1996 Celica GT - Rough Idle when warm - Toyota Nation Forum : Toyota Car and Truck Forums

allened · 04-01-2011, 02:47 PM

When the engine is completely warm the idle becomes very rough. Like it missing alot. Its very had to get rolling, its bucking until I get over 2k then its fine. and it only does this when warm.

I unplugged the TPS an it made the problem go away but it has a high Idle 1200k. SO i replaced it and when it was plugged back in the problem started again so I have left it unplugged as of now.

The plugs and wires etc are new and I just cleaned out and tested the EGR which is functioning.

Anyone have any Ideas. could this be a IAC problem its weird that unplugging the TPS makes it better.

RobMilkshakes · 04-01-2011, 03:23 PM

well unplugging it would make the ecu make the idle higher as it has no idea where it currently is. Do you have an auto or manual trans? Do you have any check engine codes?

allened · 04-01-2011, 03:30 PM

Quote:

Originally Posted by RobMilkshakes

well unplugging it would make the ecu make the idle higher as it has no idea where it currently is. Do you have an auto or manual trans? Do you have any check engine codes?

I have a manual trans. And the only one I did have was insufficient flow to egr but I just cleaned that and verified that is was working, doing a vacuum test when it was warm and causing the engine to stall.

So the high Idle is high because the TPS being unplugged I knew this would happen, But since the engine does not know where the throttle position is what would cause the engine to run fine then. So when it is plugged it it is telling some part to activate when at idle causing the rough idle so what parts could those be? I have been hitting my head against a door because of this.

RobMilkshakes · 04-01-2011, 05:30 PM

Well the TPS and idle air control valve both have an effect on idle. The control valve itself actually controls the idle. The same thing happens when you disconnect the IAC. Does this happen regardless of how fast you let the clutch out, as in, not letting the revs drop too much and easing the clutch out?

allened · 04-01-2011, 06:04 PM

Quote:

Originally Posted by RobMilkshakes

Well the TPS and idle air control valve both have an effect on idle. The control valve itself actually controls the idle. The same thing happens when you disconnect the IAC. Does this happen regardless of how fast you let the clutch out, as in, not letting the revs drop too much and easing the clutch out?

Yes, I tried all types of shifting, starting at 2k then letting it out, starting from idle then letting it roll start etc.
I went to autzone and these are the codes I pulled with the TPS unplugged so I think its best to ignore the TPS and IAC code.

P0401 Little flow on the EGR
P0125 Insufficient coolant temp for closed loop.

P0120 Faulty TPS *as Noted
P0505 IAC faulty *as Noted

So i guess even after cleaning out the EGR it still shows the code. can the EGR really cause all these problems?

PS when I spray starting fluid into the intake it causes the engine to almost stall, i thought it would cause a surge not a stall.

spider77 · 04-01-2011, 07:46 PM

P0125 Insufficient coolant temp for closed loop.
Whats up with that, its almost unrelated. And yeah, Ive heard of cases where the a bad EGR can cause the car to run like crap. To answer your question about the starting fluid. Yes, it will cause the engine to bog down. Its like spraying liquid up in there (case thats pretty much what it is), it doesn't instantly burn off. Take seafoam for instance, pretty much denatured alcohol (correct) it'll still bog down an engine if its too much.

allened · 04-01-2011, 08:24 PM

Yeah the coolant thing was new for me, the car actually operates well below range.

But the reason I ignored the egr valve itself is because I did a vacuum test and it killed the engine which from what I have read everywhere it means its still good.

I cleaned out another part on the valve cover there is a peice that screws into the back passenger side that has two vacuum hoses going to it and one runs to the vacuum ass module. It was clogged bad when I put it back the idle seemed ok but the acceleration is still weird off the line. So maybe the idle was one problem and now this acceleration thing is a second problem.

This is my third celica and I loved them all until this one, nothing but a pain in the ass.

Tech1984 · 04-01-2011, 08:31 PM

Hi, I know your problem. Fixed quite a few of them with this concern.
Ok, the bad news is, it's an expensive little bugger.
The good news, I'll save you a lot of headache diagnosing. It's the MAP sensor located on the firewall.

allened · 04-01-2011, 08:53 PM

Quote:

Originally Posted by Tech1984

Hi, I know your problem. Fixed quite a few of them with this concern.
Ok, the bad news is, it's an expensive little bugger.
The good news, I'll save you a lot of headache diagnosing. It's the MAP sensor located on the firewall.

That was the piece that I was talking about right before you posted. I unplugged it and it mad it run all weird. So if it were bad would it run more poorly when I unplug it. Thanks. I just want to verify if I have to go buy this spending part.

Tech1984 · 04-01-2011, 09:03 PM

Quote:

Originally Posted by allened

That was the piece that I was talking about right before you posted. I unplugged it and it mad it run all weird. So if it were bad would it run more poorly when I unplug it. Thanks. I just want to verify if I have to go buy this spending part.

Yes it would. Really bad. But as soon as you plug in a known good one, she purrs! I encourage you to try one out first, tho.
Here's some steps:
INSPECTION
1. INSPECT POWER SOURCE VOLTAGE OF MAP
SENSOR
(a) Disconnect the MAP sensor connector.
(b) Turn the ignition switch ON.
(c) Using a voltmeter, measure the voltage between connector
terminals VC and E2 of the wiring harness side.
Voltage: 4.5 − 5.5 V
(d) Turn the ignition switch OFF.
(e) Reconnect the MAP sensor connector.

2. INSPECT POWER OUTPUT OF MAP SENSOR
(a) Turn the ignition switch ON.
(b) Disconnect the vacuum hose from the MAP sensor.
(c) Connect a voltmeter to terminals PIM and E2 of the ECM,
and measure the output voltage under ambient atmospheric
pressure.
(d) Apply vacuum to the MAP sensor in 13.3 kPa (100 mmHg,
3.94 in.Hg) segments to 66.7 kPa (500 mmHg, 19.69
in.Hg).
(e) Measure the voltage drop from step (c) above for each
segment.
Voltage drop

allened · 04-01-2011, 09:23 PM

After looking up the map sensor and how easy it was to swap out I took one from another celica of mine and put it in to say the least all the symptoms still remain. Everything I try is just taking me back to square one.

Tech1984 · 04-01-2011, 09:31 PM

You have so many things disconnected and reconnected it's time to start that square one.
Lets first disconnect the battery (neg side) and let it sit a while.
That TPS you replaced. Was it dialed in when installed using a muti meter?
Spraying starting fluid into a warmed up running engine is a big no no.
Please don't try that again.
Sorry for leading you down a wrong path, but this is sounding more like a bad thermostat and
a faulty CTS (coolant temp sensor)

allened · 04-01-2011, 10:26 PM

how can a CTS create all of these problems? I I thought it just controlled the radiator fans.

RobMilkshakes · 04-01-2011, 11:57 PM

No the coolant temp sensor has an effect on the air/fuel ratio as well. Its inexpensive and quick to replace so would be worth swapping

allened · 04-02-2011, 07:04 AM

I will see if autozone has the part instock in the mean time I will pull it off the other car. I am also going to make a video of this thing and hopefully that will give everyone a better Idea whats going on. I really appreciate everyones help on this.

I should have a video up around 3 my time Indiana, I need to go get a ohm / volt meter so I can be more accurate rather then "Well i took it from here it should work."