Twiglet240

I've searched through a hundred of these and only a handful of them had a solution posted in them.. I'm having a bit of trouble with a 240 I bought running poorly.

-The car is a 93 Hatch with a Redtop.
-Ecu is for a Redtop.
-mafs is for a Sr.
-Stock injectors, stock fpr.
-3inch exhaust/dp.
-Meagen racing manifold.
-Fmic with DSM BOV.
-Walbarro fuel pump.
-Koyo alum. rad. w/one electric fan always hardwired.

For vacuum lines I have
-Small nipple above TB>t for boost gauge>FPR.
-Large nipple above TB> BOV only.
-Nipple under TB capped off.
-Vacuum fitting on IC pipe>Wastegate Actuator.
-T on valvecover goes into a catch can> catch can goes to intake, other side goes T into block.
-New check valve by master cylinder.

The car starts and idles with no problems. In neutral it revs up good, backfires sometimes when I let off. Car is making 18 vac at idle. Looked like the car made 8-9 psi under boost, which is kinda weird since I only have a stock actuator.

It runs good, pulls decent when its cold for a couple minutes. Then it warms up and as soon as you give the car more than 5% throttle it bogs down and doesn't want to go anywhere. When you get up to 4-5K rpm it starts to go decently hard now that I re-did the vacuum lines.

Haven't checked my timing yet, could possibly be something. The adjustment on the cam sensor, or whatever it is, looks to be 75-80% all the way one way on the right looking straight at it.

The car seems to have a battery drain issue as well, as well as the aftermarket stereo doesn't work. Not sure if this is affecting anything/part of my problem.

Let me know what you guys think I should do/check next on the car.

Things I have tried so far.
- Replaced coolant temp sensor.
- Put a used T25 with minimal shaft play on the car.
- Checked spark plugs and gapped them at .30 (They are NGKBR6KE's, I know they are a step cold but I don't think its an issue.)
- Re-did my vacuum to the setup above.
- Recirculated my BOV.
- Installed an air filter and clocked my maf so the plug is at the top.
- Pressure tested the coolant system, noticed a 3psi drop after 45 minutes, also noticed whitish gray smoke in exhaust only on start up - possible head gasket issue.
- Installed a 300zx fuel filter.
- Fixed a mostly broken TPS wire and set my TPS to .49 closed and 4.18 fully open.
- Checked maf voltage its at .80 key on and 1.56 at idle (I think this is out of spec.)
- Getting 4.87 volts to the coolant temp sensor.
- Compression test cold, 150, 142, 152, 154.
- Wired in a new plug for the mafs, and cleaned the sensor.
- Cleaned PVC on vc.
- Swapped FPR and injectors.
- Warm compression test, 154, 150, 152, 154.
- Got a used sohc maf and pigtail and tried that.
- Looked at fuel pump/filter. Filter looked good, no debris in the tank.

Heres what my plugs look like.

Mark Slide Squad

Have you checked your fuel pressure? Fuel pump might be faulty. Might supply enough pressure for a few mins but might start taking a nose dive. Check fuel pressure at idle, and while driving if you can.

Also, could be a bad injector o-ring. I had that issue on an old SR of mine 10 years ago. Replaced the o-ring and problem went away.

Clean the mafs out with electrical contact spray. Also try switching the MAFS for a known working one from another car.

You could have a bad ground or wiring somewhere. Check to make sure your ECU plug is all the way screwed on to the ECU. I've see that before too where it isn't and causes all kinds of issues.

Check for any leaks in the intercooler system. Leaks in the core, torn couplers, loose clamps, etc.

Check your coil pack harness. Make sure the wires aren't frayed on it, as they can do that with age and heat. I've encountered that myself as well.

Twiglet240

I've got a spare set of injectors I'm going to swap in soon to try that out.
I'm looking for a used FPR setup as well. I went over my vacuum and IC setup, I don't think there's any issues, though I haven't used a boost leak tester. Thing is when the car is cold it runs pretty good so I don't think those are the problem. I'll take a look at the coil wiring and see if I can look up what voltages they are and check them.

Kingtal0n

Heres what I would do if that was my car.

maintenance related:
#1 boost leak check (just to be sure)
#2 plugs look GREAT so leave those put.
#3 degrease/clean the compressor inlet rubber piece



diagnosis related:
#1 Check grounds, especially coil pack ground at the back of the head. Inspect all coilpacks and clean them up a bit.
#2 swap maf for a known good maf. You have a redtop? So use a KA24E maf sensor from a random 240 in a junk yard.
#3 change the knock sensor / verify the wiring is intact
#4 block off the bypass valve (blow-off) so that it can not release air and run the car.
#5 change the Coolant temp sensor
#6 change the fuel pump and fuel filter and fuel sock. verify fuel pressure


Bogging issue... its either a weak spark, too much fuel, too little fuel or leaking compression (leaky bypass) intermittently. the reason I lean towards spark is because your plugs look good and your cold performance is good, and you said it runs better at 5,000rpm which is why torque (and thus VE) is dropping. So not a plug issue, probably a coil ground issue or coil pack related.

But again, could be maf related / fuel related. Fuel sock / Filter I doubt since it runs good when cold. Once it warms up, maybe the fuel pump is giving up. So grounds first, then fuel pump. And the maf is easy and fast and cheap to verify (KA24E from junk yard) very simple might as well.

And last, knock sensor. Do not underestimate this guy. If the knock sensor is bad or missing wiring it will bog exactly like you describe.

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Twiglet240

Thanks for the reply, I'll keep the thread updated. I should have some more time to work on the car soon.

cotbu

Normally, when this happens I suspect fuel delivery, it's just that so many things can effect fuel delivery.

Looking at the plugs the timing band looks off, so maybe check timing before trying to find the fuel problem.

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Twiglet240

Didn't have a ton of time to work on the car, I swapped the whole rail, fpr, and injectors with the spare ones I had from previous build, no change. Cleaned up the intake grounds and the coil pack ground, no change. Fixed some wires that were worn into the copper, no change. That's all for now.

s13-LBC-562

1+ for knock sensor

Twiglet240

I got a new plug for my maf so I can clip it on like normal. I followed my maf wiring up to the gray sheath. Theres a black wire and a red wire going to pin B, a green wire going to pin C, and a white wire going to pin d. Is this what its supposed to be? Also it seems like there are some wire strands inside the sheath that don't go to anything. Please help if you have any info.... heres a pic

Twiglet240

The guys on sr20-fourm are suggesting I check my o2 sensor voltage and try a new one. That sounds plausible since my car seems to be running good in closed loop when its cold. I'm going to give that a shot next.

fast250sx

Check the fuel pump! You said you werent sure what kind of pump you had. Stock one will not provide enough fuel. Also if the strainer on the pump is filthy, it won't provide enough fuel. Check the fuel filter also.

Twiglet240

Took my car for a ride with the o2 sensor unplugged and it ran pretty much the same. I got a new one coming but I don't think this is the issue. I'm starting to think its my mafs.

I don't think its my fuel pump because when its cold it runs good and makes power. The pump would have to be crapping out when it gets warm, but it seems to me that the car is running pig rich, not lean.

89s40wyj

checking timing. on mine the cas is aligned slightly to the left of the center of the adjustment window. I'd say about 30 to 40% looking at it as 0% turned all the way counterclockwise and 100% all the way clockwise depending on if you have the timing marks right. Then I'd say drive it for a couple of days and let the ecu "relearn"

ultimateirving

Dont take advice from this guy with his first post!
Dont mess with the CAS unless you have a timing light.

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Twiglet240

Going to be installing a different maf and new 02 this weekend. Will update. Planning on looking at the fuel pump probably also. I'm going to try a warm comp. test as well soon just to see if my one lower cylinder changes.

fast250sx

Not probably, make sure that fuel pump is good. I have personally said to myself, "It can't be the pump its almost new." After days of trouble shooting, it was the pump. Have you tried the ecu? On my old ka I was having similar issues, turned out the ecu was bad.

89s40wyj

what's a timing light?

fast250sx

A timing light is that thingy that you point at that circle pulley thing ....... j/k. Its a strobe light you hook up to the motor via the number 1 spark plug wire (which the sr does not have, so you will have to make a jumper wire), you point it at the timing marks on the crank pulley and it shows you your timing.

89s40wyj

Mine did the same thing as his, runs fine cold but bogs down when warm and continues to bog more. Sometimes it would buck. go past 2 to 5 % throttle and it'll feel like you hit the brakes because it would stop accelerating. at that point the blow off valve might go off too. The more throttle you give it the more you go nowhere fast. You might hear it pop or knock once in a while. At first I thought it was the fpr because at full throttle, fuel pressure would max out my gauge at 60psi. maybe it's running rich. I have a walbro on a stock fpr. Got a new fpr and now pressures are correct now. But it didn't fix my bogging issue. rerouted my blowoff valve lines, fpr and boost gauge vacuum lines. Figured out for each of the lower nipple and the right nipple when you are looking at the engine from the front of the car, only one sees vacuum and the other only sees boost pressure. But that didn't fix my bogging issue. Found my tps sensor signal voltage would drop out during its sweep and replaced it. But that didn't fix my bogging issue. Checked wiring to O2 sensor from ECU and tested O2 sensor with torch, everything was good. ohm-ed the coils at operating temp and that was good. Checked spark plugs - good. Bled the lash adjusters. Nothing fixed my issue until I went to time it again for the millionth time. I figured out my timing light pickup when I hooked it up to the loop at the back of the engine was too close to other wires and was giving me wrong readings. Now I'm boosting 11 psi at operating temp.

89s40wyj

After I figured it out, it took driving the car for a few days to let the ECU relearn itself. Also figured out when not at operating temp the car would boost only 7 psi. I have the stock turbo, stock wastegate and spring (no washers), stock boost control solenoid. I still have the restricted vacuum line too. Redtop of course

89s40wyj

oh yea one more thing. Some idiot(me) put in the wrong cts when also trying to diagnose the bogging issue. The correct cts made a difference but it was still bogging.

Twiglet240

So it ended up just being your timing? Or was the wrong CTS affecting it?

Twiglet240

Checked fuel pump. Its a walbarro. Tried a sohc mafs. Nothing. Did a warm compression test. All cylinders over 150.

Twiglet240

Decided the timing was the next step. Took VC off, set to TDC. Noticed cam angle sensor was not lined up. Re stabbed cam angle sensor.. checked ignition timing, was about a degree off, set it to 15. Car runs great now, other that slight hesitation in low rpm, might be turbo lag tho its been a while since I've had boost.