Turbo Buick Forums banner
1 - 20 of 25 Posts

·
Registered
Joined
·
71 Posts
Discussion Starter · #1 ·
When I start the car for the first time after sitting overnight (or if it sits at work all day) it will turn right over and idle fine, but as soon as I put it in gear it starts to idle real rough like it's going to stall. Then after a couple seconds it comes back and it's fine to drive, no hesitation at all. It doesn't do it after it's "warmed up," i.e, sitting for a few minutes in a parking lot or something.
I thought it might be something with the MAF Translator settings, so I pulled the cover and checked those this weekend. IAC valve? :dunno:
 

·
Registered
Joined
·
829 Posts
Our cars do like to warm up...they sometimes will surge and idle a bit rough when first started....your scenario sounds pretty normal to me honestly. If you were to start the car for a minute then turn it off and restart it it would probably idle fine...it's the IAC setting itself...no worries!
 

·
Premium Member
Joined
·
4,001 Posts
whos chip, what maf

do you have any idle #'s from scanmaster (at op temp)

a stock closed loop idle chip takes two minutes to begin reading o2 sensor so its in open loop until then and runs off learned blms so if it has a bad maf /plug /iac it wont have the o2 to keep it in check

vac leaks ,egr leaking can also create issues but the blms should show that
 

·
Premium Member
Joined
·
1,014 Posts
Your MAF should show on the scan master with the readings "AF" between 4-7 If your idle increases the number will be higher. if its higher the car requires more air if it does not get it, can throw the fuel curve off until it warms up. IAC you have to wait until the car is warmed up values should be between 10-40 lower the # the less the IAC valve has to work. Check your TPS to make sure thats in range too.

Stefan
 

·
Registered
Joined
·
829 Posts
Blah! They idle like poo for the first 5-6 minutes....it's fine!
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #7 ·
It's a 3" LT1 MAF with Translator and a TT 93 octane chip.
IAC, TPS, etc etc are all brand new parts. A few months ago everything was calibrated using a Snap-On diagnostic tool so it was good then
Guess I should invest in a ScanMaster soon eh? :eek:
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #8 ·
So I picked up a SM 2.1 and installed it this weekend. The O2 numbers are strange. At idle (cold), I was getting something like 384. After it warmed up a bit, I took it out for a quick test run. O2 numbers literally went from 003 to 750 under throttle and were constantly bouncing all over the place in between. All the other numbers looked good with no codes. Bad O2 sensor? It was replaced right after I bought the car last year too.
 

·
Premium Member
Joined
·
4,910 Posts
That's perfectly normal. The O2 sensor "swings" between a low number and a high number. Usually in most cases you only care about the O2 reading if you're under acceleration and you get a quasi-low "high" number, like low 700's. O2 reading isn't too important at Idle, especially if you have a Turbotweak chip, because it puts the ECM in open loop @ idle so the O2 isn't even part of the equation at that point.

Whats your other numbers at idle? MAF/TPS/IAC/IAT/Volts?

If its just an idle problem and it runs good otherwise, first things I would look for are vacuum leaks, MAF, and check your volts to see if the alternator is going low at idle. I actually had both issues before - a 3" LTI maf go bad...it DOES happen (the solid intake tubing delivers a lot more vibration), and failing alternator.

Also something I've warned about on here before is that translator box is prone to water getting inside, I'd check that too if you think thats a possibility. (these should be checked every so often if your GN is driven in the rain - water can seep inside around the wires, and cause the screws mounting the circuit board to the box to rust. That "rust" CAN cause that board to act up, even though its prob rare)
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #10 ·
Thanks Jeff. All the other numbers on the SM (TPS/IAC/AF/ volts) are within "normal" range. I did notice that it goes back into open loop at idle with the TT chip installed. It was tuned pretty thoroughly a few months back so I didn't expect anything out of the ordinary, but the O2 milivolts threw me. CC's were 17 IIRC, although admittedly I don't really know how to interpret that yet. Going up a hill under throttle, the O2 numbers progressively decreased until they hit 003, which I thought was odd.
The LT1 MAF and Translator seem to be working fine, I did have the box apart just a couple weeks ago to check the settings and it looked A-OK.
I did recently change the vacuum lines going to the wastegate and all the other vacuum lines I checked look good to me.
 

·
Premium Member
Joined
·
4,910 Posts
Next I'd check each coil for resistance if you have a meter - make sure its engine off/key off - pull all the spark plug wires and check the resistance between each pair of coil terminals, front to back. They should read between 11k to 13k ohms. More importantly they should all be close to each other, so if the first pair is 12k, the other two pairs should be pretty close to 12k as well. If one seems drastically off, like 10k instead of 12k (thats 2000 ohms difference), chances are thats a dead/dying coil and you need a new coil pack at least.


Quick Reference Page For the '86/'87 Turbo Regals and '89 Turbo T/A
 

·
Premium Member
Joined
·
1,014 Posts
If everything seems within range lets go to the BLM's what is the BL reading on the scanmaster when the car is warmed up. Vacuum leak will drive you to insanity on these cars.
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #15 ·
BTW, can someone try and explain to me how to "tune" for the recommended O2 readings of 750-800 when the milivolts are constantly changing like that in closed loop? I expected to see steady numbers, but evidently I completely misunderstood.
 

·
Estimator
Joined
·
3,627 Posts

·
Registered
Joined
·
660 Posts
the blm's should be consistent at WOT, part throttle and idle they are going to sweep to either side of stoich to drive the integrator.

WOT, third gear- if the 02's arnt steady in the upper 700 to low 800's , you better get out of it. if it bounces around id suspect its time for a new 02 sensor.
 

·
aka Street Lethal...
Joined
·
268 Posts
PSU 98 said:
When I start the car for the first time after sitting overnight (or if it sits at work all day) it will turn right over and idle fine, but as soon as I put it in gear it starts to idle real rough like it's going to stall. Then after a couple seconds it comes back and it's fine to drive, no hesitation at all. It doesn't do it after it's "warmed up," i.e, sitting for a few minutes in a parking lot or something...
Sounds like a skewed Coolant Temp Sensor. Main spark advance table uses both the LV8 & RPM, then compensated by Coolant Temp & LV8. The two values are added together, and the bias values subtracted, and the spark advance is determined. If your condition is only happening when the engine is cold, the CTS could be giving a skewed reading and effecting your engine idle under a load...
 

·
Registered
Joined
·
829 Posts
I'll be selling my Powerlogger setup w/ a 2.2 SM chip pretty soon if you really want to start monitoring what your car is doing on a run....you would just add a wideband to your downpipe and it will provide a good snapshot of your 02's and allow you to record and see on a chart what's going on from idle to wot. Although I still think your car is fine..if it's the original 02, it never hurts to change a 25 year old sensor :)
 

·
Premium Member
Joined
·
4,910 Posts
And to think, Jeff came to us as a puppy!
:yup: I had a decent first teacher. I remember opening the hood when I first got the GN home and going "oh crap...no carbeurator...now what??"
 
1 - 20 of 25 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top