Random high idle and pinging

[holyford86]

In recent weeks I have been having a high idle issue, along with pinging, I can't figure it out, it comes and goes quite suddenly. Here's what I've done;

-inspected IAC for cleanliness, removed actuator from the valve assembly, checked for free play and good seal, ohms tested the actuator and found it to be within spec (10 ohms). This IAC is less than 1 year old and is a OEM replacement

-Inspected and tested wiring leading to IAC, all checks out OK and the voltage values are correct.

-Inspected and cleaned throttle body and linkage, inspected linkage and cable for binding or wear.

-checked base timing (10* BTDC) right on the mark.

-Pulled KOER and KOEO codes found CM KOEO codes 54, 66 IAT signal high, MAF signal low (converted to '90 Cali Emissions so it's the right code)

-Replaced IAT sensor (it tested way off)

-Tested MAF with snap on MODIS, following the pinpoint test, Replaced bad MAF, tested new one, It tests within spec.

-checked for vacuum leaks, will be checking torque on the lower intake and plenum tomorrow but I don't think it's the issue, the motor was installed less than two years ago and was re gasketed when installed.

I'm still having the issue... I can't quite figure it out, quite perplexed. I have started pulling apart the wire loom under the hood and looking for corrosion and broken wires, should finish that up sometime tomorrow. This thing runs absolutely perfect otherwise, when it doesn't act up...

 

[kimcrwbr1]

Did you test the ECT or check the connection going to it. It could be giving the computer a false/erratic engine temp reading. Just a thought you havent mentioned.

 

[bobbywalter]

sounds like a canp issue or possibly a bad gas cap if the temp sensors good

 

[holyford86]

Did you test the ECT or check the connection going to it. It could be giving the computer a false/erratic engine temp reading. Just a thought you havent mentioned.

I repaired the connector going to the ECT a few months ago, the prongs that clip the connector to the sensor had broken off, the sensor tested good then, it is relatively new as well... I'll have to double check the sensor and the integrity of the connection.

sounds like a canp issue or possibly a bad gas cap if the temp sensors good

I plugged the evap line going to the TB and drove it for a couple of days, It still had the same issue, I am using the evap system that came on the truck in 86, it had no valves, just the one small line running from the tank to the vapor canister and from the canister to the TB

I've seen bad ECT sensors cause pinging but could it also cause the engine to idle @ 2500-3000 rpm?

 

[kimcrwbr1]

Can you do the wiggle test the reader will give you a code when you find a fault by wiggleing and tapping sensors and connectors. In the KOEO turn the ignition on activate the test after at least ten seconds deactivate then reactivate you are now in the continuous monitor (wiggle test) go around and mess with stuff the light will blink or beep and set a code. You can do the same thing in the KOER but heat up the o-2 sensor first. Restart the motor activate the test for ten seconds deactivate and reactivate. Good for finding intermittent faults sometimes.

 

[holyford86]

Can you do the wiggle test the reader will give you a code when you find a fault by wiggleing and tapping sensors and connectors. In the KOEO turn the ignition on activate the test after at least ten seconds deactivate then reactivate you are now in the continuous monitor (wiggle test) go around and mess with stuff the light will blink or beep and set a code. You can do the same thing in the KOER but heat up the o-2 sensor first. Restart the motor activate the test for ten seconds deactivate and reactivate. Good for finding intermittent faults sometimes.

I have done the KOEO and KOER wiggle test, I didn't get anything, but I'll try it again

 

[bobbywalter]

86 Ranger, 2.9 MAF, M5OD, BW1350, D35 L/S, 7.5 Detroit, 4.56's, York OBA, 200 amp 3G, Dual Batteries, 33x12.50x15 Procomps, Skyjacker 6" class II, Belltech 6400's, XRC8, 300k miles, 63" Chebbies

what processor and ig system?

 

[holyford86]

what processor and ig system?

1990 Cali emissions MAF computer Standard trans, not sure on the calibration code. 1990 2.9 TFI distributor, remote mounted TFI

 

[bobbywalter]

wheres the fuel pressure when its pinging? maybe the injectors are boogered up

 

[holyford86]

wow, mods please put this in the 2.9 forum... I just realized my screw up, and now I need sleep (obviously JHC...)

 

[bobbywalter]

air leak in the maf hose?