Leans out/stumbles on acceleration. Broke something?
#1
Leans out/stumbles on acceleration. Broke something?
1994 Miata 1.8L, BEGI S3 Turbo kit. exhintake mod on a BP4W head.
Tune: Fine, Running Fine, no stumbling, no problems.
Gave it a good romp going through Milton Keynes (UK) on a straight.
Afterwards, hit accelerator, engine dies.
Starts normal, idles normal. But under load, stumbles for 1 second before everything kicks in.
Offset the stumble issue by no-load tapping on the accelerator to get the RPM's up, but the stumble is still there.
Problem dissipates at higher RPM's. It's still there, but seems to recover from the stumble much more quickly. Once it's up to speed, it does what it's supposed to do (come on boost, doesn't lean out, etc...) Just shifting and hitting the pedal from idle.
Connected Laptop to test TPS for a flat spot, re-cal'd it, and checked the gauges in Tunerstudio. Goes up smooth, no issues. (With engine off)
So, pulled a log. Not a super long one, and not under load (I can get it to stumble at idle in the same way.)
Log:
accel problem.zip
Tried disconnecting the TPS entirely, tried tapping on it, wiggling it, etc...
Should note that it did this one time previous, on Christmas Eve, and fixed itself before I could get home to get a laptop on it...
Tune: Fine, Running Fine, no stumbling, no problems.
Gave it a good romp going through Milton Keynes (UK) on a straight.
Afterwards, hit accelerator, engine dies.
Starts normal, idles normal. But under load, stumbles for 1 second before everything kicks in.
Offset the stumble issue by no-load tapping on the accelerator to get the RPM's up, but the stumble is still there.
Problem dissipates at higher RPM's. It's still there, but seems to recover from the stumble much more quickly. Once it's up to speed, it does what it's supposed to do (come on boost, doesn't lean out, etc...) Just shifting and hitting the pedal from idle.
Connected Laptop to test TPS for a flat spot, re-cal'd it, and checked the gauges in Tunerstudio. Goes up smooth, no issues. (With engine off)
So, pulled a log. Not a super long one, and not under load (I can get it to stumble at idle in the same way.)
Log:
accel problem.zip
Tried disconnecting the TPS entirely, tried tapping on it, wiggling it, etc...
Should note that it did this one time previous, on Christmas Eve, and fixed itself before I could get home to get a laptop on it...
#6
Tune/Settings was done on a dyno by Nick Skuzzle, who knows vastly more about tuning than I do. I haven't changed anything he put into the tune (because as I said previously, this problem didn't exist up until I gave it some right foot going through Milton Keynes. Nothing I haven't done on a fairly routine basis (didn't red-line it, or mechanically over-rev the engine).
#8
Fuel filter is brand new.
I am as "scratching my head" as you are...
#11
i had the same problem.. it was the accel enrich.
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#12
Sir, the log is posted above; accel_problem.zip
It's a short log, there are two "misfires" represented there where I turned Advanced Accel Enrichment on, and then back off again.
I checked the mechanicals today as best I could in the driveway. Lined up the pulley marks (TDC and 10 mark, going clockwise), pulled the cam cover and checked the gears/lobes. Lobes were in the right place, I and E in the right places, with 19 teeth between them. Checked over the vacuum lines (but didn't use carb cleaner or butane yet), and nothing that relies on vacuum seems out of place either.
I will have a play with accel enrichment, but it doesn't explain the going lean on tip in (like, max lean).
It's a short log, there are two "misfires" represented there where I turned Advanced Accel Enrichment on, and then back off again.
I checked the mechanicals today as best I could in the driveway. Lined up the pulley marks (TDC and 10 mark, going clockwise), pulled the cam cover and checked the gears/lobes. Lobes were in the right place, I and E in the right places, with 19 teeth between them. Checked over the vacuum lines (but didn't use carb cleaner or butane yet), and nothing that relies on vacuum seems out of place either.
I will have a play with accel enrichment, but it doesn't explain the going lean on tip in (like, max lean).
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