High RPM lean?

[kptuck]

Update, I have changed both O2 sensors out of frustration, which did not fix the issue. Both were modulating even at full throttle, now they are new and working the same as the old ones did...

I cut my exhaust pipe ahead of the cat and allowed for full flow. Did not fix the issue. Welded the pipe back together...

I had a mechanic attempt to adjust my TPS, which is unadjustable, but is giving proper voltage at all ranges. I also tested the output voltage on the TPS which is perfect. IAT voltage is good.

So I have done really well ruling out issues, but have not found the culprit.

I am now considering that the injectors were bought off ebay and could have an issue.

Now I need to find out how to test injectors...?

The only other change I made from the stock items was to a bigger throttle body, wondering if I should change back to my stock one to find if the issue is there... free and easy, might do that tonight.



I have an appointment with a mechanic buddy for Monday if I dont figure it out before then, and will leave it with him until he comes up with solution.

[SilverXJ]

If the upstream O2 sensor is modulating at WOT it is showing that the AFR is 14.7, which is lean for WOT. At WOT the sensor should be showing rich and a flat line, not a wave pattern. The range of the stock O2 sensor is very narrow, so 13 afr will be shown as rich.

Its a good possibility that the injectors are clogged. I got two sets from ebay both clogged. I sent one set off to get cleaned they now work fine.

[kptuck]

Interesting evening of wrenching.

I changed back to the stock throttle body, even though I expected to see no change.

I started the engine from a cold start, let it idle for 30 seconds, and then nailed the throttle, and bam, no issue. Rev limiter kicked in and the engine sang happily between limited pulses of RPM (5000 - 5200). After releasing the throttle the engine stayed smooth running at idle.

I was amazed the issue was gone again... until a minute later when with the temp at 180 degrees... then the issue came back. The engine falls on its face after 4200 RPM and never even hits the RPM limiter, and then when you release the throttle the engine runs rough for 10 - 20 seconds like a cylinder or two has stopped firing. Then all is well and the engine idles smooth again.

The second result of testing a cold engine caused me to think maybe I am loosing a coil during high RPM with heat. So I pulled the coil rail and checked the ohms. Drat, all in spec, or closed to it as my ohm meter showed a .09 reading on all 3 packs.

Reinstalled the coil rail on the warm engine, checked and as expected the issue was still present.

I then disconnected the temp sensor and immediately got a check engine light. Ran the engine with the temp sensor unplugged and got the same high RPM issue.

Now I am thinking it might be the crank sensor... I have anew one I carry with me when wheeling so maybe I should change it out. But again if this was the issue I should get a code.

So it is a frustrating puzzle still. Could plugged injectors cause this issue? When the engine is in warm-up mode is it receiving more fuel which could hide a plugged injector issue?

Off to bed to dream about a stroker that can pull through a gear.

[SilverXJ]

AA faulty sensor may not throw a code. If you have a space crank sensor then I would swap it out, but that doesn't seem to be the problem. They usually have stalling/no start issues when they fail. The injectors could be dirty of clogged. Too bad you don't have a wideband to see what the engine is really doing.

[kptuck]

swapped out my cps and the issue is still there. But when I started it cold the engine was happy until temp came up.

I then pulled all my injectors and took them to a machine shop here that tests them. The guy tested all of them and they are great. All flowed to spec and he even replaced all the O-rings. He ran them through a run-cycle test, and tested them at 20, 30, and 40#'s. All flowed right at 68 cc in 30 seconds, he left the results up until I got there to see it.

Anyway replaced the injectors and sure enough the issue is still there. I then swapped the injectors wire around, on the off chance that I got them connected wrong during assembly, no real change, but no arrangement fixed the issue, so I put them back in the proper order.

I am off to the races tonight so hopefully something will come to mind.

[Brian E]

I have been fighting with mine and discussing it with Lee and Dino on the Heso forum for a while now. My issue is the engine would over rev easy when they rebuilt it the first, second and third time. After the forth cam and second head it would not pull past 4000, when it hits that area it does act like valve float which I am checking now but I am also checking cam timing, and lifter pre load. I am wondering if the high pressure oil pump they use is pumping the lifters up after the first few moments and floating the valves? I am also going to check all my push rods since I doubt Titan knows there are four factory lenghts and they could have them mismatched. The only thing that changed from when it ran good and now is the cam and head. I have no cat and I have a hush 2 muffler which was all on there when I started this. Yes I know what you mean I am getting tired of going to work and to bed wondering what is wrong with it and have been doing so since last November when they put the motor in. I am checking valve lift today also because I believe they screwed me on the cam I paid extra for. I paid for a 477 lift upgrade I believe it was Crower or Comp and the last time we spoke he said he replaced it with a Elgin? I have been all through the Elgin site and found no listing for Jeep cams? On the Titan site and hammerhead they show a 420 lift Elgin as their cam choice?

[Brian E]

What cam did Titan put in yours? Or should I say what did they claim to put in yours. Specs

[kptuck]

Comp Cams

Grind A6 X4 250H-13
Part 68-232-4


http://www.summitracing.com/parts/CCA-68-232-4/ if you want to see all the specs

My issue is that when the vehicle is cold it runs GREAT; Once it gets hot, the engine wont rev over 4200 RPM.

[the_wrench116]

i think that someone should go give titan a . any one else agree???

[SilverXJ]

Count me in.

[Brian E]

I ve driven the trip there so many times I can not count. I easily have 600.00 $ in fuel wrapped up in that. Plus a couple times taking the day off from work. I have pulled my motor and am going through it piece by piece. I will post when I am done. Mine to ran better when cold but I have a fealing it just makes up for other issue when it is in open loop. Mine ran great with the comp cam. The only thing they changed was my cam the last time to a OEM Elgin which is agrivating because I paid for the up grade to the Comp. But even now it runs farther up the rpm band when cold than hot. My lifes work will be to spread the word on these people for what it cost me so far.

[SilverXJ]

Back to the O2 sensors... what are they showing at WOT? At the 4200 RPM cut off? Prior to 180* when you can rev past 4200?

[kptuck]

well since I am only reading the stock O2 sensor they are showing rich on the scanner, but the plugs are brilliant white, which means I am LEAN at WOT.

I am ordering Hesco's high performance pump and regulator set up tomorrow and hope that my issue will clear up with TONS of fuel. I have been speaking to Bennie about my issue and he will probably help me with deciding on a fuel pressure. I was not looking into fuel ressure or supply because my stock pump is putting out 47#'s at all loads, but maybe my injectors will be happier a the top of the 44 - 55# fuel pressure spec range.

I guess I will start out with a pressure of 55#'s and go from there, unless you guys have some other suggestion.

I put in Champion Platinum plugs today gapped at .050, and replaced the coolant sensor, and IAT sensor.

If the fuel pump doesnt fix the issue I will replace the MAP sensor, and if that doesnt do it I will replace the PCM. F*ck it.

[SilverXJ]

If you had larger injectors I doubt this is a lack of fuel issue. Especially since it works when cold. Why would you replace the MAP if you said it tested good?

[Brian E]

I am betting he did not put the comp cam in it. Mine had the Comp Cam and ran grea till I lost a lobe. He then put in the crap Elgin he insisted would fix the problem and it has never run decent more than one or two times for a frak moment. the comp is speced at lit 465 In 485 Ex the. Elgin is 488 In 488 Ex and was designed for the 4.2 carb engine per the conversation I had on line with an Elgin tech. He said it may be retarded as well becasue the timming chain for the 4.0 - 4.2 are different part numbers even though they fit.