A/F Ration and Fuel Pressure Regulator

[W_A_Watson_II]

Still waiting for warm enough weather to get more than a trip around the block on the 4.6L Stroker (http://www.jeepstrokers.com/forum/viewt ... f=5&t=3535), but the rubber boot that connects the vacuum line to the Fuel Pressure Regulator was fairly cracked, so I replaced it with a short section of vacuum hose.

Before I did this I had a lot of idle A/F fluctuation and even though it smelled rich, the A/F gauge showed it went lean more often that not at idle. With what I think is a better regulator vacuum signal, the A/F ration go high off the scale, way lean, and eventually comes back. No pinging or dying.

If I disconnect the vacuum line and plug it, the engine runs better than with it connected.

Any ideas or suggestions? Stock regulator and MAP sensor.

Resulting Engine build Specifications:
□ - 3.905" - Bore (30 over)
□ - 9.450" - Deck Height (not milled, measured by machine shop)
□ - 3.895" - Stroke, Jeep 4.2L 3.895" crank
□ - 6.125" - Connecting Rod, Jeep 4.0L
□ - 1.353" - Pin Height (Keith-Black Silvolite (UEM) forged stroker IC944 Pistons, 21cc dish volume)
□ - 0.041" - Compressed Head Gasket Thickness
□ - 0.0245" - Deck Clarence
□ - 0.0655" - Quench Height
□ - 57cc - Head Combustion Chamber (Head milled 0.006", need to measure to veify)
□ - 280 cu.in. / 4.6L
□ - 9.38 Static Compression Ration (SCR)
□ - 8.05 Dynamic Compression Ration (DCR)
□ - 89, Likely required Octane
□ - 240/315 Likely HP/TQ Ratings

http://www.jeepforum.com/forum/f12/star ... st14094522
http://jeep.wawii.com/93YJ_TrannyJob.htm

[SilverXJ]

Perhaps give the PCM some time to relearn the AFR with the change. What is way lean?

[W_A_Watson_II]

That's my hope/thought as it's only been around the block a few times so for. As for what's way lean, in excess of 17, as the gauge hit's 17, then goes to "--" for a while before it drops back below 17, and the bounces around 14.7.

Thanks,
Will

[Cheromaniac]

Perhaps give the PCM some time to relearn the AFR with the change.

Agree. Also check that the new vacuum line you installed isn't too soft and is collapsing under vacuum.

[W_A_Watson_II]

The weather warmed up, and I put 33 miles (for a total of 37) on the Jeep on the road today after installing the side markers. The Jeep exhaust volume has moderated downward, and the A/F ration is a little better. At road speed it's bouncing between 14.3 and 15.5, it does bounce more than I expected. It did developed a miss at speed after it warmed up, but it wasn't predictable or re-creatable or always there. Also on hard full throttle acceleration, it also misses some above 4,000 RPM before it shifts. I'm thinking I might have a fuel delivery/pressure issue.

[CENTER][/CENTER]

[SilverXJ]

Check the fuel pressure while driving. Also, check your plug gap. Too large of a gap and it could miss at higher RPMs.

[W_A_Watson_II]

Check the fuel pressure while driving. Also, check your plug gap. Too large of a gap and it could miss at higher RPMs.

Thanks, will do.

[W_A_Watson_II]

I've not yet picked up a fuel pressure gauge and checked it, but now believe it's plug related.
See my update on the Stroker Spark Plugs post: http://www.jeepstrokers.com/forum/viewt ... 748#p33748

Will