Stroker in and running.. but noise and lean condition.

[SilverXJ]

Its running.. sort of. It started, backfired, hesitated, bogged down then smoothed out. It did that for about 1-2 minutes. I contributed that to my failure to bleed the fuel rail. I broke the cam in correctly then changed the oil and drove it around a bit. However I have two problems.

One is an of fft fft fft fft sound that is rhythmic and increases with engine RPM. I can't pin point it and it doesn't sound like it is coming from the valve train. Not very loud, but its easier to hear when you step back form the vehicle, but faint up close. Although the best I can hear it it sounds like it is coming from the passenger side near the dipstick area.

The other condition is a momentary lean condition. The lean condition is a bit of a stumper. It happens in closed and open loop, when cold (should be open loop) and while just driving around up to full temp (closed loop), I haven't put the pedal down enough to force it into open loop acceleration. It also appears to happen while driving, accelerating and idling both in gear and park/neutral. Watching the AFR gauge it will go from 14.7 down to like 16-19:1 AFR. It will stay there for a bit then come back to the correct 14.7:1. When this happens it hesitates until the AFR returns to 14.7:1 or so. It hasn't stalled out from this and the PCM is not throwing any codes. No back fire or anything weird either. I tipple checked all the connections on the sensors. and they are all plugged in. So, tomorrow I will plug in my OBD II scan software (if it works) and try to see what is happening. Any ideas? I am also going to try to locate a fuel pressure gauge and test that.


-Chris

[gradon]

What injectors did you go with? W/O a map adjuster or the psc1, my WOT range with the 25.5# lt1s was 15-16s(I can imagine it'd be a lot worse w/ stock injectors). When I had the pft-pft sound, I found a clogged cat(give it a tap) due to the lt1s running too rich in warm up mode and melting the matrix(there went a nice $80, 3-month old magnaflow-- )and so the pft was the exhaust being forced out of the various junctions. It could be a cracked header or 99+intake interfering with the header and not making a good seal(why you might be super lean)Tomorrow I'll reco the previously water-logged psc1(another ) a go and see if it is working now that it's dry, if not I'll get a replacement. I currently have the adj. map set to 6 volts to keep WOT in the 12.5-.8:1 range, but my 2.5K-3K is pinging a bit at part throttle. Tuning and dialing her in is part of the build, so don't fret--just be adamant about getting it right. Anyhow Chris,

[SilverXJ]

What injectors did you go with?

They are about 24 lbs.. I don't think its the injectors.. this isn't even at WOT

When I had the pft-pft sound, I found a clogged cat(give it a tap) due to the lt1s running too rich in warm up mode and melting the matrix(there went a nice $80, 3-month old magnaflow-- )and so the pft was the exhaust being forced out of the various junctions.

the cat was fine several months ago when parked, I don't think it went bad in an hour of running.

It could be a cracked header or 99+intake interfering with the header and not making a good seal(why you might be super lean)

I doubt its cracked or the seal is bad, but I'll take a look.. doesn't really sound like an exhaust leak.

This sounds like a faulty sensor.. PCM leaning the engine out and not throwing a code? Its almost like it is in decel mode.

[SilverXJ]

Just thinking out loud here. Perhaps the sound I hear is a slight misfire and eventually it gets bad enough to cause the lean condition. But the sound doesn't get worse when the lean condition occurs and no DTC is set, which is odd. I would think it would set a DTC for the lean condition or a misfire. Perhaps an O2 sensor is faulty and is showing the computer that the AFR is good, so the PCM doesn't see the lean condition.

Other things I am thinking of are the the O2 sensors, MAP sensor, IAC perhaps? I don't think it is a vacuum leak because that usually pushed the engine speed higher, not lower. But I will check the emission tubing. First thing I will do is pull the spark plugs and check them. Since I will have the plugs out I will find TDC and reset the cam sensor position... I don't like how it is sitting as I feel it is pointing too much toward the engine block and in my experience it usually points more rearward. Also, could be fuel pressure issue. Last time I let the Jeep sit for a long period of time the rear wiper motor died.. maybe this time the pump is going.

I just hope that OBD II scanner software works this time, as last time I tried it it stopped catching data after 10 minutes or so.

[Mgardiner1]

Perhaps an O2 sensor is faulty and is showing the computer that the AFR is good, so the PCM doesn't see the lean condition.

Very possible. However, my experience with O2 sensors are they cause the vehicle to go too rich when they fail or clog.

[SilverXJ]

Well, the OBD II module worked for a bit.. then I recorded over the file.. then it didn't work.. so I have no logging on that. However, below is a good example of what it is doing from my wideband. Right around 3000 the AFR pukes and drops fuel. That was a gentle, gradual acceleration with pedal at about 40-45%. The area circled is the problem area. The other spike to the right of the circle is decel lean, which is normal. From quick looks at the screen on the data logging all sensors looked normal, however I never payed attention to the O2 sensors... bit too much data to analyze when driving.. that is why I was data logging the OBD II feed... or at least I tried to. I did notice that the short term fuel trim stayed very close to 0.



When it happens it just bogs down. The engine makes no weird sounds.. no pinging.. nothing... it is just like someone cut fuel.

As for checking the fuel pressure my gauge is in PA, I am in VA... I wanted to see if I could find something with the OBD II first... guess not. I'll probably have to buy one just to check the fuel pressure.. with my luck it will check out fine.

[SilverXJ]

Failing O2 sensors doesn't make sense. Why would it only do it then and not other times? A faulty fuel pump sounds feasible, but it comes on like a switch and then goes away. I don't think anything internal in the engine would cause this either.. except maybe valve float.. but I used the same part number cam last time as this and same valve springs and never had this issue. And besides.. 3000 rpm is a bit early for valve float.

[Mgardiner1]

I'm sure you recall my cam sensor issue's......... possibly the same thing going on here? However, mine is OBD1, not OBD2

[SilverXJ]

Its not the cam sensor.. I checked it and its dead on. I think its the closed/open loop and the injectors could be possibly a bit small... they are 23.7 lbs or so, but on the other engine the 27lbs were too rich. But it seems I can dial it out with the Apexi (I made it better today at least), which would mean it is in closed loop. I'll have to play with it more. But is is driving, and I don't think there is a problem with any sensors. I'll have to decide is I want to go to bigger injectors or not though.

-Chris

[Mgardiner1]

Can't see it needing bigger injectors..... I mean there are a lot of us running 24# injectors with no piggy back computers and have no problems. Especially when you approach the 3K rpm area with such light throttle, it would BARELY be calling for fuel.

Also, i thought in previous forum discusions on adjustable map sensors, or anything that modify's the MAP signal (like your apexi, and PSC1's), that they only work in OPEN loop when the ECU is not reading off of the O2 sensor. I think when in closed loop, the computer focuses the AFR on the O2 sensor more then any other.

[SilverXJ]

Yes, the Apexi and the like only work in open loop. I get the two confused so I may have said closed loop at some point. But the PCM may very well be going in to open loop when this happens, as modifying the curve on the apexi made it quite a bit better. I'll have better info after Auto Enginuity decides to fix their crap.

[Mgardiner1]

Hm, that being said, maybe the computer is stuck in open loop? i'd assume this could be caused by a bad sensor. Such as coolant not up to temperature, throttle position sensor, something of the sorts.

[SilverXJ]

No, it does go into closed loop.

[hatem61]

SilverXJ, injection pulse width calculation depends primarily on RPM and MAP sensors information, could you try hooking the MAP reading with the OBDII module like you did with the TPS and observe MAP behavior?
You could also check MAP sensor calibration by reading the MAP vacuum value on the scan tool and compare it to a vaccum gauge reading hooked to the intake manifold at the same moment, you do not want to see more than 1psi difference.
Any luck with the pfft..pfft sound? could you try to isolate the source by using a length of rubber hose as a stethoscope, but please beware of rotating components.
Good luck

[SilverXJ]

The MAP tested out fine. Even swapped with a spare I have. All the sensors check out.

The ftt sound actually went away. I did change the spark plugs, maybe that had something to do with it.