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Discussion Starter · #1 ·
Howdy again. as I make another post and update. For those who have read previous posts of mine, the rebuild was a success and the Stoptech stage two brake kit is impressive as balls. the clutch and rear main are going in monday or tuesday. I just got the EGR to seal properly so the vaccuum is tight and she idles like a dream. However I still have a problem.

General info to help with advice:
-91 240 w/ 2nd KA24DE
-Freshly rebuilt top end with port and polish. bottom end was clean, so
I didn't touch it
-New water pump, radiator, thermostat, etc etc.
-everything I touched I cleaned and resealed to manufacturer specs.
-new (enough) TPS, O2, water temp sensor, and fuel pump
-timing set at manufacturer specs (20 degrees I think)
-Vaccuum seems to be consistent after EGR seal, have not measured

The engine bogs when ever I am past half throttle. Reguardless of throttle, the acceleration seems a little "jumpy" as if the power band has dips and spikes in it. thats as best as I can describe it. please give me some ideas or suggestions. Sunday is the only day I really have to dedicate to my car(minus the clutch and rear main). Thanks for the feedback.

peace
truman
 

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Discussion Starter · #2 ·
OK, just reset engine management and went for the first real test drive since I worked on it last. it pulls much more smoothly, but still bogs after about half throttle. seems almost as though the engine is running really lean or rich, but I dunno. I am definately not getting the full power of the engine at WOT. the throttle response is a little slow also but I am pretty sure the problems are related. When I had the intake plenum off I sprayed down the injector tips with air intake cleaner. These injectors have probably close to 200K on them and my best guess is they are no longer spraying, just kinda pouring fuel in. The exhaust note sounds as though the engine is restricted. I am just gonna check the fuel pressure regulator vaccuum for fun just to make sure it didn't get messed up while I was working on the EGR.
As a side note, I dropped the EGR systems and carbon canister and completely redid the stock vaccuum system to work properly. I doubt this has any hold on the problem, but figured i'd mention it.

truman
 

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I have a bogging problem with my 92 jetta, and I was told it was the fuel injection system. If I were you I'd try swapping out the injectors...
 

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dj42000_2000 said:
The engine bogs when ever I am past half throttle. Reguardless of throttle, the acceleration seems a little "jumpy" as if the power band has dips and spikes in it. thats as best as I can describe it. please give me some ideas or suggestions.
Replace the fuel filter if you haven't done so.

If you still have the problem, run some good fuel injection cleaner like Techron or Redline SL-1 through the system; give the cleaner about a week or two to do it's job.
 

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I wouldn't even bother with fuel injector cleaner. All it is octane booster and it fucks up your ECU and the following tanks have shit MPG. What I would do is go to a mechanic of yours or if you have to, the dealership, and get them to perform a fuel injector service. This is costly, me about 150 canadian but i'm not sure where you are located. Also, the problem with nissans are that at a standstill to WOT there is a slight delay as you may know. It almost seems like it takes a second or 2 for the entire car to get moving and slowly builds up speed. This is a safety feature by nissan and it temporarly bumps the timing back a few degrees. JWT has a chip to elimanate this and is a immediate difference with other features as well, powerband, acceleration, slight top speed, MPG to list a few. If your looking for a good start from the tree, instead of standstill to WOT (1%-100%), go approx. 1% to 50% and build your way up, you will also notice a difference there.Anyways to cap, get a fuel injection service, you won't regret it.
 

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Also I forgot to mention that unless your running 92octane or higher, I would not recommend going with a 20 degree timing. I think factory spec is between 14-17 degrees, i have mine set at 15 degrees i believe.
 

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Discussion Starter · #7 ·
I always run premium, 92-93 octane. I also tend to go with chevron or BP(amaco). when I rebuilt the motor I cleaned the tips of the injectors with air intake cleaner. Is that what you mean by an injector service?
I do want to go to a JWT engine management upgrade with maybe the cobra 5.0 MAF. will JWT reprogram the chip if I go boosted or can I trade it in?
I will run an injector load test at work tomorrow and see if they are flowing properly and calibrated. I'll also check all other systems I can. I appreciate the feedback.

peace
truman
 

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Well if its not fuel, then it is spark. So I would check out that distributor, plugs, and plug wires. And yeah Id see what factory timing is if you are unsure.
 

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Discussion Starter · #9 ·
I checked out the engine management readout today and found that the TPS was reading wide open reguardless of throttle position, I unplugged the TPS and the loop didn't close, so I started unwrapping the harness and redoing the grounds and lead and signal wires. Now my TPS is reading properly, but I still have bogging issues and she's still runnning rich. Hopefully I'll get up early tomorrow and get another chance on the scanner to check out everything else. any ideas? thanks.
peace
truman
 

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little240boy said:
Also I forgot to mention that unless your running 92octane or higher, I would not recommend going with a 20 degree timing. I think factory spec is between 14-17 degrees, i have mine set at 15 degrees i believe.
The factory ignition timing spec for a 91 is 20 degrees BTDC. I've been running 20 degrees on my 91 for a good 10 years and using 89 octane gas with no problems. On occasion, I've run 25 degrees with 92 octane for a slight boost in performance when running at the drags.
 

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Discussion Starter · #11 ·
I finally found all the problems, I think. The knock sensor was running open loop, sending the engine management into ultra-safe mode. the sensor itself was cracked and tore up, so I replaced it, found out the harness by the water temp sensor had begun falling apart, so I just cut it and connected the wires. I still had a problem. Come to find out after about an hour of cussing and smoking half a pack of cigs, the wiring between the ECM and the sensor was shorted out, not very suprising considering the condition of most of the wires, but it didn't come to mind. so I spliced open the wires at the computer, and ran all new wire to the knock sensor, and now it's running properly. I plan to replace the entire wiring harness with one less abused. Are there aftermarket wiring harnesses available? or am I better off just using another one in better shape? Thanks for all the help.
PS. I replaced the relatively new NGK R plugs with some platinum 2s, since the NGKs fouled during the driving in ultra safe, ultra-retard mode.

truman
peace
 
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