Need help! s14 sr swap done but will not rev above ~2.5k when in gear, sputters

[wadiad]

Hi guys, i just had an s14 sr20det swapped into my 1989 240sx. The car starts with no problem and idles reasonably well. It can also rev freely before it's put into gear, but once i actually start driving it the car will not rev above about 2.5k (no tach so that's an estimate). It starts sputtering, breaking up, and bucking at that point, very similar to if it had no MAF connected and it was in limp mode. Compression is 130 in all cylinders. The guy that installed my engine is not sure at this point what the problem is, and i could really use any advice about what to look for. Can this be a wiring issue? Or some sort of non-functioning sensor? A few details that i don't think are relevant but i'll mention anyway: currently no gauges on the cluster work except fuel (i believe the wiring for them wasn't completed). Also, no o2 sensor is connected yet. The engine has no mods at all and is running a stock s14 MAF. I really appreciate any help.

[rogoman]

Either the MAF is bad or it's not wired correctly.

[bloodsport]

Either the MAF is bad or it's not wired correctly.

+1

[wadiad]

The first MAF i used was an s13 MAF. The guy who did my swap thought it was bad so he tried another s13 MAF. And then i brought in the proper s14 MAF which matches the engine. Since the problem still persists i guess i will have to have the wiring checked out.

I am still curious to know, why would it rev all the way up when the car is in neutral after i start it, but once i drop it in gear it breaks up after ~2.5k rpm's? If the MAF or wiring was bad/incorrect, wouldn't it affect things the same way irrespective of whether or not the car is in gear?

[rogoman]

Did you use the S14 SR20 engine wiring harness and the SR ECU? Also make sure the hot pipe system has no leaks.

Go to the Heavy Throttle web site for additional info:

http://www.srswap.com

[Thoughtful_One]

When the MAF on my KA went bad, I couldn't even free-rev past ~2500.

As an S14 SR owner myself, Even though you have an S14 SR MAF, it doesn't mean it'll work.

Do you have a Zenki S14 SR or Kouki? Kouki's use a different MAF then the Zenki. Check your ECU. If it says NA, it's Kouki, WC and t's Zenki.

I don't remember part numbers off hand, but look around on the web and match them. If they match up then check for boost leaks.

[wadiad]

When the MAF on my KA went bad, I couldn't even free-rev past ~2500.

As an S14 SR owner myself, Even though you have an S14 SR MAF, it doesn't mean it'll work.

Do you have a Zenki S14 SR or Kouki? Kouki's use a different MAF then the Zenki. Check your ECU. If it says NA, it's Kouki, WC and t's Zenki.

I don't remember part numbers off hand, but look around on the web and match them. If they match up then check for boost leaks.

Regarding the MAF compatibility, i was under the impression that any sr20det MAF - even an s13 redtop MAF - would work just fine, except that different ones have different maximum airflow (hence HP) limits. In any case, the MAF currently in use is a 22680-69F01. All i know is that it's from a Silvia s14 (but it did not come with the engine). I can check whether this is Zenki or Kouku, but... I don't know whether my engine is a Zenki or Kouki.

I can check the ECU code (the car isn't currently at my house so i don't know right now), but here's the problem: when i bought the engine, the ECU was NOT together with the engine. The wire harness was connected to the engine so i know it's the right one, but they grabbed the ECU off a shelf and gave it to me, i never questioned whether it was correct or not. That said, would either ECU work with my engine? Or do the Zenki & Kouki ECU's require their respective engines to function properly? Is there any way to tell which engine i have from some identifying marks, numbers, or something? It was marked as a 1995+ model year, but that could be either as far as i know...

[Thoughtful_One]

Okay, this is a tough one since the engine wasn't bought as a complete unit.

I just checked and you have a Kouki MAF.http://www.240sxmotoring.com/partnumbers.html

My MAF is a Zenki S14 SR since it ends in 00. Yours is 01, therefore you have a Kouki MAF.

Now that we know you have a Kouki MAF (which by the way are really rare to find), did it come with the engine you bought, or did the people just give it to you off the shelf?

Here are two things that you could check for:- I believe, if there are fins on the head, it is most likely a Kouki. Then again, there was one transitional year when the Zenki had fins on the head (which is what I have, and I know for a fact it's a Zenki).- Check the coil packs. Most likely they weren't replaced. If you check an older thread, in the SR forum, it tells you how old the engine is.

If you don't have fins on your head, it's likely it's a Zenki.

Finding S14 SR MAF's are hard as it is, and worse comes to worst, you could just get a Z32 MAF, that is assuming your ECU is right though.

Also, there are three S14 SR ECU's. One is black WC, red WC, and NA (Kouki). I forget which WC I have, but the different color represents that transitional year.

[wadiad]

That is some very helpful information. I am 99% sure the person who did the swap and is now trying to get it to run right does not know any of this. I think it will be best that i take a ride down to the shop where my car is myself and check the things you mentioned. I will check the ECU code and color, head fins or lack thereof, and coil packs.

Regarding the MAF, i bought it completely separate from the engine so if it matches it is only by chance.

I do have a few questions:

Would the fins on the head be on the front side of the engine? And when you say to check the coil packs, do you mean to look for a part number imprinted on them or some other distingishing characteristic? Lastly, does a z32 MAF require ECU reprogramming? I have read about the plug wiring and that looks simple, but i was also under the impression that it would need reprogramming which is why i didn't get one.

After i go and see it i will post back up what i found, probably Wednesday night.

[Thoughtful_One]

Yes, the fins on the head would on the front of the engine.

When I have some free time, I'll check my ECU and take a picture of my cylinder head.

No, if you really just want to get the car running, you can get a used AFC and program it so that it would run stock with the MAF. You don't have to modify the fuel cruves or anything I believe. Should just be a simple setting. I was considering this when I couldn't find a MAF for my car.

Check the SR forum and look for a thread made by SpeedRacer1, or something like that, and he shows you what to look for on the coilpacks.

[wadiad]

Cool, thanks. Tomorrow i'm going to go to the shop and try to identify my ECU and engine, and then i'll post back up here.

[crashcourse]

I have a na ecu for my s14 it did the same thing when I first got it running . I ended up putting a power fc and a z32 maf and tuned it out . When it was running stock maf or what i thought was stock with stock ecu it was real rich,not allowing it to rev breaking up..

[Thoughtful_One]

Cool, thanks. Tomorrow i'm going to go to the shop and try to identify my ECU and engine, and then i'll post back up here.

Also, assuming that your ECU is correct as well as your MAF, check your injectors to make sure they're the stock 370's.

The shop that was doing my swap couldn't find what was causing the problem when I had the right ECU and MAF, and it turned out that there were 550CC RX-7 Twin Turbo injectors in it. It could free-rev without a problem, and didn't smell like it was running rich, but under load, it would buck and not boost correctly after 4500. After the injectors were switched out, the engine runs very strong.

[wadiad]

S#!* i just got back from the shop, that was a good idea too... in any case, the engine has no fins and 3 of the 4 coil packs are from '92, so i'm 99% sure it's a Zenki. The ECU is a red WC code, and i also checked the actual part #, it's the ECU for a 93-95 s14 5 speed. So that looks like a match.

The MAF as we determined is a Kouki s14 MAF so that does not match. I have heard from some sources that the Kouki MAF should work on the Zenki, but i've heard the opposite from others. Ideally i'd like to get my hands on a Zenki MAF and see if that fixes the problem, although i'm having a hard time finding one. I'm not really keen on trying the z32 right now - in the future i don't mind upgrading, but right now i feel it would just be an additional variable and potential complication, being that it will require at least some tuning, whether it's an AFC, ROM tuning or what have you.

One way or another, i want to eliminate the MAF as a possibility for this problem, perhaps take a quick look at the injectors, and then as a last resort i'll have the wiring re-checked... but of course if anyone has any other suggestions i'm all ears.

[crashcourse]

One more thing how do your coilpacks look on the sides if the plastic is all cracked up you could be grounding them out on your valve cover you name it I have done it..

[wadiad]

Haha no they look to be in good shape, no cracks. But thanks for the suggestion

[Thoughtful_One]

Well, the good thing is that you don't have a Kouki engine with a Zenki MAF, becuase the Kouki's are impossible to find.

Check the FS threads because I remember a guy selling one along with an S14 SR harness.

That's the tough thing about the S14 SR, parts like MAF's are very hard to find.

I'll keep a look-out for you. Also, check eBay becuase I saw an S14 MAF on there before.

Email me at [email protected] for faster responses.

[wadiad]

The guy who did the swap (and still has the car) just called me today and said it's running ok. He didn't say it in so many words, but it seems like the MAF was wired incorrectly. I guess i'll see for myself when i go to pick it up. Hopefully this issue is resolved now, thanks everyone for helping figure it out.