RPM drop and stall on load at idle

[thatdevsherry]

So I've encountered one of the famous issues this car is known for, dropping RPM.

This issue happened right after the engine was rebuilt.

I've done some things which I'm documenting here because this issue has been driving me crazy. This is a long story and I'll be yapping so please bear with me.

First occurrence

During break-in period, I was driving the car and came up to a u-turn. I braked, and then as i steered into the turn the engine stalled. The RPM would drop when I would brake and steer a bit, and every u-turn and parking spot became a guessing game of "will it stall", until I got fed up and tap accelerator pedal during turns.

Replicating issue

Now I knew this would happen in u-turns and when i was parking, so I replicated moving the car just a bit back and forth and steering as if I was parking, and lo and behold, engine stalled.

The method I found was

1. Press brake, then release
2. After brake is released and the idle is adjusting a bit after vaccum change, start steering
3. RPMs would instantly fall down to near 500 mark and the car would stall (occasionally, but rpm would always drop and car would shake as if asking for mercy)

Now this wouldn't necessarily happen on full steering lock, but before that. The PSPS activates somewhere in middle and if it activated, the idle would go up and the car would not stall, but I did see it struggling even with PSPS activated and would die, but that was very rare. Almost all the time when the PSPS activated, the rpm would go up and the stall was avoided.

Diagnosis by mechanics

I showed this to a few mechanics and they boiled it down to

1. throttle body
2. iacv
3. power steering pressure switch
4. map

Throttle body/IACV

The guys that originally rebuilt the engine suggested that the throttle body needs to be changed as it has wore down around butterfly valve. I didn't question that since they have expertise and are quite popular (engine job was good ngl), but I had hoped that it would've been better if they had shown me the vaccum gauge reading or e.g. closed butterfly valve and blocked IACV and shown that engine is still running (butterfly not sealing properly) rather than just a look. But I'm not a mechanic so this is just my view.

We changed the TB + IACV, and well, issue still remained. Now with an additional issue that my RPMs would hang before coming down. If A/C is on at 850 RPM, i do just a teeny tiny blip, the RPMs shoot up to 1500. Made driving with A/C in traffic weird.

All to say, the new TB+IACV that I paid for, did not resolve the issue.

Power steering pressure switch

Now this was interesting. The PSPS was still the same before and after rebuild. So jumping to that didn't make sense. But I still tried. I installed another PSPS which was super sensitive. Slight steering at operating temp caused idle to go up.

This made driving in parking lots and turns bad. I don't press the clutch often in low speed turns and whenever I turned the steering a bit, the car would surge forward because the PSPS was activating so early. I could drive the car w/o applying throttle just by moving the steering left/right

This did make the RPM not drop whenever I steered. However, in a parking lot (again) the RPMs dipped down... and engine died. This happened once but it showed the sensitive PSPS was hiding the main issue, but it didn't actually resolve it. I switched back to the less-sensitive one.

Although I wish I find time to get a guy that can hook up a pressure gauge and I can verify that my PSPS activates within the range specified in manual. The super sensitive PSPS was hideous to drive with and I don't want someone to just move the steering a bit and say PSPS is bad and I should go back to the super sensitive one, because that did not resolve the issue.

MAP

The car runs fine otherwise. Pulls good, off/on throttle smooth. No abnormal engine behavior except on idle and this rpm drop when turning with clutch pressed. So I did not look into this.

Looking into electrical side

So after countless visits to mechanics and being told "sir throttle body", which I had changed twice, IACV being changed thrice, I decided to look into it myself.

Now there's this funny electrical thing in my car, whenever I brake or indicators turn on, the interior light and dash light dims. This was already present before the engine rebuild but it could be that this issue now became more prominent.

There's also a flasher thing installed that whenever a door opens, it turns on hazards for a while, and that takes quite a lot of load. Lights dim and the engine sound changes on each flash. I then checked it's interference by starting the car and as the rpms were coming down, I opened the door and on each indicator flash the rpms dipped, and on each flash end the rpm would come up a bit, so there's some interference with that.

Also, I noticed a weird starter behaviour that after engine rebuild, when the engine was at operating temp and I turned it off and turned it on a few seconds later, the first crank would get stuck, all lights would dim, and then after a moment the engine fired up. (re-enactment: AHA...HABRRRRR where BR is engine running)

Related to this, sometimes on hot day when I did the above, the crank would be super slow, as if the battery is weak. But leaving it to rest for a minute and cranking again started the car or just pushing it did. (re-enactment: aha..ha...ha...ha...ha..haBRRR)

The flasher relay is definitely interfering but it's inactive during turns so it's not entirely that.

Diagnosing it myself

A garage near me had a scanner, since generic OBD2 scanner don't work in this car, I told the guy "please let me use your scanner". He setup the scanner and told me "enjoy". Thank you guy.

So I looked at the different values and compared them with the reference values in the baleno/g13bb manual, and all were within range (MAP, TPS, IACV duty cycle %).

Now I also noticed that the RPMs drop when I turn on headlights. However the electric load switch turns on so that signal is being sent.

Now I did this dumb thing where I told myself "please take graph screenshot of IACV duty cycle + RPM + battery voltage), but then totally forgot to do it.

However I had noticed one thing, which doesn't seem too big but might hint. The battery voltage read by ECU at idle was 13.7V, but attaching my multimeter to the battery showed ~14.4V. That's a 0.8V voltage drop. I was expecting ~0.2V difference but this was larger.

Turning on headlights would drop the ECU battery voltage to ~12.7V and then it would recover. I didn't take the screenshot but I remember when I braked and steered the RPMs would drop but the IACV duty cycle did not increase (the graph here would've been super helpful). This is of course before the PSPS activates, as that does raise the duty cycle, so does A/C.

Now the manual also states you can test PSPS by unplugging and turning steering full-lock. The RPMs will drop with both PSPS connected/disconnected, just that the drop will be more when it was disconnected. However I'm able to make the car stall sometimes by steering with PSPS disconnected (not always, but it does happen).

Another weird behaviour that I'm trying to replicate is when I'm turning ac off/on and applying a bit of throttle, when I turn the ac off, the idle just gets stuck at around 900 RPM. The intended idle is 700+-50, ECU is saying bro 706 desired idle, but the idle just gets stuck indefinitely at higher RPM. I think blipping didn't resolve it and I had to turn the car off to reset this behaviour.

All in all, I have rotated the IACV near the closed position so I don't get that awful hang, and to get the IACV duty cycle to take over around 15% (manual said idle no load it should be 5-25%, so it's in range). Full closed position takes over near 20%, full open takes over near 2%.

Someone told us to adjust IACV to full open position, but that just introduces hang and on idle it still stalls, same behaviour.

Side note, I sometimes get a DTC for camshaft position sensor, but the sensor works fine. Could be a hint to something electrical.

Oh and another thing to add, some mechanic had unplugged the ECU grips and upon replugging, the RPM started bouncing around. Good ol slapping of the grips solved it. So there's definitely something about the wires and connectors of ECU.

Major notes

• Camshaft position sensor DTC pops up occasionally, but sensor functions fine, car wouldn't start otherwise
• ECU battery voltage reads ~0.8V lower than actual voltage at battery e.g. 13.7V when actual is 14.4V
• IACV duty cycle didn't increase on steering when RPMs were dropping (I hope, dumb me didn't take graph screenshot to confirm cuz if it did, I could narrow into IACV itself)
• AC on/off + blipping throttle shenanigan sometimes enters idle into a higher state indefinitely. Desired idle is at 706 but engine speed get stuck at 900
• ECU grips were removed and replugged but caused idle rpm up down 800-1300, replugging grips hard fixed it. Something is bad about the wires/connectors.
• Door opening flasher relay affects idle, brake affects interior light and dash light, but this was present before rebuild as well and didn't cause stalling
• PSPS activation delays as engine warms up. Cold engine PSPS activation happens early in steering, operating temp PSPS activation happens later. Maybe that's intended as fluid thins out with heat
• I cleaned the ground terminals of engine bay and tested voltage drop and they're good (0.02V)
• Need to clean ground points in cabin, as I don't know which grounds the ECU uses
• I tested the brake booster and the tests pass (both holding down after engine off + pressed and engine on)
• pumping the brakes raises the rpm and then holding the last pump makes the rpm drop down to 500, then engine recovers
• i saw my air filter was super dirty, I removed and pumped the brakes again, the change was that rpms didn't go up much on pumping

Possible causes to me

• If reading a lower battery voltage, ECU might be compensating by reducing idle on load e.g. turning on headlights drops battery voltage to 13.5 and then alternator ups it to 14, but the 13.5 drop would be read as 12.7V by ECU and might be reducing idle due to reading a low voltage
• I have to yet again go out and search a good TB or IACV
• Voltage drop in starter circuit (still an issue albeit unrelated as that circuit is independent I think)

[rajaatta]

Seems like voltage shortage some where in harness.
Alternator can be faulty
Starter can be faulty
Engine bay wiring harness can be grounded short little.
This is a good amount of diagnosis you have already performed.

[pwuser153796752163]

Did you check for a bad ground?

[thatdevsherry]

@rajaatta

Thank you for sharing your view.

I will try and test out the alternator and starter circuits to see if I can rule these components out.

There's certainly a voltage drop somewhere in the wiring harness, will see if I can make progress.

@pwuser153796752163

I cleaned the 4 ground points in the engine bay and did a voltage drop test on them and they're good.

The 4 grounds as mentioned in manual:
- fender side near intake, thin wire
- intake manifold near IACV
- fender side near battery (battery - chassis)
- transmission (battery - transmission)
- bonus: there's this puny little wire that connects from throttle body bolt to strut mount, cleaned that but it isn't in manual, maybe it came with CNG fitting ones as mine had CNG prev. before buying.

There are 7 remaining ground points in cabin acc. to manual that I'm currently checking:
- on top of fuel tank (i can't take off the fuel tank myself so ignoring this one)
- behind rear seat driver side (cleaned, voltage drop not verified)
- behind rear seat passenger side (cleaned, voltage drop not verified)
- near front passenger center tunnel (yet to check)
- near front driver side center tunnel (yet to check)
- on steering column (yet to check)
- behind front vents (i haven't found this. the manual has image of old GTi baleno one so I'm not sure if there's a ground there)

[pwuser150504674948]

In my case a pin hole airleak in the intake manifold caused rpm drop, lean mixture and what not.
that happened after the manifold was dismantled for cleaning. surprisingly there were no codes.
car was civic 2005 though.

[thatdevsherry]

That could be a possibility since engine was rebuilt and the intake manifold was taken off. The MAP reading on scanner was within the reference range though. But it can be possible as that falls in the engine bay where the major work was done.

Could maybe explain why the cold start rpm shoots up to 1500-1600 and then quickly adjusts to 1100, or that if i fully close the iacv, the cold start rpm seems to adjust itself i.e. starts up at 1100, comes down to 1000, then again goes up to 1100 or something.

Oh well better to verify this as well. Thank you for sharing this insight.

[thatdevsherry]

Update on the situation. It has gotten a bit better.

I went to an electrician, he was poking around. Moved the engine harness, spark noises were heard. Engine stalled... And I used to laugh at my cousin cuz his baleno does the same.

They took out the engine harness and "refreshed" it. Not entirely too happy on the job but hey, they fixed the shortage in it so I'm happy.

ECU now reads 14V at battery instead of 13.7, so that's also good.

I checked my trusty brake + steer at idle technique, and the rpm still fall to near 500, but the car is now recovering better.

This means refreshing the wiring indeed has made the ecu handle engine better. I think idle hang at ac was also addressed. Haven't thoroughly tested but the one test I did it wasn't hanging when at operating temp.

However, the fact that rpm falls to 500 is still concerning to me. When I'm maneuvering in a parking space where I might be moving the steering left right with brake, the rpm during the maneuver falls a lot and I feel the engine will stall, but it recovers.

But the rpm drop seems too low for me. The engine shouldn't be reaching the rpm where it's just barely running. This was in workshop. Haven't noticed rpm fall frequently after that.

Will be opening up and replacing intake manifold gaskit to rule out intake manifold leak.

P.S.

after wire refresh, my electric load switch is reversed. It did happen before too when connectors of ecu were removed xD

I looked at the wiring diagram and saw that the pin for EL is in the connector that isn't connected to the engine harness. So probably when they were taking out the two engine harness connectors they moved around the 3rd and and EL got reversed. Definitely a problem in the circuit which I'll try to address. Maybe it's related to the 2 connectors, maybe not.

Funny that I told electrician that the switch got inverted, and he responded "sir this is janyn. comes reversed from factory"... The manual I'm following isn't janyn i guess

The manual also shows me the normal voltage value for each connector pin. Whenever I find time I'll try to DIY it and tally each pin voltage to the values in the manual. Thank god I have these manuals. Whenever bored I can spend time learning about this car/engine XD

Next steps:

a) Replace intake manifold gaskit to rule out pinhole leak
b) Fix inverted EL (not sure if this impacts too much but better to fix what I can see is wrong)
c) check each pin of ecu connectors to see they're within the range mentioned in manual

[msabbasi]

Certainly you are much more knowledgeable than I. I am very old school. To me RPM dropping under load seems like a lean condition. In the old days we used to measure manifold vacuum to look for leaks. Nowadays a smoke machine is used to find leaks. Watching this space for more updates. Great to see someone going about it in a methodical and educated way.

Amazon.com: Solary Automotive Smoke Machine Leak Detector - 12V DC EVAP Vacuum Diagnostic Tester for Pipe System : Automotive

[thatdevsherry]

That is very kind of you, but I'm just someone that takes interest in learning about their car. Not much of an expert

Thank you for letting me know about this approach.

I will see if I can make a DIY smoke test. That will make things crystal clear about the leak before replacing the intake manifold gaskit.

[abid110]

i kept Baleno for 4+ years, 2004 JXR FF CNG version - i faced all issues you mentioned. things which helped me in solution to all issues are listed below:

*change of battery terminals as old were heat soaking and resisting flow of current to the whole wiring
*tightening/cleaning of cramk sensor located just above right side front wheel and if not fixed properly gives staring issues and stalling issues
*redone complete wiring through a competent electrician in Karachi who took care of each and every wiring issue/grips/taping and the results proved excellent till i sold the car

mechanics have hobby of throttle cleaning and this almost never helps. the Throttle you originally had would have been fixed in some other baleno in the name of kabli.

[thatdevsherry]

Irrelevant update. Not regarding the original issue.

I checked the voltage on the electric load pins. One is coming directly from blower motor (A17) and other goes through an OR gate consisting of defogger and tail light diodes (A16).

Ref. value for A17 is 0-1V when ON, 10-14V when OFF, but I was getting about 0.02V or something when blower was OFF. Not sure if my probing was wrong but oh well.

Ref value for A16 is also 10-14V when either defogger or tail light is on. It was working perfectly fine.

Seems either the connector gets weird when plugging into ECU or the ECU pins are weird.

But I plugged the connector back in with some force and locked it in place.

Started car and noticed the following (no scan tool):

defogger
a) normal idle
b) turning on defogger, idle sound increases tiny bit, rpm needle moves up a bit
c) turn off defogger, idle drops a bit back

tail light
a) normal idle
b)turn on tail light, idle sound increases same way, rpm needle moves up same as defogger
c) turning on headlight instantly from OFF keeps idle steady
d) turning on headlight from tail lights drops idle a bit, but recovers. Expected as EL was already on so it had to adjust with load

blower
a) normal idle
b) moving blower to LOW position also raises idle a tiny bit
c) moving instantly to FULL lowers rpm tiny bit before recovering. think this is also fine

Scan tool will verify this but the behaviour I'm seeing indicates it's working correctly now.

[pwuser161684645588]

@thatdevsherry Brother This issue also happened with me, Like @abid110 said it's wiring and Crank Sensor. I replaced the Crank Sensor and got the wiring redone since i thought getting a new one was expensive (now i regret not getting a new one xd). My issue was resolved.

anywayys, I also have a issue with my Baleno. The issue occurs when the car is in 1st or 2nd gear (in higher gears the jerk is very less). While the RPMs are at or above 2000, if I let off the accelerator, the RPMs drop as they normally should. However, once the RPMs fall below 1500, the car starts to jerk.

I got this diagnosed, and according to the mechanics, there was play in the gearbox where the CV axles mount. As a result, the entire gearbox was repaired. Unfortunately, the issue still persists.

Later, another mechanic suggested that the problem might be electrical—possibly something related to the current or wiring. He recommended changing the coil wires, which I did. After that, the car ran okay (not 100%) for a while, but now the issue has returned.
Can anyone help me in this issue?
@abid110 have you encountered this type of issue ever in your Baleno??

[thatdevsherry]

Another "TODO" update.

I haven't been able to find smoke test machines so I'm not replacing the intake manifold gaskit as it's a waste of time if I don't have an issue to go after.

I did try spraying carb cleaner around the intake etc and the rpm didn't change. This method isn't that good since small leaks might not show change in RPM, but I'll assume it's all ok for now...

Next step I'm gonna do is check the exhaust CO% from enercon. Manual states 0.8 to 1.3 spec. So I can look at the CO% and see if it needs adjustment due to new bore which may require AFR adjustment.

However the CO% reading can also be off if there's a vaccum leak.. but better to get a reading and see where it sits.

[thatdevsherry]

Update on CO%

So I went to enercon, and they hooked up the exhaust gas analyzer. The reading came out at 0.48.

This is lower than what's mentioned in spec (0.8 - 1.3).

However, the guy there was very reluctant to adjust it. He said this is fine and it should be near 0. Moving to 1 will be bad.

Proceeded to show me a totally modern car and said look at it's CO% which is 0.38. I'm not sure how this is relevant since that car has a cat, mine doesn't. They're supposed to have lower CO%.

Thinking I will locate the AFR potentiometer and then visit them again to have it adjusted to at least 0.8.

@msabbasi would you happen to have some knowledge about this? I know that a vaccum leak would also show lower CO%, but this feels like the AFR needs adjustment after the engine was bored.

The guy also changed my throttle stop screw and raised idle... I'll have to adjust it back. The engine has rotary iacv so I usually adjust by unplugging it and blocking the bypass port as rotary valve becomes sort of free, then adjust base idle to near 650 as spec is 700 +-50, base idle near 650 and let iacv fine tune b/w 650-750.

[rajaatta]

Is your vehicle has oxygen sensor?
If yes then no potential meter will be there to adjust the afr

[thatdevsherry]

@rajaatta It doesn't have oxygen sensor. So it should have the potentiometer under the dash.

[rajaatta]

Yes if oxygen sensor is not present then pot adjustment should be present

[msabbasi]

Sorry I can't help you.

[thatdevsherry]

@msabbasi no worries

Today's update

I had a scanner hooked up to adjust throttle stop screw. Unplugged and blocked IACV port with a cloth, engine died immediately.

Adjusted the stop-screw so it would idle around 630-650 with IACV blocked. Used machine oil to lubricate IACV in case it was stuck. AC/PSPS idle-up are smooth as before. But rpm drops still, even with super smooth IACV. Also noticed that when i turn off AC, the rpm sometimes drops to 500 and then recovers.

Throttle adjustment is perfect now. Off-on throttle is buttery smooth. Ticking off IACV and throttle adjustment.

@rajaatta I was able to find the potentiometer.

Since I had the scanner hooked up, I had an idea that "AFR potentiometer should adjust injector pulse width acc. to my googling".

I pinned engine speed, inj. pulse width & iacv duty cycle. Ignored the big "exhaust gas analyzer" because it's far away from my place xD so I thought a good first step would be to change inj. pulse width and monitor idle behaviour on load.

The inj. pulse width at ~700RPM was ~2.4ms. I rotated the knob 1 full turn, nothing changed. Rotated 2 full turns toward the rich side, still the value was at ~2.4ms.

Then rotated it back but it was a bit of guessing game. I was pretty sure I would've seen the value increase. I don't see how it would adjust the mixture in any other way. Plan was to increase the pulse width by a small margin and see if idle on load improved. But now the knob seems to not do anything

Will have to investigate more.

[msabbasi]

Hooked to your thread.