I threw your issues into my master tech AI bot we have been building over the last 3 yrs. My odb1 bot still has a few glitches but's its about 70% correct most of the time.. If this doesn't work for you We are in Colorado springs I can get it going for you . Sadly due to emissions laws If we work on the emissions which I know we will . We will have to replace the parts your removed. .................................................................................................
First — your idle at ~250 RPM
From the FSM symptom table:
- “Low idle / incorrect idle speed” → IAC system, air leaks, ECU inputs
At
250 RPM, that is
below normal control range. The ECU is losing authority over idle.
On a 1FZ-FE, idle is controlled by:
- Idle Speed Control Valve (ISCV)
- Throttle body air bypass
- ECU inputs (TPS, coolant temp, etc.)
Critical Observation (FSM-Based Logic)
You removed:
- EGR system
- Pair (air injection) system
That alone
does NOT directly affect shifting.
BUT—
You also:
That is where I’m focusing.
Your Two Symptoms Are Linked
1. Low idle (~250 RPM)
2. Won’t shift past 1st properly
These share a
common dependency: ECU load and signal integrity
From FSM principles:
- Transmission shifting is ECU-controlled (A442F)
- It depends on:
- TPS signal
- Engine RPM signal (NE)
- Vehicle Speed Sensors (you replaced both)
- Engine load calculation
Likely Root Causes (FSM Logic Only)
1. 
Idle Air Control Valve not functioning
If ISCV is stuck closed or not powered:
- Engine barely idles
- ECU sees abnormal load condition
- A/T logic becomes erratic
This alone can cause your symptoms.
2. TPS signal not reaching ECU correctly
You said TPS is “new” and checks out.
But FSM warns clearly:
If TPS signal is:
- intermittent
- open
- or miswired
Then:
- ECU cannot calculate load
- Transmission defaults poorly → stuck/short shift behavior
3. Engine RPM (NE signal) degradation
If NE signal is weak/intermittent:
- Idle unstable
- A/T shift timing incorrect
4. Ground fault (VERY COMMON after harness work)
From FSM:
- Always inspect ground points first in electrical diagnosis
Bad grounds cause:
- Low idle (ISCV ineffective)
- Sensor skew (TPS, ECT, etc.)
- Transmission logic failure
5. Vacuum routing issue (post EGR delete)
FSM states:
- Vacuum routing must be correct after service
If:
- Idle-up circuits
- VSV lines
- throttle body ports
are misrouted or open:
You will get:
- Extremely low idle
- Incorrect ECU load calculation
My Professional Call (FSM Discipline)
Given ALL symptoms together:
This is almost certainly NOT a transmission problem.
It is:
What I would do in the bay (in this exact order)
Step 1 — Force idle mechanically
- Crack throttle slightly
- Bring idle to ~650–700 RPM manually
Does it now shift normally?
- YES → problem is idle control / ECU load
- NO → continue
Step 2 — Verify ISCV operation
- Check for duty signal from ECU
- Check resistance and movement
Step 3 — Backprobe TPS at ECU (not at sensor)
- Confirm:
- VTA voltage sweep
- IDL switch function
Step 4 — Check ALL engine grounds
Key locations:
- Intake manifold grounds
- Head-to-body strap
- ECU grounds
Step 5 — Vacuum sanity check
- Cap ALL unused ports from EGR delete
- Verify no open ports at throttle body
About a shop in Eastern Colorado
You’re in a tough region for 80-series expertise. Most modern shops will:
- Misdiagnose this as transmission
- Or get lost in modified emissions systems
What you actually need:
- Someone who understands OBD1 Toyota EFI + A442F logic
Practical options near you:
Colorado Springs / Denver area:
- Look for Toyota specialty or older Japanese specialists
- Avoid general transmission shops
Ask them specifically:
If they hesitate → move on.
Straight talk
You said:
Respectfully — something
does not, because:
Bottom line
Your issue is almost certainly:
NOT:
- Transmission failure
- VSS issue
- TPS part failure
Next move
If you want, I can walk you through:
- Exact ECU pin checks (TPS, ISCV, NE)
- Ground point locations
- Vacuum routing sanity diagram (post-delete safe config)
But I will not generate a diagram unless you approve.
