Ok so I just got my S5 TII swap done in my 88 NA. No engine management system, just stock with bolt ons.

Everything was installed professionally by a rotary mechanic.

He drives the car around, parks it in front of my shop. Says it is 98% done, only issue is under load when you try to get on it, it chokes and acts like it has no fuel.

I drive the car and I verify this. It will rev freely in neutral, and even rev all the way out while driving under cruising/light throttle. Just when you try to get on it is when it happens. As early as 3k rpm.

So I put in a Cosmo fuel pump hoping it was a bad fuel pump since my car had been sitting for song long. Nope, same issue.

My mechanic is swamped with cars and won't be able to look at it again until this weekend, and well I am antsy because I want to get some miles on it and head down to 7stock in it.

So I am thinking MAP sensor myself. Anyways just looking for some opinions. This will get figured out eventually but the sooner the better and I know there are some intelligent people here on this forum that could possibly help me out. If anything just to have a thread that could possibly help someone else out in the future.

Thanks

 

I'm no expert, but have you checked fuel pressure? Maybe change the fuel filter? Tps adjusted? Sorry, it's simple stuff, but it's all stuff we sometimes forget..

 

Checking stuff like fuel pressure under load and checking the MAP sensor are things I have yet to do because I haven't had any time. I only work the smog shop during the weekends and have a full time job during the week

Just from driving it around I am almost certain it is a fuel issue, but your right best way to verify this is to check. Oh and no I haven't changed the fuel filter since I have owned the car; it is getting changed ASAP.

 

USDM or JDM engine?

 

im having the same problem at around 3000rpms its like the whole power band is absolutly gone and it is hesitating, i have a N\A engine with an cone intake and 2.5 exhaust, i dont know why, helps???

 

This is a JSDM engine. S5 harness, AFM, ECU, etc. etc... complete swap.

 

when your driving the car does it start to buck and shake when this happenes?

 

no it doesnt buck, at least for me, its just not getting any power it just wont get up and go like it used to. at least im not the only person with this problem.

 

You can simulate load by disconnecting the plug to the TPS, removing the hose to the Pressure sensor and capping it. Maybe the Pressure sensor is at fault or while simulating load see if the 5th/6th port actuators are working properly and also check the ground pulse to the secondary injectors. And last but least clean up the grounds.

 

two things come to mind.

1. the Fuel pressure regulator is hooked up wrong. there are a few ways to do it, and the vacuum diagram in the book isn't clear enough in that rear corner of the engine. if it doesn't see boost, fuel pressure does not go up when it sees boost.

2. check for codes. we had one that went way lean after 3k, and it had a code for the fuel pressure regulator solenoid. plugged that in, electrically only, and mixture went correct

3. it may also be that the secondary injectors are stuck/bad/not working

 

Did you do exhaust on the car? any free-er flowing exhaust may require upgraded injectors as well.

I think J9 has a good idea. FPR could be hooked up wrong.

 

What ECU are you using? J-spec N374 or US-spec N370? The N374 is notorious for improperly firing injectors.

If N370, try the above suggestions. Definitely test fuel pressure.

 

That is also what Comes to mind too.
although I am not Proficient in Electrical,etc,I read alot on Forum.
and it does sound like the typical JDM to USDM ECU Problem...Try another ECU.

 

Good info guys thanks. Unfortunately I have yet to get back over to my smog shop to start testing things. First thing is fuel pressure and check out the regulator. I will also test the MAP per FSM. Glad I have a dyno I can field test it on without leaving the shop

Also car runs and idles fine, and will rev all the way out in neutral at WOT, and will rev all the way out while driving just as long as its light throttle. I can give it WOT but the moment it starts hitting a certain load is when it cuts out. Which makes me believe its not a TPS or ECU issue. Anyways I will hopefully have some time to sneak over there and start testing things today, we'll see.

BTW it has 3" racing beat downpipe and presilencer to oldschool racing beat cat back dual exhaust.

 

I believe the fuel flow through the rails is reversed on jspecs. Might wanna check that out.

 

-UPDATE-

So figured out the fuel pump relay was not operating as intended, reason unknown. So the fuel pump was wired to bypass the relay and just have power when ignition is on.

So now the car runs fine, has awesome power, BUT at around 8k rpm under WOT it starts pinging. Doesn't do it anywhere else but at around 8k and up.

Car had 6 month old 87 in it, so I run it down and fill the tank with 91. Still pings at 8k under WOT.

Any thoughts? Oh and one thing, the car has an S5 NA air flow sensor (grabbed from a vert) as opposed to a TII air flow sensor as it was the only thing I could get my hands on at the time. Would that possibly have something to do with it?

 

No, you should not be using an NA AFM with a TII engine. The resistance values are different and will affect fuel calculations.

And why are you revving an S5 TII engine to 8k? Redline is 7k RPM, and the stock turbo will barely flow any air past that point. Just shift.

 

i wouldn't keep driving it pinging... but it does sound like it wants more fuel. i'd also check the plug wires if they arent new, and separate the trailings from each other and the leadings.

 

Thanks for the info, I'll get a TII AFM asap.

Reason for taking it that far is more of just a power check/make sure everything is fine check. I just know it shouldn't ping at 8k because my old S5 TII never did and it was a similar setup. Also, while my old TII's power would fall off shortly after 7k, this car continues to make power up until it pings at 8k.

 

I have one, if you are interested.

 

-UPDATE-

So I finally got my hands on a N370 (S5-TII) AFM thanks to Junpower! He had one sitting around still in its original shipping package so he just gave it to me as he had no use for it.

Put it in, and no more pinging at 8k under wot. Car runs like a complete champ and I love the crap out of it.

Raced an Integra type R and just walked away from him every time.

Thanks everyone for your input

 

strange, it should have run richer with the n/a AFM versus leaner..

 

My theory is that the N350 AFM was choking or maxing out at 8k+ WOT so in effect "unmetered" air was going into my engine causing it to run very lean because the computer wouldn't know to compensate by increasing the duty cycle of the injectors.

Ionno just my guess?