skebe22RTE

i hate to tell you this, but rebuilding that engine will most likely not solve the problem. one thing is, it seems like an electrical problem, not so much a mechanical problem, and second, i've done just that, about a month ago, i rebuilt my engine and it still has that same issue. i haven't tried replacing grounds yet, but that is on my next to do list, for sure... but judging on how nobody responded on the grounds, it doesn't sound like it's a real fix, so sorry to burst yer bubble like that, but it's always good to have hope hehe

jennygirl

I have a hunch that it is ECU related

skebe22RTE

i actually switched my ECU to 3 known good ECU's and didn't make a difference, so i know in my situation, it's not that... so this grimlin is killing me! haha

JaMTek

Hey guys, I have a 1990 thats doing the same thing. Its more involved than you think. I believe on the late 88 to 91 the fuel pressure up system VSV is activated by the ECU, via the EFI coolant temperature sensor, in conjunction with the AFM air temperature sensor. On the 87-Dn, the ECU uses an input from the #2 coolant temp sensor found on top of the coolant thermostat housing. There's not much that can be tested, make sure the VSV is operating properly and doesn't go into an open or short condition at certain temperatures. Sometimes the solenoid windings in the VSV can go open or short at various temperatures. The other possibility would be the AFM air temp sensor, or EFI coolant temp sensor is out of calibration, or open / short, but you would get a MIL light with an open or short. Another possibility would be the ECU itself, where the output transistor has failed in the ECU and no longer activates the fuel pressure up VSV. Problem being is testing this, you need specifics on the ECU circuit involving the FPU VSV and an in depth description of the operating parameters of the FPU system, i.e what temps values from both the Coolant temp sensor and AFM air temp sensor that triggers the ECU to activate the FPU VSV.

Another possible scenario that can aggravate the none operation of the FPU system, is if you run a cooler thermostat other than the original. It can upset the operation of the fuel pressure up system. After the engine is started from cold and driven to normal operating temperature controlled by the thermostat, when you stop the engine, the engine temperature then will slowly rise as it heat soaks. This rise in temperature is effected by the ambient air temperature as well, raising the coolant temp above the coolant thermostat opening temperature. If you have a cooler thermostat installed, it will start to open earlier than the original would, allowing the coolant to pass through into the radiator through convection and dropping some of the heat attributed to heat soaking.

Problem being now the fuel in the fuel rail as already boiled and some vapor has formed in the fuel rail. Now when you come to restart the engine, the coolant temp has dropped below the point the ECU uses to calculate from the look up tables when to activate the FPU VSV. So now you come to restart a hot engine and the FPU VSV is out of the loop. The engine runs rough until the fuel rail clears and the fuel in the rail cools, which doesn't take long.

I believe I've upset the operation of my system by removing the original engine driven cooling fan and clutch and installed an electric cooling fan. I've setup the fan so it will continue to run after the engine is turned off, and everytime the thermostat opens, so the thermos switch that triggers the fan activates the electric cooling fan and accelerates the process of convection, bringing the coolant temp down, but the fuel rail is still hot from the surrounding temperature in the engine bay and the ambient temperature. You have to remember that the FPU VSV is activated with a combination of the coolant temp sensor and the AFM ambient air temp sensor values.

Its one of those situations where if conditions are not just right, then the FPU system is not activated. I've learned to live with it as every sensor and setting is within parameters stated by Toyota.

Regards,

JaMTek

jhsantacruz63

Hi guys, I just read through this whole thread and it's a lot of great info. I have a 1985 pickup with a 22re and the low rpm after hot start issue. Reading these last few comments, I'm wondering if my problem could be that I bypassed the fuel pressure VSV and ran the vacuum line strait to the fpr? From one tread I read, they said that bypassing the VSV didn't cause anything bad but Im starting to doubt that. I will reinstall my VSV tomorrow and see if that helps with the hot starts.

DCMatt

I read this entire thread last night. There is SO MUCH GOOD info in it! Thx for all the details.

One thing I did NOT see in the thread is any reference to the Toyota Service Bulliten
to improve the startability and idle stability after a hot dead soak or an extended dead soak.

Or did I just miss it...

Anyway, find the document here: http://www.toyotapart.com/22R-E,_22R...T-EG011-89.pdf

There is a slight mod that must be done to the ECU connector to prevent the Engine Idle Up from working continuosly after warm-up.

DCMatt

Kodawg92

I have this issue as well but it's rather spontaneous and I can't tell when it will happen usually happens after the motor warms up the RPMs will drop from about 1000 RPM down-to about 100 to 250 rpm and it rattles and Shakes and is really rough I've tried to adjust the fuel and air adjustments on the throttle body I've made sure the mass airflow sensor is clean and the valve opens properly I'm to my wits and don't know what to do next can someone please help me?