i have a mostly stock se i rebuilt the engine ground up soid corners, apex seals,springs the whole nine internally the car never ran 100% when i bought it someone had tinkered with all the intake stuff but i ajusted everything to get it running ok and sounded the best cold it would have a hickup every once and a while and when the car was warm would have a idle that was all over the place 100-1400rpm this would happen when i was idleing after giving some gas then it would even out or when i put it in gear it would just stay really low like 200 rpm but was very drivable i would have the hick ups when i was going from a speed and let up on the throttle some to slow down other than that i loved the car and have put 4-5000 miles on the rebuild

Now my main concer is that i wanted to build up my oil system a bit changed to the 3rd gen front oil valve spring and replaced the rear oil relife valve and checked my oil pump specs went pretty smooth got front cover on and pan plugged everything in (didnt have much unplugged) got it started and timed and it sounded like crap i am getting a miss or something or bad signal from ecu somewhere

If someone can just start shooting ideas and ill jump


what i have done:
adjusted tps, fast idle cam, screwed with idle screw on top of intake it would only run before with it turned all the way counter clock wise
replaced water senor
it could really go on for days iv tested everything that i can think of
i have good compression
spark
got fuel
i havent done much since this recent problem last night check my wired plugs i though i had ignitors back wards nope im just lost
i have a fsm,chilton,haynes im horrible with fuel injection im so used to my 3 12a carbed engines i know them up and down

 

Sounds like BAC or TPS. Check for leaks and make sure each is within specs. Check the resistance on both and make sure the BAC functions properly. It should all be covered in the FSM. While you are at it, check the resistance on the AFM and make sure it is within spec as well.

 

i know tps is good iv tested same with the afm ill check the bac right now

 

ok tested bac i got the the rpm drop when i unplugged the vent/vac and the increase rpm when plugged back in.... keep em comming i only have a week to figure this out

 

Have you looked here?: http://www.nellump.net/peri/epi/firs...gslseIdle.html

 

many times i have read that and still no luck

 

what seems to be my problem idle wise is that from a 800rpm idle when given gas it will rev up fall very low shoot up to 1400 or so then bounce around in there then come back to 800 or when i put it in gear idle drops off iv checked both the clutch swich and the nutural switch both were good

 

Sounds like you've researched and covered the normal stuff.

Have you:
Cleaned the injectors and replace the o-rings and grommets.
Replaced the fuel filter
Checked the fuel pressure per FSM
Checked the fuel pressure regulator per FSM
Cleaned/replaced the negative battery cable
Checked the injector pulses at the ECU with a volt meter per the FSM
Checked the grounding points for the ECU, B-21 and B-22.

 

injectors are good o-rings were new apon rebuild ill try to get some of the other stuff check out throughout tonight and post back

 

so fsm doesnt show a diagram with coded wires besides color but it gives me the two plugs to the ecu i see 4 grounds and you mentioned only 2 the odd thing is that the chart for the ecu shows 4 grounds labled B,D,S,& T now the picture of the plug shows B,d,and S but not T! and i didnt see how to check injector pulse also i cant check the fuel pressures till i go to the parts store for a fitting same for the fuel filter even though i think it is good ill change it anyway

im still in the clouds ill still check the resitance across the ground points given and the negative battery cable

 

I'm stumped on this one.

 

B and D connect together and go to B-21. S goes to B-22. B-21 and B-22 are ring connectors that go under one of the bolts that hold the steel rack for the rats nest to the top of the engine. T terminal is mis-printed as X in FSM Chapter 4B ECU plug diagram. Second from the left, bottom of large plug. T doesn't make sense to me as a ground. It goes to the potentiometer in the air flow meter. Maybe it is a ground from the ECU.

 

so un bolted the cover for the ecu and saw a de-pinned green wire it belonged to the smaller plug of the ecu and was for the water temp switch or lower case "k" on the fsm? is this the one on the back the water pump? i know i get water temp on the dash and when i took the front cover off i forgot to plug the water pump plug back in so it wouldnt start perfectly normal and started when plugged in. Could this switch have been grounding out giving me enough connection to get started but to run like crap? now i think i need to check those ground i was checking the resitance between the ecu plug and the ignition nothing from B,D, and S and i cant seem to find the end of the grounds on the rats nest is it under the colored plugs, driver side, passenger side, ect. .....T aka X was grounded and my ground cable is just fine from the battery

so im starting to belive that my problem isnt fuel....at least up to the injectors anyways and iv heard that the ecu cuts the grounds instead of power wires so this grounding out and being able to start would make somewhat sense right?

I feel like im on my way to figuring what the F is up

 

The water temperature switch, B-6 (k, green wire) is the sensor on the bottom left side of the radiator. The water temperature sensor, B-17 is on the rear of the thermostat housing.

Here's something that might help.
http://www.jimrothe.com/mazda/84_tra...ual/index.html
1984 Training manual. Section 4B has more details on 13B emission and fuel control.

The two ground wires are under the colored solenoids on top of the engine. Larger than normal gauge black wires. They are in the engine wire harness that comes from the right corner of the firewall around the front of the intake manifold and to the top of the engine. I think they are fastened under the rear bolt that secures the metal rack the solenoids are in.

BTW The water temperature sending unit (for the gauge) is under the oil filter.

 

ok i take back that about the ecu grounds they are fine i just didnt let my DMM do its work and found the ground ends everything looks good there so im at another dead end i guess im just going to have to check wire for wire from each engine sensor to make sure there is a good connection on everything.....im glad you sent me the training manual 74RX4 but i didnt find much relevent i can use besides a few good component diagrams but i really appreciate you helpping me out along with everyone else who has posted thus far

 

ok when i put the dizzy and the cap back together to time my car when i put the fron cover on i must have put the cap on a little crooked F**K! im an idiot so ill get a cap because i broke one of the pick ups on the cap and we will see how she runs then! and then start working on the rough idle/running

I have been checking alot of conections i got half way down the chart for the ecu just checking for a good connection next ill check voltages but everything looks good so far

 

Something else to research... I remember a long time ago I had this exact problem and I found a website somewhere that talked about an issue with a transistor in the ECU. You just bought a replacement from Radio Shack, soldered it in and fixed the issue. Someone on here may know where that info is. Before you go changeing things on the ECU, you could always borrow/buy a cheap one from someone and swap it out to see if that is causing the problem.

 

hmmm yeah if someone knows of something that rotordogg is talking about i would like to know about it maybe for future refrence

 

its been a while since iv posted back iv checked fuel pressure its good and the green depined wire i put back to the ecu plug wouldnt let the car fire up so i tried to pull start her and the was a big i mean BIG F-in boom and i didnt think much of it just a back fire right? it was a little more than your normal back fire i found out to after diconnecting that green wire from the ecu the car fire right up and it was loud i shut it of quick not knowing what was going on looked at my muffler and it was almost inside out haha but car runns pretty good now still that up and down idle going 48ida to get my baby outta my yard and back on the road...and ill porst a picture of that muffler its pretty crazy