OndeOlav

Hi! I'm new to this forum btw, but now I really need your help.

To get things straight, I'm no rotorhead, but I'm learning. At the time being, there is another dude doing all the work on my car, but he's kind of puzzled about this one too.

I live in Norway, and I've just imported an 1991 FC Turbo 2 from germany with 138k KM on it.
It was completely stock, and drove like a dream, allthough it was somewhat hard to start, but I didn't find out why...

... until about a month later. Compression. The apex blew on me, and I had to replace 2 rotors and one housing. Since I had to completely re-do the car, I jerked out the A/C and airpump as I was on it.
I did not port the car, but I have changed to an open filter (that nice cony-looking thingy ) and a pop-off valve.

Well, anyhow, when i got it back, it was angrier than never before, and I enjoyed driving it. For about twenty minutes. Then something really strange occured. I could apply a very small amount of throttle, and the car would slowly speed up. But, if I tried to floor it, or just apply enough for the turbo to start spinning, it would get the hickups, and halting.
I turned it on and off, and it worked perfectly for another 20 minutes or so, and then it came again. Hicking and stalling if I tried to get a little turbo-pressure.

Last week it got worse. I didn't even get those 20 minutes I was so fond of, it would act like that all the time. This pissed me off, so today I tried to change the o2-sensor (the one directly behind the air filter).

To my surprise it seemed like it worked, but no.. it was just back to the 20-minute-config again.

I'm really out of ideas. Anybody got a clue?

Thanks alot if you bother to help me!
Sincerely,
OndeOlav

Rotory

iTrader: (1)

the o2 sensor is screwed into the exhaust so i think you are talking about the AFM. mine has this same problewm so i would also like to know the answer. i changed my air filter,fuel filter, oil, and spark plugs but none of it helped at all...you may just have to let your motor to break in. how many miles or kilometers are on your rebuild?

OndeOlav

It's probably the AFM, since you say so.
In norwegian we just call it 'luftmassemåler'.

I have about 4000 KM on the rebuild. Even tho' I'm no mechanic, i seriously doubt this has something to do with "breaking in" the engine, since it so characteristic every time it happens. I can almost set my clock by the intervals it happens. On my way to work it happens at the same spot +/- 500m every time.

Wierd?!

Anybody?

Rotory

iTrader: (1)

damn mine does it always....if i push the throttle 3/4th the way to the floor its fine but if i put it all the way to the floor it bucks like crazy... you might try replacing your ecu with a spare one or one your friends might have. did whoever rebuilt your engine make sure to reattach all the grounds? especially the one from engine to tranny?

OndeOlav

Now this is what I want! Possible solutions.
I have no idea what grounds he did or did not attach or anything at all. He did all the work, but I will take not and find out first thing in the morning. It's 2.19 PM here now, so in about 8 hours I will know.

3/4th you say? I can only push mine 1/5th maybe, anything more than that and it wil buck like crazy.
Pisses me off 2k.

Anything else that could cause such things? Will also try the pressure sensor and ECU sometime soon. I think the pressure sensor will go tomorrow, cuz we got a spare one.

OndeOlav

Oh, and just what could you expect if you don't attach the ground from the engine to the tranny?

PS: Pardon my lousy English. ^^

Rotory

iTrader: (1)

your english is great dude...you speak better english than i do and im from USA...lol. you can expect all kinds of problems from bad or no grounding. you can get bad gas mileage, your car could run like crap, bucking, hesitation. It causes a multitude of problems because the ecu runs off of very small voltages and it needs good grounds to keep the signals to and from the sensors and ECU very close to what they should be. i know im not explaining it perfect but that is the basics

13bpower

If the engine isn't properly grounded any kind of electrical component that uses the engine for a ground would faulter.

Sounds like the ECU dosent know what is going on. As in it is getting false information. This could be caused by faulty sensors (ungrounded?) or broken wire.... I don't know, could be many things.

Do you have a Factory Service Manual?

Rotory

iTrader: (1)

yeah the boost/pressure sensor would be a good thing to check also because it is very easy to change out. are u getting into boost at all? does it do it around a ceartin RPM or only when u push the throttle down 1/5th? how bad is the bucking? is it a slight bucking or does it feel like you hit a brick wall?? i really wish someone with a little more experience would get in here and help us out. i know a little but im nothing compared to alot of people on this forum. did you use the original injectors when u got it rebuilt?? and if so did you get them professionally cleaned at all?

OndeOlav

Nope, I do not have a FSM, but i do have Haynes repair manual - based on a complete teardown and rebuild - but as I said before, I'm really no mechanic.

What I'm looking for here is some ideas of potential causes, so that I can work thru them one by one.

Ok, let's say ur right, the ECU is f00ked up, because it don't know what's going on. Why does it always work for about 20 minutes before it gets the downs? My driving pattern has nothing to do with it, cause sometimes i drive hard as hell, and sometimes i just cruise. Nevertheless, it takes about 20 minutes.

I'm so puzzled, and so pissed.

Thanks alot guys,
I appreciate the input. ^^

Templeswain

Why does it always work for about 20 minutes before it gets the downs?


My guess would be that certian sensors will be altered once they heat up and do work. So once they heat up then they give different readings or compensate to give a continual reading so as not to be altered by the environments temperatures.

I mean, all materials expand and contract according to temperature. So you can set your clock to that too.

13bpower

possibly some tempature sensors? when the car warms up they read the wrong temps and send the ECU the incorrect signal.

Templeswain

Yup that's what I'm saying.

But it could be a million things. Okay maybe not a million.
Maybe 100 or so.

None of my four FC's iv'e had have blown the ECU. Plus I think that if it did blow, then the car would be totally dead or would have major major problems driving.

So I would say the sensors that go to the ECU should be checked before trying to diagnose the ECU itself as fried.

The other thing is that the ECU is a digital system, and the rest of the car is analog. So if a sensor goes whack, something gets lost in the digital to analog translation I suppose.

Templeswain

But anyway, I don't know how really helpful that is.

Maybe NZconv. Or Hailers will come along.

OndeOlav

The sensor-heating-up theroy is not applicable here, because those 20 minutes still apply if I turn the car off and on when it's warm.

It does not happen at a spesific RPM, only when I exceed 1/5th throttle. I'm not getting into boost. It stops just below zero on the original boost-gauge.

**** this car #"!¤!"

Rotory

iTrader: (1)

dont get mad at the car man...its only what WE make of it. I agree with what templeswain is saying about the temperature effecting the sensors, it doesnt explain how turning it off and back on but i think it has something to do with that. How cold is it there?

truespin88

I vote for grounding issues. Or a bad sensor somewhere.

OndeOlav

It varies alot, today it was 13 degrees below (C, not F), and some days it's like 10 over. But if I start the car, warm it up for 20 minutes - it happens - i turn it off and back on while rolling - the temp on the sensors won't change! I refuse to believe that! Yet still, the car will fail to boost after 20 new minutes.

I hope someone can shed some light on this subject.

avoid

My 87na does the same thing but at anytime and at wot or half it does not matter. Recently I replaced my battery ground wire and terminal (for some reason my terminal was a solid pice not split like the + terminal so it wouldn't get tight on my new battery) After that it happens alot less

Cliff notes:check grounds semmi worked for me

DubbayoC

the temp sensor has nothing to do with what your ecu tells the engine. check your water thermo sensor. or it could be a sticky tps

Blowtus

measure the voltages of all the pins at the ecu and compare to the chart in the manual at iluvmyrx7.com
do this when it's working good, and compare the numbers to when it's going dodgy. might need to get someone to measure while you're driving too.

Josepi

Check your tps.

20 minutes would be about warmup time, and the thermowax wouldn't be holding the throttle open.

Rotory

iTrader: (1)

i agree with it might be the TPS but he can turn it off while rolling then back on and he has another 20 minutes until it craps out

hIGGI

iTrader: (7)

possible problems

- unhooked TPS
- open filter/exhaust - hitting fuel cut ? (problems with wastegate?)
- ?

OndeOlav

Well, today I was driving it to work, and now it's all crappy again. The 20 minutes is now 3 seconds. It's like this all the time. It only happens when the turbo start to spin, that is as much as I know for a fact by now.

What is a TPS?