Help Needed! Revs drop to sub 800 after warm up

[CrazySx]

Hi Guys,

As some of you may know, my car has been off the road a while as i have cut out the rot and got it sorted.

So after a fresh MOT and Tax, I took the car to work last Thursday and all seemed fine at first but then..

Once warmed up the car would drop revs at idle, not boost properly.. kind of stutter and just generally drove a bit shit!

I had a few ideas on what it could have been (Dirty MAF, boost leak, sticky actuator, turn up idle?)

I tried the easy things first, cleaned the MAF and it didn't make a difference.

Then I checked voltage on the old battery and it was holding a solid 12v when switched off and just over 14v when idling. So all seemed well. Then I took it out for a blast and the symptoms reared there ugly head once again!!

Took it home, stuck the voltage meter on it and guess what? It was only at about 13v on idle.

Swapped the battery out and checked again, 14v and over.

Took the car out again and it was like I remembered her to be! Awesome! No more dropping idle and boosting hard!

However.. on the way to work today, the car is doing it again!

Any ideas? help appreciated!

The car drops revs at idle and then is reluctant to boost when it does and does stutter a bit if i force it to boost lol! Leads me to think its boost related, but then wouldn't it be constant? this seems intermittent to me.

[Nuts]

Keep multimeter connected while driving could be alternator.

Also could be bad earth's clean them up.

[CrazySx]

Keep multimeter connected while driving could be alternator.

Also could be bad earth's clean them up.

This is not a bad idea, shame i can't use the torque app in the car

I will also check the earths, but i am not sure its electrical now.

[CrazySx]

Drove it home just now and it didn't want to boost, instead it would shudder at about 2k

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[kingk]

Have you got a boost controller? Mines doing the same thing since my avcr has been unplugged


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[CrazySx]

Have you got a boost controller? Mines doing the same thing since my avcr has been unplugged


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Unplugged? Is it not running on actuator pressure?

I have a HKS evc. I can understand if it was just hesitating the boost but mine is struggling to idle.

I think I will check for boost leaks at the weekend. I have also never changed the fuel filter

So will do that and clean the throttle body at the same time.

I did think the boost controller could be playing up but it doesn't explain the drop in revs at idle. It's almost like it's struggling to stay alive.

Saying that, once I got home I left it running while I pulled out the mr2. And it didn't cut out.

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[CrazySx]

I might try switching off the boost controller and running on actuator pressure should all else fail

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[kingk]

I'll be honest, my drop in revs started after I fitted the turbo timer, normally stays around 7-800 occasionally hunts at lights, might stay around 1200 for a few seconds if I pull up at lights or might try to stall. But somebody did say it was probably due to an issue with boost control being unplugged, can't remember what they said now though lol


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[autosri]

Could the pcv valve be sticking open causing a vac leak at idle and a big boost leak on boost ?

[Nuts]

I had an IAC stick on me that caused the car to stall out. You could unbolt clean and refit.

Did you adjust idle as that can cause weirdness if not reset properly

[CrazySx]

Could the pcv valve be sticking open causing a vac leak at idle and a big boost leak on boost ?

Will have a look at this and clean it.

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[CrazySx]

I had an IAC stick on me that caused the car to stall out. You could unbolt clean and refit.

Did you adjust idle as that can cause weirdness if not reset properly

Horsham Dev adjusted it when they did the 2a remap back in April 2015. I aint touched it since. Worked while the car was on the road.

IAC is idle air control?

Will have a look at this also

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[CrazySx]

Ok so I changed the fuel filter. What a shitty location to work in. And then I took out the pcv valve which seemed ok but cleaned it anyway.
No difference

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[CrazySx]

Ok another update, changed the MAF over, no difference. Took out the IAC Valve and gave it a clean.

Before

After


Then wound out the screw a little. Seems better but the idle still doesn't sound settled to me.

Any other suggestions?

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[CrazySx]

Think I will change the lambda sensor next.

Logic behind my decision is that the car boost fines most of the time but some of the time it holds back (in 3rd) Then boosts really hard!! Is this a fuelling thing (running rich) or is it a boost issue?

Also if the lambda was at fault would I get an engine light?

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[CrazySx]

Ok so took the car out on a 72 mile drive today and at first it was fine. Soon as it warmed up the revs wanted to drop at idle. Also when off boost on the motorway and coming back on the accelerator the car would start to jerk badly!!

If I dropped down a gear and booted it it would be fine on boost.

I got it home and whipped out the lambda sensor (and most of the thread).

Need to test it but not sure how. Have also ordered a new one and a thread chaser.



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[shikari chaos]

By what you've said it sounds boost related but hard to know for sure.
You checked these thread? : http://www.sr20forum.com/technical-i...5497?_k=y6vyaa
http://www.sr20forum.com/classic-se-...0303?_k=7dy2p8

[CrazySx]

By what you've said it sounds boost related but hard to know for sure.
You checked these thread? : http://www.sr20forum.com/technical-i...5497?_k=y6vyaa
http://www.sr20forum.com/classic-se-...0303?_k=7dy2p8

Hey Man,

Thanks for the links. I am going to put a new o2 sensor in as soon as I can get one that is. Then I will by pass the evc solenoid and see if that makes any difference.

It's really annoying this issue

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[skyshack]

Put the O2 sensor in a vice. Connect a voltmeter to the signal wire and case. Get a blow torch and heat the end of sensor. Voltmeter should show close to 1V and down 0V depending on where the flame is playing on the sensor.

Voltage shown in this test is correct for Nissan sensors.
https://www.youtube.com/watch?v=YL6xkOZxHZ0

[CrazySx]

Put the O2 sensor in a vice. Connect a voltmeter to the signal wire and case. Get a blow torch and heat the end of sensor. Voltmeter should show close to 1V and down 0V depending on where the flame is playing on the sensor.

Voltage shown in this test is correct for Nissan sensors.
https://www.youtube.com/watch?v=YL6xkOZxHZ0

i actually tried that, but my multimeter starts at 20v and was showing nothing, i will try again with a lower rated multi meter.