wvumtnbkr

Okay, i got one that is driving me crazy!

I just finished putting an S5 engine in my 87 GXL. I used all of the S4 stuff (manifolds, sensors, etc.).

I have no emissions equipment on the car.

The idle is steady at 850-900 rpm. The timing seems to be dead nuts on. I did try to change the timing around to see if it would help and it did not.

The TPS has been adjusted 2 different ways (1 v and 1K). There are no breaks or dips in the TPS sweep. I tried a seperate TPS with the same result.

I can rev the engine in idle and it "breaks up" but will kind of go to redline. It seems to be better if I go slowly, but it still breaks up.

Obviously, the engine will do this under load as well.

I have new connectors for my primary AND secondary fuel injectors. I have a 1 guage cable going from the battery (negative) to the engine where the injector(s) ground is located.

I checked continuity from ALL of the TPS wires to the pins on the computer. They all have continuity (each seperately).

The problem is there whether the TPS is plugged in or not.

My fuel pressure is steady at 37 psi at idle and goes to 40 psi when I crack the throttle. This is pressure after the fuel filter.


Any ideas?

Thanks!

Rob R.

hvaltierra

iTrader: (2)

6 Ports?

RotaryEvolution

iTrader: (30)

test the plug wires and replace the spark plugs.

wvumtnbkr

will do.

One thing I was thinking about while searching this issue....
I replaced the connectors on the injectors. I know the injectors all share a common power source.

Is it possible to have the wires switched going to the injectors?

Or in other words, if the wires on the injector plugs were switched, would it make a difference? I would think it would not make a difference.

Also, maybe somebody can clarify something for me? if the ground is the pulsed "input" to the injectors to get them to fire, why is there a common ground for the "injectors" under the UIM?

Thanks,

Rob

satch

iTrader: (1)

The ground under the UIM is for the ECU as a whole. The ground for each individual injector comes from the ECU. The wires can be switched to the injectors as they are a coil and don't care which side gets the voltage and which side gets the ground. Are the injectors high or low impedance?

wvumtnbkr

I don't remember which they are.

To clarify, they were the original ones in the car. They are the square orangish reddish injectors from an 86 or 87. They have the resistor pack with them under the AFM.

I guess another way to answer is to say they are the correct ones for this ECU when used with the resistor pack.


Just a question: Why would they place A ground for the ECU under the UIM? Seems weird. I am not arguing or anything, it just seems weird is all.

satch

iTrader: (1)

Because it's best when the ground comes from the engine block as opposed to the body.

And are you aware of the condition of the exhaust system?

Is it possible you have the secondary injector clips on the primary injectors? A quck continuity test on one of the secondary injectors would tell you this.

silver fc

iTrader: (1)

if you are using a s5 engine and ecu you need the s5 omp plugged in. If the ecu does not see the omp present it will put the ecu into limp mode. I had this problem on two of my s5's and plugging in the omp fixed both of them

wvumtnbkr

I am using the S4 ECU and all S4 electronics. I am running pre-mix.

The exhaust is a borla cat-back and an RB header with no cat (Track car).


How would you perform a continuity test on one of the secondary injectors? Just check both sides of one of the injector clips? Where exactly do you mean to put the leads of the DMM? In other words, are you saying to check to see if (one of or both) of the secondary injectors are firing when only the primary should be?

I am thinking about hooking up my spare CAS to the cars wiring adn taking all of the injectors and placing them in my spare fuel rails to see if the primaries spray only. Would this test accomplish the same thing as what you are asking?

I still have not changed spark plugs and wires. I will do that tonight (if I can find some locally).

Thanks everybody!

Rob R.

satch

iTrader: (1)

Pin 3H of the ECU (Light Green/White wire) is the front secondary wire. Pull that ECU plug and one meter lead on that wire and then pull the injector clip off of the front secondary and the other meter lead to the injector trigger/ground wire which should be LG/W as well and w/the meter set to continuity and no key in the ignition the meter should ring out. If it does then you know the wire at the ECU is running to the correct injector. No ringing means the wire runs to the wrong injector or the wire is broken.

wvumtnbkr

Okay, gotcha.

I just wasn't understanding what you meant. Got it loud and clear now. I will check my FSM for all of the different colors and check them all properly. If I remember correctly, the injector wires are all the same base LG color with different stripes.

Thanks!

wvumtnbkr

Spark plugs and wires didn't do it.... Boo.

I hooked up my AFR wideband. It is running LEAN!!!!

I checked that the 2 secondary injectors have continuity to the computer.

I will check the primaries tonight. (intake manifold off again = PITA)


Thanks for all the help so far!

Rob R.

P.S. I had all 4 of the injectors serviced at Marrin. They all were good.

satch

iTrader: (1)

If ECU pin 3H had continuity w/the front secondary and pin 3F had continuity w/the rear secondary then the secondary and primary injectors are not mixed up. As far as the primary injectors are concerned, you could check for battery voltage at pins 3E and 3C w/key to on and if they do then the injector plugs are connected to these injectors properly and not suffering from a poor connection.

wvumtnbkr

Good idea.

I will try that. If that checks out, I am swapping my injectors for some other ones I have on the shelf.

I rechecked my TPS yesterday and noticed something interesting. When I was checking for continuity between the computer and the plug, I accidentally had one lead of my DMM on one of the TPS wires and the other lead on the wrong pin at the computer. Essentially I found out that there is some continuity between the bottom 2 prongs on the TPS connector. Is this normal?

Thanks,

Rob R.

satch

iTrader: (1)

Since there are three wires to the TPS it would make some sense that there would be some degree of continuity between them but I'm not certain of this.

RotaryEvolution

iTrader: (30)

how lean is lean? and do you still have the smog pump hooked up?

wvumtnbkr

No smog pump. Ports are currently wired open.

Lean is 14.5 at its best and goes off the chart with any aggresive throttle opening.

I can hold it at 3000 rpm if I am really gentle. At 3000 rpm my AFR is 14.5. With ANY throttle opening more than holding it at 3000 rpm, the AFR goes to 17 or higher.

I am wondering if I have an injector that isn't doing anything. However if that was the case it would only run on 1 rotor (right?)

Thanks for all the help!

Rob R.

satch

iTrader: (1)

Probably a waste of time, but it takes just a few moments to do. Disconnect the TPS plug and unplug the vacuum hose to the Pressure Sensor and while idling try and rev it to see if there's any change.

wvumtnbkr

Okay... here is what I did.

I took my primary fuel rail off with the injectors attached. I hooked my fuel line supply and return to the primary rail. I held open the AFM. I hooked up a spare CAS. Then I turned the Key to run. The injectors sprayed fuel (into a bucket) when I turned the CAS. Everything seemed to work.

I checked my fuel flow by pumping it into a bucket. It was rather alot!

I put everything back together and verified that my injectors all had continuity (they should have since I just saw them working). I checked all 3 wires of the TPS once again for continuity. They were good.

I checked the injectors light green wires for batt+. They were good.

I checked that the computer was seeing +1.00V for the TPS G/R wire. Good there too.

I unplugged the TPS and vacuum hose to the pressure sensor and started it. It ran well!

I plugged teh TPS back in. It still ran well.

I plugged the hose to the pressure sensor back in. It STILL ran well.

I shut the car off and started it back up to confirm.

It STILL ran well.


I have no idea what happened, but now the car works.

No smoking gun, no obvious flaw, nothing.

THis pisses me off worse than a broken part. I would not be happy if this is a recurring issue.

The ONLY thing I can think of is the main ground under the UIM. As previously stated, I have a large guage wire going from this ground straight to BATT-. So basically, the computer and large diameter wire BOTH bolt on in the standard location. When I removed these wires (So I could move the injector clips for my test) I noticed the washer I was using on the bolt was rusty.

That shouldn't matter because the computer grounds and BATT- cable were touching and the bolt was tight. I changed the washer for a non-rusty one and didn't think anything of it.

I feel like I am willing the rusty washer to be the issue.


ANyway,

Thanks for all the help!

Rob R.

RotaryEvolution

iTrader: (30)

probably a bad connection at the injector clips or the ground wasn't as good as it seemed the first time.

it's not that uncommon to fix either of those 2 things without knowing it.

i know i've pulled apart cars before noticed absolutely nothing, put it back together and problem solved. these were 2nd gen FCs running on 1 rotor with obvious injector continuity issues. it's the joy of working with 25 year old crusty wiring.

clokker

iTrader: (2)

Maybe so, but don't lose sleep over it.
Remember, there are a lot more wrong ways to assemble something than right.
This is compounded by the age of the car, which I firmly believe confers a personality and awareness to the components. They like to be "just so" and anything else just pisses 'em off...that's why vac leaks, bad/missing grounds, etc. are so common after motor work. It's not tech error as much as it is a failure to communicate.

The lack of a smoking gun is frustrating from a purely diagnostic perspective but the fact is, you successfully negotiated a truce with your engine...it made you do a bunch of testing, apparently to no avail since everything checked out, and then decided it would work.
And wasn't a working car the ultimate goal of the entire exercise?

wvumtnbkr

Yep, working car is good. However, this is a track car and I don't want it to re-occur mid race.

I hope, if it is something intermittent, that it shows up while driving it around this fall (the car is still registered).

I will update if anything changes.

Thanks Again for all the help!

Rob R.

RotaryEvolution

iTrader: (30)

wiring issues will generally present themselves when cold versus warm, if it is going to do it again it will either happen when you start the car on a cold day and go away when warm or happen under certain circumstances like wiring pulling when taking a certain turn hard.

jimmydanny

That is modern electronics! Had a computer with a dead mainboard, it just didn't work. Sending it back on DOA, just tested it in the box before I shipped it. Worked fine all of a sudden. Worked for 1 year after before I upgraded.

The tale of modern electronics randomness.

wvumtnbkr

The car runs very well now except for one thing. It is running lean. It is about 15 to 1 during hard acceleration.

The car pulls hard, so I am curious what is going on.

I have a aem wideband tht is installed about 12 inches from the engine. I am pretty sure that is to close, but that is where the bung is.

My fuel pressure is 35 at idle and goes up to 40 when I touch the gas pedal.

Any ideas?

Thanks!

Rob R.