CraftHell

Hello everyone first let me start with some information

91 s13 /w 95 ka24de.. automatic tranny..

The engine was swapped professionally @ localshop.. Original engine was knocking, so they pulled it before i purchased the car from them about 2 months ago.. The car was driving perfectly, still is except for this hesitation from a dead stop around 1800-2100rpm.. Only does it when im "trying to save gas lol" it wont hesitate if i push the pedal down a little more and get up to speed..

Entire egr system was removed during swap, I have replaced the spark plugs (gaped 0.044), replaced stock fuel pump with walbro 255, checked the wires they look great, fuel filter and engine bay fuel lines replaced @ swap, newer steering rack ,w TEIN inner/outer just installed (old one was leaking bad).. Cleaned the MAF twice now, check for vacuum leaks but didn't see anything odd (could have missed something tho)

I do know the guy who did the swap advanced the timing ~2 degrees but i don't believe this would be related to the issue im having cause the engine was doing great for a while..

Anyone have any ideas or experience in the similar issue it would be greatly appreciated

Thanks in advance.

Butcher240sx

Check the O2 sensor.

__________________
Don't Mess With Texas

CraftHell

Yea? alright ill try that..

Denso/Oxygen Sensor (234-1000) | 1991 Nissan/Datsun 240SX 4 Cylinders M 2.4L SFI DOHC | AutoZone.com

Will this one be a perfect replacement?

CraftHell

No1 else? man this problem is going to be the death of me :/

godsmack

are you running rich at all? how's the idle?

CraftHell

i do smell gas fumes here and there, and the rough idle occurs more freq now than last couple weeks.. thinks the problem is getting worst..

But mostly idle around 700-750ish at a red light etc..

godsmack

keep looking into the vacuum. might be a leaky injector start the car turn it off and then check the plugs. if one has fuel on threads there's something going on in that cylinder. if all checks out good then i'd say timing or vacuum leak

CraftHell

Thanks for your response, ill try the plugs idea tomorrow.. Whats the best way to check for vacuum leaks? Water-bottle /w soap? spray when engine is running and watch for bubbles?

godsmack

i always traced all vacuum lines and unpluged them one at a time. if you unplug it and nothing happens then somewhere in that line is the problem

CraftHell

true ill try both ideas tomorrow

Have you had a similar issue b4 ?

godsmack

I've just been around cars my whole life and picked up stuff along the way on trouble shooting things. not sure if those are the problems but its something to rule out.

CraftHell

alright cool thanks ill let you kno

CraftHell

Update: wasn't able to try the injector or vacuum leak check cause of this wonderful Florida weather.. ugh but before it started storming I disconnected the brake booster hose and dumped 1/2 bottle of seafoam while the engine was running (had my cousin in the car keeping it alive) and turned the engine off let it sit for 15 min~ and put the other 1/2 bottle in the gas. Turn the car back on and let it do its job and i believe it did pretty well lol.. Almost got the cops called on me there was so much smoke lol. (i live in a apt complex).. once the smoke died down i drove her around for 30-45min~ and i must say the idle is like better than when i first bought the car 3~ months ago and the acceleration around 1300-2000 is there and not bogging.. Let is completely burn out and fill the gas up with reg gas and see if the problem comes back or not.. I'll keep everyone posted for people having the similar issue

Edwin562

could be a faulty MAF.... usually any hesitation below 3k, is MAF related.

CraftHell

Thats what i read and heard about also the MAF but it seems to be running normal, i cleaned it 2 different times about a week apart just making sure its clean.. I unplugged it while the car was running and it limited the rev to like 3k so i assume its working? im not sure tho :/ Also its hesitation with light throttle around 1800-2000 but if i get it mid to high throttle it runs soo smooth so i don't kno :/ After the seafoam today seems to have fixed the issue.. we shall see though.


EDIT sorry is there a better way to clean the maf than just unbolt it and spray it with MAF cleaner? like could you physically take it apart and clean it with cuetips or something?

Edwin562

my method of find vacuum leaks is spraying carb cleaner around the intake side. if car reacts(revs up) then you have found the vacuum leak.

Frank_Jaeger

Starter fluid works as well.

CraftHell

Hello people. Let me start by saying that seafoam did clean the engine, and it ran awesome last night.. Until this morning its back to running like it was.. So when i got off work i tested the injectors by pulling the connector to each one 1 by 1, and each one had the same effect it would start to run really rough.. So i believe the injectors are fine.. Got a can of carb cleaner on the way home i sprayed every single hose i could find 1 by 1 and the engine had no reaction either.. So this only leads me to believe its the MAF sensor is faulty? if anyone could clarify it would be great

Butcher240sx

If you are using the stock FPR with an aftermarket pump you should be running rich. Fouling the plugs. Seafoam probably just cleaned the plugs enough for it to run fine.

__________________
Don't Mess With Texas

CraftHell

understandable,

but this issue im having me came to believe i had a bad pump so i swapped for a new one, changed the plugs a week ago with bkr5e-11's and checked the wires as well.. still the same issue..

either its a grounding issue.. or a bad maf..

reason i say grounding issue cause the motor was swapped once upon a time before i bought the car and possible a ground or 2 wasnt attached properly, or at all.. even though a shop did the swap.. things happen. and the car from cold start takes a cpl sec to start even when i let the pump prime..

this shit is really getting frustrating lol.. my gas mileage is as bad as my cousins rb25 @ 16psi and 468hp..

Butcher240sx

Did you pull any ecu codes? What do the plugs look like? I had a slight bog off idle to 2500 rpm. Was the O2 sensor being fouled. The ecu stops referencing the sensor at 2500 rpm. The one wire sensors foul pretty easily.

__________________
Don't Mess With Texas

Butcher240sx

Fuel pressure does need to be checked of you have an aftermarket pump.

__________________
Don't Mess With Texas

hardtime21

Just a thought, have you pulled the ditributor cap and checked for residue? Sometimes it can be a build-up between the rotor and the distributor cap. I had a similar problem and did a complete runthrough but didn't find shyt! A little light went off in my head and it said, "Hey Dumbass, Check the Distributor!" I did and BAM! That was the problem! I kicked myself for such a noob problem but the distributor could also be a culprit! By the way, I have a 95! Hope this helps!

CraftHell

Nice thanks both for your help daylight tomorrow ill pull the cap off and check and is there only 1 o2 sensor right ?

Butcher240sx

Only 1 O2 on S13 its a maintenance part to be replaced every 15k miles. It's cheap and if the car has been running rich its likely to cause problems.

__________________
Don't Mess With Texas

hardtime21

Yes, there's only 1 for an S13 but if it's setup like an S14, you're gonna need two! Lmk what you come up with after you pull the cap.

CraftHell

Checked the cap all is good under it :/

I been reading about possible grounding issues, today i took home a digital reader from work. Im gonna measure the ohm resistance and if its bad ill put together some kinda grounding kit and yea.. we shall see ;/

hardtime21

Keep us posted! Are you using the 95 engine harness?

CraftHell

alright i will the entire engine it self (intake, head, block) is from the 95.. rest is factory from the 91.. ecu, harness, accessorys, etc..

Zilviasr20

Sounds like a bad maf. Swap with a friend and check. How does it idle?