boost = NO torque

[BrianV8]

post whore = me... clearly.

anyhow, like wild said I am going to go with a new fuel pump. thats the issue.

thanks!

gtr pump, or walboro?

In my opinion definatly go walbro.

[Heyst]

I installed a new stock 240 pump tonight and I realized the car only acts ups when its warm.

when the heat gauge is still on the cold side, it has its normal pull. As soon as it warms up, ANY gas makes the car jolt/bog out...

If I press the clutch in and give it a shot, the car will maybe rev up to 4k if I am lucky, and sounds like I have a rev limiter.

[Skym]

Can buy a adjustable FPR and drop the rail pressure. Basically more fuel returns to fueltank instead of going through injectors that makes engine rich.

MAF or knock sensor problems can make engine ECU enter limp mode and rev limit engine. The rev limit is higher with knock sensor problems.

[Heyst]

how do I get the ecu out of limp mode?

and why does the car start the jolting / bogging out when its warmed up, and not when its cold?

[Skym]

Fix the problem and reset engine ECU. Check engine ECU for fault codes.

Can be TPS related (acceleration enrichment). Check engine ECU for fault codes.

Running rich makes engine bog, stall and can damage the o2 sensor.

[GTS-TRB25]

Hey man if your car is bogging when the car is warm.. check your coil packs . that was my problem before.. mine didnt act up till it was warm.
GL

[Heyst]

well I checked the ecu tonight for codes, I only have one red LED (I guess thats normal) and when turned all the way clockwise, it doesn't come on or flash. when half way it will stay lit, and when all the way Counter clockwise it will flash a code 55 I believe (5 long, 5 short).. meaning no issues?


I will clean my coils tomorrow.. maybe tonight depending how drunk I am when I get home. I can only clean them because I don't have a multimeter.

I'll unplug one at a time when the car is warm and see if the car will run like junk.

thanks everyone for the help. Maybe eventually we can throw together a help thread about this issue, because its not quite hesitation, but a bogging down.

[WildCard_]

OK. If u really wan to get into diagnostics, then this is how I would proceed.

You've already said you've tested the entire fuel delivery system and said its "ok". I'm going to go ahead and assume for the time being then that the fuel delivery system is working as intended.
First step would be to A) hook up a smoke machine - B) hook up a vacuum/boost gauge.
The smoke machine is a quick way to determine where a leak may be in the intake system. Check once when car has been sitting for 3 hours or more. Run car until fully warmed up and check again.
Having a Vacuum or boost gauge hooked up while the car is warming, with the car still in neutral bring the engine to 2000rpm and hold for 30 seconds. Proper vacuum when at idle is between -17 and -20 PSI. when holding rpm, vacuum should decrease to 0, and increase as the turbo spools. you most likely wont get anything above 5 PSI due to low back pressure, which is normal.

"IF" you find everything working as intended, then I would hook up a Data scan tool. I prefer a Snap on Modus or something similar due to familiarity. Whatever tool you can get access to, using a nissan 2 adapter and entering the ECU under a 1990 300zx will provide you with proper on board monitoring such as 02 sensor, TPS sensor, MAP sensor, and fuel trim ratios. Being able to view all of these at the same time while changing the load conditions of the engine will greatly cut down on individual sensor testing.
Sensor basics:
O2 sensor when cold will favor a slightly rich mixture, but must switch from rich to lean. Sending the 02 unit to digital graph allows us to see the 02 sensor MV range and switching times.
TPS sensor is simple, .5V at idle with +/-.1 V variance only.
MAF sensor should be approx 2.5V at idle.
After the engine has warmed up, idle rpm is 750rpm-900rpm(with no idle hunting). As you open the throttle, the MAF sensor will increase in Voltage(max 5V), TPS will vary .1-.4V, and 02 sensor will increasingly favor Rich until WOT(wide open throttle).
simply play with the throttle while monitoring these 3 sensors. If one sensor Appears to have odd behavior, then we can test it further.

that's what I would call step 2. All of this can be done with a $20 Auto ranging Multimeter from Canadian tire as well, but u cant do them all at once with just one meter, and graphing and recording is pen and paper.


Its seems like alot, any questions ill try to answer.

[Heyst]

ok so..so far I have:
- checked ecu, throwing code 55 still
- replaced and tightened all clamps on IC piping
- replaced 'bosche' spark plugs with ngk bcpr6ey with a gap of 1.0
- cleaned and resoldered maf
- replaced fuel pump
- cleaned my coils, stretched my springs
- pulled one coil off at a time and none appeared to be dead as the idle changed with every one

heading out to replace my fuel filter right now then
I am going to make a trip to canadian tire and try to find this "Auto ranging Multimeter" thats only 20 bucks.. all I found were $200 ones.


my idle when warm is at 700 ish
vacuum at idle shows just below the middle hash mark

[Skym]

Sometimes sensors are faulty but aren't outside the voltage range that sets off the error code. You need to test them by multimeter or oscillioscope for sensors like CAS. I found that with one of my cars TPS failures (been through 2x TPS already) as ECU showed no error codes, yet when tested manually, voltage was slightly out. TPS causes drivability problems, missing at idle, surging, etc.

[Heyst]

so I went out and got the autoranging multimeter.
found the wire I am supposed to tap into.

now what mode do I use to gauge it? theres so many haha

[WildCard_]

If your doing your TPS voltage, which is 0-1V range...set the meter to 1V. If your doing MAF sensor or something 1V or more, then set the meter to 20V.

[Heyst]

thanks, I'll report with voltage

[Heyst]

well, replaced the fuel filter. old one had rusted coloured gas inside. yummy.

I tested the voltage on the TPS, at first it was around .42 so I upped it to .495

I hope that is fine.

still having this issue though. seems now under any load the car will surge/jolt. makes getting to 60 a lifetime haha. Still not driving the car further than around the block to warm it up.

but now even when cold the car is doing this. I have a fellow GTRC member coming over tomorrow, hopefully I can plug in his maf.

should I be worrying about my IACV or AACV?

I am going to call around to see what garages have a smoke machine. I seen a vacuum test kit at canadian tire for cheap (maybe $40) but I'm not certain how to use it.

[Skym]

If new, you can adjust TPS voltage when wrong. If TPS voltage is low on old TPS = TPS is stuffed. Replace TPS. I bet the surging will disappear when you change TPS.