D jet Wont Hold Idle

[914]

Put Rebuilt MPS Unit In, Head Temp Sensor,Car Runs Great But It Wont Hold Idle.I Adjust It Once Its Ok But Then Not At Restart/All Adjustment Are Done At 180,Its Too Fast Warm Then To Slow At Warmup,Any Ideas ?? Can It Be The MPS Unit/Aux Air Reg. ?? Thanks For All The Help.....

914

[Bleyseng]

You need make sure first of all there are no vacuum leaks anywhere.
To set the idle you must do it with the engine hot and make sure the AAR valve is completely closed (no air thru it).
Timing must be set to 27 degrees BTDC at 3500 rpms
Then adjust the idle with a CO meter if you can't then play with the air bypass screw and the idle mix knob on the ECU to adjust it until its smooth.

The car should idle at 15-1800 cold then drop down to 1000 after 3-7 minutes. You probably will have a little hunting until its completely warm at some point.
I haven't been impressed with some of the rebuilt MPS's. How is your off idle transion? should be smooth as glass.

Geoff

[pbanders]

Can you describe your idle behavior more clearly? I can't understand what you've posted. Something like:

1. Start the car from sitting overnight
2. Idle goes up to 1500 after about 10-15 seconds
3. Start driving. Idle is at 1500 for the first 10 minutes of driving.
4. After 10 minutes idle drops to 1000 rpm. Some small idle oscillation for the next 10 minutes until engine is fully warmed-up.
5. Stop car. Go in store for 30 minutes.
6. Restart. Idle immediately goes to 1000 rpm.
7. Drive for 10 minutes. Switch on headlights. Idle drops to 800 rpm, remains stable.

thanks!

[914]

I Adjusted The Idle When Hot 850-900,But When Cold Dies.Tested The AAR When Hot Cant Blow Air Threw It,Got The Tester From Pelican All Cks Out ECU. Replaced The MPS/Brets Rebuilt Also Cyl Head Sensor.The Car Ran Great On Sunday Up The Coast But When I Got Home It Idled High/Readjusted Idle Hot But When Cold It Dies,Today Took It Out For A Spin Stopped At The Store Went To Restart/Hot,Running Very Very Rich,I Limped It Home.Can It Be The MPS/Bad Fuel Pressure Regulator.What Am I Missing?? Remove All The Plugs There Black/Rich Looking,Thanks For The Help.
PS.Brad Looked At Your Djet Trouble Shoot Page Wow Where Should I Start??
914

[Bleyseng]

Wrong CHT or unplugged?

[914]

Tested With The ECU Tester From Pelican/Thanks Tom,Test Ok Green Lite. Thanks Bleyseng!!!
914

[Dave at Pelican Parts]

I think you've got a vacuum leak somewhere. You went through and checked the AAR, and so on, and all was right with the car. The next day, while you were driving, the idle went up and up... Vacuum leak or over-advanced timing (possibly sticking). Then when you adjusted the idle back down again, if the vacuum leak went away so did your cold idle...

--DD

[pbanders]

I'm with DD. Check the points plate in your distributor and see if it's sticking. If you tested your system with the Pelican VW1218 tester and it said it's OK, then it's not your FI system.

How are you setting your idle CO?

[Dave at Pelican Parts]

Wellll.... Mostly the tester checks the ECU. I think it also is able to see if most of the other electrical parts are plugged in at all, and check that they are somewhere in the reasonable range of resistance. But I don't feel that it can check very precisely, nor will it see anything in the vacuum system or fuel delivery system...

--DD

[914]

Thank Everyone For The Replys !!!
914

[pbanders]

DD, you're right about the mechanical/vacuum aspects of the FI system, it can't check those things. But as for the harness and the components, the testing is comprehensive. It even does dynamic testing of the TS1 and TS2 sensors through self-heating, and checks the operation of the trigger contact points and MPS.

It would be helpful if "914" would post more details on the idle behavior of his car from cold start through normal operation. We can pin down likely component problems that way. Also, how is he setting the idle CO? Is it being set to factory spec with a shop quality meter? I've seen cars where the owner had the CO set to as high as 8% - no wonder they had problems!

[914]

Brad,Started The 914 Today Run Great When Cold,Let Warm Up Turned Off For 20mins Went To Restart Wont Idle/Runs Very Rich,As For Adjusting The Idle This Is A 3/71 Car Only Idle Adjustment Is On The Intake Throttle Body/ Screw.All Fuel Lines/Vac Lines Replaced, When Running Rich Took Off The AAR Hose Plugged The Hose,Still Runs The Same,Pulled All The Plugs There All Black/Rich.May Be I Should Bypass The Cold Start Valve With Hose And Or Test,I Also Cked The Dist Plate An It Is Moving Free,Any Ideas. Thanks,914

[Dave at Pelican Parts]

Originally posted by pbanders
... the testing is comprehensive. It even does dynamic testing of the TS1 and TS2 sensors through self-heating, and checks the operation of the trigger contact points and MPS.

Color me very impressed! I figured that was beyond the scope (no pun intended) of the little blue box.

914, I for one am finding it somewhat difficult to read your style of writing. It generally isn't necessary to Capitalize Every Single Word Of Every Single Sentance.

--DD

[pbanders]

If the MPS and the CHT (TS2) sensors check out, then check the fuel pressure (this is actually the first step in checking the FI system). It should be right at 29.4 psig. Very rich running as you describe is usually due to one of the following problems:

1. Leaky MPS
2. Open CHT (TS2) sensor
3. High fuel pressure
4. Leaky cold start valve
5. Defective trigger contact points