Rich on decel, sometimes dies when pushing in the clutch

Agallington

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As the title says....

I will give a little background on the motor below. I am pretty sure I covered everything. I don't post often, but get a lot of info from everyone's posts on here. My problem is (and yes I have looked everywhere and tried almost everything, I believe for an answer) on deceleration, my AFR's drop to about 9 or 10 for a brief moment and then the computer looks like it is trying to compensate and leans it out for a moment to correct. This causes the exhaust to smoke (decent amount sometimes) and sometimes die when coming to a stop. This will happen at lower RPM's as well as higher ones. Any insight someone could give or help out with would be much appreciated.

I have tried finding a mechanic that will look at it and no one will work on the car since its been modified quite a bit. The car has been sitting in my garage for the last few years and every summer I get it out to try and fix and get frustrated enough to put it away again.

I had an SAFCII on for a while, but didn't know how to tune it, so I removed to try and eliminate a variable. I have read in a few places that it isn't necessarily required with my mods? Also, I don't think the SAFCII can adjust the fuel curve on that low of throttle.

I have gone through and did an intercooler piping pressure test. Found a couple small leaks at clamps and fixed. Otherwise this seems good. I pressurize up to 15 psi and the pressure seems to take about ten-fifteen seconds to drop to 5 psi and then really slowly after that. test was done with gauge and air pressure hooked up to turbo inlet and capped off at the end of the 3000 pipe.

My vacuum holds a steady -18psi at idle and every vacuum line seems to be hooked up and running fine.

Has newer copper spark plugs.

Timing is set at 10 with the terminals jumped.

Replaced my iascv (with another used one) recently, but seems to work fine, it clicks when the car is shut off.

checked my TPS per TSRM and it seems to check out.

Have swapped the AFM sensor with another before. I guess I could try getting a new one to see?

So I have no codes. My question is, what else could it be? Can a stock o2 sensor cause this or is 35 psi to high on the fuel pressure? The car seems to run great cruising and at higher RPMS, It is smooth power (no hesitations), and I have had it up to 17 psi so far on boost and has lots of power. Haven't been around anyone else's Supra before, but I do think my valves seem a little noisy (on the other hand I do know older Toyota valves can be a little noisy). The mechanic I did have take a look said the sounded normal though.


- 88 7mgte
- fresh rebuild with MHG (less than 1000 miles ago)
- wiseco pistons
- ARP studs
- BOSS TO4E 61 turbo ceramic coated
- 3.5" turbo back exhaust (no cat)
- 255 fuel pump
- RC 550's
- AFPR (set at 35 w/o vacuum)
- J tube bypass
- Larger aftermarket aluminum radiator
- flex-a-lite dual fans
- Cooleeze ceramic coated intercooler piping (including between AFM and turbo)
- cone filter
- BCC
- LEX AFM housing
- Greddy RS BOV (recirculated)
- Wideband o2
- Aluminum flywheel
- 6 puck sprung hub clutch
- Cartech intercooler
- deleted vacuum canister
- AEM Boost controller
 

Nick M

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It could be DTC 51. Injection is halted when you coast. It seems as though you are not hitting fuel cut off. 51 is when the throttle is showing 12v to the computer (open circuit-open throttle) and it is not expecting the IDL to be open.
 

Rollus

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I'm with Nick here. But you have no code and your TPS seems to check out.
How is your BOV recirculated?
 

Agallington

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BOV is recirculated back into the Cooleeze pipe I have between the AFM and turbo. I am not by the car no so cant take a picture now.

Could the Boost cut controller I have be doing this in any way. It is the HKS FCD. It has a dial and I have it turned about half way.

I can check the TPS again. Is that what DTC 51 would be?
 

Rollus

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OK for bov. If there is any leak, from it, it can richen on foot release and the car stall.

FCD usually lean out near top end. I don't know them because for me it's devil. Fuel Cut is a security for when boost exceed injector capabilities. So why not bigger injector instead?

DTC may be the new Nick's expression for Diagnostic Trouble Code. In french, DTC is "Dans Ton Cul", litteraly "In You Ass"!
You can get the diagnostic codes according to the page FI-23 in EFI section of the TSRM, here (if the direct link doen't work you can access via my blog).
 

Agallington

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Are you saying that you think that is a good spot for the BOV?

I will try and remove the FCD for now and see if that helps for what ever reason.

I don't have any codes.

Does Anyone think that it might be valve guides? Is it normal when they rebuild a motor, that these are replaced?
 

3p141592654

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You need to look for boost leaks/BOV leaks very carefully. Also, check your EGR is functioning properly. If it get actuated during idle the car will stall.
 

Agallington

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I assume the TSRM must explain how to test the EGR. I will try that- Thanks.

I checked for boost leaks already. With the tester on the turbo inlet and the 300 pipe blocked off before the intake, how long should the system hould 10-15 lbs of boost?
 

S.A. supra

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Vacuum leak anywhere? mine did the same push in the clutch getting ready for a stop and it would die. Ended up being a vacuum leak. And those can be a pita to find.
 

Agallington

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How can you accurately check for vacuum leaks? I have a digital boost gauge that reads a steady minus 18 at idle. I also have a mechanical needle type tester I have hooked up under the hood and it says the same.
 

3p141592654

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Nick M

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If the egr was the problem,
What? EGR is not the problem. If it was, then all the cars from the factory new would not run right. I know what you meant. Think about what you post.


If he does not have 51, then you need to check your throttle and dash pot. I assume your car is always rich on decel and sometimes stalls.
 

Agallington

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Just asking for opinion on egr. No need for comments.

What are the steps to test dash pot and throttle?

On throttle, ate you referring to plate adjustment or tps? If tps iI have already checked per my original post.

Good info, I work late usually, so this weekend will bee my time to check this stuff. Thanks
 

Agallington

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OK, So I will check egr, vacuum leaks, intercooler piping leaks, dash pot this weekend to make sure all is good again. I did take it by a shop to get their opinion yesterday and the census was that it is definitely oil smoke. A little at start up, on decel, and after sitting idling for a few minutes. Does NOT smoke at cruising, or when accelerating. I am beginning to question the valves. Wouldn't the valve guides cause this? The AFR's go rich on decel because it is seeing the oil? Let me know your thoughts, I will still check the above.
 

3p141592654

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The oil burning will not impact AFRs unless you are burning oil as fast as you are burning gas (not likely). Could well be the valve seals, but it is a separate problem from your AFR issue. I doubt it is a guide problem, the guides seem to last forever.
 

Nick M

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The only way for fuel to be injected is that it is leaking through the injectors, which it would always do, or it is not halted when you are coasting. You claim the conditions to halt injection are being met. That is how the system works, or it would smoke on decal.

So not all the pieces of the puzzle are in fact here.