All, I’m looking for some help trying to get my FD ready for spring again…

My car seems to have a strange breakup at 3000rpm or under any load. I haven’t tried to drive the car anywhere yet but it should rev freely. Any load will get it popping and backfiring out of the tailpipe

Parallel turbos
PFC

The car sat for about 3 months while I finished other projects. I drove it into the shop to do the following:

Install an hks v mount with new koyo rad and new hoses
Banzai Oil pan brace and new oil w/ filter
New oem coils and new ngk plugs and plug leads
Fixed the knock sensor plug that was completely broken
Replaced alternator and battery
Fixed cas wiring that was hanging on by a couple strands
Ast delete

The car ran great before I started this project. I’ve checked compression, pressure tested and smoke tested the engine 5 times, changed plugs again (plugs still looked new when I took them out), changed plug leads again, changed where the map sensor was plugged into, changed coils with other oem coils and the tps is within spec

Any suggestions would be greatly appreciated. I searched and have tried all the suggestions I’ve found as listed above

Thank you

 

Have you run codes?

Check that .......I see you have PFC.

Did you re-program the PFC for the new set up?

Do you have an AFR gauge?

Are the leads hooked up to the right plugs?

Are the replacement coils the same as 1993? After 1995, the position of the coils changed.

Is the MAP sensor filter installed in the right direction?

Is your idle air control valve sticking?

Is fuel pressure regulator getting vacuum?

The TPS can test fine, then go out of spec once the car is hot.

Is your oil filler neck breather still venting.

 

Before you start replacing anything…. Make sure you’re testing your TPS after you’ve warmed up the car.

 

thanks for the reply. Tps is adjusted when warm but I will check to confirm. that it didn’t move out of place when I did my spark plug leads again

My oil filler neck is now routed to a catch can. Perhaps I have the catch can setup incorrectly?

The coils are correct, both sets from a 1993, tried the old ones that were tested fine just in case. All within spec.

Idle control valve has been removed.

no afr gauge unfortunately.

only the intercooler was changed that would have an effect on the pfc tune. It was a bigger stock mount one before I put the hks one in. Same injectors. Same turbo setup

pressure regulator is routed as per the single turbo diagram. With the orange solenoid in between

map sensor has the arrow facing the right way and the pfc reads vacuum and boost

thanks for the suggestions

 

thank you. I will triple check this to confirm it didn’t move out of adjustment when I did the spark plug leads

 

Did you mix up your CAS plugs?

 

3000 RPM is when the secondary injectors start to come online. Possible you have one that is stuck or flowing poorly after sitting all winter.

Also triple-check your ignition wiring - make sure plug wires are on right!

Dale

 

I’ve tried them both ways. Didn’t run at all the other way around

 

I had to replace the connectors on the secondaries… do secondary injectors have an effect on how the car would idle as well?

 

Nope, all the fuel needed for idle & low load cruise should be coming from your primary injectors. So unless your secondaries happen to be leaking, there's no effect on idle. If they were leaking, the car would idle like crap and you'll probably have flooding issues too (hard starts, fouled plugs, etc.).

 

no leaks anywhere. starts right up and plugs arent gassy.. it seems to idle higher than normal when its warmed up. it used to hunt but after i fixed a misrouted vacuum line, it seems to idle normally, however it sounds like its missing a tiny bit at idle

 

This almost sounds like an ECU input being skewed due to a failing ground, resulting it running lean (possible buy not as likely) or rich (more likely, inputs usually move "higher" like this). What are you seeing from your O2 readings? If it's running LEAN, the poor ground is affecting the injectors and coils' function. If it is running RICH, one more more sensors are being nudged AWAY from ground (higher voltage than normal). This means more fuel is being put in than normal, so a higher idle could easily occur.

Also, "JDM 93" is a bit vague as one could need either the 10/1991 manuals or the 7/1993 ones/supplements. Plenty of differences between the two and I'd hate to see things go worse from having the wrong information. Providing the Production date would clear this up a bit and make it easier to get help straightening things out.

 

Did you do anything else with the fuel injectors? Polarity on the injector plugs doesn't matter but is there a chance you didn't terminate a connector properly or properly seat the connectors? If you took the injectors out are you sure that you didn't mix them up?

 

i would have to look at what the o2 is reading at. I think it’s running lean. If it were rich, the plugs would be pretty dark, correct? I’ll check the grounds again (it does have a grounding kit) but perhaps the one from the - to the body is inadequate

thanks for your suggestions

also the car is a 1992 build

 

injectors stayed in. I just replaced the connectors since they were pretty brittle. And just the secondaries. Primaries weren’t touched

 

TPS may test fine cold or warm. Issue is when it gets hot.

Catch can set up is likely ok. The catch can is vented to air, I suppose.

I always wondered what would happen if the catch can actually filled itself up.

I beleive that there is now a program you can subscribe to that assists the PFC to self tune to your build. Also there is a link wire so you can fiddle with it live on your laptop.

I don't know what happens when you delete an IAC valve. What is it there for?

AFR gauge would seem a must if you have gone to an enhanced induction build.

I have seen a shop clamp a sensor to the tailpipe outlet and run a line up to a hand held gauge in the cabin.

Only if it gave a vague idea of what is going on.

O2 sensor burn out fairly easy as well. They used to be cheap enough to replace every time you did your plugs.

Do PFC even bother with the 02 sensor?

We have a number of Sensei's on the case.

I am a simple Deshi that has learned the hard way.

(For example: I was about $16,000 in only to learn that a simple ($.05) o-ring near the fuel pump was pinched. It was one of the first repairs I had had done.)

 

Update: I redid all the grounds, adjusted the tps when the engine was at ot and removed the catch can. The car idles fine now but any gas will cause misfiring and will barely rev past 3k at all. Lots of blue smoke from the tailpipe when I rev it but none at idle

I’m reluctant to buy a wideband and install it now that my engine could need a rebuild

 

Not sure what your fuel pressure regulator set up is, but on a stock set-up if the FPR is not getting vacuum, it will stay closed and push the fuel pressure back to your injectors.

Are you doing premixing/ Have you got the ratio correct?

Is the OMP deleted?

On very early cars there was some problem with the way the oil injectors were positioned.

What does the compression test read?

Note that there is an error in the 1993 USDM workshop manual stating that 85 psi is acceptable. In all other manuals, including later USDM manuals, the lower limit is 100 psi..Because of that error, unless it was corrected by some service bulletin, a whole generation of owners and mechanics could have been running around in cars with inadequate compression.

The list of possible remedies, for low compression, essentially point to engine rebuild as a necessity.

 

the fpr has a like from the intake, to the orange solenoid, then from the orange solenoid to the fpr. Said solenoid is plugged in. Omp is still hooked up and has steel lines.

I don’t have a compression tester anymore since moving into my new shop and there isn’t a shop anywhere within a few hundred miles that has one. The engine sounds like it has good compression when cranking and the engine has less than 10k miles on the build - not like that means much. I may just leave the car until later in the summer when I can afford another tester/whatever else it will need to get going again

 

Can you test function of the orange solenoid?

The orange solenoid only restricts vacuum to the FPR in certain start up situations when more fuel is needed to the injectors..

As it is almost always open, perhaps you can feel if there is suction. I don't know if you can actually sense that.

In rare cases the FPR itself may be stuck shut.

If you have an operating OMP and have the premix ratio wrong, you may be getting just too much oil into the combustion chamber. It is not unheard of when people have been dumping way too much oil into the gas.

In my case I still have an OMP, but I still premix at about half the recommended level, just in case the OMP quits.

I burn very little oil, so I suspect my OMP might not be working very hard.

Any oil in the coolant or coolant in the oil?

Any coolant smell in the exhaust?

Opening the coolant cap, is there exhaust bubbles in the coolant flow?

In the big air intake pipes before the intercooler, is there any oil in there?

The source of oil could be oil leaks in the turbos.

 

no coolant in the exhaust, coolant flows fine and is new, no abnormalities there. No oil in the intakes. The car sat with less than a 1/4 tank of fuel that’s currently 8 months old. I tried to put fuel stabilizer in it but it didn’t run with it for very long in the tank. I run premix with the same rationale as yourself - just in case the omp quits so as small ratio as possible. I can try putting new fuel in but last winter I left it for about the same amount of time and it ran perfectly fine after. Are there any way to read trouble codes with a pfc?

 

also, the vacuum ran through the solenoid fine when I put it back in

 

I don't know how to read a pfc, but I understand it should show faults in one of the menus.

In the JDM stock set up the ecu will go into "limp" mode if a fault is detected.

"Limp mode" disables the car to the extend you literally have to limp it home.

I do not know if the pfc would do the same.

Is there a chance you have the wrong version of pfc?

Check the pins on the PFC to see none are bent.

Check inside the pfc ecu for any water incursion (unlikely)

In another case a guy installed a gauge wire through the same hole in the firewall as a main harness causing a short out.