#Rough idle /Toyota/Celica/St20/7afe/

101 messages · Page 1 of 1 (latest)

pine hedge
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I got a rough idle with vibrating steering wheel at idle.
Engine idles at 900 rpm, going up to 1200 after warm up and dropping down again to 900.
The rpm slightly goes up and down at idle.

The engine makes weird noises. Sometimes whistles on and off continously.
Wrrrrrrrrr brrrrrr wrrrrrrrr brrrrrrr.

It use to run at 1100 rpm with no issues at idle. A couple of months ago the engine was consuming oil, it was a failing pvc valve that was sucking up oil. Fixed it with a new pcv valve.

After that the problem started to occur.

Ive changed the throttle body to a used one + cleaned it out and the hoses that connected to it. Changed the o2 sensor + got a new exhaust.
I have a old obd1 port and did the paperclip bridge to check for engine codes. Got no engine faultcodes.
Had sparkplugs changed, new oil ect..

What can it be?

quick hamlet
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A few things worth checking. Assuming this is an early 90’s Celica, yeah? I think this has an idle air control valve around the throttle body. If you haven’t already, pull that and clean it up (not sure if it was part that was swapped when you changed the TB). Additionally, you had spark plugs changed, but how are the wires/cap/rotor, were they also changed at the same time? Also, how’s the ignition coil?

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A stuck open EGR may cause issues at idle as well, though I’m not familiar with how to troubleshoot EGR concerns on this engine.

quick hamlet
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Also, sanity check…. Look for vacuum leaks. Car running, spray starting fluid around engine bay. And of course visual inspection of the lines.

pine hedge
pine hedge
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one thing that kinda ticks me is a little bit of white smoke that is smelling sweet out of the tailpipe.

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I think i have a blown head gasket, but there is no loss in coolant, no bubbles of exhaust gasses in coolant either and there is no brown sludge in the oil

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  • i got a new gasket for the oil pan cause its leaking
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still waiting for it to arrive. In the meantime, i will check for whatever else unless my car paranoia gets to me and my bank account will completly dry out

pine hedge
quick hamlet
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Sounds like you’re doing a good job bringing this thing back to life! Worth a compression check just to be on the safe side, since head gasket may be in question

pine hedge
pine hedge
quick hamlet
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Haha I know that feeling

pine hedge
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Just wanted a cool car 💀

quick hamlet
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Yep. It will be, for sure. My experience with doing these things after a couple decades it’s usually cleaner to replace/refresh/update everything that is even remotely questionable and that’s how to stay ahead of having a new problem every week. Which is pretty much the road you’re on now. Once you get to the other end it’s a more rewarding driving experience!

pine hedge
pine hedge
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opened it up and the knobs just disintegrated

quick hamlet
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Oooooh, good follow up

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Is the whole distro bad, or are you able to replace the cap and rotor on their own?

pine hedge
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Just ordered a new distributor cap. I have to reseal it so moisture wont get in easy.

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The engine is not giving any codes, the are no vacuum leaks anywhere. The distributor cap was badly worn.

fresh stagBOT
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GG @pine hedge, you just advanced to level 6! Chat more to level up and earn top roles!

pine hedge
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Well, when i get the part and change the old one. I will follow up, hopefully it will fix the rough idle

pine hedge
pine hedge
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So i did replace the distibutor cap + rotor. The steering wheel vibration dissapeared but and i got a 50rpm increase

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so now it is idling 950 rpm. Yet i am not satisfied, it does not dile like it use to 1100rpm. Need to investigate further

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I have a little oil leak, got the new gasket. Will get a new throttle body gasket and new injectors. Already had the new radiator delivered and just waiting for March to come by. Will change oil (again) and the radiator fluid while the oil pan gasket and radiator get changed.

quick hamlet
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Does it still fast idle when cold and then settle after a few moments?

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I’m circling around a questionable temp sending unit, but if it does properly cycle between fast idle and then normal idle, then I wonder if the distributor has been slightly clocked. The Toyota forums seem to indicate this was an old method for adjusting idle speed.

pine hedge
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Here, a cold start video. Any hints on what it could be?

hybrid egret
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all signs pointing to an intake manifold leak

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check that out for me pls

pine hedge
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Yeah, i am cheking it out

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I did change the fuel injectors

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I did not change the manifold gasket tho, might have worsened it

pine hedge
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So update on fixing rpm.

I installed the new manifold/throttle body gaskets that came today from the US

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Still shit rpm, so I opened up the intake manifold a little and it got 1500 rpm

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So I'll keep it at 1500 for now. Better than 800-900 with stuttering itself to death

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Both videos are after I installed the new gaskets, the one to the left is the one where I didn't fiddle with the throttle body plate screw. To the left, it is the one I fiddled with

sudden raptor
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Like coffee mentioned earlier, it could be the IAC, I’m sure this car has one.

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But good job doing the maintenance. In my opinion I think you’re replacing a lot of things and doing less diagnosing. Which isn’t necessarily a bad thing, just gonna spend a lot of money that way.

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Try replacing your o ring on your distributor that the cap since on. If you can get it fine a replacement, put some o ring grease or even dielectric grease on the ring. That will help the o ring seal better

quick hamlet
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Man I was set on intake manifold gasket leak, even though wasn’t my diagnosis it made the most sense. Thats interesting

pine hedge
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I have been to the mechanic and checked out the distributor. It is fine, what i am looking at right now to do is replacing the old radiator and changing the gasket for the oil pan since it is leaking a little. SInce my country has a bad parts-market, i source my parts from the US.

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it might be that 800-900 rpm is good, i might be wrong about trying to keep it 1100 at idle

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Maybe worn engine mounts, but ill have to double check that

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My old exhaust manifold failed just now by leaking exhaust in the engine bay, so i have to replace it with a different one.

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My priorities: 1, Exhaust Manifold 2, Radiator 3, Replace oil pan gasket

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Then i can focus on less concerting things, like vibrating steering wheel at idle. We will see, i will post a new update after ive done theese things

sudden raptor
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Is your cat connected to your exhaust manifold? Can you get away with repairing the crack rather than buying a new manifold?

pine hedge
sudden raptor
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Ahhh ok

pine hedge
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we reused the manifold cause it is difficult to get hands on a new one or even a used one at a reasnoble price

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i managed to order a used one today for 50 bucks in europe

pine hedge
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i can maybe se a little more wear on the bottom motor mount, id change that

pine hedge
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Which one of these manifolds should i get?

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Cause one of them is 50 and the other one is 90 bucks. The first one looks to be in terrible condition

pine hedge
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Okay, i made a major mistake

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I figured out why my rpm needle was dancing.

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A few months ago a changed my fuel injectors with new ones from ebay that cost 40 bucks. They where the problem! My engine was shaking and running like crap, i though that it was a vaccum leak, then gaskets, so on and so forth.

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I though that my engine should run at a stable 1100 rpm. I was wrong, it is supposed to be at 900 rpm

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The dancing needle was caused by the new fuel injectors

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I started by thinking, when did the rough idling started to happen. Like really bad idiling

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i figured it was around the time i changed the fuel injectors, produced in malaysia

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Lesson, never trust cheap fuel injectors

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I changed back to the old injectors and they worked like a charm, it deleted the engine misfiring

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I still have a little bit of steering wheel shake, but that is caused by a blown motor mount, which i overlooked. Ordered a pair of new motor mounts to deal with that issue

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Either than that, the vehicle runs very fine. Does not blow white smoke anymore, exhaust manifold got changed so no more puff puff sounds

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Got radiator changed for better cooling, oil pan gasked changed. The mechanic asked me if i glue the oil pan, said no, never even touched it. Someone else didnt bother to change the oil pan gasket so they just used a ton of silicone glue.

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old radiator xddd

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probably burned from all the exhaust leaks this car has had, and previous owners didnt care to adress it so extra costs xdd

sudden raptor
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Nice! Easy fix and lesson learned

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That’s awesome.

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Can you upload a video for us please?

pine hedge
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Yeah, i can do that

pine hedge
sudden raptor
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Sounds very good. Good job!

pine hedge
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Thank you, torturous months have brought joy

pine hedge
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So, an update. I have bought the new engine mounts. I have done some basic maintenance by changing the 25 year old fuel filter into a fresh one. I am waiting for a new fuel pressure regulator to freshen that up as well.

quick hamlet
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This is awesome. Rock on!

pine hedge
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In a week or so i will go to the mechanic to change the engine mounts, front and back. Cause the side ones are in good condition. I was able to get a picture of the front mount, which as shown in this picture has deteriorated and has a visible crack

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Oh, and there is the old fuel filter. I just hand to open it up to see what 25 years of dirt does to one 😄

IMG_20240409_230401_897.jpg
pine hedge
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Soooooo, my engine is overheating now. I had a little coolant leak cause the clamp didnt fit the new hoes. So i clamped it donw, filled it with coolant and filled the oil again because it burnt all of it away. The rpm fluctuation didnt dissapear, replaced the fuel pressure regulator because fuel in the air intake manifold, managed to replace the idle air control valve for a fresh new one, still waiting to replace the engine mounts.

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I will be at mechanics this week, so i will ask him to check out the spark plugs. I think the plugs are toasty due to all the issues, i will check spark plug wires too. Altough i doubt it, but still, does not hurt to look.

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Pressing the gas pedal, letting it go makes the rpm go down and up again

fresh stagBOT
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GG @pine hedge, you just advanced to level 7! Chat more to level up and earn top roles!

pine hedge
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I dont think it is a gasket leak, no, not a dirty iacv, no distrubutor cap issue

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It might be 1. Bad spark wires/plugs, 2. Fuel pump that is failing, 3. A bad seprentine belt tensioner.

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The seperate issue is that it takes a long time for the temp-guage to show coolant temp and the heating is not working propertly. Already got the new coolant temp sensor, fan sensor, second coolant temp sensor (because there are 2) , the guage indicator sensor and a new thermostat. So we will see if that yields anything