TT Headgasket on Stock Motor and ECU?
09-12-18, 02:16 PM
#1
TT Headgasket on Stock Motor and ECU?
Long story short, My car is a 92 SC300 5-speed that I bought in none running condition and had to replace a lot of parts along the way. I had to replace the head and head gasket, so while I was there I switched to an OEM TT head gasket and ARP head studs for future turbo plans, but other than that everything else is stock (I have an aftermarket intake, like Injen and did the 12v mod).
The car fires right up, but then idles really rough and eventually dies after a few minutes, kicking CEL code 31. I have changed both the IACV and the MAF, but still get this code. I checked my plug to the MAF with a multimeter and the MAF is receiving 5 Volts. Could The TT head gasket cause my issue since I now have a little less compression than stock which is possibly messing with the ECU causing it to get confused which eventually kicks the code? Would I need to regap my spark plugs to compensate for the decreased compression (please say no, intake manifold is a *****)?
List of parts that have been replaced
-Water Pump, thermostat, Fuel Pump, fuel filter, Radiator and hoses, Head with new valve train, polished aluminum pully's, HKS cam gears, Timing belt and belt tensioner, IACV, MAF, Ignitor, plugs and wires, distributor and cap, fuel injectors
Thanks In advance
The car fires right up, but then idles really rough and eventually dies after a few minutes, kicking CEL code 31. I have changed both the IACV and the MAF, but still get this code. I checked my plug to the MAF with a multimeter and the MAF is receiving 5 Volts. Could The TT head gasket cause my issue since I now have a little less compression than stock which is possibly messing with the ECU causing it to get confused which eventually kicks the code? Would I need to regap my spark plugs to compensate for the decreased compression (please say no, intake manifold is a *****)?
List of parts that have been replaced
-Water Pump, thermostat, Fuel Pump, fuel filter, Radiator and hoses, Head with new valve train, polished aluminum pully's, HKS cam gears, Timing belt and belt tensioner, IACV, MAF, Ignitor, plugs and wires, distributor and cap, fuel injectors
Thanks In advance
Last edited by SCott300; 09-12-18 at 02:20 PM.
09-12-18, 02:31 PM
#2
Sounds familiar
https://www.clublexus.com/forums/per...-31-sc300.html
The headgasket alone won't make it run rough like that, you wouldn't really notice the difference very much.
If you tried changing the maf with a known good one, then I would check the wiring to it for breaks in the insulation, broken or pulled out wires on the connector etc..
sounds like it could be something to do with the ecu or another sensor, if it runs fine when you first start it and gets worse, I would kind of suspect the coolant temp sensor (the 2 wire one that goes to the ecu). this is one of those codes that is hard to solve unfortunately. I have even heard of this code with a bad IACV (idle valve), or tps issues.
try this, unplug the maf completely, pull the battery cable or efi fuse for a minute to reset the ecu, and then start it without the maf in.
It might just start and stay running cause it should go into open loop mode.
if you can get your hands on another ecu to try then I would give that a try after all the other stuff.
I hope you used good fuel injectors, bad ones can cause those issues also.
https://www.clublexus.com/forums/per...-31-sc300.html
The headgasket alone won't make it run rough like that, you wouldn't really notice the difference very much.
If you tried changing the maf with a known good one, then I would check the wiring to it for breaks in the insulation, broken or pulled out wires on the connector etc..
sounds like it could be something to do with the ecu or another sensor, if it runs fine when you first start it and gets worse, I would kind of suspect the coolant temp sensor (the 2 wire one that goes to the ecu). this is one of those codes that is hard to solve unfortunately. I have even heard of this code with a bad IACV (idle valve), or tps issues.
try this, unplug the maf completely, pull the battery cable or efi fuse for a minute to reset the ecu, and then start it without the maf in.
It might just start and stay running cause it should go into open loop mode.
if you can get your hands on another ecu to try then I would give that a try after all the other stuff.
I hope you used good fuel injectors, bad ones can cause those issues also.
Last edited by Ali SC3; 09-12-18 at 02:34 PM.
09-13-18, 07:21 PM
#3
Sounds familiar
https://www.clublexus.com/forums/per...-31-sc300.html
The headgasket alone won't make it run rough like that, you wouldn't really notice the difference very much.
If you tried changing the maf with a known good one, then I would check the wiring to it for breaks in the insulation, broken or pulled out wires on the connector etc..
sounds like it could be something to do with the ecu or another sensor, if it runs fine when you first start it and gets worse, I would kind of suspect the coolant temp sensor (the 2 wire one that goes to the ecu). this is one of those codes that is hard to solve unfortunately. I have even heard of this code with a bad IACV (idle valve), or tps issues.
try this, unplug the maf completely, pull the battery cable or efi fuse for a minute to reset the ecu, and then start it without the maf in.
It might just start and stay running cause it should go into open loop mode.
if you can get your hands on another ecu to try then I would give that a try after all the other stuff.
I hope you used good fuel injectors, bad ones can cause those issues also.
https://www.clublexus.com/forums/per...-31-sc300.html
The headgasket alone won't make it run rough like that, you wouldn't really notice the difference very much.
If you tried changing the maf with a known good one, then I would check the wiring to it for breaks in the insulation, broken or pulled out wires on the connector etc..
sounds like it could be something to do with the ecu or another sensor, if it runs fine when you first start it and gets worse, I would kind of suspect the coolant temp sensor (the 2 wire one that goes to the ecu). this is one of those codes that is hard to solve unfortunately. I have even heard of this code with a bad IACV (idle valve), or tps issues.
try this, unplug the maf completely, pull the battery cable or efi fuse for a minute to reset the ecu, and then start it without the maf in.
It might just start and stay running cause it should go into open loop mode.
if you can get your hands on another ecu to try then I would give that a try after all the other stuff.
I hope you used good fuel injectors, bad ones can cause those issues also.
I replaced the coolant temp switch already too, if your referring to the one that is in the head. I also replaced the IACV. I bought a set of referb'd Toyota Injectors that came with a 10yr warranty.
Im heading to the junk yard tomorrow bc they supposedly have a 93 5-speed, so Im gonna try to snag the ECU and it MAF as well to see if I can make any progress there.
Im definitely dreading/dragging my feet on having to tear into the wiring harness to look for splits and breaks
Thank you again for the suggestions, it is much appreciated!!
I couldn't get the car to turn over with the MAF unpluged
09-19-18, 08:40 PM
#4
Sounds familiar
https://www.clublexus.com/forums/per...-31-sc300.html
The headgasket alone won't make it run rough like that, you wouldn't really notice the difference very much.
If you tried changing the maf with a known good one, then I would check the wiring to it for breaks in the insulation, broken or pulled out wires on the connector etc..
sounds like it could be something to do with the ecu or another sensor, if it runs fine when you first start it and gets worse, I would kind of suspect the coolant temp sensor (the 2 wire one that goes to the ecu). this is one of those codes that is hard to solve unfortunately. I have even heard of this code with a bad IACV (idle valve), or tps issues.
try this, unplug the maf completely, pull the battery cable or efi fuse for a minute to reset the ecu, and then start it without the maf in.
It might just start and stay running cause it should go into open loop mode.
if you can get your hands on another ecu to try then I would give that a try after all the other stuff.
I hope you used good fuel injectors, bad ones can cause those issues also.
https://www.clublexus.com/forums/per...-31-sc300.html
The headgasket alone won't make it run rough like that, you wouldn't really notice the difference very much.
If you tried changing the maf with a known good one, then I would check the wiring to it for breaks in the insulation, broken or pulled out wires on the connector etc..
sounds like it could be something to do with the ecu or another sensor, if it runs fine when you first start it and gets worse, I would kind of suspect the coolant temp sensor (the 2 wire one that goes to the ecu). this is one of those codes that is hard to solve unfortunately. I have even heard of this code with a bad IACV (idle valve), or tps issues.
try this, unplug the maf completely, pull the battery cable or efi fuse for a minute to reset the ecu, and then start it without the maf in.
It might just start and stay running cause it should go into open loop mode.
if you can get your hands on another ecu to try then I would give that a try after all the other stuff.
I hope you used good fuel injectors, bad ones can cause those issues also.
Thank You for your help!
The following users liked this post:
1997Soarer (10-13-18)
Thread
Thread Starter
Forum
Replies
Last Post
2jzforlife
Performance & Maintenance
2
10-24-12 06:02 AM