I did not want to hijack Mavrick 70004 thread so I started a version 2.

I have almost the exact same symptoms (high idle) that I have been fighting since spring. I have replaced IAC's, Dist Cap, Rotor, Plugs, Plug Wires, EGR, TPS.

In prior troubleshooting I found the TPS to be faulty (Code 22 in FSM). Bought a new one installed and the same thing. The code 22 went away for a while, however, it is back with a new wrinkle in troubleshooting. This is where things get weird.

A few weeks ago, I went through the code 22 diagnostics. Code 22, clear code, jump 416-417, code 22, remove jumper voltage 5.05. ckt 417 seemed to me anyway that is was ok and it was a fauly ECM connector pin 5 or ECM.

I ordered an ECM, but they are in short supply, finally Rockauto had one. I put this in, started it up and the exact same thing, high idle, immediate code 22.

So, on to my latest odyssey. I put the old ECM back in and went back to the code 22 diagnostics. This time when I get to step 2 (FSM Code 22) and jump ckts 416-417 and run engine, I cannot get the code 22 to come back. I did some further troubleshooting by hooking up a digital volt meter at the TPS and connected the ALDL cable to the laptop. I can see 5 V at the TPS but the ECM is only showing .2V and therefore throwing the code 22.

So, it looks as though the circuit is bad, but, being an electrical idiot I am not sure how to diagnose the circuit. I am going to try and clean all the grounds or at least the ECM grounds which I believe are located at the back of the heads.

Any other ideas would be appreciated. I will share my results on the other thread as well. Although the car can run and sometimes the idle will go down to a "lower" level at about 1200, it is really bugging me now.

 

Have you checked for vacuum leaks? Lid gasket leaks are the number 1 cause of high idle on a CFI engine. If you completely close off the IAC inlets, what RPM does it idle at? Has the throttle stop screw been tampered with?

As for your TPS issue, I wonder if you're measuring voltage correctly, but you can test for continuity through each wire, from the three pin connector at the TPS, to the ECM.


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Thank you!

I have tried using propane to check for vacuum leaks. I went through the entire engine and specifically under the lid. That said, I will replace the throttle body gaskets to be sure and double check the lid.

I should have mentioned this. I did get continuity from the TPS connector(s) to the ECM. But, now that you mention it I was measuring voltage between B and C which (I assume) is going to be 5V regardless (5V reference). As I said, I am clueless on electrical.

When they say "check for open or shorts to ground". I honestly do not know how to do that. I mean I know what an open circuit is or I know what a short to ground is. I just have no idea how to test those three wires for open/short.

 

Test for open by unplugging the plug at the TPS and the ECM. Set your meter on "Ohms" or "Continuity test" if it has that feature, then touch the leads together....the reading you get is what you'll get if you have continuity. The reading you get when the leads aren't touching is what you'll get if you have an "open" (broken wire).

Now probe one wire at the TPS connector, and the same wire at it's other end -at the ECM. What kind of reading do you get?


TO test for short to ground, unplug both ends of you harness (like above) and probe each of the three wires at the TPS connector with one probe, while touching ground (engine) with the other probe. If you get continuity with that test...that is a short to ground.

 

OK I did a couple things.

First, similar to Mavrick70004 thread. I stuck a rag in the IAC ports and the idle drops to around 1100 Rpm.

Now for the open/short. I used continuity test. 1 not touching 0 touching.

All three tested positive for continuity (0) from the TPS back to the ECM.

For the short to ground at TPS.

416 and 417 showed no continuity (1).
452 showed a reading of about 800.

 

Is that w/the harness at the ECM unplugged?

 

Replacing the throttle body gasket should be a last ditch effort! If you remove the throttle bodies, you'll need to re-balance them. Not an easy task. As Tom asked, has the throttle body linkage been tampered with, or is the adjustment still welded as from the factory? (240,000 mi. on mine, and it's never been touched!)

 

Yes

 

I will check...

 

Im really wondering about the tps connector is it dirty or corroded?

 

You're getting the 800 ohms through the CTS circuit, as they share that same ground.

I don't think you have a short to ground, you proved you have continuity.

 

Yes, the weld is broken. I assume PO did something. I saw a link to balance TBI's. I guess that may be my next move. I am still confused about the code 22. I sprayed some deoxidizer on the TPS connector. Going to drive it this morning so will see how it does. Battery has been disconnected which will clear codes and the IAC's will adjust.

http://www.thecubestudio.com/Crossfi...yBalancing.htm

 

If you don't have a water manometer you can simply balance the TB's by bottoming both blades in the bore, then re-setting min/air.

 

To late I'm sure, but i have the original ecm from my 84 i don't need.
i also have the original chip, and a hypertech chip.

I have an ebl flash ecm due to my engine mods... And i had to convert my wiring for the newer style plug. So it's never going back in.


But it sounds like that's not the problem...

I used a vacuum gauge set for syncing motorcycle carbs.
To get a good reading i did need to rev the engine.

Also i would suggest capping some vacuum ports going into the intake.
Mostly to rule out a an issue with the evap system and maybe even the brake booster.

Also make sure the intake manifold top plate is tight, and all grounds are connected to their respective bolts.

I recall i have a ground wire near the iac's on the driver side front of the engine... I think it might be for the iac's...

I stuff rolled up paper towels into the iac ports while the engine is running to plug them off, you should feel them get sucked in and the idle should lower.

​​​​​​​Also i found un plugging the spark advance wire helps to get the most solid and low idle...

 

Are you using this diagram? Is the harness good "not open or shorted"?

 

yes this is the same....I think I will buy a new harness.....current one seems brittle....

 

Thanks for the help everyone. I wanted to give an update. I cleaned all the grounds that were related to the ECM. I also was able to adjust the throttle bodies (I think). Anyway, I have the idle down to about 1000 RPM's still high but not like it was. Also, raining and miserable here in the northeast so I have not been able to take it out and get above 25 30 MPH to adjust IAC's. Will update once I can get out.

Thanks again for replies and I will update.

 

Ok. I went through the resetting of min/air after bottoming both TB's. The car runs pretty good. But, it still seems to idle high, but, only sometimes and sometimes it seems to idle normal (900). I am still getting the code 22. Right now the car seems to run great and I am getting good response when moving.

I did get some data and have attached it. Not sure what to make of all the data. Any insight would be appreciated. Seems like TPS data is weird and maybe a bad connection in wiring. BLM data looks normal, I think anyway.