Bogging at 4000rm when warm?

[Steaver]

hi, i just bought my skyline about a week ago and it had some bogging issues. its a 1992 GTS-T with a RB20DET. its running about 10 psi boost. compression is good. its 134-137 across all. Idle seems to change between 900-2000. we told the previous owner that he would need to fix the bogging, which he said was just the TPS. he thought fixed it, until we drove it home. about half way through, (30ish minutes) it started to bog at 4000rpm. he told us that the TPS would need to get replaced/adjusted. we replaced it with one and it seemed to be fine. we have it set at 0.48 or so, which is what iv read it is supposed to be at. we cleaned the MAF we also checked the IC hoses for leaks. we found one hose clamp that was stripped, so we replaced it. it seemed to fix it momentarily, but it went back to bogging. today, we took off the coil pack cover, took off the coil packs, they all seemed clean and in good condition. they were recently replaced. they are yellow jackets if that helps :P we also took out all the plugs, checked them, re placed all 6 with brand new delco cross referenced (41-602) plugs that we gaped at .8mm. we put it all back together, started it up and it ran SMOOTH. best iv heard it yet. drove it around for about 30 minutes, (usually starts to bog after 5 minutes or so) ran GREAT. very fast, responsive, NO BOGGING. after 20-25 it started to bog again at 4000rpm and wont go over. (sounds like its hitting a rev limiter) i was very disappointed. it seems to run great after it has cooled down for a while. in the mornings it runs great, and after work when it hasn't been run all day its good, but only on cooler days. so when its cold it runs smooth, when its warm it bogs. the warmer it is the lower it bogs. if its really warm out and its been running for a bit it will go down to 3000rpm even. or even if it hasn't been running for a few hours and its just been sitting in the sun in 28*c it will bog with out being driven to warm up at all. iv seen a few forums on here about things like this but nothing that seems to match it exactly. not that everything will be the same but not close enough to make me think that its the same problem as them.
If anyone has got any help, or has experienced this issue, please help. i love this car and want it to run smooth again! <3
Thanks in advance!

[Skym]

Idle up and down could be lazy o2 sensor. Revlimiter could be leak between airfilter, MAF (hitting load / boost cut).

Bogging could be ECU pulling ignition timing due to engine knocking or o2 sensor being lazy (running engine rich or lean).

TPS is around 0.44v on idle contact. BOV can be another cause of bogging.

[Voodoo_ChildR32]

I had a similar issue on one of my old gts's. I wound up unplugging the IIAC valve under the throttlebody and beside the fuel rail it idled perfect and ran with no issues. When I plugged it back in, the idle would bounce around. Might be worth a try, just watch the cold starts. This valve controls the cold idle so u may need to babysit it for a minute or two after startup.


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[Steaver]

so does this thing actually have a revlimiter? oh and we checked the O2 sensor today and it flat lined so i ordered a new one. should be here tomorrow morning so i will hopefully be able to switch that up and see if it made a difference!

[gtrjerry73]

Let us know. I am curious if the o2 sensor can do this to our cars. My car is doing the exact same thing and I'm 90 percent sure that it's one of my mafs. (working fine until warmed up is typical of a Maf malfunction) but these things are getting old so I'm in the process of replacing absolutely everything with new oem or better.

[h4X6]

What's the part you used for the gtst o2 sensor? I think that may help with my issue as well.


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[Steaver]

so i got the new O2 sensor this morning. took out the old one, installed the new one, didnt fix it. how ever, it did seem to fix the exhaust spitting out a blackish murky residue.... any ideas on what it would be spitting out? i smelled it and it didnt really smell like anything... O.o and the O2 sensor i ordered is actually for a 300zx which has the right connector and the right threads so it works no problem... it was a little pricey tho. the universal sensor was 64 vs the 120 i had to pay :P the model number is: 13091. its made by Bosch. actually in the middle of writing this i came up with an idea of what the black stuff was. could it have been that it was black due to carbon build up in the exhaust from running rich, and the fluid could be water vapour from running low quality "premium" gas from co-op? i had just switched to Shell V-power a couple days ago, so it might have just run through the rest of the crap gas??

[gtrkrauss]

black out of the exhaust? running rich. is the car tuned or running completely stock. what did the plugs look like when you pulled them?

[Steaver]

it was running rich actually. changing the O2 sensor completely fixed it tho. and its not stock. it has been lightly modded, but it has an after market ECU. its called "stay tuned"? never heard of it but iv also never looked into aftermarket ECU's. so yes it has been tuned i would assume. we pulled the codes today, and its coolant temperature sensor is done. atleast that is what id assume. the code was 13,54. 13= coolant temperature circuit, 54= auto signal to ECU. this means the sensor is done correct? im not exactly sure what "auto circuit to ECU" means tho.... and the plugs.... the tips were a light cardboard colour, and the end of the threads were black. the guy before me only replaced 2 of the 6, and the other 4 were as old as the hills. so we changed them all and gapped them to .8mm.

[Skym]

Means coolant temp sensor is out of spec = failed. Coolant temp sensor failure is common.

That's the communication to autotrans ECU (autotrans ECU is located in same place as engine ECU, but on drivers side) that makes engine ECU pull ignition timing (programming for this is on autotrans ECU). You probably can earth the wires to engine ECU to turn it off (consult auto electrician on how to do this properly and need a engine ECU plug pinout diagram). Sounds like car was converted to manual. Check blue ID plate on firewall, as that would tell you if it was a factory manual or factory auto.

Some chip type tunes can run too rich, as use a generic tune (tune from another engine that's sometimes tuned on dyno and is used on multiple engines with similar mods). ECU should be tuned on dyno with engine, as each engine is different (wastegate psi, type of intercooler, diameter of exhaust, etc), even with same type of mods.

[Steaver]

we cleaned the AAC and it seemed to help out the idle alot. it runs smooth at about 950-1000 ish. we also checked the coil packs today. they were at 1.1-1.0 all the way across. is this good or bad? iv seen some people saying that they should be between 0.6-0.9, and others saying between 1.0-2.0. so im not exactly sure what is right here... we also changed the coolant temp sensor. that also could have been part of the problem. OH and we adjusted the timing. its was at 35 degrees. we set it back down to 17 or so. i think a mixture off all that helped a fair bit. now it will still bog after warm up, but it will usually go past it, and its only happening from 4000-5000 RPM nowin stead of 3500-4000. i think this is a good sign? im hoping its pointing me in the right direction anyways.

[Skym]

Buy english engine manual, as it's mentioned in there (or ask someone who has that manual) -

http://www.jpnz.co.nz/afawcs0131170/CATID=24/SUBID=273/page=1/products.html

35 degrees base ignition timing probably would have meant engine = knocking, as ECU adds ignition timing to that base ignition timing figure via ignition map to get the ATDC where it fires sparkplugs (also affects timing of when to open injectors, as if you remove CAS, have ignition just before turning engine on and turn CAS, can hear injectors click, but doing this will produce CAS error code on ECU).

Base ignition timing for CAS should be mentioned on a white sticker that's located on front of under hood on passenger side. It's in Japanese, but 650rpm, 20 degrees BTDC (auto engine ECU, autotransmission), 650rpm, 15 degrees BTDC (manual engine ECU, manual transmission) should be in english. If was auto engine ECU, it probably works best with 20 degrees BTDC (ECU was tuned with that base ignition timing figure).

Stock ECU can pull ignition timing from 3500rpm to 6000rpm and switch to knock maps if knock is detected by ECU. That results in a drop in torque on dyno graph (feels flat). Faulty coilpacks can make knock count higher thus ECU pulls ignition timing and switches to knock maps. Anything banging against engine (false knock) is another cause.

[Steaver]

Alright so I realize this is a very old thread already but I've finally figured out what was wrong with my car! It was the cam angle sensor. I noticed that it was extremely hot when I was working under the hood so I took it off, put it into a sandwich bag and put it in cold water for a few minutes. Threw it back on and BOOM. Hit 6000rpm without a problem. I took the CAS apart and wouldn't you know it, the spindle or shaft inside was actually cracked right in half. So when it was cold, it would catch a little bit, enough to run alright but once it warmed up, wouldn't touch at all and turned my car into a pile of crap! So there ya go. Hope this can help someone else out. Oh and side note, figured out what it's problem was exactly one year to the day after I bought the car!