wvumtnbkr

So I checked the ECU terminals for the following items (I have included the values I found, vs. the appropriate values)

I am now stumped as to what the hell is wrong with my car!

All values are based on idle values!

Terminal (Measured) Expected
2E Air flow meter (1.8V) 2.5-3.5V
2G Throttle Sensor (.25V) 1.0V
2I Water thermo sensor (4.9V) .4-1.8V
2L Intake air temp sensor (3.83V) 1-2V

All of the injectors are reading 13.3 volts or above at idle.

I am trying to eliminate an extreme hesitation! THe car will barely rev past 3000 rpm.

It is an 87 GXL with turbo swap (using NA harness).

Two different ECU's give the same values. I have tried two different TPS sensors and two different CAS's. I have also used two different AFM's.

The CAS, TPS, and AFM I am using now have been checked out and verified good by the FSM procedures.

j9fd3s

iTrader: (3)

you're probing from the harness side of the connector right?

wvumtnbkr

Yes, I am checking them from the correct side. I used the locations from the FSM and crossed that over with the wire colors to verify.

I have the ECU unbolted from its cradle. I grounded one of the multimeter wires and use a bent paperclip to backprobe the connections.

I only listed the locations that are not within the FSM specified range. All other locations read correctly.

Thanks!

HAILERS

Tell you what you do now. Get the engine fully HOT. Go to 2G and measure it. IF its as low as you say, then go around to the engine bay and turn the TPS screw til the reading at 2G is ONE volt dc. See if this happens and write back one way or the other. Forget about setting the TPS those *OTHER* ways. It's output should be approx one volt dc with a fully hot engine.

Are you SURE the airflow meter is a TURBO afm? Has N318 written on it?????? Should.

The Water Thermo Sensor reading what it is, means the plug is off the sensor or one of it's pins in the plug is pushed back. Fully HOT it should read .4 to .5vdc. Disconnected it will read what your reading.

Same applys to 2L. The sensors plug is off or one of it's wires is *open*. That sensor is the small sensor on the intake duct. Two wires. Small spade terminals. That metal duct is just after the intercooler outlet hose.

wvumtnbkr

Yep, I double checked twice, on two different ECUs. THis equates to a total of 4 times reading the same value per discrepancy.

As soon as I get off work today, I will adjust the TPS and see what that does to the value.


As far as the coolant sensor, I was thinking that it could use a new one. I will take one off of my other motors and test it per FSM first. Same with the intake air sensor.

Thanks!

HAILERS

It's really, really hard for the water thermo sensor to go bad unless you strike it with a hammer. It's the one on the back of the water pump housing. Green in color, two wires.

With a cold engine and no key in the ignition, try the following:

I'd go back to the ECU plugs. Put the meter on ohms. Pull the middle plug off completly and put one meter probe on the 2I wire on the plug. Then put the other meter probe on 2C (brown/black wire). You should be reading thru the water thermo sensor when that happens. If the reading shows no continuity, then there is indeed a wire open on/at/around the water thermo sensor.

The resistance you read will be ??? well look in the Fuel and Emissons section of the FSM. Look in Secondary Air Injection System and there is a checkout of the water thermo sensor. It shows a picture of the sensor in water with a chart next to it. The meter should read somewhere close to the 2.5 K ohms if the engine is cold. Anything near that will prove the wiring is good or bad. Bad wiring will mean the meter reads zippity.

I don't think there's anything seriously wrong with the ECU/car. Adjusting the TPS when the engine is HOT should get you to the one volt dc. DO NOT adjust the TPS with the engine cold. It's a waste of your time and effort due to the water thermowax etc. Engine MUST be hot when adjusting the TPS (there's ways around this, I know. Too much trouble to write how).

Both the air temp sensor and the water thermo sensor if disconnected will default to a given value inside the ECU. That value is close to what it would be if the engine was HOT. Unfortunatley that is not good for cold starting the car(too little fuel injected during cold start) but is ok for a hot engine.

I forgot the airflow meter reading. That is obviously connected up, but the reading is a bit shy. I'll muddle think about that. One thing you could do, is put the meter back on the ECU wire. Look at the reading with the key to just ON. Have someone slowly push the vane in the afm aft and watch the meter. The value should slowly change and go downwards from a high voltage figure (from 4.5-5 vdc to ??? a half volt or so). Not sure what this proves. I'll muddle think on it.

You can look at the attached jpg and see how if you had the ECU plug off and with a meter on ohms, read b/t the 2C and the 2I you'd be reading thru the sensor. Same with 2C and 2L, you should get a reading IF the items have their plugs on them and no pins in the plugs are pushed back. You'd have the ECU plug off and no power on the car, and read thru the wires on the ECU plug, not the jack on the ECU.

I've done this conversion from na to turbo using the na EM harness with little to no real problems.

wvumtnbkr

Okay, I set the TPS so the value is 1 volt at the ECU. THe car runs like crap! It won't idle now.

The other two items (inlet air temperature sensor, and water thermo sensor) had bad wiring. I fixed this up next, and they are both within specs now.

As far as the TPS goes, I lengthened the wires to the TPS by making an "extension cable". I took an old broken TPS and cut its plug off and tehn took the opposite plug off of a wiring harness I have. I soldered the two ends together with about 1 foot of wire between them. THis allowed me to use the NA EM harness on the turbo motor.

Whenever I set the TPS with a DMM, I unplug the TPS and extension to read the values (I wasn't sure if the extra connection and wire would cause more resistance).

If there is anything else you can think of, I would appreciate it!


Thanks for the help!

wvumtnbkr

Quick Question:

If I had my primary injector connectors crossed, would it greatly impact the running of the car?

I was thinking that if I crossed the front and rear primary injectors, it wouldn't be that big of a deal.

There is no fuel "timing" on these vehicles, correct?

I am grasping at straws here to figure out what is wrong! I will tear the UIM and intercooler off tonite if this could be the cause of my problems!


At least I am learning a SHITLOAD about the FC's wiring!

HAILERS

Yeah. You really need to get the primary wires on the right injector. I don't know of any easy way for you to tell without pulling the intake and comparing the wire colors as shown in the attached jpg. I believe it's the secondary injectors that *batch* fire. Not the primarys.

I don't know what to say about the TPS. It's a given that it should read one volt at idle with a fully hot engine. One volt at 2G at the ECU is what I mean and with all the elect plugs connected up. Does the voltage vary at 2G when the throttle is opened up? Should. Engine idled good with the old reading?????????????

Do you have a Turbo pressure/boost sensor or a non turbo pressure/boost sensor on the car?

What does the afm pin read with the engine off, key ON. Car does not have to be hot when looking at this reading. Pin 2E. This a turbo or non turbo afm??????

Does this car have the solenoid resistor package? I forget if you mentioned that or not. If it does not, then the injector wire colors in the jpg won't be right for you. It does sound a little like the injector plugs are on wrong.

If you take the intake off, key to ON, you could put the meter on pin 3E on the small ECU plug, like you have been doing, and with the key ON see the batt voltage there. THEN pull the injector plug off the FRONT primary injector and see if the voltage disappears at the pin 3E. If it does, then you had the right plug on the Front primary injector. Then do each of the other injector plugs the same way to see if they're on right. Moving the meter to the proper ECU pin for each.

Two jpg of a Solenoid Resistor Package attached. PAY NO ATTENTION TO THE WORDS ON THE JPGS. If you have one of these bolted to the fender below the afm/filter, then you have one. If not, say so and I'll attach the right picture of the wires at the injectors.

wvumtnbkr

N318 boost sensor and AFM.

I do have the resistor package and the cooresponding injectors.

When I get home, I will try the DMM on the injector wires and pull them off one at a time to determine that they are indeed correct.

I don't believe the injector connectors are on wrong, but it seemed like this could be an issue that I should double check. I will check tonite.

As far as the other questions you have raised, I will double check the AFM reading, and report back.

Thanks! I appreciate your help immensely!


I did ignore the wording from the attachment, but busted out laughing when I saw "BURY IN THE BACK YARD!"

HAILERS

Oh. Now I remember what idea I had about the afm reading low. It's dependent on the idle rpms. I suspect your idling above 800 rpms???????? If so, that would explain the slightly lower figures you got. The voltage goes down as the vane in the afm moves aft. Higher rpms make the vane go aft more.

Sure you have the primay injectors on the primarys and secondarys on the secondarys?????? I remember a thread on this site that INSPIRED me to go to my ECU small plug and depin the fuel injector wires where I now put the primarys in the seconday slots and vice versa. The engine would start but ran crummy. I started backing it out the driveway to see how it would run around the block.........but chickened out. Ran too crummy even for that. Just a thought.

Depinning ECU plug wires takes a small jewelers screwdriver inserted in the plug side opposite the wire being extracted. You use the screwdriver to push down on a tab inside the socket so the wire/termination can be unlocked and pulled out.

I was thinking you could do this with the two PRIMARY fuel injector wires. That would keep you from having to remove the upper intake manifold. You'd swap the two primarys because somewhere in your head you think you MIGHT have gotten those two on the wrong injectors. For me it'd be easier to swap two injector wires at the ECU small plug than pull upper intake off. Just to see if things get better or not. GONE

wvumtnbkr

I checked my injector plugs (I pulled the manifold to be sure) and they were correct!

Also, I did have my idle set at about 1100 rpms, so that verifies the AFM measurements.

Is there a procedure or order of operations for setting the timing, idle, and tps for an S4 TII without emmisions (no BAC)?

Also, would a downpipe to open air cause these hesitations?

THanks!

Rob

HAILERS

Somewhere around the 1100 rpm figure, the ECU starts messing with advancing the timing. So it's fruitless to use a timing light on a engine that is around 1100 rpms.

Anywhere below the 1100rpm figure, then a timing light will work right. I'd stay well below 1100rpm if using a timing light to set the timing. Like 900 rpms and below. Some tachs will be off a hundred or so rpm, that's why I say 900rpm or less.

The 1100 rpm indicates the throttle isn't completly closed. Water thermowax stuck open a bit????? Throttle cable too tight? IS the throttle stop screw touching the throttle linkage? YOu have to remove the intercooler to see it. If it's touching the throttle linkage, then maybe the water thermowax is holding the throttle open a bit. Or if the stop screw is touching the linkage, then back that screw off a touch and see if the idle drops a bit.

Or maybe there is a air leak somewhere. 'Got me. I don't think a open downpipe is causing the problem at all.

Slight cracks on the Turbo Inlet Duct cause a lot of problems at idle. Remove it and look hard at the duct where it clamps to the turbo. Cracks are bad.

http://www.teamfc3s.org/info/articles/idle.html