About to give up

So far I’ve replaced the MAP, fuel pump, injectors, TPS, IAC, verified no cracks in the intake. Tightened up the exhaust bolts to fix a minor leak and put a new flow master 40 series muffler on with no converter. Replaced the upstream O2 sensor. It’s still running lean. Still turning the exhaust red. The further I drive it the weaker it seems to get. I’m at my wits end. The next thing will be the coil…the plugs and wires look brand new. I suspect the PO had this issue and that’s why he was so eager to swap me it for my 2007 H3 Hummer with a bad transmission. Anyone got any ideas where to go next ??? I’m officially stumped.

These are the codes I’m getting using a snap on Modis Ultra. I have a video of the live data with it idling but I guess we can post videos.

A chip as in like a performance chip ? No. The list of symptoms are. Poor gas mileage. Even for 32” tires and 4.56 gears. Runs very warm, near hot. Tends to run lean per scan tool on highway which I’m assuming is causing the glowing exhaust manifold. At the beginning of driving it runs rather well. Will maintain 60-65 mph for 6-8 miles. Then it does good to maintain 55-60 for the next 6-8 miles. By the time I turn around a make the 10-15 mile trip home it does good to maintain 52-53 flat on the floor. It will idle good. Slightly rough idle but nothing I wouldn’t expect from a 170k mile 2.5L. I’m not getting near the performance reported by other owners with the same setup.

I have replaced:
Fuel pump
Injectors
Muffler (no cat)
MAP
IAC
TPS
High Flow Air Intake (CAI)
Upstream O2

I have used the scan tool to run all the diagnostics available to this old system. I’m getting nothing. O2 reads bounce from .08 to .64ish upstream. MAP runs 15.2 at idle and around 1.5 at full throttle. Intake air is showing normal per scanner at about 160F while idling. I have a video of the live data on the scanner but I cannot post it. I’ll see if it will let me PM it to you. See if you see something I’m not. At this point I feel like it’s something simple I’m overthinking and just not seeing. At idle the timing is running +15 TDC (varies by 2-3 degrees).

I’ve gotten desperate for answers to the point I used my raytech and shot each brake to make sure I didn’t have a sticking caliper or drum lol. Those were 115ish both read drums and 250ish on one front and 215ish on the other front rotors.

I tried the old shade tree vacuum leak test with carb spray while the motor was running. No discernible changes in RPM. I have not sprayed after a drive and the exhaust gets extremely hot for fear of igniting the spray. lol. I’m wondering now if there isn’t a crack that’s opening up wider as the manifold gets hotter hence the worse drivability the longer I drive. I’m stumped.

ItchyDong said:

So the only symptoms are a glowing exhaust? Otherwise it runs and idles fine? What are the details here?

The codes listed are simple circuit checks I can walk you through. It doesn't have a chip on the PCM does it?

Click to expand...

I thought I tagged you in the response. Sorry. The short term FT seem to act normally at idle and float into the negative on the road. The long term FT is around -16.5. I have reset the memory a few times and drove it. Always returns to the same.

Daryl said:

Sounds like the timing is retarded.

Click to expand...

I’m wondering. The PO put a new timing chain and cover on it not long before I got it. I know timing is computer controlled BUT could he have gotten off one tooth and it still run ? What’s the easiest way to verify he did it right ? It has timing marks. Can you old school it with a timing light ?

LostintheForest said:

I was thinking a cracked manifold or leaking manifold gasket, and or that ECT being involved. Coolant temps have a lot to do with fuel mapping. Idk that it would pull fuel to the point of melting the manifold, that’s telling me air is getting in where it shouldn’t and the computer doesn’t know to compensate with more fuel.

You may consider a smoke test to check for leaks, but I have no suggestions on how to get a hold of a smoke machine

Click to expand...

I have access to a smoker at my old man’s mechanic shop in town. It’s nice to have friends with toys lol

ItchyDong said:

I'm a sucker for chasing DTC's. The PCM is pretty smart. Circuit high codes are generally open or intermittently open signal wires. Does your MAP sensor reading show barometric pressure with the Key on/Engine Off?

You have negative fuel trims which means the PCM's understanding is that there's a rich condition present. Sounds to me like it's a false indication. MAP and Coolant temp are two offenders for false conditions like this. Also, the air intake.... Does the piece of crap aftermarket intake you put on still utilize the Intake Air temp sensor?

What's the freeze frame data for the ECT and MAP codes?

I don't see you mention your ECT temps or data pids. What do they look like? You mention air temps but I didn't see you address any data for the ECT code you have.

Are you going into closed loop?

Click to expand...

I can’t seem to locate the intake air temp sensor. I assumed it would be in the intake plenum like most stuff but it’s not there on the old intake housing. As I mentioned before the PO really hacked this poor jeep up. I was getting an intake air reading last night of 163 degrees and it was moving with throttle so it is still plugged up somewhere. I’ll look more for it today to see if PO stuffed it somewhere. The ETC reads on the scanner vs the engine are a bit off. The temp at idle last night was 193 but the gauge was reading about 215. Yes it goes into closed loop on the fuel after it warms up. I wish I could send you this video where I click through all the live stream data with it idling and the engine warm. You may spy something I’m overlooking. Like I’ve stated earlier my knowledge on computers and engines this old is pretty limited. I know all the concepts are the same as newer stuff I’m used to working on but I’m not familiar with nominal values and their norms. Thanks for the help. If there’s a way to send this live stream data to you let me know. I’ll sure shoot it that way.

ItchyDong said:

I'm a sucker for chasing DTC's. The PCM is pretty smart. Circuit high codes are generally open or intermittently open signal wires. Does your MAP sensor reading show barometric pressure with the Key on/Engine Off?

You have negative fuel trims which means the PCM's understanding is that there's a rich condition present. Sounds to me like it's a false indication. MAP and Coolant temp are two offenders for false conditions like this. Also, the air intake.... Does the piece of crap aftermarket intake you put on still utilize the Intake Air temp sensor?

What's the freeze frame data for the ECT and MAP codes?

I don't see you mention your ECT temps or data pids. What do they look like? You mention air temps but I didn't see you address any data for the ECT code you have.

Are you going into closed loop?

Click to expand...

I missed one answer. Yes I’m getting readings on the MAP with engine off key on. It was shaped g a barometric pressure about 29.85. Give or take a few behind the decimal. With the key on engine off. I was seeing around 7 on the MaP and engine on about 15.2 at idle. It drops out to around 1.5 on the highway at full throttle. I’m gonna go look for that damn intake air sensor. If that’s the issue I’ll #1 be happy it was simple and #2 kick myself in the ass for not realizing something so simple. lol but I’m a sucker for getting pulled into a vehicle issue and over analyzing to the point of missing the small stuff. I work part time at my dad’s mechanic shop in town to help out when I can when they get swamped so I have access to all sorts of wonderful toys and technology. He’s 71 but the man still keeps current on all the scan tools and things to work on the newest technology. I think he has put three of the Snap On mans kids through college

LostintheForest said:

I meant to ask, have you verified grounds?

Click to expand...

I’ll go pull a ground wiring diagram off the old man’s Shop Key today and check them. Good thought.

hear said:

You can’t post videos natively here. You’ll have to upload to YouTube and then post the link here.

Click to expand...

Never done that. I’ll give it a try.

That wasn’t too hard. Here’s the video I took last night. Ignore the dog that won’t shut the hell up in the background. He thinks if the jeep cranks he’s supposed to be in it

ItchyDong said:

A cracked manifold will give a false lean reading to the upstream O2 sensor, which in turn will tell the computer to add MORE fuel not take it away.

Anyways, I looked at the data. The only thing that stands out to me is the -17 LTFT. She's taking away fuel for some reason. You have two codes that you posted that deal with exactly that issue, you're telling me you don't know where your IAT is, and you still haven't posted freeze frame data for the ECT and MAP. Hell, even a stuck open purge valve can cause the computer to pull fuel away, and you have a code for that too.

What happens when you clear codes? Do they come right back?

If I were you, I'd trouble shoot each of these codes and quit blindly throwing parts and theories at it.

Click to expand...

There is absolutely zero places for it to go into the old intake plenum. So no sir. I haven’t a damn clue where it is. When I cleared the codes this time the only one that came back so far was the purge valve. The stuff I’ve blindly thrown at it I would most likely have anyway since I am trying to totally restore the fucked up stuff PO has done to it. I’ll get you the freeze frame data in a few minutes. I’m actually running an hour long motor vac chemical clean on the motor as we speak. It was the old unit my dad originally purchased and it found its way here. Still works great. I figure a 170k mile motor could use it. I did find some small vacuum leaks when I went to the car wash today. I repaired two of them. They were the lines to the brake booster and the purge valve solenoid. Not large but reacted when water hit them. The other vacuum leak I found is the butterfly valve shaft seals on the TB. Leaking at both ends. I just ordered a new TB. They aren’t expensive. I’ll get the freeze frame data for you now. And by the way. WHERE THE HELL IS THE INTAKE AIR SENSOR !!!