Hi guys.

I finally got the RHD FC temp plated after fixing the body electrical issues, and took it for a drive.

Car is a Turbo car (JDM) VIN is FC3S-130407 build date Oct. 29, 1988. Emissions and mop blocked off. Running premix. ECU is N340. Engine has about 50km on it and is stull under break-in (nothing over 3500rpm).

I noticed a strange bucking and the car would fall on its face under light throttle, then backfire and be fine for a second, then fall on its face again. If I put the clutch in and rev it in neutral it usually backfires, wakes up for a second, and bogs again badly when i let the clutch back out. I took it out tonight and as the car warmed up the problem got worse. When fully warmed up, it's stumbling 50% of the time. The stock boost gauge was also behaving strangely, when the bogging happens, it shot to 40 (KPA? not sure what the units are.), then when the bogging stopped, the gauge went back down to the bottom and stayed there. Obviously not measuring anything and electrically screwed up somehow I though.

I found the black wire of the 14-pin connector on the ecu broken. Someone has been splicing wires into the ECU connectors. I cleaned it up and soldered up the suspect wires, as well as fixing the broken wire.

I checked the TPS sweep and set it to 1 ohm at throttle closed. I tested the full sweep and resistance climbed steadily to 5.2 ohms at full extension.

I also checked the resistance of the fuel injectors, all tested at 13.1 ohms.

After fixing these problems I took it for another spin. The first thing I noticed was with the key in on position, boost gauge went to the top and stayed there, but once the car started running it appeared to operate corretly for the first time since I have owned the car.

At first I thought the bogging was fixed, but as the car warmed up at the end of my drive, it came back just like before. The exact same feeling, like it has 15hp. I was right in front of my house when it bogged again and decied to call it a night at that point and put it back in the garage.

When I turned the car off and tried to fire it up, it flooded and i haven't been able to get it to start back up since.

I am also getting this terrible whining howling noise that may be turbo related. I checked endplay at the cold side and it seemed within spec, and the fins all looked ok too. It sounds like a giant supercharger.

 

do you have the MOP still plugged in? if not you may be simply feeling limp mode.

the other thing i would check is the pressure sensor circuit, if the ECU is reading full voltage from the sensor intermittently it will be going into boost cut and only running the engine off the front rotor. try unplugging the pressure sensor and drive the car out of boost and see if it acts normally, replace the sensor if it seems to be cured while unplugged.

the s5 has a clear flood feature that keeps fuel from the engine when the throttle is open, so alternate on and off throttle first to try to clear the flooded engine. pulling the egi fuse to deflood the engine is still a better method though. but if there is an issue like the pressure sensor one above killing ignition to the rear rotor, it will be difficult to start on one rotor.

 

It starts and idles perfectly fine when cold; bac and tb mod are done to it but the idle is surprisingly solid considering.

The car is an s4 and has a mechanical omp. There are no wires at or near it. The mop is still physically there, waiting for blockoff plate from banzai that should be here this week, but no lines or linkage or wires are connected. I kinda got stuck with a basket case here, it was supposed to be running and driving with a freshly build engine, but it looks like somebody cut lots of corners. I feel incredibly ripped off right now.

Thank you so much for your reply! The presure sensor markings are all worn off and I can't tell what the code on it was.....I need N318 for an s4 turbo, correct? That's what my air flow meter says on it. I will try what you suggested regarding the pressure sensor when I get home from work tonight. Might be kinda late because it snowed a foot and a half and I'm gonna have to dig out when I get home, but I will try this tonight and post an update. Is there a way to test the actual pressure sensor on the car?

I was also considering buying new fuel injectors from mazda to eliminate that as a possibility. I hate throwing parts at a problem without being sure it's actually the real issue, but could it be a sticking fuel injector? I had them out yesterday, they click with 12v and all read 13ish ohms, but I have heard that bad injectors are very common.....

 

Mazda wants $377.00 PER INJECTOR....

 

And $462 for the pressure switch! Looking on ebay now, hopefully it doesnt come down to spending almost $2000 on parts.....

 

Injectors can be cleaned and flow tested if necessary. Other injectors (new) are available at lower costs. Used parts are plentiful in the classifieds section for rather cheap prices.



And check the Brown/Red wire at the boost sensor w/key to on and see what voltage reading you get.

 

I'm looking now. I would like to have a new set I know are good, rather than get them back from being tested in a few days and find out they leak and end up with even more downtime while I am waiting for stuff I haven't even ordered yet to get here....i just wanna drive this thing and I'm getting frustrated with it. I paid for a running car and to have a new motor built (you don't even want to know how much I am into this thing so far, definitely 5 figures), and in six months I've put 20km or so on it because of all the problems I am constantly having. I paid to have the work done because I don't have time, and yet here I am doing it anyways.

Is this the correct part number for my car?

88 13b T high square offset 550cc purple 195500-1370 high impedance???

I get different informatiion from every online store i visit. A lot of them do not specify low or high impedance.....


EDIT: thanks for the tip re the boost sensor wire; i'll check that tomight.

 

yes, though those late S4 high impedence injectors are going to be rather difficult to find.

and don't just go throwing parts at it, you will likely wind up creating new problems.

 

Thanks, I don't see how I would create more problems from replacing the injectors with new ones, I am comfortable doing it and had all 4 injectors removed, tested, reinstalled and car running in less than an hour last night. But I do want to make sure I need them. I guess I'm going to have to accept that this may take some time and patience to get them checked and cleaned by a professional....not sure where to go to have this kind of service done, do engine rebuilders rebuild fuel injectors?

I bought a new set of low impedance injectors for and 87 t2 from mazda about a year ago and the whole set of 4 cost me under $600 new from Mazda...I still have them in a ziplock bag, took them out of the car before I sold it....really is a shame that they are the wrong ones, especially with Mazda's price for the new ones being retarded....my jaw dropped when I heard the price for the high impedance versions.

found these on ebay, not knowledgeable enough to know if they would work...
http://www.ebay.com/itm/2-Siemens-De...f_iR-Q&vxp=mtr

Starting to feel like I have 2 seperate problems; the injectors causing flooding and something in the boost sensor or associated wiring causing limp mode.....correct me if that makes no sense....

I really appreciate any more input and things to look for before I get back home tonight and get back into it, so keep the ideas coming; thanks guys!

 

I have no brown/red.

the 4 wires are black, black/white, brown/white and green/yellow.
black/white is at 13.1v key on engine off
green/yellow is at 3.9v key on engine off
brown/white is at 5.6v key on engine off
black is at 0v key on engine off

black/whie is at 15.9v key on idling
green yellow is at 1.5v at idle and goes up with manifold pressure (reving to 3.5k in neutral hits 4v)
brown/white is at 5.5v at idle and fairly static with rpm changes.
black 0v

If I unplug the pressure switch, the idle does not change.
When i plug it back in, the idle drops and then comes back to where it belongs.

Took it for the drive with the pressure sensor disconnected. Did not bog, drove properly.

I also just turned it off and started it back up 3 times in a row. It started all three times. That was never possible before.

Could I have an n/a pressure switch on here? It seems to behave properly when I tested it but that was all at idle. And I have no idea how many volts it should be reading.....

 

Since your car is a JDM I'm going to assume some of the wire colors are different. In your case the Green/Yellow wire would be the sensor's output voltage. For an NA the reading would be between 3.5 to 4 volts while the turbo sensor should read between 2.3 to 2.7 volts w/key on and engine off (taken from the FSM). It appears you have the wrong sensor.

Another thing is the B/W wire voltage w/car running is too high it appears, as the alternator should be outputting just 14.5 volts or so,

 

Just tried to start it again and it flooded.
Can't get it to unflood with or without the boost sensor plugged in......

I have a video of it running that I am currently uploading, I'll post a link when it's done.
Hopefully tonight's troubleshooting gives you guys some ideas.......

 

Video.

Does that whining mean i gotta get the turbo rebuilt?

https://drive.google.com/file/d/0By2...ew?usp=sharing

 

Would that mean the voltage regulator in the alternator is going bad?

I will start searching for a n318 boost sensor on the cheap.

I think i might need that $400 to get my turbo rebuilt by the way she sounds.


EDIT: N318 boost sensor ordered, found it on ebay for $107US ($140 something CAD)....international economy shipping from Taiwan was the only option so itll probably be 2 weeks at least before I get it.

I will pull the injectors tomorrow night and try and find a place to rebuild them.

I will update as soon as something changes, hopefully you guys have some more Ideas.

 

its possible it could be the turbo but there is no easy way to check it on a AFM operated car, if it had a standalone i would simply suggest locking the compressor blade and running the engine shortly to see if the sound goes away.

for the injectors, you can have them flow tested but injector leaking is rather uncommon but it is possible.

 

Did the video work for you?

Tomorrow night I'll run it without the belt to see if the sound goes away. What else could make a sound like that?

 

just an accessory or the transmission. does it sound the same with the clutch depressed?

 

A boost sensor in the classifieds here would have run you about 15 to 20 bucks.

 

worse under load, if i am really gentle with the throttle it doesn't happen. Exact same sound with the clutch depressed. All gears have the same sound....so maybe pilot bearing??? I've never had a car that sounds like an air raid siren before so I'm not sure what it could be. I just left for work, ill be home in about 15 hours and will check the accessories when i get home.

 

I looked and couldn't find one a new one.
The price there is shipped to Canada and it is a NIB OEM Mazda sensor with a warranty.
I know these sensors usually do not fail but I didn't want to take chances on a used sensor that is almost 30 years old. I'll try and take a little more time in future and not just hit buy it now as soon as I find one on ebay....thanks for the advice.

 

They never go bad, just get a used one.

 

changing clutch on/off alternates which bearings are used in the clutch and tramsission. the fact it didn't change rules those out so it's either an accessory driven by a belt or the turbo.

 

You mentioned an over charging alternator before and it's fairly common for bad alternators to growl if the bearings are shot. Remove the belts one at a time and check the accessories.

 

Removing the belt will be the first thing I do when I get home tonight. I am really hoping for it to be the water pump or the alternator. There is no ac or ps or air pump on this car.

I have found some cheap new and used ones here on the local classifieds, it would be nice if that's my issue. Hopefully it isn't the turbo, but if I have to get it rebuilt or replaced I will.

This car hates me.....someday it better be worth it! hahaha!

 

If it turns out to be the alternator that would be a good time to upgrade. Although it's not as straight forward a swap on the s4 I was very pleased moving to the fd alternator on my s5 turbo.