Car Backfiring After Each Shift, Poor Acceleration Immediately After

Hi,
Is it throwing any Codes? May be there even though it’s not throwing a CEL.
Did you go back & retorque the Intake to spec’s after the 1st time, sometimes they require another retorque check or two. Don’t overtorque or you’ll lift the Heads.
Backfiring, Check your Header Bolts, Exhaust for leaks, any melted 02 sensor or other wires that are settling again.
Running an EGR?
If you have one, verify your Chipset is still secure on your EEC. No excess noise under the Valvecovers?
Check your Cool air intake clamps, spray the MAF with CRC, IAT.
See what that uncovers, if anything, will eliminate some of the typical swap items..
Will look for a follow up, move on if required.
Good luck!
-John

Hi,
This a 94’ or 95’ 5.0,? Any other aftermarket components added when you did the swap? Any already present? added (specifically Ignition)?
1) The motor ran fine before, no issues at all as described, how did it first present?
2) You just changed the Intake, not Heads or Cam? ANY other Mod’s?
Troubleshooting:.
1) Make your ground connections to from the Battery to the block, Block to Chassis are solid. Remove them, clean, reinstall.
2) Pull your Battery Cable for an hour, reconnect, see if things change.
3) You did clear the Codes after jotting them down, addressing them?
4) The IAC May be a part of it, Idle, but doesn’t line up with the rest. Check it’s operation & verify connectors & its gasket’s not leaking.
5) I’d be looking at the Dizzy, take it apart & brush, clean, spray any debris out of the bowl with CRC MAF Cleaner.
6) 12 Degrees Advance isn’t ridiculous, but rechecking it might not be a bad idea. Did you mark the balancer @ Zero & 10 Deg? Setting it at 10 won’t hurt, ran fine before @12, and it should now.. I usually shoot for 14, unless it pings, then back off. You set it with the SPOUT removed- correct? Verify it’s still there & making good contact.
7) Surging May also be a sign of Coolant being low, (CTS) top it off & ensure it’s not airbound.
8) Pull a plug (or use another, spark tester) and look for a strong (fat blue spark). Block as ground. What’s your Gaps set at, what Plugs?
9) Did you fill up at a spot you normally do, did this start shortly after getting new fuel?
10) Check continuity from Battery ground to Dizzy Chassis with a VOM.
11) Do things clear up when running well below operating temp, just started & run through its paces (don’t overkill it when running cold), just look the midrange change before it’s running closed loop.
12) Did you set the TPS with a VOM to < 1V closed, 4V when WOT? If not, unsure, recheck.
13) Pull your TFI off & bring it into Advanced Auto, bring a hair dryer. As it’s being tested, hit it with some heat to see if it remains OK, if not- replace the TFI.
14) What’s your Fuel Pressure at the Rail, if you don’t have a gauge in place, test it via the Schrader Valve.(Advanced should have one if you don’t).
15) Check your Fuel Pressure regulator, pull the line & induce a vacuum, can you taste or get a strong odor of fuel? If so, replace.
16) These Yr’s had an issue with the internal Fuel tank baffle breaking loose, causing issues similar to this.
17) Verify the Vacuum lines are not only solid, but going to the right spot(s), if unused & live vacuum exists, plug.
18) Carefully follow your wiring harnesses that were disturbed, check every injector connection, ECTS, T.B. is tight, etc.
19) Fire the Car when dark to look for stray arc’s in the ignition or wires, etc. raise the RPM & see it it changes in your problematic RPM ranges.
- A Lean condition is usually the cause of backfires, look at Injectors if this list doesn’t catch an issue.
-A manifold, header crack should be repaired, it will eventually be an issue, pulling in cool O2 will cause popping, but don’t believe it’s an issue now, if not before.
-I was looking for something that’s changed since the swap, things get stretched out & plugs get moved, check all your connectors & connections.
Did you clean your MAF by blasting it with CRC MAF Cleaner? Most other cleaners will leave a residue & cause issues.
Engine running, Pull the MAF Plug & see if the Car drops Idle & runs worse?
- Try these, it should uncover something, if you have another Dizzy- try it. All aftermarket ignition parts are 1st suspect. If you went aftermarket, swap out OE parts you may have that worked previously. One by one, check, so you don’t get lost.
If you’re uncertain about troubleshooting a part, just ask & I’ll explain, or give you a link.
See what you find.
Good luck!
-John

I had that problem with I had a spark plug that was grounding to the header through the boot.