Author Topic: U12 low range stuttering problem  (Read 9182 times)

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Offline Cheezel

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U12 low range stuttering problem
« on: Jul 3, 2011, 10:34PM »
Hi guys!

Long time reader, first time poster, wished we could've met on better terms. :P

Having a bit of trouble with my '90 U12 TRX. At low revs and high load the engine stutters quite badly. I've sent out the feelers and I've understood that - well, this problem can come from just about anywhere. Given the tiny amount I know about cars, I've been able to rule out the following;

Exhaust is 2 1/4", so (im assuming?) better than stock (car came like this. =.=) - given the engine is stock (and, I might add, relatively new having been reforged ~70,000km ago) I assume backpressure couldnt be causing this.

The following I did myself in an attempt to remedy the situation;

Fuel filter is brand new. Fuel injectors have been cleaned (figured neither would be the problem, since it's only in low revs, but it needed to be done regardless)
Intake is a high flow pod filter (this I did myself - yet to do it properly, it's just a short ram atm. Heh, kids these days...  :-\ ) - this was actually one of my desperate measures to fix it myself, but alas, throttle response improved marginally, and with it the stuttering.

So I'm not sure where to go next, or what to check. Kinda lost now :-/

Offline Colby

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Re: U12 low range stuttering problem
« Reply #1 on: Jul 4, 2011, 09:53AM »
Manual or auto

Autos do tend to need a tune up after a while, my money would be on that for an auto.

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #2 on: Jul 4, 2011, 02:51PM »
Manual.

Just had the clutch replaced fwiw, only done ~1000km on it. Gear ratios are apparently not stock (except second gear, and it's quite noticeable. No idea why it was left like that..)

Could be a clutch problem? Clutch would still be under warranty, I suppose.

Edit: Just read about le Swirl Control Valves causing issues very similar to mine. That's another potential culprit I should probably check. So, uh... How do I check it?  :-[
« Last Edit: Jul 4, 2011, 04:36PM by Cheezel »

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #3 on: Jul 11, 2011, 01:49PM »
So, I checked all the vac lines, despite one being a bit rusty at one end closest to the battery, all seem to be in pretty good nick. The problem's progressed a fair bit and now I've lost a fair amount of power, worrying amounts. It also stalls while idling (I assume this is more to do with the removal of the airbox than the stuttering - mounting a new airbox asap, will post here regarding this).

It's weird, this problem, since it's progressively getting worse. Still random, but occurs more often than not. Spark plug leads are fine and only recently replaced, mayswell check the spark plugs.

Offline krip88

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Re: U12 low range stuttering problem
« Reply #4 on: Jul 13, 2011, 09:55PM »
well when you find out that would be great. took my car out for a spin today and had the same thing. it wont rev past 2500 before it starts shunting pretty bad. ive got a feeling that it might be a timing issue of something simular. has the same sort of feeling to miss firing, its wierd because one day its fine, the next completly crap.

Offline Kranzy

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Re: U12 low range stuttering problem
« Reply #5 on: Jul 13, 2011, 11:09PM »
well when you find out that would be great. took my car out for a spin today and had the same thing. it wont rev past 2500 before it starts shunting pretty bad. ive got a feeling that it might be a timing issue of something simular. has the same sort of feeling to miss firing, its wierd because one day its fine, the next completly crap.

Sounds like yours is in limp home mode. Do a diagnostic check and see if your getting any fault codes of sensors that's forcing it to limo home mode.
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Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #6 on: Jul 14, 2011, 12:18AM »
A bit of an update on my car; now have a custom airbox fitted (aka a paint tin. ;D lol) with an air inlet, which has helped my newly-developed idling issues. The temp sensor that was in the airbox is still out. I've noticed that the stuttering, which would be more accurate to say "quick transition between regular power and almost no power" is completely gone. It's now just low-power 24/7. However, it drives fine at all rev ranges, but consumes twice as much fuel.

I thought it might be the Swirl Control Valves, but if it was an issue with those being constantly shut, I should get a bit of a kick at 3k rpm, shouldnt I? AKA an "invisible turbo" as i saw someone else say. But I don't. It just has half as much power. It feels like the car wants to go but it can't. The revs aren't responsive at all, either. Still idles slightly lower then what it did when I first got it (all of 3 months ago). So I'm getting at my wits end. I also noticed the accelerator cable is in desperate need of replacement, but I doubt that's the cause of my problem - since it's still burning as much fuel as before, just going half the distance. BTW - twice as much fuel isn't an exageration. 600km a tank down to 300km (313 to be exact). So... this is quickly going to become an expensive problem... Will keep posting as I go I guess, 'coz this seems like a common enough issue on the forums, just havent found a lot of definitive fixes.

So far the only one I remember was "fiddle with vacuum lines", and "check the SCVs". I'll check the SCVs as soon as I find them.  ;D But I don't think it's going to do much. =/

Offline krip88

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Re: U12 low range stuttering problem
« Reply #7 on: Jul 14, 2011, 09:02AM »
i would say mine is in limp mode. does and one rear ipswich have a dignostic computer i can borrow and even better land a hand? trying to get a rwc and i dont think it would pass with this problem

Offline FuzzyDropbear

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Re: U12 low range stuttering problem
« Reply #8 on: Jul 14, 2011, 11:03AM »
Hi mate,

The computer itself has a diagnostic mode. Get the FSM here and look for the error codes it returns.
Datsun boys, we like 'em fast, so we drop 'em low, heavy on the gas!

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #9 on: Jul 18, 2011, 12:19AM »
So! Finally got around to checking the ECU. Got a code 41 (air temp sensor) which is probably due to the fact it was disconnected.  :D So i've popped that back in properly, and vwah-lah! Not fixed, perse', BUT it's gone back to being much lighter in the acceleration. And stuttering is back. So! That's fixed my newly developed problem (which is weird since it ran fine without it, then just one day stopped.. running.. fine... =S ) Cleared the computer, took her for a quick spin, checked it again and all is well.

So... now I'm back to square one. I've noticed the Swirl Control Valve is disconnected completely - always has been, since I got the car. There are rubber caps on the ends of the pipes near the swirl control solenoid. So if it's been like that since day one, swirl valves mustn't be the problem, unless they're fluttering around in the manifold? I thought they just seized open when they got old...

Quick recap:
After-market intake
After-market exhaust
ECU is clear
Cleaned out fuel injectors
Replaced fuel filter
Checked all connections in the engine bay

How do you go about cleaning the intake sensors? I'm guessing it's not just a dab of water.

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #10 on: Jul 19, 2011, 06:27PM »
Update for anyone following along with this. Car sat in the garage for a day unused, took it out for a quick spin and everything was fine! Today, as I pulled up my street (with oh-so-many new speed bumps...) it stuttered slightly and went back to being all heavy and slow. Childishly, I cracked the shits and planted my foot ::) It ran perfectly though. Not heavy in the pedal, not sluggish, just fine. So I'm guessing there's a blockage in the fuel system? Would that be it?

It also still starts to pull harder at ~2900rpm, getting a stage 3 chip soon so lets see if it can kill the <3k rpm deadspot.

Edit: It now runs fine after putting my foot down. Needed to make that more explicit. Just for anyone reading in le future. Still not happy though. I keep saying this but I *will* get around to changing the spark plugs. I just dont have any of the tools to do it. Yet...
« Last Edit: Jul 20, 2011, 10:35PM by Cheezel »

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #11 on: Jul 25, 2011, 09:57PM »
Update time:

So, installed the stage 3 (or more appropriately stage 2.5) chip, and the car runs fantastically (albeit with a bit of a backfire. :P) Stutter is removed completely, the car drives super smoothly, however I still had that dip in power for the last minute or so of a short trip around to the gym. When I drove home, it was beautiful again. Now I'm just lost. =/

Offline Kranzy

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Re: U12 low range stuttering problem
« Reply #12 on: Jul 25, 2011, 11:29PM »
check your fault codes again. See if anything is showing up.
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Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #13 on: Jul 26, 2011, 11:03AM »
Already did. Code 55 - ive never been so disappointed to see "everything is ok". Lol
As i was driving along this morning i noticed a whistling noise increasing with the engine speed (not wheel speed) through first and second gear, couldnt hear it in third. Sounds like its coming from the RHS. Any ideas?
I also think theres a loose belt in there somewhere. Will have a look for that tonight.

Edit: Eeeep. Loose belt noise sounds like it's coming from the engine. Closest to the drivers side. I don't have an old-timey hearing horn so I can't stick my head down there to check. I'm brand new to all this sorta stuff (trial by fire is the fastest way to learn I guess! :P), so I've got no idea how to check this. I can't pull off the belt assembly while the cars idling to check. =/ Is there some way of checking it *is* the belt assembly after it's all off? From a quick glance at the Gregory's this seems like a massive job. =/
« Last Edit: Jul 28, 2011, 05:47PM by Cheezel »

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #14 on: Jul 28, 2011, 05:47PM »
We should really change this thread to "The ever increasing list of problems with Cheezel's car". Or TEILOPWCC for short. Kinda rolls off the tongue.

1.) As above. Only thing I can ascertain is that it's not loose pulleys or belts, since there's no give down there. I guess this is one of those jobs I need to send off to the mechanics, since I dont have the tools to pull the engine out. :(

2.) If I turn hard right while accelerating from pretty much a stop, i get this awkward knocking noise from the rear of the car. I'm assuming this is the exhaust tip knocking on the rear bar? Is this common?

3.) While driving in second/third there's a winding noise that increases with engine speed. Is this the alternator starting to go?

ANY HELP WILL BE REWARDED WITH CANDY! ;D

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #15 on: Aug 1, 2011, 07:12PM »
An update for everyone following at home.

So, I replaced all the spark plugs (my GOD were the old ones dead! I'm surprised the car fired at all.), and figured mayswell test all the spark leads. the head of one of the leads came off as i pulled on it (the metal connector inside the right angled section of the lead). So i hadn't been able to check the car since. Got new leads in there today, but no different unfortunately. It also sounds like the pulley on the alternator has done a bearing, or is about to, since it's making a rather unpleasant noise. Anyone got a spare alternator kicking around in half decent condition?

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #16 on: Aug 2, 2011, 08:25PM »
C-C-C-COMBO UPDATE

So, yeah, I feel like a twat. It was spark plugs  :-[ . In future for any users stumbling across this;

Car revved normally, didn't really 'go'. Worked fine some times, others not. Backfired with an aggresively tuned ECU. Cause was a misfiring/non-firing sparkplug or two.  ::)

END OF THREAD.  :P

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #17 on: Aug 3, 2011, 10:59PM »
Edit:

Spark plugs AND water pump.  :'(  Well shit...

Offline Habibosaurus

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Re: U12 low range stuttering problem
« Reply #18 on: Aug 4, 2011, 11:32AM »
Anyone got a spare alternator kicking around in half decent condition?

I have one that was refurbished last year. Offer?

We should really change this thread to "The ever increasing list of problems with Cheezel's car". Or TEILOPWCC for short. Kinda rolls off the tongue.

It can be done if you want... ;D
Ill fight you. May even throw a bar of soap your way. Maybe a few wax strips and some clip on brembo brake calipers for your fooly sic civic.

Offline Cheezel

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The ever increasing list of problems with Cheezel's car
« Reply #19 on: Aug 4, 2011, 11:43AM »
It can be done if you want... ;D

HAH! Doooooo ittttt.  :D

Are you a fellow melbourner by chance? I don't trust Aus Post with interstate hauls anymore.  :P

Offline Cheezel

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The ever increasing list of problems with Cheezel's car.
« Reply #20 on: Aug 5, 2011, 02:36AM »
So I've pulled the thing apart, flushed the radiator, car is currently sitting in bits in the garage.

I'm thinking it is the water pump, not the thermostat. Flushed the radiator, put just water in it with the intention of flushing it. The hose leading from the block to the radiator heated up quite quickly from the engine side, but almost not at all from the radiator side. My fans also automatically come on full bore.

Once the engine was turned off, the heat eventually drifted to the rest of the hose. The hose was hot to the touch. Like, "ow my freakin' hand" hot. (Technical term. :P)

 My theory is that since the heat is reaching the radiator, and the odd way it's doing it, means that the heat is the part that's moving - not the water. IE the pump is not pumping, water was boiling (or near boiling), in the block, the heat rose and drifted through the rest of the coolant system. To further emphasise this, the radiator cap was ice cold while the hose was boiling hot. Even the inside is ice cold.

Going to pull off the pump tomorrow if I can manage.. I have a feeling this is a bigger job than I'm expecting. Already struggling with 5 allen bolts (one from alternator [it'd be nice to have it out of the way], four from thermostat housing). Any tips? Or just get an allen key in there and whack with a mallet? Already tried WD40... If WD40 doesn't work I'm usually out of ideas.  ;D

Offline xxcbonexx

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Re: U12 low range stuttering problem
« Reply #21 on: Aug 5, 2011, 03:59PM »
Might it be worth it to remove and check your thermostat before tackling a water pump? Just get it out with curses and knuckle blood, boil it in a pot of water and check its operation. Without a thermostat, it should open before the water boils. The temp should be somewhere like 185-195F, where water boils at 212F. I don't know the temp on this thermostat offhand.

Time and again I've proven the maxim that you start your process of elimination with the smallest and simplest items by starting out with the most arduous task and working my way to the eventual face-palmingly simple solution.

Offline Cheezel

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Re: The ever increasing list of problems with Cheezel's car.
« Reply #22 on: Aug 5, 2011, 04:14PM »
I don't see how the thermostat is any harder than the waterpump, seeing as how it's just about inside the waterpump. But I'm picking both of the parts up tonight (stock permitting) and replacing both anyhow. I'll test the old parts regardless, and *hope* that one or both of them are actually busted. If not, then I'm seriously boned. Overheating issue with a working pump/thermostat and an unblocked radiator? Le sigh...

Quick question; the fans come on automatically at startup. The temp gauge doesn't work. I'm guessing there's an electrical failure in there.. anyone got an anecdote for me? :D

« Last Edit: Aug 5, 2011, 04:16PM by Cheezel »

Offline Kranzy

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Re: U12 low range stuttering problem
« Reply #23 on: Aug 5, 2011, 05:04PM »
There is two sensors to the left hand side of the intake manifold. One is for the ecu, the other is for the temp gauge on the dash.

If the fans are kicking in automatically then the larger plug (ecu sensor) has a faulty connection or issue.

The smaller one is the sensor for the dash gauge.

You can remove the sensors and clean them with some wet and dry paper to make sure there is no corrosion as this will stop the readings from being correct.

The fans come on by default if there is any issue with the sensor for the ecu.
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Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #24 on: Aug 6, 2011, 03:31AM »
Ahhhh fantastic! Thats exactly what i needed to know.

I just fitted the new pump and thermostat. The thermostat was dead, the pump a little stiff, but working perfectly nonetheless. For anyone doing this in the future; i took the alternator, heat sheild, and water pump pulley off before i even tried to put a socket on the pump bolts ;D all told took an hour or three (broken bolt. FFFUUUU--)

The gauge has been playing up since around the time the thermostat wouldve stopped working... Point of interest i guess. Maybe related? Will see.

Offline Burga

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Re: U12 low range stuttering problem
« Reply #25 on: Aug 7, 2011, 09:52PM »
Did you sort out the fuel economy issue/svc/surge at 3k rpm?


I have pretty well much the exact same symptoms.

getting less than 300km per 1/2 tank


 

Offline Burga

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Re: U12 low range stuttering problem
« Reply #26 on: Aug 7, 2011, 09:55PM »
Actually, 130km per half tank. very bad.

Anyone else have any ideas?

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #27 on: Aug 8, 2011, 01:43AM »
@Burga, Yeah mate I updated a few posts about. It was crappy spark plugs, as far as I could tell. Not that i've been able to keep the thing on the road long enough to go through a full tank. SCV valves were disconnected anyhow. Check your grounds as well, make sure they're clean and rust free, and check your ECU for error codes. Check the oxygen/petrol mixture ratio (through the ECU). Failing that, give it a proper service. I'm assuming you drive well here, obviously. :P




So everything is running well. Except...  ::)

I'm at my wits end and have no idea what to do. My car runs fine now, the pipes all stay nice and cold, the fans dont come on at start up, I replaced the temp-gauge sensor with a brand new one (since it was only $10), and my temp gauge now likes to climb. Quick. The car does heat up, yes, but not to boiling point. It's like the gauge needs to be calibrated? I have no idea what to do! Everything's running. Pump is pumping, thermostat was mounted correctly and sealed, no leaks.

ATM the car is only running tap water, just because it was going to be flushed and ran, until I noticed that issue. Seriously, wtf. Also, my belt noise is back, but I think it's due to pulley tensioning...

Anyone got a good rule of thumb for checking pulley tension? And WTF is going on with this heating crap! *le sigh*... The radiator cap is cool, the water in the radiator is warm, so it *is* flowing into there, the thermostat (new one) isn't seized. The top radiator hose is very warm, bottom very cool. It seems like liquid is flowing as it should. The temperatures in there are MUCH cooler than what they were - it's working *properly*. It's just that temp gauge. And I don't like driving with a disconnected temp gauge... >:(

Edit: There's only one connection to the sensor. What does it use as a negative terminal? If this was a poor negative, could the temp gauge have a capacitive effect? 'coz it increases linearly. Seems fairly irrelevant to the temperature of the car..
« Last Edit: Aug 8, 2011, 01:53AM by Cheezel »

Offline Cheezel

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Re: U12 low range stuttering problem
« Reply #28 on: Aug 9, 2011, 08:36PM »
Sensor was munted. Swapped it over for OEM one. Works perfectly.

Need to flush the radiator a couple (hundred) times, and the same for just about every other fluid in the car, but otherwise it's all good. For now! XD

Offline mudmav

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Re: U12 low range stuttering problem
« Reply #29 on: Oct 6, 2011, 07:25PM »
More than likely something in the ignition system playing up