Bogging after Coasting

[Dmod81]

I'm still having the problem with bogging on throttle after coasting. This started after I had the intake ported and removed the secondaries. It seems to not happen until the car gets hot (fully warmed up in the 190s). What happens is when I let off the throttle and coast, the o2s read full rich. When I get back on the throttle, they go to full lean and the car feels like it has no power and bucks. After a few seconds of that, it starts to clear up and drive normally.

Everything seems to check out. I've replaced the pumps (was getting instant leak down), fuel filter, o2s twice (though it might have been the issue), coils (I had a miss that the first set fixed, I thought maybe one was breaking up under heat. Second set had no change), wires, plugs twice, injectors (manual pointed to a slight leak after pumps replaced. FICs installed now), tps, iac, full exhaust (old exhaust had many leaks from bad welds and was kludged together).

Could it be that dfco is not enabled? Or an ECM problem?

[secondchance]

Check map sensor hose and make sure it's correct one - hard plastic hose with rubber ends. I've seen this piece substituted with rubber vacuum hose. This will work fine for awhile until the rubber soften. Under deceleration, increased vacuum will collapse the hose sending wrong vacuum reading to the MAP sensor.

[XfireZ51]

Originally Posted by Dmod81

I'm still having the problem with bogging on throttle after coasting. This started after I had the intake ported and removed the secondaries. It seems to not happen until the car gets hot (fully warmed up in the 190s). What happens is when I let off the throttle and coast, the o2s read full rich. When I get back on the throttle, they go to full lean and the car feels like it has no power and bucks. After a few seconds of that, it starts to clear up and drive normally.

Everything seems to check out. I've replaced the pumps (was getting instant leak down), fuel filter, o2s twice (though it might have been the issue), coils (I had a miss that the first set fixed, I thought maybe one was breaking up under heat. Second set had no change), wires, plugs twice, injectors (manual pointed to a slight leak after pumps replaced. FICs installed now), tps, iac, full exhaust (old exhaust had many leaks from bad welds and was kludged together).

Could it be that dfco is not enabled? Or an ECM problem?

Who modded the calibration?

[Dmod81]

Originally Posted by secondchance

Check map sensor hose and make sure it's correct one - hard plastic hose with rubber ends. I've seen this piece substituted with rubber vacuum hose. This will work fine for awhile until the rubber soften. Under deceleration, increased vacuum will collapse the hose sending wrong vacuum reading to the MAP sensor.

I've a new oem map hose on the car. It's all good

[Dmod81]

Originally Posted by XfireZ51

Who modded the calibration?

Marc did the cal.

[Paul Workman]

Sounds familiar...

Mine is fully ported, SW headers n X-pipe, POS Magnalfow muffs, sans secondaries (see my signature).

Sometimes...not every time...when I coast down or down-shift too, especially during some aggressive driving scenarios, it sometimes will cut out on me as well. And, as you pointed out, temperature (i.e., fully warmed up) is a factor.

If I have the clutch disengaged and am decelerating when it happens, the motor will stop. However, if the motor stalls with the clutch engaged and in gear (i.e., such as when downshifting prior to a turn), a quick blip of the throttle and suddenly it's "all good again"!

I don't recall if it had this behavior prior to the mods/porting, etc. - that was 7 driving seasons ago. But, I definitely noticed it after completing the porting and tune, as well as some hunting at idle with the clutch depressed as I'm rolling to a stop. (Soon as speed reaches ZERO, the hunting stops.)

Dominic is always tweaking his tune - I think partly because he enjoys the challenge of ever-so-fine tuning his LT5. But, none the less he seems to have achieved success and feels he has a handle on the issue. I may give him a shot next season and see what he might be able to do for my 90.

However, in the mean time,I've learned to anticipate the quirk, and deal with it should it occur - almost w/o paying attention much at all: I'm living with it...for now.

All this said, Ami's 91 ZR-1 does NOT display this phenomenon (yet). And, in addition to mine, the "TURQ MONSTER" has also been blessed with Pete's cams and tune: difference in chip and/or tune Perhaps?? We'll see...

[Scrrem]

Paul,
Yes, my car motor is fully ported as well and does exactly what you describe. I notice it at BG at high RPM and decelerating on a down hill slope and the motor will just die but like you said, a simple blip on the gas and it cleans up. I have chalked it up to the tune. Mark did my Chip base on the modes I gave him, but this can probably be cleaned up with a formal tune.
Rich

[Vette73]

Pretty interesting about the MAF hose ...When I was putting mine back together after the porting,one of the rubber ends came off, could not find it....Of course I improvised and cut a piece of hose that fit really well....

Did not know that could lead to maybe a glitch if you want to call it down the line....I will order the part from Jerrys and replace....

Interesting...

[secondchance]

Originally Posted by Vette73

Pretty interesting about the MAF hose ...When I was putting mine back together after the porting,one of the rubber ends came off, could not find it....Of course I improvised and cut a piece of hose that fit really well....

Did not know that could lead to maybe a glitch if you want to call it down the line....I will order the part from Jerrys and replace....

Interesting...

2012 (I think...) drive to Carlisle my car kept stalling out as I slowed to a stop. I ran it by Marc at Carlisle and he pulled my MAP hose which was pretty soft from fuel vapor and heat. Replacement fixed that issue.

[Dmod81]

Originally Posted by Paul Workman

Sounds familiar...

Mine is fully ported, SW headers n X-pipe, POS Magnalfow muffs, sans secondaries (see my signature).

Sometimes...not every time...when I coast down or down-shift too, especially during some aggressive driving scenarios, it sometimes will cut out on me as well. And, as you pointed out, temperature (i.e., fully warmed up) is a factor.

If I have the clutch disengaged and am decelerating when it happens, the motor will stop. However, if the motor stalls with the clutch engaged and in gear (i.e., such as when downshifting prior to a turn), a quick blip of the throttle and suddenly it's "all good again"!

I don't recall if it had this behavior prior to the mods/porting, etc. - that was 7 driving seasons ago. But, I definitely noticed it after completing the porting and tune, as well as some hunting at idle with the clutch depressed as I'm rolling to a stop. (Soon as speed reaches ZERO, the hunting stops.)

Dominic is always tweaking his tune - I think partly because he enjoys the challenge of ever-so-fine tuning his LT5. But, none the less he seems to have achieved success and feels he has a handle on the issue. I may give him a shot next season and see what he might be able to do for my 90.

However, in the mean time,I've learned to anticipate the quirk, and deal with it should it occur - almost w/o paying attention much at all: I'm living with it...for now.

All this said, Ami's 91 ZR-1 does NOT display this phenomenon (yet). And, in addition to mine, the "TURQ MONSTER" has also been blessed with Pete's cams and tune: difference in chip and/or tune Perhaps?? We'll see...

Paul,
Your issue does sound similar, but mine never stalls. It just hesitates bad as I tip in the throttle after decel. If I mash the throttle, it'll jolt back to normal, almost like a really bad shift. I'm now wondering if it in fact can be tuned out. I've got a military PCS coming in a few months, and I'll need to get this fixed before then. Since I'm in CA now, I'm looking at a mid (CO) to cross-country (VA) move.