On my 3.4 DOHC manual swap I’m having a problem with the TB? When coming to a stop, with the clutch in, my engine is at ~1500 rpm’s until I stop. Once stopped it drops to 1000 rpm’s. I'm also noticing that during shifts the RPM hangs and doesn’t drop to what I think it should for the next gear. Have checked the spring on the TB and it looks and feels like it should. Replaced the TPS and cleaned and adjusted the IAC. No change No codes?
I believe the automatics have it built into the programming to idle slightly higher at speed over anything but zero. What Chip do you have? Perhaps it hasn''t been removed from the programming to suit your manual transmission.
[This message has been edited by The Aura (edited 03-04-2013).]
Yep, mine is the same way and I really don't like it. Apparently this is how GM "fixed" the engine dying problem when you go off-throttle. Mine was bad enough with the stock BFCA chip (It dropped to idle at about 1500 rpm because it was reading the Fiero speedo sender). I had Darth do me a new chip with a few tweeks and while he was at it he corrected the pulse count. Now it acts just like you describe. He offered to try masking over the the off-throttle with the automatic chip's program, but I never followed through on it.
I think they have it right. My 5spd LQ1 had to be pulled out of gear or blip the throttle otherwise it would die. It was a manual vs auto issue. Get with Darth, he seems to be the man.
------------------ And so she walked out of our lives forever.
The manual trans programming has that "fast idle hang" characteristic built into it from the factory. It could very well have been put in there by GM to prevent stalling issues.
If you want, you can send me the chip and I can try lowering it for you - but I cannot guarantee it will work as desired as it could cause other issues (ie: such as stalling).
But there are things we can try.
-ryan
------------------ OVERKILL IS UNDERRATED Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com
This is all great info and glad I'm not the only one having the issue because I was running out of ideas and cash to throw at the issue. On long trips and hot daysI have a stalling issue from time to time. Have to turn on the AC to compensate but is doesn't always work.
Which engine management are you running? 91-93 I assume? Is your clutch switch connected and working correctly?
OBD1 and yes the clutch switch is connected. No code since the install years ago. Have close to 40k on the swap. Can you explaine why you asked these question? I'd like to know what you know please.
Nothing really, I just wasn't sure if you were 91-93 management, or 94-95. I've been running a manual with a modified 94-95 code (auto delete) and have been very pleased with it. But it too holds a slightly higher idle till I come to a stop.
I'm not totally sure what the clutch switch controls, but I would venture to guess it would have to do with closed loop idle control somehow.
I raised the threshold for Max MPH for Closed loop idle to 20 just to see how it felt on my 94-95. It had a side effect when in first gear at low speeds, the car would start bucking heavily, but it did allow a low idle long before coming to a stop. I'd be more helpful if you were 94-95.
It is worth noting the differences between the computer systems...
1991-93 3.4 DOHC computers are speed density and will work with ANY 3.4 DOHC engine, regardless of what year it is. These PCMs were used in factory applications that came with 4T60-E auto transmissions or 5-speed manual transmissions. These PCMs have removable mem-cals/chips.
1994-95 3.4 DOHC computers work in SFI mode, use a MAF sensor and will only work with 1994-newer 3.4 DOHC engines because of the need for the additional crank sensor (24x) and cam sensor (1x). GM discontinued the use of the 5-speed manual transmissions with 3.4 DOHC engines after 1993 model year so this PCM and the later OBD2 systems were only used with automatics. This PCM can control a 4T60-E auto or it can work with a manual trans if custom programmed for it. These PCMs have removable mem-cals/chips.
1996 3.4 DOHC SFI OBD2 PCMs use MAF and MAP sensors, and will work with a 4T60-E auto trans (or manual trans if custom programmed for it). These PCMs must be reflashed to be reprogrammed, and will only work with 1994-newer 3.4 DOHC engines because of the need for the additional crank sensor (24x) and cam sensor (1x).
1997 3.4 DOHC SFI OBD2 PCMs use MAF and MAP sensors, and will work with a 4T65-E auto trans (or manual trans if custom programmed for it). These PCMs must be reflashed to be reprogrammed, and will only work with 1994-newer 3.4 DOHC engines because of the need for the additional crank sensor (24x) and cam sensor (1x).
-ryan
[This message has been edited by Darth Fiero (edited 03-05-2013).]
Been thinking about putting a VSS kill switch on the clutch pedal. Do you see any problems that this may cause?
Yes, killing the VSS signal unexpectedly can give the ECM fits. Have you had the chip reprogrammed to try to lower the fast idle hang problem yet? If not, I would try that first.
