240sx, weird idling, slight hesitation

[skydragoness]

i'm going to post my dilemma here, i previously had it in the 240sx Technical Section.

Here goes:

When idling (usually after coming to a stop) it flucuates from 700 to 500rpm, the needle dips down to 500rpm and then goes back to 700rpm and stays there

Secondly, when acclerating there's some hesitation between 2krpm and 2500rpm and then normal afterwards.

My car is a 5spd

Fuel injectors/system already cleaned, and i cleaned the throttle body too, all these help make the engine run smoother, quieter, and have more response. But it still idles funny and hesistates. It is like this rain or shine. And happens often, but not constantly.

What can it be??

My mech says that maybe that one of the cylinders is having a slight, very slight misfire, and he wants to put it on the analyzer when i take the car in tommorow to be steam-cleaned (another matter).

A prompt response will help a lot! (so i know what to say to him when i get there):help

[911/Q45]

Sounds like a vacuum leak, check for cracked hoses and plastic hose connectors.

[drjohn]

This sounds like a case of the base idle being to low and when you come to a stop the idle hunts or fluctuates. Have the tech check and adjust the base idle and timing if needed. Also check to see if it's running rich,this will cause the same problem.

[skydragoness]

ah, i see

s14pimpin, told me that maybe it's a stuck EGR (sp?) and to lube it, also something about tightening the throttle cables too, damn i forgot what he wrote already

and what about the hesitation? can it be affected by that too?

[drjohn]

Yes the egr can cause this problem but in most cases the idle will continue to be rough if the valve is stuck open. The egr can cause a hesitation on accel. and is easy to check by removing vac. hose and plugging it and roadtesting it to see if hesitation is gone. If this is a KA24E single cam these have a problem with the egr ports clogging in the int. man. and the ports need to be cleaned out.

[skydragoness]

This is a ka24De--if that makes a difference

ok, my mech disconnected the EGR and let me drive it around Friday, the idling was still erratic with the EGR disconnected-- but the hesitation........seemed to be gone, i couldn't really tell since it wasn't very pronounced to begin with, since then i have hooked it back up

do you think maybe the erratic idling has to do with my timing chain needing to be adjusted?

i'm just so puzzled

[Just another 240]

that happened to me once and when it dropped to 500 it'll even shut off on me. For me, it was the alternator belt, it was loose and sending incorrect current to things. After i tightened everything was GOOOD!

[skydragoness]

all my drive belts were replaced about 2 months ago too

[drjohn]

Timing chains don't have a adjustment on Nissans of that mod. If the chain is loose or noisey it needs to be replaced.If you adjusted the throttle cables to tight the tps can't find it's idle contacts and if the tps is bad or out of adjustment the idle will hunt.Was it running rich? This will cause idle problems,check the coolant temp sensor and connection for green corrosion.

[skydragoness]

well, the timing chain isn't the culprit the car runs quiet for a ka24de, since it is a ka24de, do they have the same prob of the egr clogging the intake manifold? do i need an induction system cleaning or a new valve for the EGR?

i don't know if it's running rich or not, and i don't think my mech said anything about my throttle cables, i'm thinking about taking it to the nissan dealer, but i'm afraid of being ripped off

at least i know it's not my timing chain, so they can't tell me it's that at least

[drjohn]

Check around with other Nissan owners and see what thier view is on the local dealers to see if there are some reliable ones in your area.

[NateDogg]

Get some contact cleaner and clean all the electrical harnesses as well as the MAFS. But be careful not to break any resistors!!!

[skydragoness]

oh i forgot to mention that my tech said that on the analyzer, the car 's ecu gave out a code 55--no malfunction

so the ecu thinks nothing is wrong

i've been driving around with my EGR disconnected and it seems better, hesitation has pretty much disappears, the idle now is at 1krpm now!! so i'm going to hook it back up when i go to get gas today

[skydragoness]

actually i just realized that it idles (with the EGR connected) @ 1000rpm when the a/c or heat is on/fan etc. when i turn it off it the idle goes back down to 700.

Think it is the EGR causing the idle/hesitation (@ 2400rpm)??

[drjohn]

This is a little out of range and should only go up to about 800 rpm at the most. This is do to the load sensor signal the ecm gets when the a/c or fan etc. are turned on and the ecm compensates. Although slightly out of range it's nothing to worry about but if it concerns you have it adjusted.

[skydragoness]

now... i just need to get around to that, but thanks for all your help guys!

[I_eat_hondas]

I have the same problem with my car, where exactly is the EGR valve located?

[drjohn]

Egr valve is at the back of the int.manifold and has a large steel line going to it from the ex.manifold behind the eng.

[skydragoness]

i have to revive this thread, since i haven't had the prob fixed yet.

how do you go about cleaning the EGR?

the hesitation has become more pronounced these days, the idling is still acting the same erratic way.

[hudy]

I use oven cleaner to clean EGR valves. Easy-off will do the job. Try not to get it on aluminum though.

[Nismo_Freak]

Hey Sky,

Check for the following babe

1. intake leaks2. vacuum leaks3. EGR4. MAF operation5. 02 sensor operation

Intake leaks and vacuum leaks easily cause funky problems down low when the 02 is switching from rich to lean, back and forth to maintain the stoich fuel ratio. A vacuum leak also can cause fuel regulators to act funny, causing hard start-up and other issues.

As for the EGR, brake cleaner works excellent for removing carbon/oil build-up without any scrubbing. Spray it down once, then let it sit for a few seconds then hit it again. Be liberal with it. The brake cleaner won't leave any residue either. I've seen plenty of EGR related issues cause idle misfires in the B-series and MPV Mazdas. Although they aren't the same engine, they all operate in similar fashion.

MAFs sometimes get dirty when they are used with an open element filter, especially oiled units like a K&N. Hose it down with some of the before mentioned brake cleaner, carb clean will leave a residue which can cause incorrect metering.

02 sensors go out whenever they feel like it, or so it seems. You can always check the harness and readout from the 02 to verify it's working correctly.

[p00t]

Sky, I had the same problems as you. I originally thought it was a brake booster malfunction, since it would randomly happen when braking hard. Its common, I have done a few things and now the car runs perfectly. I have a 93 FB.

Redone engine grounds got rid of the slight acceleration hesitation I had. All it took was some beefy amp wire. I redid the rear engine to chassis ground, and intake manifold to chassis/battery ground.

The rear engine to chassis ground is alittle flimsy.. and gets kinda corroded easily. The engine ground comming off of the intake manifold grounds to the battery tray first and then to the battery (-) after. The problem I had was the part where it grounded to the tray. All they did was strip a 2" section of insulation, and then clamped it to the tray, this exposed copper wire got pretty corroded.

when i redid the wires I also didnt use the battery tray ground, the same thing was only going to happen. I ran a wire to the intake manifold from a ground connector on the chassis that a black ground wire from the harness runs to. (its located on the wheel well area near the intake manifold on the chassis.) that took care of the chassis ground.

Another area to check is the AIV, since this can dump exhaust into your intake, and if your egr is already adding alittle.....well you get the picture. You can just clean it or remove it, its your choice.

I did other routine engine maintence things, but the two that had the most impact were the ones mentioned above. The AIV removal/cleaning helped my idle, car would still bog to 550rpm, but wouldnt stall out. The engine regrounding fixed the rest, originally i was only aiming at fixing my hesitation but it fixed the idle under braking too. Something else must have had a bad ground also... maybe the Idle Control Valve?

Good Luck

[240sxOwner]

I used to have a severe idle problen and whenever coming out of gear my rpm's would drop very low and sometimes it just shut off. All i did to fix it (don't know if you need these brands) was get Accel 8mm spark wires, and NGK Iridium plugs. Hope you figure it out.

[sullivan864]

I'm having the same problems on my 90 240. at least the rough idle, however on top of it my computer keeps throwing the egr systems code. have replaced egr, all vacuum lines, and the bpt or bvt vavle(can't remember the name, runs off the egr though) and have had no luck. can any one tell me what else ties into the egr system, so that i can check it or replace as necessary

[NISTECH]

you may have a bad egr temp sensor,restricted passage or bpt tube. or your exhust may not have enough back pressure to to close the bpt.

[sullivan864]

i was wonderin bout the sensor. also i just put on new exhaust and i put on 2 1/2 in. piping cause thats what they recommended. but it gave me that code even before i put the new exhaust on. I have been messing with this off and on for bout 6 months, but now its time for smog check so i'm tryin to get everything dialed in before i do it.

Is there a way to check that sensor?

[NISTECH]

yes use a volt meter the voltage should be somewhere in the neighbor hood of 3.5 volts. and when the valve is open it should drop to nearly 0 volts. this does not happen immediately. the best way to do this is back probe the connector. rig it up with some long jumper wires so you can have the meter inside the car. dirve the vehilce and see if it drops if not you have either a carbon coated sensor or a plugged egr passage. you can remove the sensor and clean its sensing surface with carb clean and also while its removed try to get a look in the passage for black heavy carbon deposits. cleaning those passeges can be a real pain. if you can get your bpt steel tube off try removing it to inspect it for carbon deposits first. since it is so small and exhuast gasses travel up the tube it is very easy for it to get build up.

[boycelaforest707]

Hey everyone, I have a 91 DOHC s13, same exact problem 700 idle, then drops to 500 then back up some times it dies at stop lights, with A/C on it raises it to 1000.

[NISTECH]

Try this little trick and see if it offers some assistance, on the intake tube running acroos your radiator shroud you should see 2 hoses coming off it on the passnger side of the engine. 1 is about a 1/2 inch in daimeter and the other is about 1 inch. They are side by side and easily accessable from the top. with the car off pull the 1 inch tube off and shoot some carb clean in there. hook the hose back up and fire up the car, do not give it any throttle just let it idle. If it dies due to choking on the carb clean restart it again. do this till it stays running and let the carb clean run through. This will help remove SOME of the carbon build up in the idle control valve. That one inch tube is the feed for all the idle valves. Warm the car up to operating temp before you do this as you want the main air feed to be the IACV at idle not the fast idle control as that will bypass the valve you are trying to clean. after you do that take it out and push it a bit to clear its throat of the carb cleaner.

[boycelaforest707]

Spark plug wires and AIV clean fixed my problem! Sweet!