TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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I am having a hunting idle problem and have searched posts for three days and am no closer to a resolve.
I believe the car ran fine until I used throttle body cleaner the spray type directly into the butterflies.
I ran the car on the freeway, once I exited, it would not idle properly. Hunts now for idle from 500-2500 rpm swiftly swinging setting no codes. I have a scan tool and found nothing out of the ordinary. I did find the following and ran the following tests:
1. tested dist. Components using a meter for: pick-up and module…both tested good.
2. new cap/rotor/plugs/wires. (plugs were black (throttle body cleaner?)
3. tested injectors (one out of ohm range) replaced all with ford pink 22 lbs.
4. tested afpr by: grounding g term/setting afpr @ 42 lbs. Holds steady. No inj. Leak down or pump fade.
5. replaced: tps set @ .54 new iac as well. Tried to set an idle off the t.b. (these three set in proper order by: iac/idle/tps.
6. base timing @ 6 deg. Btdc. Ecm not connected.
7. tested maf burn-off and power relays…test good.
Engine cold, running in open loop, maf disconnected. Car runs off ecm presets fine. Idles around 1000 rpm constant no hunt.
Engine cold, running in open loop, maf connected. Tries to stall out, disc. Maf as car is running in open loop, constant idle again from ecm table. Now, closed loop operation at running temp, maf connected, still hunts 500-2500 rpm for idle. My scan tool shows nothing strange other than battery/fuel pump voltage low at 11.4 volts. I do have 5 volt ecm sig. And 12 volt power at the maf itself. Tapping maf provides no change during run time. Should I see the burn-off working while in closed loop/maf installed?
I had this weird thing happen same time as well………………in service mode, primary fan was not on. After testing/checking relays,fusable links,ign. Switch 12 volt power source, I had no 12 volt source getting to the relays from the under dash fuse. Fuse good, power there, but not at relays. I found another 12 volt source/key on to piggyback on…don’t like this, but can’t trace wires thru the firewall.
Take an old rag a spray the crap out of it with chemtool. Open the throttlebody wide open and wipe the back side of the throttle plates and the surrounding area of the body until clean. This is going to get you nasty dirty and it will not wash off easy, but it needs to be done.
Disconnect the battery to clear the ECM memory. Start the car and let it idle in gear till the cooling fan comes on and goes off twice with a/c on. Shut the engine down and let sit for 3 minutes then start and repeat.
You have changed the air flow and the computer has memorized it. This will relearn it's idle.
That may work if I had never taken the throttlebody off . I had it off when the injectors and regulator were changed. That throttlebody is clean all around. as a matter of fact, I put a hotcam and rollers in and the car still acts this way.
You should only see a burnoff cycle after the engine is shut off.
Can you back probe the MAf connector and read the output voltage at idle? Does it seem to follow the idle RPM closely? You should read about 0.800V at a 1,000 RPM idle.
If it wasn't still connected, you wouldn't have to probe the wires on the back side of the connector ("Back probing") 'cause you could use the front side of it where the connections are easily reached.
If it wasn't connected, it also wouldn't read any voltage coming out of the MAF.....
