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Senor Grizzly

Does the MAF sensor need to be adjusted for EGR delete?

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So i recently deleted the EGR system on my 1977 Datsun 280z. The car sputters and loses power at higher RPMS only under load (as if it doesnt get enough air)

My theory is:

The egr system is ment to suck air from the exhaust system and push it back into the intake system. So the car is designed to have that 'extra' air coming in. So if i delete the EGR and leave the MAF as it is the car will lack air because the MAF does not know that the car is no longer getting the recycled air and is not compensating for it. And if i buy a new MAF then it might have the same problem because that MAF is designed to be on a car that is getting that extra ait from the EGR system.

 

so my question is does that make any sense? Do i need to adjust the MAF sensor if i delete the EGR system?

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I'm going to guess the MAF you're talking about is the AFM (air flow meter) but I didn't when I deleted all that stuff from my '77.

Removed the egr and blocked off that hole, removed the BPT valve and two vacuum lines, one line went to a vacuum switch on top of the warming plate, removed all that.  Plugged the coolant line that comes off the warming plate and goes around the front of the head to the suction side of the radiator by the alternator and the other one at the thermostat housing.  The other vacuum line went to the bottom of the BCDD I think, plugged that too.

the yellow circle in this picture

SDC10703.JPG

 

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Here's something I did when I removed that stuff.  It sucks air like you wouldn't believe, stock air filter. :)

DSC00411.jpgDSC00408.jpg

I think you should also put a vacuum gauge on the intake and see what you're pulling.  I'm thinking "under load" could be an air problem too.

Read over this link real quick, courtesy of @240260280

http://atlanticz.ca/zclub/techtips/vacuum/

EDIT: scatter brains here to explain why I said what I did above. While I was working on the 280, about 6 months worth, Alvin and the chipmunks that live nearby made a food storage facility out of my air cleaner. It would rev up fine in the garage but didn't have any power under load. Damn chipmunks.

Edited by siteunseen

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It's not air, it's exhaust gas.  Essentially inert, the oxygen has been burned up.  You shouldn't need to adjust any air-fuel ratio components.

Might just be coincidental.  Did it run perfectly before the EGR system removal?  Has it had a tuneup recently, including lash adjustment?

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Maybe you're sucking air at one of your delete area's, like at the egr plate, etc?

 Spray some stater fluid at those spots, being careful, to see if you get a rpm spike. 

And then what ZH said, how was it running before the delete?

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10 minutes ago, rcb280z said:

Maybe you're sucking air at one of your delete area's, like at the egr plate, etc?

 Spray some stater fluid at those spots, being careful, to see if you get a rpm spike. 

And then what ZH said, how was it running before the delete?

i never got to drive it before the EGR delete. the motor sounded fine but it sounds fine now as well until im actually under load

so you say try starter fluid around the delete plate?

Edited by Senor Grizzly

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11 hours ago, Senor Grizzly said:

 The car sputters and loses power at higher RPMS only under load

This sounds more like an ignition problem.  Electrical.  The EFI system runs pretty rich at high RPM under load (the system just dumps an extra 27% of fuel in when the TPS shows full throttle), so any vacuum leaks would probably be compensated.  Plus, vacuum leaks are more significant at low air flow levels.  At high RPM there's so much more air coming through the normal pathways that the leaks don't really matter.

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9 hours ago, Zed Head said:

This sounds more like an ignition problem.

It does actually. I was thinking more of idle. Clearly Senor Grizzly mentioned higher rpm's. Don't know why I went that direction.

At what rpm's does the sputtering happen? Does it clear up as soon as you let off the throttle? 

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14 hours ago, rcb280z said:

It does actually. I was thinking more of idle. Clearly Senor Grizzly mentioned higher rpm's. Don't know why I went that direction.

At what rpm's does the sputtering happen? Does it clear up as soon as you let off the throttle? 

it starts to sputter around 3000 rpms and if im in neutral the car is fine. i can rev it wherever i want and yes it stops when i let off the throttle

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"Sputter" can mean a lot of things.  Does it stall and buck, or pop back through the intake, or is it popping out the back end?  Does it fell like it's running out of fuel?

Could be a fuel supply problem too.  I said electrical but I had a vision in my own head of sputtering.  Might not be the right one.  Just guessing right now.  

Lacks power after 3000 RPM under load.  Sputters (makes me think of misfiring) as it loses power.  Never actually tested under load before.  That's what I get so far.

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Sounds like mine before I put the CTS tweak on but opposite. Mine spit and sputtered bucked like crazy until 2500 or 3000 rpm then pulled good.

Could your wires be reversed where the CTS and thermotine plugs are, the thermostat housing and the other place about a foot towards the windshield? 

You could try clamping the return hose to build more fuel pressure and see if that makes it run better. 

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If you deleted the EGR, then you removed the intake/exhaust manifolds to plug the exhaust port? If so, did you replace the intake/exhaust manifold gasket? Did you remove the Throttle Valve Switch for any reason?,

 

 

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Maybe he should install a fuel pressure gauge and observe it at full throttle. Just to rule out fuel flow.

I had thought lack of advance timing but now I'm not sure that it would give the symptoms Senor Grizzly describes. 

I think some history on this car would be nice also. Did he just buy it,

Has it sat for any length of time,

Is it all stock except for egr delete and why did he delete it.

Edited by rcb280z

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Also not clear if it's an easy increase to 3000 or if it's wide open and hold on.  The ECU and TPS dump a lot of extra fuel if you put the pedal donw, but meter in slowly if you keep a light foot and wait.

Senor might be out there troubleshooting so hasn't come back yet.  I just worked my way through another Oregon emissions check myself.  Passed, on the third try, but my numbers were a lot better last year.  I was starting to get worried.

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12 minutes ago, Zed Head said:

Also not clear if it's an easy increase to 3000 or if it's wide open and hold on.  The ECU and TPS dump a lot of extra fuel if you put the pedal donw, but meter in slowly if you keep a light foot and wait.

Senor might be out there troubleshooting so hasn't come back yet.  I just worked my way through another Oregon emissions check myself.  Passed, on the third try, but my numbers were a lot better last year.  I was starting to get worried.

Thanks to everyone who has replied. Ive been super busy with work and haven't had time to do much trouble shooting. To answer your question the sputtering is more like a lack of air. l

the car loses power and the engine makes a deep sound and it smells like gas. it happens both at light and heavy throttle quick or slow

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 I'll bet there are some good? stories about passing emission tests. We had a real challenge with an 81 RX7. Not known to be a clean burning engine even when new. It took eleven tries (thanks to some creativity and the smog pump) but we finally got it thru. The crew at the DEQ Station were all rooting for the car to pass as the emissions dropped with each test. There were high fives by everyone when it passed.

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15 hours ago, Senor Grizzly said:

the sputtering is more like a lack of air. l

the car loses power and the engine makes a deep sound and it smells like gas. it happens both at light and heavy throttle quick or slow

On the EFI system the fuel comes from counting sparks, and from the AFM vane position.  It might be that somebody has adjusted your AFM, loosening the spring.  That would cause the vane to open farther than it should, flooding the engine.  Just a guess.  The gas smell is a clue. The AFM calibration has worked for people, on the link siteunseen provided above.  Look for clues that somebody has messed with it, the black cover might have new silicone or the glue blobs on the wheel have been moved.

Another possibility is a bad ECU or bad ECU connections.  They tend to go rich or just die completely.  Tough to diagnose.

You have the PO problem.  Who knows what's been done.  Somewhere out there is a 77 with a low compression engine, that a PO got running using this site.  We told him, but he did it anyway.

Forgot to say, it would be worthwhile to go through the testing in the FSM or the EFI book, in the Downloads section of the site.  At the ECU connector.  This one covers all years up to 1980 - 

 

Edited by Zed Head

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