1995 pickup 2.4 wont idle

[xrjoe]

ive got the egr apart, and im wondering what the vacuum servo going into back of intake is/does? the egr passes a little air through small tube to egr-bpt valve, but valve to intake is holding flow, i checked tps volts, starts at .41, then goes up smoothly, i took t-body out and replaced idle air control valve, it was filthy, plugs and compression good, fuel pressure at 35 key on not running. i have not looked into ignition or o2 sensor, there are no codes on display, im hoping someone has dug into a similar idle problem might offer some direction, thanks for looking.

[Niti QX4]

What is the "won't Idle" mean specifically.

Hunts for idle set speed; dies when cold, dies after running for a while, etc..?

I have a thread from 2022 where I maybe have the same symptom:
topic631639.html

[xrjoe]

well, to start it, im giving some throttle then it fires, it seems like there is no fuel at no throttle crank, i havent confirmed spark at initial start, i found the tps has a pedal off circuit that has no continuity, otherwise position volts are correct, waiting for tps. i also pulled and cleaned injectors, found out the vac servo was scv , not related to idle. thanks for the reply,

[Niti QX4]

Okay, so the TPS is coming in for the open circuit at 0 volts at no pressure on the pedal; and you have a new one coming in.

Whats SCV?

[xrjoe]

yes, and i bypassed it sending current through circuit, and it still wasent idling, havent tried since injector clean, and i tested coil primary, calls for 7 ohms, had 11 ohms, not far off, all injectors at 11.6 ohms, and ignition transistor had correct continuity. thats where im at for now.

[Niti QX4]

So have you checked the FPR for fuel smell (I think what you are calling SCV?)

[xrjoe]

i think you mean to see if diaphragm is passing fuel to vacuum side, no traces of fuel, pressures with and without vacuum are good

[Niti QX4]

i think you mean to see if diaphragm is passing fuel to vacuum side, no traces of fuel, pressures with and without vacuum are good

Yep, that's right. When's the part coming in?

[xrjoe]

by thursday, but hopefully sooner, im also thinking i should check crank to cam chain timing, this has 235k and no history of replacement, they can stretch quite a bit before making noise, just to rule that out. thanks again for the replies niti qx4, really appreciate that!

[xrjoe]

by thursday, but hopefully sooner, im also thinking i should check crank to cam chain timing, this has 235k and no history of replacement, they can stretch quite a bit before making noise, just to rule that out. thanks again for the replies niti qx4, really appreciate that!

[xrjoe]

yes, and i bypassed it sending current through circuit, and it still wasent idling, havent tried since injector clean, and i tested coil primary, calls for 7 ohms, had 11 ohms, not far off, all injectors at 11.6 ohms, and ignition transistor had correct continuity. thats where im at for now.

[xrjoe]

not sure why this repeated previous posts

[VStar650CL]

Coil primary is supposed to be 0.7 ohms, not 7.0 ohms. 1.1 is sort of okay, but if it's actually 11.0 then that coil is screwed.

[xrjoe]

got me thinking, ill recheck tomorrow

[Niti QX4]

Coil primary is supposed to be 0.7 ohms, not 7.0 ohms. 1.1 is sort of okay, but if it's actually 11.0 then that coil is screwed.

Good point. I didn’t see that above. I had to change out a coil too.

2004-nissan-2-4l-blew-out-3-spark-plug- ... 33834.html

I had to select a special coil because the Amazon picker was wrong

[xrjoe]

your right, pulled it back out, and fluke tester showed 1.0-0.9 ohms, at a colder ambient temp

[Niti QX4]

So the coil tested okay. Looked okay I would guess?

[xrjoe]

yes on one side, and no secondary test value to confirm, when engine stumbles at low rpm, spark cant be ruled out, old school test would include watching a timing light inductors ability to monitor spark, and it runs like fuel is leaned or cut off if that makes sense?

[xrjoe]

forgot to mention coil visibly had no cracks or carbon tracks, i did get the front visible to ck t-chain, tdc marked on crank is 2nd from left of 6 notches, cam is 1 full tooth stretched on cam sprocket at tdc, looking across cover deck. ive seen a few motors with stretched chains, that ran perfectly well idling and starting, but some more elaborate cam and crank sensor controlled types might throw codes or limp in this condition, thoughts?

[Niti QX4]

If the chain is stretched that much, I would change it. The only way to get it to idle right, IMO, is to fix all the things you CAN find wrong, and then it makes troubleshooting much easier.

As if stand, FAST; fuel, air, spark, timing. If you can idle, no matter how bad, you have all four. Idle quality is any one of the four.

For me, I start with the easy things first, by visually finding everything that is suspect. Then thinking through if it might have an effect on the symptom. In this case, the timing chain seems to be a suspect - maybe not the real problem, but an issue nonetheless.

I would recommend a smoke test (DIY types on YT are cheap to make), and like you said earlier - a timing light OR a spark plug tester so you can check the strength of the spark. If your timing is wandering, it's either the chain,the dizzy bearings, or the cam gear/dizzy gear is worn out. I've seen some issues with dizzy's mounts being loose also causing issues.

Please keep us updated on what you find

[xrjoe]

got some more work on the pickup, this weekend, installed tps, now has closed throttle circuit working, i got it close to barely running, using timing light checking inductor sensitivity at lowest surge light was still hitting strong, as it was stumbling i shot starting fluid into mass airflow/idle port, it could recover and run, doing that at partial throttle without fluid it would backfire through throttle body indicating lean condition, and im seeing that o2 sensor is not used in idle position, correct?

[Niti QX4]

In the first post, no codes were mentioned?

If still applicable, then the O2 sensor is working the way it should or it would have a code in the ECM
(Code 33)

Also don't know if you have a California truck or 49 state model?

The O2 sensor should always be online, and the ECM is open loop until the EGT shows time for closed loop. If the idle is poor in open loop, then I would check the ignition for sure (spark and timing) as long as the other sensors are known to be good.

From Chilton's:

"When the sensor reaches a predetermined temperature, (usually around same time that the engine reaches normal operating temperature), the signal should fall within certain parameters. At this point, the computer begins to accept information from the oxygen sensor. Up to this point, the computer had ignored oxygen sensor signals, favoring instead the information from other sensors in the engine compartment. The O2 sensor produces a small voltage level, between 0 and 1 volt, that varies depending on the amount of oxygen in the exhaust. This voltage read by the computer as oxygen content in the exhaust stream, which is an indication of combustion. The computer works together with the fuel injectors to vary the air/fuel mixture based upon this information."

[xrjoe]

its california, os is still single wire, my wiring diagram shows 3 or 4 wire for 1995, those would be hego sensors that fail the heating elements and set codes. so now im looking at sensors contributing to fuel delivery, as far as distributor is concerned, tach shows rpm right to stall, as did timing light. ecm shows no codes in tier 3, maybe i should do another drive to confirm what ecm is thinking.

[Niti QX4]

its california, os is still single wire, my wiring diagram shows 3 or 4 wire for 1995, those would be hego sensors that fail the heating elements and set codes. so now im looking at sensors contributing to fuel delivery, as far as distributor is concerned, tach shows rpm right to stall, as did timing light. ecm shows no codes in tier 3, maybe i should do another drive to confirm what ecm is thinking.

Sounds like a plan!

[xrjoe]

did a 5 mile cruise through residential stop and go, ecm is still code 55 happy, only after a dozen stalls, i dont see anything else that would inhibit idle fueling, ecm will be my next replacement, diagnostics are very limited compared to next year obd2, im going to try to source from p.a.p. showing same year and engine, i cant tell whether its manual or auto, and it will need to be cal emissions, tag shows MECM-E210 on this one, if anyone has a resource.

[Niti QX4]

Have you checked here:

https://www.nicoclub.com/nissan-service-manuals

I can try to find more info if that link is not going to help

[Niti QX4]

Are you getting code 55 in Mode 5?

Mode 3 is only for stored codes and if the fault is not setting a code, maybe Mode 5 can give you real time information.

(from Chilton's):

"In Mode 5, the ECU will report one of 3 fault codes while the engine is running: malfunction of the crankangle sensor, the ignition signal, or the air flow meter. These codes are not stored, but can be reported while the engine is running or while vehicle is being driven, if desired. Should the ECU detect a malfunction, an LED will flash on and off at different rates for each sensor. The codes are reported differently from Mode 3. If no fault is detected, no LEDs will flash.

With the engine running, put the ECU into Mode 5.

Watch the LEDs for more than 5 minutes while the engine is operated at different rpm. If any LEDs flash, write down the number of flashes and note the time between groups of flashes.

Compare the notes to the diagnostic codes and related diagnostic charts, to find which of the sensors (or circuits) is faulty.

This diagnosis procedure is a very effective measure to diagnose whether the above systems cause the malfunction or not, during a road test."

Also, from before:

"Mixture is, of course, not readily adjustable in this system. All system adjustments require the use of special diagnostic equipment. Thus, they should be entrusted to a qualified dealer or Automotive Service Excellence (ASE) certified technician with access to the equipment and special training in this system's repair.

It should be noted that proper operation of the system is entirely dependent on the oxygen sensor. Thus, if the sensor fails during normal operation, the engine fuel mixture will be incorrect, resulting in poor fuel economy, starting problems, or stumbling and stalling of the engine when warm."
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So the way I read it, if your problem is occurring during closed loop AND open loop, it seems to be a issue that is not related to the O2 sensor, but instead crank angle and/or ignition related, so maybe Mode 5 will help with real time diagnosis.

[xrjoe]

ill give it a shot, i dont think ive seen the procedure your showing in mode 5, i do use the nico hard body manual, along with other options i can dig up, ill post results and thanks again!

[xrjoe]

alright, i see the one time ignition surveylance mode 5, so wife running throttle was maintaining 1000 to 2500 rpm, at lower rpm its trying to stall, keeping it running i switched to mode 5, no leds lit up, i tried repeatedly with same result, it dosent post 55 either like you asked, mode 3 will post 55 engine on or off.

[Niti QX4]

Ok, I'll do more digging