suck_my_rotor

iTrader: (8)

I have had a recurring problem with my 1986 GXL. I would go into detail about the problem, but it would help better if everyone would tell me this. What could cause my Secondary Injectors to not open? but not only that, instead of the engine continuing to revv off of the primary injectors, it hesitates at about 3700 RPM, or when the secondary injectors are SUPPOSED to come on. BUT, if I let off the throttle enough to where the amount of throttle applied is where the engine only needs the primary injectors open until more throttle is applied to where the secondary injectors are supposed to come on, the engine will continue to rev until it redlines. so. idk wtf to do. I'm going crazzyyy. I can almost guarantee its the weirdest problem posted on the club, EVER. btw here are the things I have done to try and fix this problem.

• An N326 ECU from a 1987 GXL N/A
• A Solenoid Resistor Box from A 1986 GXL N/A
• Rewired The Secondary injectors from the wiring harness with new 16 gauge wire (i think, the same gauge as factory wires) to the ECU and Resistor box. Which resulted in, My problem Being fixed! for a week... But it returned, with a vengeance.
• Re-Grounded the ECU back to the engine, and the neg. terminal of my battery. I also cleaned up all of the grounds in the engine bay with new connectors and cleaned up the surface, and added some dielectric grease to protect my grounds.
• gone crazy.
• Tested my Secondary Injectors. They are working correctly.

What I have discovered about this problem is that Something in my cars electrical system is running too much voltage to my secondary injectors and therefore frying the wires that are necessary to operate the secondary injectors. That is what the problem, to my knowledge, seems to be. I bought the car in April of 2009. Its had the problem since I've had the car. I've been told its the 3800RPM hesitation, but i heard the solution is to Re-ground the ECU. I've done that. Can anyone help mE???!!

RotaryRocket88

iTrader: (7)

I can't see how it's possible that only the secondary injector wires would burn up. Have you physically seen damage to them, or is this just an assumption? 16ga. wire is rated for about 4 amps, but the injectors and ECU should never see anything close to that.

On an '86 putting out a perfect 14V to the injectors (more likely closer to 12V) you'd have:

I = V/R = 14V / [6 ohms (resistors) + 3 ohms (injectors)] = 1.6 amps

Your car is an '86, so did you ever try re-grounding the pressure sensor? That's one of the fixes for the 3800 RPM hesitation on early FCs.

1SWEET7

iTrader: (1)

Do you have low or high imp secondaries? What about your secondary injector clips. I had one work it's way up off until it didn't contact anymore. Check to make sure they are contacting properly.

suck_my_rotor

iTrader: (8)

I Have seen physical damage to the wires, When I first ran the new wires, which were probably closer to 20 or 22 gauge wire (whatever size that were from the factory, I Just looked at the wire and matched it), they were brand new and the copper was shiny as a new penny. one week later when the hesitation recurred, they were a very dark brown color, therefore they were fried. and also yes I have tried re-grounding the pressure sensor. I also tried re-grounding another pressure sensor off of another car from the junkyard... neither worked.

suck_my_rotor

iTrader: (8)

My Secondaries are low Impedance, since I have a Solenoid Resistor box. And Yes I have Brand new Injector Clips. The are working properly. lol I know, this is crazy. there is no possible explanation.

joe_yoh

This thread is so helpful...I need to know about this thing too...

HAILERS

Go to the small plug on the ECU. Pull the small plug off the ECU. Put the key to ON. Make sure there is batt voltage on the light green wire...........the light green/white wire.........the light green/black wire and the light green/red wire.

IF it's there on all four wires, then the ECU should operate the secondarys when there is load on the engine while being driven. It also proves the plugs are on the injectors good and there is no *open* in the injector wiring.

I'd also go to the pin 2B on the middle plug with the key ON and read the voltage. Write back as to what it is with Key ON, engine off. It should be 3.5 to 4vdc.

On a 1986 and grounding the ECU's internao wiring...............The ground wires for the ECU are pins 2R..........2C......3A and 3G. These wires ground to the top of the rear rotor housing. This ground cannot be seen from just looking at the engine. IT can only be seen if the upper intake is removed. IF you did some kind of grounding to the small gnd strap on the rear of the engine that runs from the engine to the chassis.....that AIN'T the ECU ground.

Those wires mentioned are all spliced together about a foot from the ECU inside the EM harness. Strip that wrapping off and find where they all come together inside that harness. Solder a new wire to that splice and ground the new wire on one of the studs that holds the ECU mounting bracket to the chassis. THAT is what is meant about grounding the ECU's guts to the chassis or regrounding the ECU. The original ground remains on top of the rear rotor housing.

IF the new wires you made are brown from something other than engine heat, then it has to be a short in that new wiring. Got me where. You'd have to undo the connector off the injectors and pull the ECU's small plug off. Then ohm each injector wire and see if it is shorted to gnd. Like one lead on the injector wire and the other meter lead to a KNOWN gnd point. Meter should show *open* or infinity. Well I take that back. You'd have to disconect the solenoid resistor package for that to work right or you'd get resistance on the meter thru the power wire for the solenoid resistor.

So what happens if you doing light throttle up to 4500 rpm then stomp on the pedal til you reach 6 grand? Car keeps going? or?

The grounding of the boost sensor was done for one reason..............the ground for the boost sensor is spliced to ALL the other sensors grounds and is also tied to pin 2C on the ECU (2C was mentioned just above). The boost sensor gnd is also spliced to the ECU gnd on the top of the rear rotor housing. I read that factory service bulletin and if memory serves the additional boost sensor gnd was added to help the afm's gnd. Remember all the sensors gnds are tied/spliced together inside the EM harness using what looks like mechanical splicing. See the wiring diagrams for series four and follow pin 2C to the various sensors on the engine and you'll see what I mean.

That said, grounding the boost sensors gnd or adding an additional gnd to it did nothing for my 86 non turbo. Only adding an additional gnd wire to the wires I mentioned above did anything for me.

Also make sure your boost sensors vacuum line has a orifice inside it. The orifice is located about an inch inside the vacuum hose and on the end of that line that attaches to the engine.. Also idle the engine and pull that vacuum line off the boost sensor and make sure you feel a vacuum on the end of that line verifying that that vacuum line is indeed attached to a vacuum source.

suck_my_rotor

iTrader: (8)

WOW. Dude your the man, most of this info I did not know. This is very helpful. Um and to answer your question about revving it to 4500 rpm and stomping it. it will continue to rev, but it hesitates WHILE revving, at the same time it revvs slower. it almost sounds like as if the engine is farting lol. Now. if I do that When I'm driving and its in gear, it will hesitate and will hold that rpm that its at. Also if I am freely revving the engine, Then Stomp it past about 3800 RPM it WILL hesittate, BUT If I let off the gas enough, at about half throttle, it will revv freely and sounds like a healthy engine all the way to the redline.

HAILERS

I meant at 4500 while driving with light pedal, then stomping the pedal. You say when doing that it just stays at the same rpm flogging away.

That does sound like one or both secondary injectors not firing.

In that case go to the small plug on the ecu and see if you have batt voltage on the light green wires I mentiond. Just key ON, plug off and look at the wire in the ECU's small plug that are what I described in the other post.

I'd also check the voltage at 2B as described in the other post and also make sure the boost sensor is seeing vacuum at idle. gone for the day.

suck_my_rotor

iTrader: (8)

Exactly. Do you have the ECU pinouts? I've done some wiring and its a mess. It would be much easier to see it on a pinout.

1SWEET7

iTrader: (1)

The ECU pinouts are available for your series car in the Fuel and Emissions section of the FSM. (factory service manual)