1990 Maxima terrible idle

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daniels740
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Joined: Sat Dec 26, 2020 8:57 pm
Car: '90 Nissan Maxima
'89 Volvo 744 Turbo

1990 Maxima terrible idle

Postby daniels740 » Sat Jan 22, 2022 6:45 pm

My 1990 Maxima has developed a terrible idle, dropping to 4 or even 3 cylinders at times with a shaky miss. This only occurs at idle. When accelerating, if you go very gentle on the throttle it will hesitate, sputter, and move slowly. However, if you employ a heavier-foot, the engine will snap out of it, and run well on all cylinders.

Once it does this, you can cruise fantastically and the engine pulls great as well. As long as you're accelerating, even if just slightly after that 'snap,' the engine purrs like a kitten.

Then, coming to a stop the engine may at first idle well. After a little time, it starts to have a miss, then it worsens and it feels like the engine is running on maybe 4 cylinders. Then, again, the heavy foot, sudden change, great performance, and back to a stop where we started.

What could be the cause of this shaky, miss-ridden idle?

Thanks in advance for helping keep a 'vintage' maxima on the road.


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VStar650CL
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Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: 1990 Maxima terrible idle

Postby VStar650CL » Sat Jan 22, 2022 8:04 pm

You'll have blinky lights on a '90, have you checked for codes? If it isn't throwing any then I'd suspect an induction or fuel issue, but it can't be fuel starvation with it running okay above idle. Add some supplemental fuel (Brakleen, carb cleaner, etc) at idle and see if it gets better or worse. If it improves then suspect a vacuum leak, if it gets worse then suspect a bad or leaky fuel pressure regulator. You don't say whether being warm or cold makes a difference, if it's only warm and more fuel makes it worse, check the coolant temp (ECT) sensor for a little over 1V. If it's much higher at warm idle then the car will think it's in Siberia and run way too rich.

daniels740
Posts: 10
Joined: Sat Dec 26, 2020 8:57 pm
Car: '90 Nissan Maxima
'89 Volvo 744 Turbo

Re: 1990 Maxima terrible idle

Postby daniels740 » Sat Jan 22, 2022 8:59 pm

Thanks for the reply.

No CEL on, but could there still be codes nonetheless? How could I check, IIRC, a screw on the ECM?

I have done a smoke machine vacuum leak test, and it hasn't revealed any leaks so it's not that. I've also added 'supplemental fuel' as you have suggested, and it doesn't cause the engine to accelerate, so we can be fairly sure there's no vacuum leaks.

Next, I have not considered the fuel pressure regulator, so I will take a look at that. I'm pretty sure I've replaced the vacuum hose going to it, though, and haven't smelled any fuel for it to be leaking that way. Could an internal failure cause running rich?

Last, it runs the same hot/cold, no difference based on temp.

Thanks again for the help.

macgiver
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Re: 1990 Maxima terrible idle

Postby macgiver » Sat Jan 22, 2022 9:55 pm

Backlash from loose timing belt , crank position sensor and or housing got VERY sloppy - when rpm's come up the parameters ' settle ' into a nice run , and aren't those tensioner's a little goofy that they slack when idle , yet kinda bunch-up on the backside with revs and tightening up ??

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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: 1990 Maxima terrible idle

Postby VStar650CL » Sat Jan 22, 2022 10:03 pm

macgiver wrote:
Sat Jan 22, 2022 9:55 pm
Backlash from loose timing belt , crank position sensor and or housing got VERY sloppy - when rpm's come up the parameters ' settle ' into a nice run , and aren't those tensioner's a little goofy that they slack when idle , yet kinda bunch-up on the backside with revs and tightening up ??
+1, good thought. The VG30's are known to do some very goofy stuff when the timing belt gets sloppy, and it usually won't cause codes.

daniels740
Posts: 10
Joined: Sat Dec 26, 2020 8:57 pm
Car: '90 Nissan Maxima
'89 Volvo 744 Turbo

Re: 1990 Maxima terrible idle

Postby daniels740 » Sat Jan 22, 2022 10:57 pm

Forgot to mention something - unplugging the MAF makes the engine go from a shaky miss-ridden idle to smooth running, although it stalls under load. I've cleaned it, and even tried to replace it but the engine ran the same.

However, there was one problem, the MAF on the car right now has 5 pins but the replacement I tried and returned only had 4. I was told they're compatible, but should I try again with a 5-pin MAF sensor?

Also, while this may put a kink in the timing belt theory, I am glad it was brought up. I've left all the belts go a little past due and should replace them soon; this is another good reason to get to it.

Thanks for the help so far.

macgiver
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Joined: Wed Jul 04, 2007 10:21 am

Re: 1990 Maxima terrible idle

Postby macgiver » Sat Jan 22, 2022 11:01 pm

Aaaah .........MAF ..............back around full circle wowie , a very liable culpret there !! :rotflmao
I got the VG30DE with the DOHC , yours the SOHC ?? very similar 'cept for 2nd cams. Mine lost it's response from idle while it had slack belt .

daniels740
Posts: 10
Joined: Sat Dec 26, 2020 8:57 pm
Car: '90 Nissan Maxima
'89 Volvo 744 Turbo

Re: 1990 Maxima terrible idle

Postby daniels740 » Sun Jan 23, 2022 5:35 am

Plain old SOHC VG30e.

So, you think it may be worth it to try another, this time 5-pin MAF?

Actually, I think it may be a good idea to check for resistance from the MAF to the ECM first; the MAF connector does appear to have some corrosion. Would anybody happen to know where I could get an ECM pin-out?

Thanks.

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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: 1990 Maxima terrible idle

Postby VStar650CL » Sun Jan 23, 2022 6:56 am

I'm not sure how far back the manuals go in ASIST, I'll take a look for you tomorrow afternoon. If they go back that far, I'll link a copy of the engine controls.

daniels740
Posts: 10
Joined: Sat Dec 26, 2020 8:57 pm
Car: '90 Nissan Maxima
'89 Volvo 744 Turbo

Re: 1990 Maxima terrible idle

Postby daniels740 » Sun Jan 23, 2022 11:20 am

Thanks.

daniels740
Posts: 10
Joined: Sat Dec 26, 2020 8:57 pm
Car: '90 Nissan Maxima
'89 Volvo 744 Turbo

Re: 1990 Maxima terrible idle

Postby daniels740 » Tue Jan 25, 2022 6:18 am

Any luck?

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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: 1990 Maxima terrible idle

Postby VStar650CL » Tue Jan 25, 2022 6:21 am

Got sick, I haven't made it to the shop. Hopefully tomorrow.

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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: 1990 Maxima terrible idle

Postby VStar650CL » Tue Feb 01, 2022 6:49 am

Sorry this took so long. The '94 SM they have here in Nico is as far back as they go electronically. I can get you bulletins back to '87, but the SM's prior to '94 are paper-only.

daniels740
Posts: 10
Joined: Sat Dec 26, 2020 8:57 pm
Car: '90 Nissan Maxima
'89 Volvo 744 Turbo

Re: 1990 Maxima terrible idle

Postby daniels740 » Wed Feb 02, 2022 6:33 pm

That's alright, I'll figure it out. Thanks, anyway.

Glad you're feeling better.


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