LP76
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Posts posted by LP76
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7 hours ago, rebuilder86 said:
mm i understand that frustration.
that sort of surging every 2-3 seconds is often a result of an IAC valve doing its thing with a faulty senaor, so the closeat equivalent of that in this car, like everyone else is saying, is this auxiliary air valve, controlled by the collant...
are u able to just temporarily bypass the throttlebody by putting a simple brass nipple between the coolant in and outs to simulate a cold engine? this would allow u to finally rule out or in this as the problem. that seems like the best analysis methid at this point.
there is also an idle speed screw on this thing i believe, at the top i believe, which if not adjusted propperly, is effectively a vacuum leak that u canr see or hear or test for.
I assume you mean bypassing the IAC valve by linking the two coolant lines together, yes? Won't that make the car just idle at around 1100rpm (which it does upon cold starting)?
Also, I thought messing with an idle speed screw was generally frowned upon with an EFI motor? In any case, I noticed yesterday that there is a screw/bolt that appears to set the resting position of the throttle arm. Is this the screw you are referring to? When the car is idling well, and not surging, it stays around 750-800 rpm. This is a correct idle speed, surely? I increase the resting position of the throttle arm, that'll just make it idle higher won't it? Seems like an easy way to mask a problem, but creates another one by making the idle too high.
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6 hours ago, rebuilder86 said:
do not give up.
can u explain what the old surging was like? how long would a single up and down surge last, ie would it cycle between high and low about once a second, or was it relitively long like a few seconds up high, then a few seconds down low?
i can feel ur frustration, but wed all really like to see u get it sorted.
the stalling while coming up to lights sounds like a fuel supply issue, either too much (way too much) or just not enough. here is one particularly common cause of stalling while cold after deceleration with EFI.
while relitively cold, the engine needs more fuel to combat the poor atomization, especially at idle. so before the engines computer switches over to leaned out closed loop mode with readings from O2 sensor, the only things which has a physical impact on fuel flow is the pressure regulator (vacuum vs spring strength). seeings as tho this is happening only before it gets hot, id again be suspicious of a vacuum leak on the actual hose to the fuel pressure regulator. (causing an extremely excesively rich mixture just after deceleration to idle).
The other potential problem could be that the regulators spring is becoming weak, making the suction signal have more effect on the FPR valve and potentially opening up the return line too much leaning out the mix and stalling out. This could be overcome by the hot engine as the fuel atomises better and the idle doesnt need as much fuel like that. So when cold it is so problematic it cannot run. when u restart the motor, the spring goes from completely relaxed (highest fuel pressure) to a nice mid level and doesnt become an issue again until a deceleration event occurs, including, simply revving the motor ans coming off the throttle abrubtly.
the electronic parts which may influence the fuel supply are the injectors and TPS and temp sender. but all of these can probably be ruled out because the issue goes away when they become more prominent in closed loop, whixh u would expect to see more problems from vacuum leaks and sensor faults.
i hope this makes sense
Ok I totally understand what you are saying.
The surging is/was fairly slow; dropping down to around 400-500 over a second or two, then surges up to around 1100 over the same amount of time, then repeat, repeat...
I checked the vacuum hose going from the the manifold to the fuel pressure regulator. Seems okay, no cracking present. I also checked the hose from the regulator downwards as far as I could without getting under the car/really clambering around to follow where it goes.
I bled the coolant again with the rad cap off, and no bubbles came out.
I also made sure a code hadn't been thrown after the stalling event, and of course there isn't one present.
I dunno, I'm ready to give up. If it was a consistent thing it would be much easier to diagnose and fix, but because it so inconsistent, it seems like there is no way of trying to eliminate the potential problem through trial and error.
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3 hours ago, Hiro Protagonist said:
If it goes away for good, then yes it was most likely the cause :P If not, them time to keep ticking things off the list.
I do notice a little flat-spot just off idle in my 7A, the old shell was worse though and could possibly be a stretched throttle cable, check to see if the butterfly moves straight away when you press the pedal or if there is a slight delay from a loose cable (you do need _some_ slack there, but not much).
Okay will check the cable tomorrow.
The idle surge has not been as frequent as of late, though one thing that has happened quite a few times is that when the motor is warming up, just after starting driving, it has almost stalled (and today it actually did stall) when coming up to a set of red lights. I notice it coming back down through the gears, going into neutral when finally coming to a stop. The revs drop almost to stalling speed (as I said, today it stalled once) and then surge back up before finally smoothing out. This has happened three times I think, and each time it has been after the car has been driven, stopped for a few hours, then driven again. Once it's warmed up to full operating temp it doesn't happen. It's very strange.
I'm starting to think I should maybe just sell it and get something else, as I'm pretty over it. Aside from this ongoing problem, the car is great, but the problem irritates me enough that a lot fo the time I wish I had something else.
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On 17 December 2017 at 10:26 PM, Hiro Protagonist said:
Trust me, anyone who has ever owned a 4AGE will have experienced the air-bubble in the T/B at some stage causing a hunting idle speed.
Gas is a poorer conductor of heat (convection) than liquid (conduction) too, remember.
Hi again.
So, I ran the car from cold to hot, and then for an extra 10-15 minutes, with the rad cap off AND the heater on (which I forgot to do last time).
Numerous bubbles came out when the motor became warm, and then finally stopped after several minutes. Could this have been the cause of the intermittent idle surging? I might re-iterate that the surging is not always present, and starts and stops with no apparent rhyme or reason.
More annoying to me is the dead spot at the very beginning of the throttle. It is small, but definitely present. Surely it is should not be there?
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On 20 December 2017 at 1:12 PM, Hiro Protagonist said:
The easiest way to determine if it is an idle-valve issue and not a vacuum leak is to take the intake pipe off to expose the throttle body, and then stick your finger over the hole for the bypass whilst the engine is warm and idling. If the idle stops surging then the issue is in the ISCV (and either a faulty valve, sensor or air bubble), if it continues then the issue is a vacuum leak downstream of the throttle (or with the MAP sensor or TPS).
So, literally just close in the hole in the bottom of the throttle body (the one that leads to the ICV) when it's running? Problem is, every time i go to solve this fucking problem, the idle is fine!
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On 16 December 2017 at 12:46 PM, kickn5k said:
This ^^^
This is a well known problem for late 80's and 90's Toyotas, only did this yesteray on a non turbo jz80 supra. Air gets trapped in the T/B area and tricks the ecu to believe it's running cold.
I did run the car with the rad cap off a few days ago, with no noticeable bubbles coming out over a period of 10-15 minutes of running, from cold to warm. I can't see how you could possibly jack the front of the car up enough to make the radiator cap higher than the throttle body though?
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Pulled the PCV valve again and checked it - seems fine. Can blow through it one way only.
Sprayed carb cleaner all over the chamber to manifold and manifold to head interfaces - no noticeable change in revs at all.
Of course the car was idling just fine when I was checking these things again though.
I'm out of ideas.
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Also, for the manifold gasket, I assume the one between the intake manifold and the engine, not the one between the intake manifold and the intake chamber?
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Sorry, I should've been more succinct. I meant that the PCV didn't appear restricted in that I could definitely hear the "rattle" when shaking it, and from memory I could only blow through it in one direction. It's easy enough to access though I suppose, so will double check.
I checked the coolant level yesterday. Still as good as gold, and running the car with the cap off didn't produce any noticeable bubbles.
The thing I don't understand is if it is indeed a vacuum leak, why would the symptoms not be present all of the time?
Anyway, it's a bit too dark to muck around now, but will try pointing some carb cleaner at the intake manifold tomorrow evening and see what happens.
Will be reporting back.
Cheers again folks.
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On 2 December 2017 at 10:55 AM, rebuilder86 said:
Try not to become fixated on what I am saying, but ensure u really thoroughly check that gasket. then
PCV valve, shakes freely and blowing through it should be heavily restricted in one direction.
Brake booster, (see if it happens more when u push the brakes, if so new booster needed)
fuel pressure regulator vacuum hose ( a small leak here would have more effect on fuel pressure than the same size leak elsewhere, true fact)
check those and get back to us.
Am I able to detect a leak at the intake gasket with the motor running by spraying with carb cleaner or soapy water? I've never removed an intake manifold before, and am a little hesitant to do so.
Pushing the brake makes no difference. I had the PCV out a month ago; inspected and cleaned it, it didn't appear restricted.
The surging (revving up to 1100 rpm or so) happens immediately after the idle drops down to 400 or so. It doesn't all of a sudden sit at correct idle and then go straight to ~1100; it's always a noticeable drop down first, THEN a spike up.
And there is a small, but definite, flat spot right at the beginning of the throttle.
Thanks for your help.
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On 26/11/2017 at 3:24 PM, rebuilder86 said:
I'm almost certain u have a large vac leak and it will be the intake manifold gasket itself. Usually a few mm of it gets sucked in from deterioration from oil and gasoline.
If u had said u had code 31 with no noticable symptoms at idle i would have told u it was the MAP sensor itself.
but the surging idle of up to 1500 rpm is in 95 % of cases a large vac leak.
cet up close at idle and listen around the manifold connection.
The car had some other work done at the mechanic a few weeka back and I got him to check the throttle problem as described. He removed and thoroughly cleaned the throttle body and the IAC valve. There was no noticeable deterioration of the gasket between the throttle body and the intake. I got him to check the error code 31 I had previously detected, but it was no longer present. I assume it had been cleared after my previous attempts at cleaning the throttle and various valves, which I described earlier.
When the problem arises, which is intermittently as I mentioned above, the idle fluctuates slightly between ~600 and 1100rpm. It never stalls or goes much higher than 1000. The most annoying part is the small dead spot at the start of the throttle.
I inspected all the vac lines last time but couldn't hear/see/find a leak.
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Turns out the dreaded problem I described never actually went away. I thought it did, but is still occurring intermittently.
Most noticeable when car is cold and starting to drive. Small dead spot at the beginning of the throttle, and jerkiness when driving at low rpm until the motor warms up a little.
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So, after all the mucking around, the car has settled into a nice idle, no hiccups, surging, or hunting, and most importantly, no dead spot in the throttle. I didn't end up bleeding the coolant system, so I assuming that it was one or more of the components that I cleaned that were causing the problem. Thanks very much to all who offered their opinions and time. Now, to replace the rear shocks....
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1 hour ago, Hiro Protagonist said:
Just checking, how is your coolant level? Classic 4A/7A problem with an intermittent idle is an air-bubble in the cooling system causes the cold idle valve to open and shut even when the car is warm - might be worthwhile topping up the radiator and then bleeding the system (jack the front of the car up so the radiator cap is the highest point in the system, and then run the car until warm with the cap off and the heater tap open to try and force any bubbles out of the system).
Okay, will give that a go. Cheers.
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So, I cleaned:
* the throttle plate & body in-situ
* PCV valve (removed and cleaned)
* IAC valve (removed plug, removed middle hose, filled hole in throttle body with cleaner, turned valve back and forth many times, drained cleaner - moves very freely)
I checked visually for signs of vacuum leaks, but can't see anything.
Car started fine, no hesitation. No noticeable flat spot in idle when pulling on throttle arm a few times. Did a few laps around the local area, then went back home. Sat car in neutral in carpark, intermittent idle still apparent - fluctuating between approx 700 and 1100 rpm. Seems to be when the engine is near or at correct operating temp. Any ideas?
Should I just go ahead and replace the MAP sensor (I didn't want to remove it and mess up its adjustment)?
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3 hours ago, ke70dave said:
Anything to do with the throttle points at TPS too. Unplug the tps, try again and report back.
Did you mean unplug the TPS and then run the motor to compare before/after?
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19 minutes ago, ke70dave said:
Anything to do with the throttle points at TPS too. Unplug the tps, try again and report back.
Okay, will do
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7 minutes ago, ke70dave said:
Therse not much on a 7afe, i would pull off the rubber hose that goes between the airbox and the inlet and inspect. Inspect all the vac lines.
Worst case, get some throttle body cleaner and spray it around where you think there might be leaks.
With a map sensor you are really looking for issues after the throttle body.
also keep in mind map sensors are dirty cheap from the wreckers, if you have a wreckers close go and grab one. Note the code on the map sensor it self and go and look at Toyotas of similar era if you can't find exactly your car, they used the same map sensor on loads of cars.
Okay thanks.
Also, just now, I notice there is a definite flat spot right at the start of the throttle.
Would that help narrow down the cause of the problem?
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9 minutes ago, ke70dave said:
Map sensor code I think can indicate a vacuum leak too, as the map sensor gets a funny signal.
I'd be removing the ICV and cleaning the crap out of it, then check every vacuum hose for leaks especially the big rubber hose on the inlet manifold.
I think I can hear some hissing coming from somewhere near the throttle body.
Can you suggest a good way to find the source of the potential leak?
Thanks so much.
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10 minutes ago, Hiro Protagonist said:
31 should be the MAP sensor, I think 33 is the idle valve.
That doesn't necessarily mean that it's a problem with the sensor though does it?
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Hey folks,
I have a '99 Corolla with the stock 1.8 7A-FE motor.
It intermittently surges when idling (i.e. - pulling up at lights, fluctuates between ~ 500-1200 rpm), but doesn't do it all the time. Sometimes a quick press of the accelerator will stop it and it'll return to an idle of around 800 rpm or so, sometimes it doesn't. For the first few minutes after cold starting, the car will jerk a bit at low speed, but goes away within a few minutes of running.
Local mechanic has sprayed the throttle body, and it's had a recent full service (air and fuel filters, plugs and leads etc.), but it hasn't made much difference, aside from alleviating the sticky accelerator pedal.
A quick diagnostics check is returning fault code 31.
Possible MAP sensor or IAC valve problem?
If anyone is good with these motors here, please tell!
Cheers.
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Hi folks,
Just thought I'd share the successful wiring of spotlights onto my 1999 (AE112R) Corolla.
I thought it would be very helpful, as searching the entire internet for a correct wiring diagram is a day's job in itself. Most folks know about the negatively switched headlights in Corollas, and the associated difficulties in adding additional lighting. A lot of posts claim that the only way to do it is to tap into both the common and/or hi beam earth wires behind one of the headlights, but the following way avoids splicing into the massive loom, and thus keeps the messiest work inside the car, away from the elements.
I copied the following diagram, which was posted for a Hilux on another forum:
http://www.4wdaction...42584&mode=view
I tapped into the trigger wire (RED WITH GREEN STRIPE) on the steering column headlight combination switch, right after it leaves the plug. I found this the easiest to get at, and simply cut a few centimetres of the heat shrink back and used a quick splice connector.
I passed the wire from the switch to terminal 85 on the relay through one of the existing wiring grommets that comes out basically behind the clutch pedal. Again, this was the easiest to get at, as far as I could make out.
I mounted the switch for the spotlights just above the bonnet release latch, as this allow easy access through the removable fuse panel faceplate / coin drawer.
Spotlights are activated only when the switch is on AND the main headlights are pushed to high beam, which is law here in Australia, as far as I know.
I really hope this helps someone who may want to add spotlights or other lights to their Corolla by saving them the hours I spent searching for a correct wiring diagram.
Cheers!
AE112R / 7A-FE intermittent idle surging, fault code 31
in AExx Corolla Discussion
Posted
Yes I've read this too.
The screw I refer to is behind the throttle arm, and appears to simply change where its resting position is. Is that the scree you are referring to?