94 Isuzu rodeo started to idle high - 1994 Isuzu Rodeo

need to look at the idle control motor on the side of the carb.

i changed mine took to 3 shops last one said computer i would take pos cable for 30 sec turn on to acc and tap post 3 times if it helps

fuel filter, fuel pump

Took me a couple of views to figure out what HC means.
You would need to know what the limit is for your area and what the exhaust is producing, then find out what the cause is.
It stands for unburned hydrocarbons which is supposed to be controlled by the O2 sensor among other things. Could be a sensor or the engine not getting up to normal temp.

standard according to manual is @ 8 PSI I too thought that it was low. but when you drivce the presure rasies to @ 45- 50 PSI so it is normal.

if there is no power to the fuel pump check relays and fuses....UNDERHOOD FUSE & RELAY PANEL IDENTIFICATION Fig. 2: Underhood Fuse & Relay Panel Identification Courtesy of ISUZU MOTOR CO. Fusible Link Identification ? A - 80 Amp (1991-92 3.1L) ? A - 60 Amp Main-1 ? B - 30 Amp Main-2 ? C - 30 Amp (1993-94) ECM (3.2L) ? D - 30 Amp Condenser Fan (A/T Models) Relay Identification ? 1 - Headlight Relay ? 2 - A/C - Heater Relay ? 3 - Starter Relay ? 4 - A/C Compressor Relay ? 5 - Charge Relay ? 6 - Fuel Pump Relay ? 7 - ECM Relay ? 8 - Wiper Relay Fuse & Circuit Breaker Identification ? 1 - 15 Amp (1991) ECM, Fuel Injection System ? 1 - 15 Amp (1992-94 2.6L) ECM, Fuel Injection System ? 1 - 10 Amp (1992-94 3.1 & 3.2L) Heated Oxygen Sensor, Fuel Injection System ? 2 - 20 Amp (1991-92) Fuel Pump ? 2 - 20 Amp (1993-94 2.6L) Fuel Pump ? 2 - 15 Amp (1993-94 3.2L) Fuel Pump ? 3 - 10 Amp (1991) ? 3 - 15 Amp (1992-94) Turn Signal Lights, Hazard Warning Flasher Lights ? 4 - 10 Amp Horn, Door Locks ? 5 - Not Used (1991 3.1L) ? 5 - 10 Amp Charging System, Charge Warning Light WARNING: Always disconnect battery ground cable before servicing "high- current fuses. It is recommended that "high-current" fuses be replaced by a qualified technician. Page 1 of 2 FUSES & CIRCUIT BREAKERS -1994 Isuzu Rodeo LS? 6 - Not Used (1991) (1992-93 2.6L) ? 6 - 10 Amp (1992-94 3.1L & 3.2L) A/T Interlock System ? 6 - 10 Amp (1994 2.6L) Heated Oxygen Sensor, Fuel Injection System ? 7 - 20 Amp Heater/Air Conditioning Blower Controls ? 8 - 10 Amp Air Conditioner Compressor Controls ? 9 - 10 Amp Right Headlight ? 10 - 10 Amp Left Headlight © 2008 Mitchell Repair Information Co., LLC.

Underhood fuse block swap out relay #7 thats the ECM relay.
Ground Circuits Using a DVOM, touch negative voltmeter lead to a good ground. Touch positive voltmeter lead to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If reading is greater than one volt, check for open, corrosion and loose connection on ground lead. See ECM GROUND LOCATION table for ECM ground location.
Page 1 of 1 SYSTEM/COMPONENT TESTS - 2.6L EFI -1994 Isuzu Rodeo

silly reply BUT have you checked return spring on throttle cable???or cable sticking....

alot of the 4clys had ajustable tappets that might need adjusting
V6 have tappets adjusted also but are shims on top of bucket over valve spring, this is hard to do as you may need to change shims to get correct valve clearances suggest dealer to do.
if the noise comes in and out while maintaining 1500-2000rpm when stationary it is possibly worn valve guides which is common on high km vehicle.(head repairs)

It sounds like it might be your throttle position sensor. Is your check engine lite on?

Good Day
Vale clearance cold
intake .006 in (.15 mm)
exhaust .010 in (.25 mm)

Timing
1. With transmission in Neutral or park, start engine and warm to normal operating temp. turn eng,and all accessories off. connect Tachometer. Connect timing light to no 1 spark plug wire.

2. Disconnect and plug fuel vapor canister purge hose and EGR vacuum hose. Start and ensure idle is 900 RPM. adjust idle as required. Check ignition timing ( 12 @ 900)

3. If adjustment is required, loosen distributor hold down bolt and turn until timing is within specification. Tighten distributor hold down bolt and recheck timing. adjust idle speed as required.

hope this helps

Cheers