trouble shooting bounty- rough idle

[robbyredneck]

ok guys put your thinking caps on. i have been fighting a rough idle to no start problem for two months. i actually have information via scan tool and known good parts. now heres what happened ran fine- then idle got real choppy and started popping. i shut it off and jiggled wires maf etc. and restarted and it was fine. then drove it and all was ok. went out later and same thing choppy idle popping and smoking. i put a new o2 and plugs in it and it starts right up but idles like dog fudge it will eventually foul the plugs with sooty kind of residue not wet and greasy. turbolink shows o2 doing the typical bouncing in the middle and maf at 7 typical kc at start up lv8 is at 90-108 blms at 128 and int at 128 all at start up(might be locked due to extreme chip) when ecm goes closed loop eventually blm goes to 90.

a month ago i smelled something funky like burning like butyl not plastic. i took off the volt booster as well. i will try new gas and new gm regulator(currently atr adjustable and i can't get lower than 40). first guy who nails this gets $50 bucks. i will chase down all suggestions as i am ready to light this thing on fire or put a blow thru sbc in it.if any body has a spare coil/ign module that i can borrow i will make it worth their while and return it promptly of course.

lets start with known good items.
1. ecm- sent to full throttle and they bench tested and replaced chip
2. maf trans+ - again full throttle tested maf i put on camaro and ran(cold)
3. good batt. good plugs, good wires, grounds look ok
4. esc seems good as do injectors and fuel pressure seems good at 42 psi.
5. tps at .43 iat seems accurate cts also shows good via turbolink.

questionable or not proofed:
1. ignition module/coil
2. crank/cam sensor
3. injector timing/amount

sorry for the novel but i am trying to be thorough if you want call 585-394-1191, 585-394-0327 ask for rob

 

[dougie]

Does it run OK off idle? Or is it undriveable when the idle is acting up?

 

[turbot2496]

Sounds like a big vacuum leak somewhere. Check all the vac lines real good.

 

[robbyredneck]

yes undriveable and when i unscrew iac motor till it leaks(a lot) the idle smooths out albeit at 2000 rpm and my o2 volts go to about 850 (from what i recall) which is real weird.

 

[84BuickGNYorkPA]

Check your MAF sensor wires for resistance, make sure that they are not bad, I believe that the problem is electrical and not fuel or timing related. I forgot to hook up my MAF sensor after a modification and it ran like yours is. Start the car with the maf sensor unhooked and see if it runs worse, if that is possible, if it runs the same check out the wires like a mentioned. Also it could very well be the coil, but usally they act up at the higher boost/rpm's when they start to go and it pops like crazy. You will find the problem, good luck and be patient. I don't think that the car will start if the crank sensor is bad, the cam sensor's have something inside that needs checked, someone else can chime in on that, there is something inside that will need checked to see if it is stripped or broken.

Chuck

 

[Getsidewayz04]

Check your connectors to the ECM. I just had problems with idle on my 86, not the same as yours, but similar. I was getting weird readings from the scan tool too. I had every code in the book. They would come and go.

One of the forum members advised me to check the ECM connectors, make sure they had no corrosion and make sure they're tight. I did this using a pin to pry them a little tighter, cleaned everything with electrical contact cleaner and problem solved.

Good luck. I agree it's probably electrical.

 

[robbyredneck]

thnks for the input. i forgot to mention this breaking up happens everywhere not just at idle. and it puffs in cycles sooty smoke. so on my 50th sleepless night i thought maybe its simply incomplete combustion. but i hate blaming the mystery box and coil. i am still objective even with 40* rain running down the back of my pants.upstate ny weather stinks. keep them coming and i promise i will chase them down i have already checke maf leads. can a goofy maf run in my ls1 before it goes on closed loop?

 

[ijames]

First, you cannot believe O2 readings when the motor is misfiring. Black sooty plugs means rich, kind of confirmed by the 90 BLM (kind of because that is based on the O2 which I just said you cannot believe ). Sniff the oil and change it if it is getting loaded up with fuel. Any smell of fuel (or acutal liquid) in the vacuum line going to the fuel pressure regulator - I'm thinking maybe a leaky diaphragm in the regulator bleeding fuel into the manifold?

If you reset the ecm by unplugging the orange wire by the battery, all the blms will be reset to 128, and set the fuel pressure to 42-43 psi (check it while the pump runs for 2 sec just after turning key on, without cranking the engine over; after the 2 sec turn the key off and wait 5-6 sec before turning it on again and the pump will run another 2 sec), and unplug the O2 sensor, it should start and run fairly well. It will set error 13 for the O2 sensor but the fueling should be in the ballpark in open loop and shouldn't really change after the motor warms up. If it is still running badly I'd go to the maf next. Shut the engine off and reset the ecm again (for luck ), unplug the maf and start it up again and see if it is better.

Oh, one last thought - the coolant temp sensor. Watch it with your scan tool and make sure it is reading correctly, and doesn't change when you jiggle all the wires and connector. When it fails it usually reads -40 F, and I think an open wire reads the same, which makes the ecm think it's in the Arctic and it throws all kinds of extra fuel at the motor.

 

[robbyredneck]

hadnt thought of diaphram. and i checked cts with a hot gun and multimeter versus chart in gm shop manual and it checked ok- turbo link showed a typical increase in coolant temp. also another side, the downpipe doesnt get fleshmelting hot like usual. i have a bosch regulator i will throw on. keep em coming.

 

[robbyredneck]

also old turbolink files have my maf gps@idle at 2

 

[robbyredneck]

last night i crimped all ecm pins and ignition module pins. also i removed head grounds and cleaned/scuffed leads and head surface found that my atr regulator was leaking vacuum but not fuel. put the bosch on and i holds fuel pressure much better.checked return fuel line and no binding. still way too fat. i am going to compare tlink files from when the car ran fine and throw a new set of plugs in it. as long as injector noid it. my spark plug noid flashes pretty good but they arent exactly quantifiable measuring tools. any more suggestions?

 

[84BuickGNYorkPA]

I would monitor the oil very closely, and change it if it smells like gas....

 

[mikestertwo]

I'm kind of siding with Chuck, sounds like a Mass Air Flow problem. Can you get a known good stock MAF from someone just to try? Maybe there is something wrong with the translator. Can you try your translator and MAF on someone else's turbo car?

 

[robbyredneck]

i ,my friends, am an idiot.

i figured it out last night and i feel really stupid. you see when you use a translator and you dont have the dips set right your maf and spark appear to be goofy. so when you set a dip it only checks the status on key up. well i either had a instance of stupidity and fogot to key on and off or had a dip not seat in the on position (mechanical malfunction). i am 100% positive i checked that as it is crossed off my check list and its a rookie boo-boo. i thank all of you guys for scrathing your heads with me and i will be more apt to check and answer threads in the future. again overthinking can be a bad thing. thanks robby