Having idle issues with my SE converted 85. The engine will start and idle roughly. It seems as though its not getting enough fuel. If I depress the plunger on the TPS, the engine's idle will increase and smooth out and run normally. Sometimes if i run the engine at half throttle, it will smooth out and run to redline at half throttle. Full throttle causes the engine to stumble. I have replaced the following parts with no change in running condition:

-ecu and surrounding sensors
-tps
-afm
-cleaned the air filter, tube in front of the radiator, and ruber intake boot
-cleaned the throttle body
-replaced the exhaust with a system with gutted cats to test for restriction issues

I cleaned the wiring to the ecu and surrounding sensors and replaced all of the surrounding sensors with known good units. The injectors were cleaned and tested by witchhunter in 2009. I pulled the dynamic chamber and upper intake manifold off and inspected the wiring and the injectors an all appeared to be good condition. The engine has ran perfectly since i swapped it into the car in 2009. The car got some mice in it and this is when it started running funny. I have pulled the enterior out and cleaned all of the nests and scrapped the fabric sound deadening. i did not see any chewed wiring. I have not adjusted the other tps that I installed and will not until I figure out what's going on. The other tps would cause the idle to smooth out near instantly when the plunger was depressed. The one I installed takes a few seconds of full plunger depression before the engine decides to run well.

Here is a video of the engine starting and running:



video-2013-10-01-18-03-16.mp4 Video by mazdaverx7 | Photobucket

 

What about the fuel pump and filter?

 

I haven't dug into those yet. Seeing as wide open throttle on the TPS seems to bypass this issue, I was first concentrating on the electronic part of the injection system. I wouldn't rule out either though. The filter is 4 years old and the pump is an original SE assembly from 84. The pickup screen is new oem Mazda, though I have not checked the screen in the large feed line.

 

Sounds a lot like cruddy injectors, or even one with a steady leak.

 

Definitely check fuel pressure and fuel volume (as well as the systems ability to hold pressure once the pump is off) I had a hell of a time figuring out why my T2 swapped FB wouldn't run right back in 2009, went all through electronics etc and it turned out to be a failing fuel pump that wouldn't maintain enough pressure.

Similarly if i messed around with my AFM it would start to run a bit better. It's likely the reason yours smooths out by increasing the TPS is that the ecu increases the injector duty cycle and gives it more fuel - a sign something is up with the fuel system

 

well, it can't hurt to start with a filter and see where that gets me. i have a fuel pressure gauge, but there's no way to test for proper fuel pressure that i know of. the only thing i do not have is a spare pump. but i can always buy one down the road as i diagnose this issue.

 

i blame the mice , although i could see where its time for a fuel filter anyways.

um odd places where mice could effect things are the heat hazard sensor on the floor, when this is "on" the ecu tries to cool down the exhaust by dumping the air pump air, and adding a ton of fuel.

it might be worth looking at the o2 sensor too

 

the o2 sensor may be original.. i'll have to check. i have spares that i can swap in. the heat hazard warning sensor is long gone but the wiring it still in place. i zip tied the remnants under the car. the mice were under the driver's seat as well. i pulled it to clean a few days ago. maybe i'll recheck the wiring there.

i also blame the mice because it ran great before i parked it for the 2 weeks that i didn't use the car. a lot can happen in those 2 weeks..

 

agreed! the fuel filter usually doesn't clog up all of a sudden sitting.

 

i got a new fuel filter on order. going to change it just to rule it out.

 

Have you checked the ignition? Plugs,wires,coils,ignitors,timing etc? Sounds like its flooding at lower RPM. A bad TPS would make it sound fluttery. What was the last thing you did to the car before it was parked?

 

BTW at the end of the video it starts fluttering. Have you checked the TPS with a meter? Try unplugging the TPS and see what it does.

 

i replaced the tps but did not set it. i have check the ignition and it seems to be fine. the last thing i did before before i parked the car was drive it. it was running perfectly.

 

How old is the fuel?The fuel in my 80 was a year old when I bought it. Needless to say after draining the tank (I recycled it in my lawn mower!), new lines, filter, and fresh gas with a bit of Seafoam it ran like new.

 

the gas is no more than a month old. i was driving the car and i parked it for a couple weeks and then it started acting up. came on slowly though. it started and ran fine and then started bogging at anything over half throttle and then it quickly degraded to its current condition.

i put about an hour into the car last night after work and replaced the BACV. I also found a vacuum leak at the BACV diaphram that I corrected. I rechecked the ignition and the spark is NOT blue, but more of a yellow color. i replaced the cap and rotor, checked the plugs, and stopped there. it ran better for a short time and when i was backing it out of the garage it ran perfect at light throttle. i decided to take it down the road and it was running fine and then all of a sudden again, started bogging and running like crap. maybe i should consider a fuel filter replacement and start with that. can't hurt to start messing with the fuel system.

 

I'm tellin ya, do a pressure and volume test All symptoms sound like a fuel issue to me.

 

they do seems to be fuel related. how would i do a volume test without a fitting?

 

SE's use the same type of fuel hose as FC's right, just a push on type with a clamp? The pressure gauge I have (Harbor Freight) has the option to use barbed fittings, so you just put it inline between the feed line and the fuel rail (easiest to do in the engine bay) so just hook that up and run the pump. Even if the pressure seems ok at first, leave the gauge on there and turn the pump off, and make sure it maintains pressure in the system - this was ultimately what the problem with my T2 FB was, the pressure would leak down very quickly (back into the tank) and was preventing it from maintain enough fuel in the rails...

For a rough volume estimate I just ran a longer piece of hose off my feed line into a gallon container (I think I used a empty washer fluid bottle) and ran the pump for 1 minute. Again this is a rough test, but it'll give you an idea of what kind of volume the pump is putting out. It'll be obvious if the volume is way down

 

I did both of these tests recently on my SE. Marginal on pressure, failed the volume test. Turned out to be a clogged inlet screen at the fuel pump inlet. Check that first. If it is clogged, it is likely the tank needs to be pulled and cleaned/sealed.

 

i will check the inlet screen. that was next on my list. i replaced the fuel filter and drained the tank tonight to no avail. the tank was clean when i installed it 4 years ago. i also replaced the pickup screen with a new oem unit. at that time. i will do as Sean suggested and perform a volume and pressure test and check that inlet screen tomorrow. Sean has me leaning towards the fuel pump as being culprit.

 

A friend of mine had a car that would illustrate similar symptoms as yours. He went through a bad break up with a girlfriend at the time. He just couldnt get it to run right at all and parked it for quite some time. He decided one day to just rip it apart starting with the fuel system. He dropped the tank and removed the pump to find that someone had put a ziplock bag inside the filer flap and when the car runs pump would suck it up and choke itself. When the car turned off the bag would release from the pumps suction. I bet the ex girlfriend shoved it in there.

 

ok, here are the parts i replaced yesterday with known good parts.

-fuel pump
-fuel pressure regulator
-fuel injectors
-variable resistor

i cleaned the little filter in side of the fuel pump that is prone to clogging, cleaned the check valve inside of the fuel pump. i check both coils and they were both at 2 ohms.

the engine is acting as if its flooding when its running. its backfiring from unburnt fuel in the exhaust. when i replaced the variable resistor, it cleared itself up for a few seconds and ran perfect. i thought it was fixed and then i let it idle and everything went to crap again

est thing i can think of at this point is that maybe the mice got to a wire and chewed through it enough that it can't pass full current though..

 

Did you try a spare ECU?

 

I have heard that noise before.....Sounds like it's almost running on one rotor or the engine is extremely tired. Not really sure how is your exhaust setup but to me, that engine doesn't sound 100%. Either you are not getting fuel to one rotor or you have one rotor that went out on you....

 

nope, engine is strong. it will clear up intermittently and run perfect. i believe its a fuel or wiring issue.

i replaced the ecu with a known good unit. it was one of the first things i did.