Experiencing problems after swapping a D16Z6 engine for a D16Y7 in your 95 Civic? You’re not alone. Many Honda enthusiasts encounter challenges when mixing OBD1 and OBD2 components. Let’s diagnose the issues you’re facing, specifically focusing on timing, distributor compatibility, and ECU considerations when dealing with a D16y7 Obd1 Or Obd2 setup.
Timing Issues After D16Y7 Swap
You mentioned your timing is significantly off after installing the D16Y7. This is a critical area to investigate. Incorrect timing can lead to poor engine performance, backfiring, and overheating catalytic converters, which you are experiencing.
You described setting the timing using marks inside the timing belt cover. Yes, these are the correct marks to use for setting the mechanical timing on a D16Y7 engine. Ensure the crankshaft pulley mark aligns with the TDC (Top Dead Center) mark on the engine block, and the camshaft pulley mark aligns with the UP mark pointing upwards and is level with the head surface. Double-check that the timing belt is correctly installed and tensioned.
However, if the timing remains significantly off even after proper mechanical setup, consider these possibilities:
- Distributor Issue: You’re using a non-VTEC distributor, assumed to be from a Civic DX. While physically similar, there might be subtle differences affecting timing accuracy. It’s crucial to confirm the distributor is indeed compatible with the D16Y7 and the OBD1 system. A mismatch could cause timing inaccuracies.
- Incorrect Distributor Installation: Even with the correct distributor, improper installation can throw off the timing. Ensure the distributor is correctly seated and that the rotor is pointing towards the correct cylinder #1 position at TDC.
- Damaged Crankshaft/Camshaft Pulley: Though less likely, a damaged or mismatched pulley could lead to timing discrepancies. Verify the pulleys are the correct ones for the D16Y7 engine.
Distributor Compatibility: OBD1 vs OBD2 Dizzys
You raised a valid question about distributor compatibility between different D-series engines and OBD systems. While non-VTEC distributors for similar displacement engines might appear mechanically interchangeable, electrical differences and internal components can vary.
For a D16Y7 (typically OBD2), using a distributor from an older OBD1 system (like a Civic DX) might create issues. Although you intended to swap internals to match the OBD1 harness, the distributor housing or reluctor could still be incompatible, leading to incorrect signals and timing problems.
To ensure compatibility, ideally, you should use a distributor specifically designed for an OBD1 D-series non-VTEC engine. If possible, identify the exact origin of the distributor you are currently using to rule out any incompatibility. While 1.5L and 1.6L distributors can sometimes be similar externally, internal configurations can differ.
Injectors and ECU Considerations for D16Y7
You’re right to point out the difference in injector sizes between the D16Z6 (235/240cc) and D16Y7 (180/190cc). With the smaller D16Y7 injectors and the P28 ECU (originally for the D16Z6), the engine might be running lean, not rich as you initially expected. However, running lean typically doesn’t directly cause backfiring or a glowing catalytic converter. These symptoms are more indicative of unburnt fuel entering the exhaust system, which could be due to timing issues or misfires.
Regarding the ECU, using the P28 (OBD1 VTEC ECU) with a D16Y7 (non-VTEC) is causing codes 21 and 22 (VTEC system malfunction). While cutting the VTEC line (J1) on the P28 might stop the VTEC error codes, it doesn’t optimize the ECU for the D16Y7 engine’s fuel and ignition maps.
Consider these ECU options:
- P06 ECU (OBD1 Non-VTEC): This ECU is designed for non-VTEC D-series engines and would be a more appropriate match for your D16Y7 in an OBD1 setup. It should provide more accurate fuel and ignition mapping compared to the P28.
- Chipping the P28: While possible, chipping the P28 to run a non-VTEC map requires expertise and might be more complex than simply swapping to a P06.
- OBD2 ECU: If you want to use the D16Y7 in its intended OBD2 configuration, you would need to convert your Civic to OBD2, which involves harness modifications and ECU replacement. This is a more involved process.
For your goal of fuel efficiency and stock-like performance, the P06 ECU is likely the simplest and most effective solution.
Uneven Exhaust Manifold Heat: Cylinders 3 & 4 Running Hot
The significantly hotter header tubes on cylinders 3 and 4 compared to 1 and 2 is a strong indicator of a problem specific to those cylinders. This uneven heat distribution is not normal and suggests incomplete combustion or other issues in cylinders 3 and 4.
Possible causes for hotter cylinders 3 & 4:
- Misfire in Cylinders 1 & 2: Paradoxically, if cylinders 1 and 2 are misfiring (due to injector issues, spark plug problems, or compression issues), the unburnt fuel could be routed more towards cylinders 3 and 4, causing them to run hotter as the catalytic converter tries to burn off the excess hydrocarbons. However, you’d likely notice misfire symptoms.
- Lean Condition in Cylinders 3 & 4: A localized lean condition in cylinders 3 and 4 could cause them to burn hotter. This could be due to partially clogged injectors on these cylinders specifically. Swapping injectors between cylinders, as you suggested, is a good diagnostic step to see if the hot cylinder issue moves with the injector.
- Exhaust Restriction: While you checked for a clogged catalytic converter, there might be a partial restriction specifically in the exhaust passages for cylinders 3 and 4 within the manifold itself, though this is less common.
- Valve Issues in Cylinders 3 & 4: Less likely but possible, valve problems in cylinders 3 and 4 could affect combustion and heat distribution.
Conclusion: Steps to Diagnose D16Y7 OBD1/OBD2 Issues
To effectively troubleshoot your D16Y7 engine swap issues, especially concerning d16y7 obd1 or obd2 compatibility, follow these steps:
- Verify Mechanical Timing: Reconfirm the mechanical timing using the correct marks on the timing belt cover.
- Distributor Check: Identify the exact origin of your distributor. Ideally, switch to a known compatible OBD1 non-VTEC distributor for a 1.6L D-series engine or try to source a distributor specifically for a D16Y7 if aiming for an OBD2 conversion later.
- ECU Swap: Consider swapping to a P06 OBD1 non-VTEC ECU for better compatibility with your D16Y7 and OBD1 harness.
- Injector Test and Swap: Test your injectors. Swap injectors between cylinders 1 & 2 and 3 & 4 to see if the hot header issue moves.
- Spark Plugs and Wires: Inspect spark plugs and wires for cylinders 1 & 2 to rule out misfires.
- Compression Test: Perform a compression test to rule out any major mechanical issues.
By systematically addressing these points, you should be able to pinpoint the root cause of your engine problems and get your Civic running smoothly and efficiently after the D16Y7 swap. Remember to prioritize accurate timing and ECU compatibility when dealing with OBD system variations.
