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ANAM427
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DEC 13, 07:07 PM
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Hi all. Any help would be appreciated.
I installed a re-manufactured 3.4 long block in my 88 GT auto. It turns right over but definitely has a misfire you can hear and feel. Increases with throttle. If you let it run up to operating temp, will idle fine (with the miss) for a bit and then stall out. I had a friend adjust the valves awhile back but I can still hear some noise. I intend to get back in there and readjust the valves in the coming days. Also, this reman engine didn't come with fuel injectors so I bought some from Fuel Injector Connection and they said they were OEM replacements for a 93-94-95 Camaro/Firebird 3.4 (17lb). I didn't know at the time that the Fiero Store sold injectors for the 3.4. So my questions are...
Would a bad valve adjustment cause a misfire? Would incorrect injectors (non pintle) cause a misfire? What else should I check?
AC Delco plugs are new and gaped correctly
Timing is set on cylinder 1 and 4 at 10 BTDC
Plug wires are a little dated but in good condition
No apparent vacuum leaks (new stainless lines)
Aftermarket MSD coil (may try an AC Delco and see what happens)
New distributor, cap, and rotor
New grounding strap from block to battery tray
Tried disconnecting tach filter. No change
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Adam
1988 Pontiac Fiero GT
2014 BMW 428i
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Patrick
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DEC 13, 07:26 PM
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| quote | Originally posted by ANAM427:
Would a bad valve adjustment cause a misfire?
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It's possible... if one or more rocker arm nuts were cranked down so far that one or more valves were being prevented from closing. Seems unlikely, but mistakes can be made.
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Gall757
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DEC 13, 07:33 PM
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MSD.
It seems that those coils on Fieros often cause trouble. I would get a stock coil and new spark plug wires. MSDs operate at a higher voltage and cause problems for other components (such as spark plug wires).
You can check for arcing by idling the car in the dark and spray misting water on the wires.
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Notorio
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DEC 14, 11:15 PM
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Take out and examine your spark plugs to see if they are all evenly wearing. You may find that one of the cylinders has not been firing. In my case I had fresh plugs in so it was easy to see that one cylinder was not firing (i.e. there was Spark but no gas.) I guess you could kill two birds with one stone: first pull the plug wires and crank the engine to get fuel in the cylinders. Then when you quickly pull the plugs you'll see First if they have gas and Second if they've worn the same.
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Dennis LaGrua
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DEC 14, 11:36 PM
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Remove connector and then the 2 screws that hold the ignition module in place. Remove module and wipe the bottom mounting surface clean. Clean with alcohol and buff the mounting plate with very fine wet dry paper. Coat it with conductive thermal grease and put the module back in place with the two screws. Do not over-tighten. Start engine and see if that cures it.
Easiest valve adjustment. Loosen all rocker arm bolts. Remove plugs. Put balancer at TDC. Now move each pushrod up and down as to just to take out any movement but not more. Turn engine 1/4 turn. Snug all rockers down again to remove slack but do not tighten. Do this again turning balancer 1/4 turn at a time for six more tries. Now all the clearance should be out of the valve train. Now go to each rocker arm and turn each a full turn for the preload. The valves are now adjusted perfectly, ------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "
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OldGuyinaGT
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DEC 15, 12:59 PM
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This may be stupidly obvious, but since you've done all that work, could you have accidentally crossed up the firing order with the plug wires? Whenever I disturb anything involving them - distributor, plugs, wires anything -, Icheck this several times before starting, ever since I once crossed up #4 and #6 on an SBC. In that case of course power was down but idle wasn't all that rough, and I even passed an emmissions test that way! I like to think I don't make mistakes like that, but I sure did that time!
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Dennis LaGrua
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DEC 15, 01:54 PM
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Its easy to check the firing order as on the Fiero it is 1-2-3-4-5-6. That is assuming that you have the 3.4L P/R V6 engine ------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "
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Notorio
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OCT 14, 05:18 PM
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Adam, were you able to find the problem?
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Patrick
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OCT 14, 06:38 PM
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| quote | Originally posted by Notorio:
Adam, were you able to find the problem?
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I think Adam has been busy with Eve the last ten months.
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