Missing when accelerating

JCLEMO

MEMBER
1997 NISSAN HARDBODY
2.4L
4 CYL
238,000 MILES

I replaced my MAF sensor due to truck surging. Not going over 2,500 rpm.
$126.00 fix. Problem solved. Now the problem is missing when accelerating up to around 2,500 rpm seems to smooth out. Can my MAP sensor be causing this? I smell gas after I step out of the truck. I replaced the MAP with one I bought at a local salvage yard. Got my used MAP off of a Pathfinder around 1995-1997 year. I am wondering the odds of both sensors being bad. My question is, can the MAP cause the truck to be sluggish on acceleration? Does it affect the advancing or retarding of the distributor? My spark plugs look good they are not black like when my MAF sensor needed replacing. Before I replaced the MAF my plugs were black five minutes after cleaning them and restarting the truck. Does a bad MAP sensor cause the engine to loose power and misfire too? Thank you, JC

7 Replies

KENW1

MECHANIC
213 POSTS

Thanks for visiting 2CarPros.

Your MAP sensor detects engine vacuum and this does contribute to spark advance. If you have a scan tool with live data MAP voltage should be around 1.3 volts at idle and go up to 4.5 volts as vacuum decreases.

If the MAP shows the proper data the next step would be to verify fuel pressure. It should be 34psi minimum with the vacuum hose connected to the regulator and 43psi with the hose disconnected. Also check the hose to the pressure regulator and see if any fuel comes out of it. I've seen small tears in the diaphragm do this. You'll need to install the pressure gauge inline after the fuel filter. Be sure to plug the vacuum line to the regulator when testing. I'll post pictures below showing gauge set up and regulator location.

Images (Click to make bigger)

SPONSORED LINKS

Was this

answer

helpful?

Yes

Monday, January 14th, 2019 AT 2:59 PM

JCLEMO

MEMBER
161 POSTS

Thank you Ken you have been very helpful. This will be my next step. Also, I want to ask your opinion on time serts. I've tried helicoils and they failed. I have drilled a stripped exhaust manifold bolt out to 5/16 and tapped. That failed. I re taped to 3/8 without drilling. I used a 3/8-16 bolt and still does not hold to tighten bolt enough to stop the leak. They have a kit called Time sert. Uses carbon fiber threaded inserts instead of coils. I am afraid to drill any larger. What do you think? Thanks. JC

Was this

answer

helpful?

Yes

Monday, January 14th, 2019 AT 11:39 PM

KENW1

MECHANIC
213 POSTS

I've found time serts to be very effective and superior to heli coils. There's a little sticker shock at the price, but I can confirm they work great.

Was this

answer

helpful?

Yes

Tuesday, January 15th, 2019 AT 5:48 AM

JCLEMO