Home / Toyota Supra Forums

Go Back   Toyota Supra Forums! Join the Supra forum! > Performance, Modification, and Maintenance Forums - for generation specific discussions > MKIII Supra

Reply
 
Thread Tools Display Modes
Old 01-24-2011, 03:31 AM   #1
Fr0sTbY7eX
Stock
 
Join Date: Jan 2011
Location: San Diego, CA
Posts: 11
Fr0sTbY7eX is on a distinguished road
Default Rough idle and low RPMs at startup when cold...

Hey guys, I'm a supra noobie but I've always loved the MKIII, just bought a 1990 supra turbo with a rebuild. HKS MHG, ARP head bolts etc. It's very, very clean. I'm having a problem with rough idle and low RPMs at start up. The check engine light is on and is providing me with error code 26. Something about Air-fuel rich malfunction. I took it to my mechanic and they suggested it be the MAF meter, but it was just replaced so I have doubts. I think it may be the cold start fuel injector because the low RPM and roughness of idle only occurs when the motor has been off for a while. I'd appreciate any input I could get.

Here are some pics...


MAF Meter that was replaced...




What I think is the cold fuel injector...




I hope I didn't break any forum rules! Thanks guys.
Fr0sTbY7eX is offline   Reply With Quote
Old 01-25-2011, 01:57 AM   #2
cre

Toyota
Racing
Development
 
cre's Avatar
 
Join Date: Apr 2007
Posts: 5,038
cre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond repute
Default

That's not a MAF (Mass Air Flow) sensor. It's a KVAFM (Karmen Vortex Air Flow Meter), but if you need a generic term call it an AFM (Air Flow Meter).

The cold start injector ONLY injects fuel while the ignition is in the start position (while the engine's cranking, unless your ignition switch is broken). ONLY DO THIS IN A WELL VENTILATED AREA: To see if it's flowing fuel when it shouldn't just unbolt it and let it hang down. Put a clear plastic bag over it and tie it on. Clean up ANY amount of fuel which may be present. Now jumper FP and B+ in the diagnostic box (THERE WILL BE SOME LIGHT SPARKS!) this will start the fuel pump... if you see the CSI spray or drip fuel, it's bad.

You should approach this by the book and wallet. Go through the list of suspects and test, then replace the cheapest one that's out of range and move up from there.

  • Injector circuit
  • Injector
  • Fuel line pressure
  • Air flow meter
  • Cold start injector
  • Oxygen sensor circuit
  • Oxygen sensor
  • Water temp sensor
  • ECU

Has the AFM been modified or abused? Did you have the problem since you installed it? Usually when someone posts with trouble from this code it's either a situation where they thought it'd be cool to gut the honeycomb, clean it with carb cleaner, or drop it (BTW, these will all destroy the meter equally well).
__________________
If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum.

If you're so inclined I'm always more than happy to accept tips via PayPal.
Tip Jar --->
cre is offline   Reply With Quote
Old 01-25-2011, 02:02 AM   #3
cre

Toyota
Racing
Development
 
cre's Avatar
 
Join Date: Apr 2007
Posts: 5,038
cre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond repute
Default

Check the TPS and its IDL switch and check the ISCV while you're diagnosing things. IDL signal is used in the calculation of that error so it's worth inspecting even though those two components aren't on the TSRM's list.

TPS inspection and calibration:
http://www.cygnusx1.net/Supra/Librar...ction=FI&P=100

ISCV inspection:
http://www.cygnusx1.net/Supra/Librar...ction=FI&P=106
__________________
If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum.

If you're so inclined I'm always more than happy to accept tips via PayPal.
Tip Jar --->
cre is offline   Reply With Quote
Old 01-25-2011, 05:09 AM   #4
Fr0sTbY7eX
Stock
 
Join Date: Jan 2011
Location: San Diego, CA
Posts: 11
Fr0sTbY7eX is on a distinguished road
Default

Thank you! Would the fact that it's a straight cat be a possibility too? I may just have to change the idle speed... that would be an easy fix, and a great relief. The previous owner had replaced the AFM, so I'm guessing it has no problems. It's mostly stock. Just a aftermarket radiator, MHG, studs, hoses, seals.


P.S. That site is amazing...

Last edited by Fr0sTbY7eX; 01-25-2011 at 05:17 AM.
Fr0sTbY7eX is offline   Reply With Quote
Old 01-25-2011, 06:40 AM   #5
cre

Toyota
Racing
Development
 
cre's Avatar
 
Join Date: Apr 2007
Posts: 5,038
cre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond reputecre has a reputation beyond repute
Default

The idle is computer controlled.... screwing with it for the sake of masking a symptom is simply stupid; If you are really running rich you'll still be getting the error code, still be losing power and still be getting worse mileage than normal. Fix it or sell it.
__________________
If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum.

If you're so inclined I'm always more than happy to accept tips via PayPal.
Tip Jar --->
cre is offline   Reply With Quote
Old 01-25-2011, 04:27 PM   #6
Fr0sTbY7eX
Stock
 
Join Date: Jan 2011
Location: San Diego, CA
Posts: 11
Fr0sTbY7eX is on a distinguished road
Default

Ok, I understand what you mean. Thank you veru much for the time you took to help me, your input is very helpful. No way am i selling it, i just bought it, so im gonna figure it out. Thank you!
Fr0sTbY7eX is offline   Reply With Quote
Old 01-25-2011, 06:51 PM   #7
Fr0sTbY7eX
Stock
 
Join Date: Jan 2011
Location: San Diego, CA
Posts: 11
Fr0sTbY7eX is on a distinguished road
Default

Sorry for the double post, but I let it crank a little longer this morning and the rpms were just fine, so now I'm wondering if its the straight cat? I dont know much about cars, I apologize if I trouble anyone.
Fr0sTbY7eX is offline   Reply With Quote
Old 01-27-2011, 02:15 AM   #8
Fr0sTbY7eX
Stock
 
Join Date: Jan 2011
Location: San Diego, CA
Posts: 11
Fr0sTbY7eX is on a distinguished road
Default

Quote:
Originally Posted by cre View Post
Usually when someone posts with trouble from this code it's either a situation where they thought it'd be cool to gut the honeycomb, clean it with carb cleaner, or drop it.
What did you mean when you said "gut the honeycomb"? I know there is no cat on my car...is that the same thing? Sorry for my noobness, I appreciate your help.
Fr0sTbY7eX is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump


All times are GMT. The time now is 11:06 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

1986



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87