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Old 08-06-2019, 06:47 AM   #1
Join Date: Aug 2019
Location: Mesa, Arizona
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Default Stutter/misfire on deceleration

Hey guys first post here.

Have an 87 base model na 7mge.

Had a bhg so I changed the head gasket and head for a newer head. Swapped old cams, lifters, and put in arp headstuds torqued at 90 ft lbs.

Block was hand scraped and cleaned. Apex headgasket with copper spray. Head was milled at unknown amount and pressure tested.

Put it all together checked the timing marks 10 times before I went to start the car. Wouldnít start ended up being dizzy off one tooth. Got it started and it idles great and drove perfect for the first 100 miles.

I have since encountered a stutter/misfire after 3k depending on where I place the accelerator pedal. I get lots of pops and backfire on decel with a bit of blackish blue smoke when the stutter/pop happens. I can let off readjust the speed and itíll be fine til I start to let off then it misfires and stutters.

Car doesnít misfire on idle, it will free rev all the way up in WOT or neutral. Doesnít misfire when holding the pedal down or at any rpm in neutral.

I have checked the timing at the cams and crank. Checked with a timing light set at 10*.
Checked the tps.
Changed plugs.
Checked plug wires.
Retorqued the head.
I donít lose any water. I donít have any oil or water leaking near the plug galley.

Iím stumped and annoyed as hell after all the hours I put in this car. Any help would be appreciated.

I can provide pics, whatever info needed as well.
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Old 09-10-2019, 09:27 PM   #2
Bone Stock w Upgrades ;-)
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Location: Tampa Bay
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Is the ECU throwing any codes? If not check the throttle position sensor. You need a Ohm meter with a needle and some feeler gauges and a bent S-shaped Phillips screwdriver to get the bottom Phillips screw. The throttle should have a dash pot to cushion the closing of the throttle plate so it doesn't snap shut. If you don't have a dealer manual here is the online supra manual. http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx
Check your high tension leads to make sure you have the correct firing order and the resistance isn't excessive in the high tension leads. The procedure is in the manual. Is the intake and exhaust valve lash within specification?
Check your EGR system based on the procedure in the manual.

Last edited by Bru; 09-10-2019 at 09:30 PM.
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Old 11-07-2019, 06:57 AM   #3
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Does it only happen when the engine is warm?
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