High RPM lean?

[kptuck]

Hello all, stroker newbie here -

I have just installed a 4.9L Titan, I know some are against Titan...

The cam break-in went fine, and so did the first drive.

The only issue I am experiencing is power loss at 4200+ RPM that feels like the mixture is going lean. I installed 27# Bosch III injectors and a 63mm Throttle body. I stuck with the stock exhaust.

Since I only have one drive on the new engine the PCM is still dealing with the changes, but I have no experience with adjustable MAP or other tuning solutions with computerized vehicles. I am a Holley carburetor and small block Chevy guy from the 70's...

Questions -
Will my PCM deal with the changes I made and eventually correct the lean issue?

Will the stock fuel pump supply enough fuel at pressure to run above 4200 RPM?

Do I need to buy a "chip" or something?

Other than the high RPM issue the engine runs GREAT off idle and pulls strong smooth and quiet right up to 4000 RPM.

Any other thoughts?

Thanks,

Kevin

[SilverXJ]

The PCM's learning isn't going to do much for the WOT area. I doubt you are running lean with 27lb injectors. Mine runs rich with 26.5# injectors.. or are they 25.6#.. I don't recall. Could be valve float, but I would check other areas first.

[kptuck]

Thank you for your comment.

Titan engines suggest more drive time to allow for the PCM to adjust. They also suggest to confirm my cam sensor is properly timed. I will consult my shop manual to confirm properly "timing" of the distributor sensor.

Any other thoughts? I will reply here on timing and additional drive results.

[gradon]

If you truly want to know, you'll need a wideband o2 to see what the afrs are at WOT. They can be found for $150-200 on ebay(innovate's a good brand). The map adjuster is a $10 build it yourself circuit that takes a 12v in(instead of the pcm's ~5v) and has voltage regulator and an adjustable resistor to knock the voltage down. Most people stay in the 5-6v range(except those that are running too rich, who are in the 4s). I removed mine a few weeks ago to find my no start culprit(coil), so at the moment with 25.5# injectors, mine runs 14.5-15 at WOT=lean. You'll want to shoot for 12.5-12.8:1 for best power at WOT.

[SilverXJ]

Search on here for cam sensor. There are a few threads with a good link on how to do it. Doubt that is the problem though as it should show problems prior to 4200

-Chris

[Cheromaniac]

The PCM's learning isn't going to do much for the WOT area. I doubt you are running lean with 27lb injectors. Mine runs rich with 26.5# injectors.. or are they 25.6#.. I don't recall. Could be valve float, but I would check other areas first.

Agree. Valve float is a possibility but I hope that even Titan would have enough sense to upgrade the valve springs on their strokers. Then again you never know.
The stock fuel pump can supply enough fuel for up to ~300hp so it should be up to the job.

[RAPTORFAN85]

If it runs absolutely fine until high RPM's then it also sounds like valve float to me. Valve float will feel almost like you are hitting a rev limiter. I wouldn't put ANYTHING past titan. It wouldn't surprise me to see stock valve springs in there and if they used a high lift cam valve float is a possibility. Try asking them what they put in your engine they won't be able to tell you.

[kptuck]

Well, I adjusted the cam sensor based on shop manual and mechanic's advice.

The issue was seemingly fixed, until I got to full running temperature, +/- 205 degrees. Then the issue came back, and I am still "running out of fuel" at 4200 RPM.

When the engine was in warm-up mode I was able to run right up to red line without an issue, this lasted for 1 minute tops... good news is this rules out the valve float idea as valve float would not be subject to temperature change.

Any other thoughts now? Still think I may need to adjust MAP to effect WOT mixture at running temperature?

[SilverXJ]

When in warm up the engine is still in open loop. When in WOT the engine is in open loop. I would start testing sensors after it has warmed up. MAP and TPS first. And check your fuel pressure too. Also, check the IAT.

I don't think its anything a MAP adjuster will fix. They run rich from the factory after ~3500 RPMS in WOT and your injectors should be a good match for the engine. What is the part number on your injectors?

[kptuck]

The part number on the side of the injectors is 0 280 155 849

They are supposed to be Bosch 27#, they do have 4 orifices in the them.

I assume my shop manual will have instructions to test the sensors? Weird as I am not getting any codes but the issue is very evident.

Thanks for helping.

[kptuck]

Just checked fuel rail pressure at idle, 47#, which is within specs.

Is there a link with details on the MAP voltage adjuster? Just in case I end up going that way...

I am also considering Jet's V-Force Plus Power Control Module 68030 if I keep not finding the issue

http://www.autoanything.com/performance ... 0423bb4e79

[SilverXJ]

Just checked fuel rail pressure at idle, 47#, which is within specs.

Is there a link with details on the MAP voltage adjuster? Just in case I end up going that way...

I am also considering Jet's V-Force Plus Power Control Module 68030 if I keep not finding the issue

http://www.autoanything.com/performance ... 0423bb4e79

I am not sure that the Jet thing will actually do anything useful. Going off their manual it doesn't have a setting for you to adjust the AFR manually, although it does intercept the MAP signal. I'm thinking it modifies the MAP slightly for a stock vehicle with no user adjustable parameters, similar to their line of chips.

Still, I don't think that is where your problem lies.

I assume my shop manual will have instructions to test the sensors? Weird as I am not getting any codes but the issue is very evident.

I don't know what shop manual you are using. The FSM gives specs on what it should read and you can go off that.

[kptuck]

Just checked the fuel pressure while driving and it stayed constant 47# at all loads, even when experiencing the lean high RPM issue.

Attached a Snap On scanner with the proper diagnostics for my Jeep and received no codes. Did a drive with the scanner attached and the only anomaly was the second O2 sensor, (past the cat), was staying at a constant 4.98 volts with an always rich reading. The front O2 sensor was modulating as expected. The TPS, MAP and IAT all were performing as expected.

Question - does anyone know if the second O2 sensor actually helps with air/fuel ratios? or does it serve some other emission purpose?

I am close to changing the second O2 sensor just to see if it helps, but why am I not receiving a code for an evident issue?

As a shade tree mechanic, I was thinking low fuel pressure - but we ruled that out. Now I am thinking my cat could be partially plugged which is the reason for the 2nd O2 sensor reading rich all the time and maybe effecting A/F ratio? A restricted exhaust could even be causing my lean feeling and could be the reason I have no codes...?

[Flash]

Just because you have 47# at idle, does NOT, mean you still have sufficient pressure when the eng is a 4000 rpm, and the skinny peddle is thru the floor board!

[SilverXJ]

Just checked the fuel pressure while driving and it stayed constant 47# at all loads, even when experiencing the lean high RPM issue.

Attached a Snap On scanner with the proper diagnostics for my Jeep and received no codes. Did a drive with the scanner attached and the only anomaly was the second O2 sensor, (past the cat), was staying at a constant 4.98 volts with an always rich reading. The front O2 sensor was modulating as expected. The TPS, MAP and IAT all were performing as expected.

Are you saying that the front O2 sensor was modulating even at the 4000 RPM wall?

Question - does anyone know if the second O2 sensor actually helps with air/fuel ratios? or does it serve some other emission purpose?

Its purpose is to check the efficiency of the cat. So you either have a bad cat or bad O2 sensor. It doesn't modify the afr. A clogged cat is a possibility. Do you have an IR thermometer?

I am close to changing the second O2 sensor just to see if it helps, but why am I not receiving a code for an evident issue?

Don't know.. maybe the PCM doesn't monitor the after cat sensor at WOT?