My zed has developed an idle problem when stationary. The vehicle always starts but sometimes idles ok and at others the idle dies away but rarely stalls.

 

If the accelerator is depressed/feathered then it appears to bog down and tries to stall unless its then left to idle again. When idle dies it can restart immediately and continue driving.

 

The car drives fine once going (under load).

 

In the last 3mths its had a new knock sensor, new alternator, timing belt, cam belt, power steering belt, air con belt, new plenum gasket, all injector seals replaced, clutch pedal repair & improvement, new spark plugs, Thermostat, new IACV air regulator, heater matrix, replaced fuel pressure regulator, fuel dampener, coils replaced.

 

Am i right in thinking that the most likely causes for this issue are mass air flow or throttle position sensor????

 

Any other things to look for or check??

 

Any help greatly appreciated :)

if it was maf, it would stall at 3k revs, so doubt its that, could of popped a vac hose off though.

if it was maf, it would stall at 3k revs, so doubt its that, could of popped a vac hose off though.

 

 

I'll have a check tomorrow.

 

Forgot to mention its an NA also

I'll have a check tomorrow.

 

Forgot to mention its an NA also

 

still has a few vac hoses bud.

 

Yep all hoses are on fine

Mines an NA and doing the same thing! Came on gradually over a couple of weeks or so and I replaced the spark plugs but that made no difference. After resetting the ECU it's even worse (I did reset it when cold, maybe you have to do that when it's warm?).

 

It does idle at around the right revs but it feels lumpy and occasionally stalls when cold. When hot it doesn't stall but still feels lumpy.

Goes ok when warm and under load but definitely not 100%.

 

The revs compensate ok when air con is switched on and off. Vacuum hoses all appear fine and the Vac gauge reads the same as before so don't think it's vac related.

 

Going to start cleaning up all the sensor connections when I get a moment.

 

If you suss yours first please let me know and vice versa!

Mines an NA and doing the same thing! Came on gradually over a couple of weeks or so and I replaced the spark plugs but that made no difference. After resetting the ECU it's even worse (I did reset it when cold, maybe you have to do that when it's warm?).

 

It does idle at around the right revs but it feels lumpy and occasionally stalls when cold. When hot it doesn't stall but still feels lumpy.

Goes ok when warm and under load but definitely not 100%.

 

The revs compensate ok when air con is switched on and off. Vacuum hoses all appear fine and the Vac gauge reads the same as before so don't think it's vac related.

 

Going to start cleaning up all the sensor connections when I get a moment.

 

If you suss yours first please let me know and vice versa!

 

Will do.

 

My ECU is also showing no codes whatsoever.

I haven't run a code check yet but will try and find time this weekend.........

Firstly check for green corrosion on the injector plugs and injector terminals, i just had this problem and it sounded like a scooby lol.

The check the voltage on the TPS with a multimeter, should read .44v when closed and 4.0v at WOT.

Then check connectors on the IACV, IAA and FCID at the rear of the plenum for corrosion, check the hoses and vac pipes.

 

There are some write ups in the faq section for erratic idles etc..

Will do.

 

My ECU is also showing no codes whatsoever.

 

In beween the pain in the ass showers I finally got to run the code check! Code 55 was the only code repeatedly displayed which I understand is no fault found code!

 

Helpful eh?!!

Edited August 27, 201114 yr by snowleopard
missed out word

I had idling problems with mine, I had set the tps correctly and adjusted the base idle, maf was giving correct readings as well.

 

I then pulled the yellow plug off the ficd valve at the back of the engine and turned the idle screw right down so that the car was about to stall. Plugged the ficd yellow plug back in and nothing happened. What should have happened was that the ficd should have taken over the idle from the ecu signal and settled around 750rpm.

Result was a sticking valve, took it off cleaned it all up and re did the above.

 

When it was plugged back in it took the idle upto 750rpm. Problem solved.

Firstly check for green corrosion on the injector plugs and injector terminals, i just had this problem and it sounded like a scooby lol.

The check the voltage on the TPS with a multimeter, should read .44v when closed and 4.0v at WOT.

Then check connectors on the IACV, IAA and FCID at the rear of the plenum for corrosion, check the hoses and vac pipes.

 

There are some write ups in the faq section for erratic idles etc..

 

Groover, did your motor throw up any codes when you had these problems?

 

Mine doesn't really do the scooby bit, well maybe a bit but not for long! When I start her up it's like an older motor without the choke pulled out, so I guess not running rich enough.?

 

Revving up you get flat spots and sort of dieing but picks up to rev freely then down again.

If you try and drive normally it pops a bit, very hesitant, then sort of backfires(?) a couple of times then picks up and runs slightly better until she's warm then all is much better but still not 100%. The idling, when hot, though correct on the rev counter, sounds lumpy but doesn't stall.

 

I just don't have the mechanical knowledge to do too much on my own so am reluctant to start pulling bits apart etc.

 

Would getting a conzult cable and one of the softwares available help diagnose what the ECU has failed to pick up?

Mate,

i think you are better off checking a few connectors for corrosion first rather than waiting for conszult and maybe not finding anything anyway!!!

 

most of the connectors are easy to get off, a very small screwdriver will help to un-clip the wire fastener.

 

i think you have to start getting your hands a bit dirty or it's going to cost you a fortune... LOL...

The issue you have is dealt with in the link below, well documented and with pictures too. The actual issue is you not getting the extra by pass revs (air) when cold to go with the extra fuel and then no idle stablisation when warm, yours may not need replaceing but just cleaning or even the yellow plug is just a bad connection, either way the result is the same.

 

Jeff TT

 

http://www.twinturbo.net/nissan/300zx/tech/iaa/iaa.html

Well, I removed the IAA unit cleaned it all up, cleaned the connections, tweaked the connector end crimps so they hug the terminals even more tightly and lo and behold......

No difference...gutted!

Did you reset the base idle and check if the IAA "takes over" the idle? It may be that you have a faulty IAA.

Ah, no I didn't reset the base idle. Should this be done with the engine warmed up?

Edited August 30, 201114 yr by snowleopard
Typing error

Ah, no I didn't reset the base idle. Should this be done with the engiine warmed up?

 

Yeah, warm the engine up. Pull the yellow plug off the IAA then set the base idle to about 700rpm. Then plug the yellow connector back in and the revs should increase to 750rpm. If nothing happens when you plug the connector back in then you either have a duff solenoid on the IAA or the wiring is faulty.

 

Are you also able to check what the tps volts are when the throttle is closed? It should be between 0.4 - 0.5 volts but best set around 0.44 - 0.46.

 

Check and adjust (if needed) the tps before you do the base idle on the IAA.

Well, I removed the IAA unit cleaned it all up, cleaned the connections, tweaked the connector end crimps so they hug the terminals even more tightly and lo and behold......

No difference...gutted!

 

Hi Trevor, i have a consult cable with Nissan scantech software, so we could plug it in and see what everything is running at, let me know when you are around i can pop over.

 

Cheers

Graham

That would be brillianr Graham. Can you do next Monday evening?

Yes mate no worries, let me know a time and where.

 

Cheers

Graham

Will do, text later. Cheers matey.

So, my AAC gasket arrives and I fit the AAC AND FICD (many thanks Groover). But now I can't set the baseline rpm (was also a problem with the old stuff on). Turning the idle screw seems to make no difference.

At least with the old stuff on it idled. Now with the donated stuff on it won't idle.

Any more clues anyone? This is driving me mad so shortly it's gonna have to go to a garage if I can't suss it......ps the missus is already pushing me to get rid of it!!

Im just wondering if you have a vac leak, it will affect the idle and overall running so adjusting the idle probably wont help as it cant compensate for the air escaping.

If you want to drop it to me one day, i can run you to work and have a good look over it for you. I know how frustrating it can be when its not running right.

 

Cheers

Graham

In the last 3mths its had a new knock sensor, new alternator, timing belt, cam belt, power steering belt, air con belt, new plenum gasket, all injector seals replaced, clutch pedal repair & improvement, new spark plugs, Thermostat, new IACV air regulator, heater matrix, replaced fuel pressure regulator, fuel dampener, coils replaced.

 

Am i right in thinking that the most likely causes for this issue are mass air flow or throttle position sensor????

 

Any other things to look for or check??

 

Any help greatly appreciated :)

 

OK,

what I would do is check all connectors again particularly the CAS & PTU,

check the connector to the ECU... disconnect the battery first if you are going to take it off and reposition it.

 

also you say that the timing belt was done, what was the timing set to? if you want to check you have to use a timing light.

it should be set to 15 degrees (I believe for a TT, not sure about an NA) but you could adjust it to see if it improves.

Im just wondering if you have a vac leak, it will affect the idle and overall running so adjusting the idle probably wont help as it cant compensate for the air escaping.

If you want to drop it to me one day, i can run you to work and have a good look over it for you. I know how frustrating it can be when its not running right.

 

Cheers

Graham

 

LOL.. and yes that too... as was mentioned at the beginning of this ....