Another break in my wireing harnes would not surprise me. Two of the three wires running to my TPS were broken. Is it better to backprobe at the ECU or at the injector itself?

I've got my multi-meter, my stethoscope, and hopefully an extra set of hands.. I'd love to get the injectors fireing, the TPS adjusted, and perhaps start on replaceing my cat. (BTW, ~$320 from NAPA for a two cat w/ return air to replace the factory three cat. Mazda wanted ~$2800).

If all goes well, next week I'll have a daily driver...almost 7 months to the day I baught it.

Please tell me if my logic is BS.

Back probed the all 4 injector lines @ the ECU. ~12vdc on each one. From the diag I looked at, the grounded side of the injectors passes through the resistors and then to the main relay, not the ECU. Technically I could still have a break between the injector and the ECU, or between the injectors and the main relay.

I'm going to have to pull the injector connectors and retest. I should have ~12vdc on the line from the ECU & I should have the resister value between the injector and the main relay.

Or better yet.... from the ECU, unplug the cannon connector for the injectors and check for resistance to ground. infinity or 0 = bad.

resistance results - ~.64 ohms across each injector form the ecu cannon connector (disconnected from the ecu) to ground.
I'll have to test with the engine running to verify if the injectors are cycling. Time for an extra pair of hands (or feet as the case may be. )

Voltage results while running. ~12vdc on primaries, 0vdc on 2ndaires while at idle. I'll need an extra body to bring the idle up while I watch the DMM.

Side note, I think I still have too much backpresure from the cat. At idle the aux ports are actuating.

Todays Update - I've been adding 3 holes to my cat every day. Each time my engine starting and response has improved. Today I was able to acheave 40 mph.. Mind you, under load I can not hit 4k rpm, but I'm close. I'm running at about 3k rpm when I hit 40 in 3rd, yesterday I could not get over 35, and 3rd gear was right out of the question.
I've also noticed my aux ports are no longer actuating at idle.

It looks like a cloged cat is a major part of my issues. As soon as I get a new set of Cat's from NAPA I'll get it replaced. Untill then, I'll just keep on drilling a few holes until I get enough air flow to get the RPM's up, or until it stops making a differance.

Why not just disconnect the cats all together? will be loud as heck but at least you will know once and for all if that is your problem.

I contemplated the idea. I'd like to stay friends w/ the neighbours. :) And the lift I'm going to use when I replace the cats is a 45 min drive away. I don't think I could stand the drive w/o cats. It's starting to get a bit loud already w/ 12 holes.

Use a stethescope, check for sounds from the secondary injectors while revving to the 'wall'

Fuel pressure check at rpms

Codes?

I have a stethoscope, I just need to figure out how to simulate load (I know there is a write up somewhere) to get the 2ndaries to kick in.

I don't have a fuel pressure gauge, but I know my top rail is getting fuel (had a torn o-ring on an injector) I suspect I could "rent" a guage from advanced or AZ. Cleaning the "sock" is in my to-do list, already replaced the main filter.

I haven't seen any codes yet (check engine lite has not come on). But worth checking again. Will the ECU kick out codes w/o the check engine lite illuminating?

Don't need to. If you just hold the stethescope on a secondary with one hand, and push on the throttle linkage with the other, as the engine accelerates past 3800 rpm the secondaries will come on, and you will hear the clicking. If not, they are not coming on.

Harbor Freight, $16. If it is any kind of restriction in the fuel supply system (sock, filter, blockage, etc) you will see a fall off in pressure as you rev the engine and hit the 'wall'. If all is normal, the pressure actually increases as you rev, due to the way the regulator works.

I'm confused... I thought your car was an 86? To my knowledge, the 86-88 cars do not have a check engine light...my 86 surely does not...

If you pull off a connector to a secondary injector, you should be able to see 12v between one of the two pins in the connector and ground. The injector works when the ECU pulls the other pin to ground. If the 12v is not there, the injector will never come on; likely an open in the wiring harness.

The secondaries will not open at 3800 when not under load. They only open there when under load. If not under load they open later.

Mine open just fine when the engine is revved in neutral, no load other than that due to acceleration.

No. They should not move at all. It sounds like the secondary fuel rail is not properly bolted down, or the injector is not the right one.

You don't need to pull of the LIM, just the UIM. You can pull off the throtttle body, plenum, and UIM as a unit. It's held on with a series of 12mm nuts and bolts; five on the UIM where it meets the LIM; one on the front, near the left side; and two on the left side. There is a complete drawing in the FSM with parts depicted in order, though they missed the AWS solenoid and bracket, which you will have to pull off to get to one of the 12mm nuts on the left side of the plenum.

Mark all of the vacuum lines as you pull them off, so you do not get them mixed up when you reassemble.

If you are going to go through this amount of work, recommend you send out the injectors for professional cleaning and testing.

Have a new gasket ready for the UIM LIM junction (mazdatrix calls it the center gasket...)

I used Permatex #2 on both sides of the gasket, just to make sure there were no leaks...

I found multiple points of deterioration in the wiring, and the plastic shells of the injector connectors were crumbling in my hands... new injector connectors are available for $10 each; I did all 4.

Plan on having to cut off the two coolant hoses (3/8"). New molded ones are available from Mazdatrix, or you can just use 3/8" hose. Have some 5/16 fuel injection hose ready to replace those going to and from the fuel rails, they may not come off intact either.

But, before you do all this, check to make sure there is 12v on one pin of each secondary fuel injector connector... without power, none of this will help...

Wow, go on vacation and now I have a bunch of work to catch up on. :) Thanks guys for the sugestions. I will follow through as quickly as possible.

Just a note. As I reduce back presure from the cat, the responsiveness and max rpm have improved. I managed to get over 4k RPM last nite in 3rd, and it's running cooler. I'm going to check the fuel sock when I replace the carpet in the back, and order the replacement cats when I can get some time on a lift.
BTW, anyone have any expereance w/ the CAT's from Eastern Catalytic - (pn: 40137)

I went with the CATCO #4689. A little more ( $160+shipping) then the Eastern Catalytic, but a better waranty. While I need to go through basic system adjustments to get the idel back under control, I would have to say my injectors are fine. I can run the RPM's well over 4k under load. Even managed 55 MPH in third gear for the first time since last fall.

i have this same issue. i have power in all 4 light green wires but when i checked DV on the brown/red wire it showed 11.65V

Pin 2B, mentioned by Hailers, is on an S4. Is your car an S4 or S5? And is the car a turbo or NA?

1986 s4 na. I can get passed the threshold with light throttle but when you hit the gas hard it hits the wall. Could a had apex seal cause high Rev performance problems? just yesterday i noticed when i do get passed 4k and hit 7k and shift there is quite a bit of blue smoke

You have 4 wires at the pressure sensor. Black/White reads 12 volts w/key to on. Brown/White reads 5 volts w/key to on. You already know the Brown/Red wire reads 3.5 to 4 volts w/key to on. The 4th wire is the ground wire and thus should read close to 0 volts w/key to on (on an 86 NA the ground wire is Brown with a stripe). Remeasure each of these wires and post the results.

With key in ON position. Engine cold. Unplugged Boost Sensor and took DC readings. My results were Black w/ White = 12.22V. Brown w/ White = 5.01V. Brown w/ Red = 4.55V. And the other wire was a Ground.

The readings are supposed to be taken w/the sensor plugged in because the Brown/Red wire is an output wire and if unplugged then you're not able to get a reading from the sensor, plus if there were an internal problem to the sensor or connector then it would not show up w/the tests taken w/the sensor unplugged.

Wont rev past 3k mpms
 

I have a 86 w a tii swap and I just got car back front the builder and drove it 50 miles home and belt started to become lose the closer I got to my home I' parked it when I got back and when I woke up in more morning it was completely dead tried jumping it and it started as soo as I took the jumpers off the terminals she shut right off I changed ecu alt and battery new and now she wont pass 3krms