Weird idle

[kotu100]

When the car is warming up it has a teeny high idle like its supossed to, to warm up. sometimes it will idle fine afterwards until randomly it will drop to 300 then bounce back to 500. it hovers around there for a bit but will keep fluctuating and sometimes die. however the car still pulls real strong @ WOT.

oh and when the idle problem is happening if i hit the gas to keep the RPMs up it sounds like its missing.


the problem started when i put my 550's and lex AFM in the car. i've swapped out the AFM electronics and tested w/ a multimeter, no luck. got a scope to check injectors, they're all firing. swapped out spark plugs, that didnt help. tested IAC, TPS with multimeter, they're good.

im getting code 31, the AFM code. i know the electronics are good cuz they worked on the stock AFM and i tested w/ multimeter. even swapped out my IAC, and CPS for known working units from my other engine. timing is set @ 10 BTDC w/ the diag block jumped. puel pressure is 28-30 @ idle set w/ aeromotive AFPR.


if anyone can think of anything to help me out, please done be afraid to throw ideas out there.


[cliff notes]
installed 550cc injectors, and lexus AFM now car has intermittent rough idle problem.

 

[Moy]

Did you also install and tune a fuel-tuning piggyback (i.e. safc)? You're probably running lean, the stock computer is set up for 440cc injectors, and the lexus afm lets in (I believe) about 25% more unmetered air than the stock afm

 

[kotu100]

oh and when the RPMs drop real bad and the CEL comes on, some black smoke starts coming out the exhaust.

the lex AFM housing had a small imperfection in the honeycomb, it was only 2 of the holes,but i straightened em out best i could.
could this possibly cause the problem?

 

[kotu100]

Did you also install and tune a fuel-tuning piggyback (i.e. safc)? You're probably running lean, the stock computer is set up for 440cc injectors, and the lexus afm lets in (I believe) about 25% more unmetered air than the stock afm

i put 550's in... :nono:

 

[AjWit]

i put 550's in... :nono:

i would like to second the fact that you need a safc or equivelant tuning device to be sure a/f is stoich.

 

[kotu100]

what about everyone else that runs the lex AFM and 550's, whay dont they need it.

and it wont matter if i put my safc in, since i dont have a wideband.

anybody have any ideas BESIDES that?

 

[RockPaperSwoRD]

get a wideband and then tune

 

[Moy]

If you're going to be doing any drastic upgrades to your car (i.e. fuel system in this case), you want a wideband O2/gauge to tell you what your air/fuel ratio is. Your ratio is probably running too lean, as the stock ecu is calibrated to 440cc injectors. Even if you install 550's, your computer is still running the fuel map for 440's.

 

[kotu100]

ok so clear this up for me, even though damn near everyone does the lex AFM + 550s and dont need to tune except to get the most power from it, im the only one that HAS to tune it...

sorry guys, doesnt make sence to me.

and modding and tuning turbo cars inst anything new for me, and it wouldnt blow black smoke running lean, it would do that if i was running rich.

anyone have any other ideas BESIDES getting a WB and tuning it? seems like that would only be a band-aid fix.

 

[jdub]

You are correct...you should not need a SAFC for the motor to run correctly. It is useful to tune at high RPM...the Lex/550 combo runs rich at WOT.
The responses you've got so far are way off (at least concerning this problem).

The minor damage to the honeycomb will not cause this.

Did you happen to clean the AFM sensor with carb/MAF cleaner?

Have you checked the connector at the AFM?

Have you checked for leaks...what you decribed is a lot like running the car with no AFM.

 

[kotu100]

You are correct...you should not need a SAFC for the motor to run correctly. It is useful to tune at high RPM...the Lex/550 combo runs rich at WOT.
The responses you've got so far are way off (at least concerning this problem).

The minor damage to the honeycomb will not cause this.

Did you happen to clean the AFM sensor with carb/MAF cleaner?

Have you checked the connector at the AFM?

Have you checked for leaks...what you decribed is a lot like running the car with no AFM.

First, thanks for your response.
what type of leaks exactly are you talkin about? i've triple checked all the IC hoses, PCV hoses, vac lines.
i only wiped the sensor off with a dry cloth (should i not have done this?)
the only thing i didnt test yet is the wiring to the AFM, but i couldnt really find the TSRM for it. im not too savvy w/ wiring diagrams but i learn quick.

i also realized today that the filter adapter i was using was actually blocking a teeny bit of the AFM around the edges (1/8" at most) not sure if this could cause anything. i took off the adapter but the problem persists.






and on top of that, today my factory alarm went on the fritz... Thank you Shaeff for this http://www.supramania.com/forums/showpost.php?p=1515&postcount=4

 

[kotu100]

well i seem to have fixed the problem, did some rewiring on my CPS (3 wires were frayed near the connector)

swapped out coil packs as well as grounded it (was never grounded before but never had a problem.

and i swapped out the AFM housing with one i got from a local junkyard.

not sure which of these fixed the problem, but it only stumbles a couple times now, and it never drops below 550rpm.

i was also wiggling the AFM wires around but i dont think that's what fixed it, as i've done it several times before and it never seemed to make much of a diff.














just figured i would post my conclusion in case someone else has a similar problem.

thanks for the help anyway Jdub!

 

[Jason Is Dizzy]

i hate thread jacking but i have this issue to but with no 550s or a lexAFM just a walbro its irritating

 

[kotu100]

i hate thread jacking but i have this issue to but with no 550s or a lexAFM just a walbro its irritating

yea.... and?

 

[boostaddict]

mine was just doing that so i put new afm sensor on it and it seems to have fixed the problem on mine. but i also have 550/lexus afm and mine i cant seem to solve the lean problem

 

[boosted2085]

im having the same issue with the idle after i installed maft pro in speed density mode...throwing black smoke...fpr is set at 40psi wo vac...getting cels22,24,31,34,51...