with everything)
I have already checked spark/spark plugs, coil packs, compression etc with no problems
Thank you in advance
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Without knowing the fuel pressure, flow and specification we are all pissing into the wind. If you’re able to supply that info it might help.
How can the fuel pressure be low after replacing all fuel related components (regulator, filter, pump), whats left in the equation? If i have to buy a gauge to test i will.
34/43 PSI is correct spec according to Nissan service manuals.
If i clamp the line it takes a little while before excess pressure builds up (past the regulator) in the lines and then everything starts to work normal.
What does adding extra fuel pressure (aka more fuel) into the mix translate to? Could it be the MAF sensor reading wrong air volume and under-fueling everything? (and by me adding extra pressure adds the extra fuel required?)
Part of repairing cars is to remove guesswork. When you have the numbers for everything in front of you then you have all the facts to make a diagnosis. I have been fooled by new parts too many times before.
Good advice that, ill check it out some time this week
Meanwhile any other components i should focus on which could cause the engine to nearly die when opening the throttle when cold? – MAF? TPS?
seeing the problem gets better with the clamping
the return line.I wonder if the injectors have
junk in them? try doing a power balance test also
clean the MAF.here is a link to help.http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
i actually did just this afternoon remove the injectors and physically inspect them all, clear all fuel out of the rail and do a general inspection – all perfect and absolutely clean, no buildup what so ever so i put it all back together
i also cleaned the MAF sensor the other day and a week earlier with no change
compression is within spec no major difference between cylinders
i get the feeling the issue is being solved by higher fuel pressure because something is telling it to run with less/limited fuel or something similar – what could cause this?
other things i have tried (when cold because its most apparent then):
disconnect MAF sensor – runs worse, when opening throttle same near stall
disconnect o2 sensor – runs worse, when opening throttle same near stall
disconnect TPS – car runs better for ~3 seconds (idle raises then back to normal) (2 TPS connectors?)
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