Jump to content

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

backfire


Recommended Posts

I'm dealing with a 1999 hammerhead engine. Backfires through intake when advancing throttle at lower throttle settings. Sometimes dies at idle in neutral. Replaced cap and rotor, Distributor module, plugs, both fuel filters. Fuel pressure is good, but have'nt tried pressure test under load. Tried new tps, iac valve, map sensor. Sent injectors out for check/service. Sent computer out for test. Compression is good and even. Checked for vacume leaks. Cleaned grounds. Ohm tested spark plug wires. No codes logged. Tore top end apart and checked out cam and heads at machine shop. Installed new lifters. Timing chain seems fine. Ran engine with remote fuel tank. Put engine into "service mode" and adjusted timing. Adjusted timing under load manually. Checked continuity between computer and sensors. Spark plugs look ok. No wet, lean or rich looking plugs. Connectors at computer are clean and in good condition.

When disconnecting IAC, there's no change in idle speed. When disconnecting MAP, engine dies. Will restart, but dies right away. Distributor gear is good. All wiring looks good. Battery voltage is good and alt output is good. Vacume guage on intake reads ok (for 9000 ft). Motor will rev to 4200 rpm with prop that was on it for lower elevation. Swapped out coil. Made sure firing order is correct.

Short of changing out distributor, wiring harness, and ECU I don't know what else to do. I'm starting to suspect the ECU, even though it was sent out for testing.

What the heck is wrong with this thing? It's driving me crazy!

Please help.

Link to comment

I'm dealing with a 1999 hammerhead engine. Backfires through intake when advancing throttle at lower throttle settings. Sometimes dies at idle in neutral. Replaced cap and rotor, Distributor module, plugs, both fuel filters. Fuel pressure is good, but have'nt tried pressure test under load. Tried new tps, iac valve, map sensor. Sent injectors out for check/service. Sent computer out for test. Compression is good and even. Checked for vacume leaks. Cleaned grounds. Ohm tested spark plug wires. No codes logged. Tore top end apart and checked out cam and heads at machine shop. Installed new lifters. Timing chain seems fine. Ran engine with remote fuel tank. Put engine into "service mode" and adjusted timing. Adjusted timing under load manually. Checked continuity between computer and sensors. Spark plugs look ok. No wet, lean or rich looking plugs. Connectors at computer are clean and in good condition.

When disconnecting IAC, there's no change in idle speed. When disconnecting MAP, engine dies. Will restart, but dies right away. Distributor gear is good. All wiring looks good. Battery voltage is good and alt output is good. Vacume guage on intake reads ok (for 9000 ft). Motor will rev to 4200 rpm with prop that was on it for lower elevation. Swapped out coil. Made sure firing order is correct.

Short of changing out distributor, wiring harness, and ECU I don't know what else to do. I'm starting to suspect the ECU, even though it was sent out for testing.

What the heck is wrong with this thing? It's driving me crazy!

Please help.

Man, it seems like you covered everything. Hows yer intake manifold gasket? 4200 rpms seems too low at wot but that's a separate issue.

Link to comment

Hmm. Timing is near factory spec? Did you change the cam, or take off timing gear...if so, it's not off a tooth is it?

It's got fuel and spark, but not hitting correctly for some reasonNor, to the point the idle is weak. Hmmm. Maybe one of the injectors is just dumping gas?

Normal engine temp? Or is there a chance the distributor is off a tooth? I've heard it can be done.

As you figure it out, please let us know what's going on with it,

Steve B.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...