95cherokee89

Update.

somethings still not right, it's still underpowered on the highway, if I floor it, it wont go past 140k. And when it's cold and I accelerate, it will bog down and sputter a bit then pick up and go.

It's always had a missfire at idle and slightly rough idle, even after changing plugs/wires/injectors. Never figured out the cause, it may be related however

I have a hunch that it might be the egr valve, if it were leaking, would it cause similar symptoms?
I manually opened the valve at warm idle and it died right away, but if it weren't sealing properly, would it cause this?

DFlintstone

Booger that. I might look for 16 or so inches of vacuum at idle. Then one old girl (280K) could hold 12 at 55-60 MPH. If the EGR is leaking one of those might be low.

"won't go past 140K" ...K means thousands. Do you mean 1,400 RPM?

Goof-shot...try unplugging the CTS down under the intake, heck the IAT behind the TB up top as well while your at at it. The ECU should make it run OK on defaults without them....

95cherokee89

I meant 140km/h on the highway, it just feels underpowered.

I checked the reading on the iat and cts with a multimeter and they seemed to be good.

'90Cherokee

A leaking EGR could give a rough idle but do nothing noticeable under load.

95cherokee89

I was looking around again and I pretty sure I have a fairly substantial vacuum leak somewhere, I can hear a loud hissing sound, I'll try and fix it and see if it changes anything.

'90Cherokee

I gave more thought to your 140 top end. The aerodynamic drag of these things at that speed is substantial, I can feel mine getting pretty hard to push at that kind of speed and it's almost stock; 28" tires and a tiny lift. Your lift will increase drag as will the bigger tires, and who knows what the snorkel is doing at those speeds. It could be adding pressure that the system can't compensate for, or creating a negative pressure and starving it for air, as well as more aerodynamic drag. If you haven't re-geared it'll add more load making it feel weaker at all speeds and if you're not geared and haven't re-calibrated the speedo an indicated 140 might actually be 155+. This doesn't mean you don't have an issue, just pointing out that your power output may not be as bad as it seems. Also, since your speedo is metric and many of us are US people I assume that most people responding think you have 307k miles and not kilometers. For us you're at about 190k miles which generally isn't much for this engine where 300+ starts to raise doubt and influence some of the responses.

95cherokee89

I went around again, couldn't find any vacuum leaks.

The point I was trying to make, it just feels under powered over all compared to what it used to, I could hit 165 no problem, now if I floor it for over a minute, it will hit 140. It also will bog down and stutter for a few seconds before actually accelerating when its cold. Does that sound like a lack of fuel pressure problem? if I prime it (turning key to run without starting) the fuel pump sounds king of weird, but still not that bad, when my last one went, it got reeaaally loud.

Any thoughts?

toasterknight

My 99 is having an issue with bogging at start when its cold. I've narrowed mine down to the front o2 sensor. The motor mounts were shot and the engine shifted enough that the sensor was hitting the front shaft. Im not sure if it applies to renix as well but I would check the o2 sensors.

cruiser54

Apples and oranges.

toasterknight

Just an idea. Sorry to be off base.

'90Cherokee

And the O2 sensor is ignored under heavy load and until it's warmed up enough. Even within the operating parameters where the sensor is controlling fueling if it stops working the computer uses fixed programing which is close enough to perfect that you generally won't notice the difference. It's very unlikely that your O2 is causing your bog issue. If your sensor is dead it should be triggering the check eng. light. It might be externally damaged but still function ok.

Enough derailment, we should return to our previously scheduled program.

'90Cherokee

You'll need to test the fuel pressure to know. Many auto parts stores have pressure testers on their loaner program.

cruiser54

Not true on Renix. O2 sensor is working within 45 seconds. No CEL on Renix either.

cruiser54

Overrichness is caused mostly by, and in this order:

MAP sensor/ CTS/ IAT.

Many times the MAP gets a bad vacuum reading from that crappy tube/hose from it to the throttle body being messed up in different ways. Melted/split/ cracked/disconnected......

'90Cherokee

I was referring to the guy with the 99, but good to keep it clear. I also had no idea it comes on that quickly, interesting.