Weird idle issue, can anybody chime in?

[modmonster2008]

Alright, so i have recently picked up an 89 supra turbo. Needless to say the tabs have expired 4 months ago and before i can renew this year, i need emissions. The problem is lies in two things. 1) There is no cat, the previous owner cut the cat off and welded a straight pipe to the flanges that the cat had, so it basically has a bolt on test pipe sorta thing. 2) Sometimes the idling is perfect, and sometimes, not so perfect. It would usually idle around 900-1k and then slowly goes down to about 600rpm, then it starts to feel like the engine wants to shut off but then the car automatically raises its idle, something like loping idling, and when that happens the car puts out a slight blue smoke out the exhaust, but NOT all the time, only when the engine feels like its going to die. Now my question is, what should i start looking for first? It has stock 7mgte components, all hoses for vacuum seem to be in tact, accordion hose seems like its alright though ill double check tomorrow, would it be possible its somewhat of a timing,fuel or AFM issue? anything helps guys, thank you!

 

[honeydew]

I don't want to talk down to you as it looks like you've had many cars and should seem to know what the next step is after finding a symptom. Get some codes. It could be a lot of things.

Saying that you recently picked up a car with a straight exhaust might be an indicator that the car has been played and fiddled with more than you know. Try to determine exactly what has been done to the car either by examination or asking the seller, if they know.

A MKIII Supra with a lope is fairly common among Supras that have been played with.

Could be a bad AFM, could be a bad O2 sensor, could be bad fuel components, could be a vacuum leak, could be a bad ground or corroded harness somewhere and on and on. Or could be a combination of issues. You've got to find some codes.

I can tell you it doesn't seem to be a timing issue. It would run like crud all the time.

Just as an aside, You will need that Cat. You have options there but you will need to outfit a Cat for a car that needs emission testing. What's really great is usually some high octane with a new Cat can hide any nasty problem you have so at least you can get it licenced while fixing problems. Usually, not bulletproof. I had a Cat from a MK2 on my MkIII forever and worked well.

 

[mikeoc1]

Throwin any engine codes?

 

[modmonster2008]

Has no CEL at the moment, but i shall check tomorrow when i jumper the two connections on the diagnostic connector, does anyone know where the two jumper pins are? the cap is missing so i can't really identify the two pins that i usually jump together


Oh and btw, it has an aftermarket cone filter if that should make a difference..

 

[honeydew]

No to worry the manual is very specific: you will need this link, save it.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/

You want to go to the "EFI SYSTEM" then Diagnosis which is FI-23. pictures and everything.

Is a cone filter a difference? Well, kind of. What it could mean is someone was probably majorly F-ing around with that car before you. Remember to check your car and give us as much info as possible, be specific, you are graded on poise.

 

[modmonster2008]

Ill check on any others, here ill try to be as specific as i can. When the car is first started up the idling is fine, then after a while the temp gauge goes to almost 1/4 of the way and then i drive it and its usually fine no idling problem yet, maybe after 10-15 minutes of the car driving and i come to a stop or park the car, the idling would be at 1000 then slowly come down to the 500-600rpm mark and the car would feel like its going to stall then pick itself back up, sometimes it idles less than 500rpm which makes the car want to shut off and to keep it from possibly doing so i have to keep my foot on the gas a little bit. When the idling problem shows up, i notice a bit of bluish smoke coming out of the exhaust, not thick blue smoke, but you can slightly see it. That's the only time bluish smoke shows up, other than that it doesnt smoke when the idle is fine, Ill see how much more things i can diagnose and find out later today. I know this can alter emission test results, so id rather try to pinpoint the problem before i get a cat and take her to get emissions

 

[modmonster2008]

Alright I have pinpointed the problem, i floored the gas pedal all the way at a straight road and came to a stop, engine stalled. After i started her back up the CEL light came on steady, drove home and jumped the E1 and TE1 terminals as stated on the TSRM, had a Code 31 "Air flow meter faulty". Im thinking that should be the cause of the weird idle at times and the cause of the car to stall. As fas as I heard Lexus AFM work with the 7mgte correct?

 

[mikeoc1]

I had a code 31 and similar symptoms, I cleaned the connections at the afm and it took care of the code and the symptoms. May be worth a try before you spend some money.

 

[honeydew]

I was Just going to say AFM. You were very specific, A+. Those AFM sensors are very delicate and not hard to foul. Especially if you have a bad filter. Get a new filter, god knows how long it's been on there.

+1 mikeoc1: try cleaning it first. Lexus will work and can metre much more air if you ever want more power, right there is a slippery slope. LOL.

 

[modmonster2008]

Lexus AFM works? I heard that if you upgrade to lexus afm u gotta upgrade the injectors correct? I tested out a Lexus AFM, the car idles a bit more stable in a way that it won't bog or feel like its going to stall anymore though it idles rather rougher than what i expect, thus needing the 550cc injectors right?

 

[Pokey2301]

you can run it without 550cc's as long as you arent hard on the car, but once you start racing it, that's when stuff can go wrong, your car is goin to be running leaner since you are letting more air into the engine

 

[modmonster2008]

Ah, that explains the not so smooth idling, so after i upgrade to 550cc injectors is there anything else id need to look into?

 

[Pokey2301]

Ah, that explains the not so smooth idling, so after i upgrade to 550cc injectors is there anything else id need to look into?

shouldnt really affect your idle at all, its really more about having supporting modifications rather than going for power the cheap way, get a good exhaust, intake, boost controller, fuel pressure regulator, fuel pump, safc2, air fuel ratio gauge, etc...

 

[modmonster2008]

Well, the thing is. The car already had a K&N filter kit, an aftermarket turbo-back exhaust welded with no-cat, the other thing i only know of that is now not Supra-spec is the Lexus AFM, gives the Supra a bit of a uneven and somewhat rough idle, no hesitation or anything just has a rough idle at around 600rpm's

 

[Pokey2301]

Well, the thing is. The car already had a K&N filter kit, an aftermarket turbo-back exhaust welded with no-cat, the other thing i only know of that is now not Supra-spec is the Lexus AFM, gives the Supra a bit of a uneven and somewhat rough idle, no hesitation or anything just has a rough idle at around 600rpm's

no, your car is goin to idle the same with either afm on it, seems something else is causing your idle problem

 

[modmonster2008]

Even after resetting the battery and whatnot i jump the two diagnosis terminals together code 31 still shows up, so idk why its still pointing out the AFM. Ill try to source out another lexus AFM and at least a Supra afm for comparison.

 

[Pokey2301]

try resetting the ecu, mine was acting funny for a little while, and after i reset the ecu, it worked fine

 

[modmonster2008]

How do you reset the ECU? im gonna have to give this a try tomorrow.

 

[Pokey2301]

unplug the battery for about a min or so, and it resets the computer

Edit: you can also see how it idles witht he afm unplug, the car will idle, you just wont be able to rev it up, if it still idle rough, it wont be your afm

 

[honeydew]

The Lexus AFM just has the ability to metre more air than stock. It should idle fine if everything else is good. I've gotten 2 bad Lexus AFM's in a row. Not uncommon. They are delicate and they happen to be old.