hiway speed power loss

hey my renix 4.0 acts like it outruns the fuel supply. pump at idle is 35psi and when you rev it is pegged at 40 psi. could the TPS or CPS be stopping the timing to advance? i can barely do 55 to 60 mph.everything works and shifts, just no top end.no vac leaks, new vac line assemblies . the EGR is disabled and not leaking.

Check your cat

Does it get worse the hotter the engine gets? That's really the tell tale sign of the Cat. My 98 XJ would be okay(not right) when I first started it up, would buck if I tried to give it too much gas, and would get worse as I approached operating temperature. 1/2 the insides of the cat was missing and clogging the system. Once that was changed out, it ran great and not as hot.

The fuel pressure (as I recall) at idle should be about 29-31 with the vacuum attached and 39 with no vacuum attached on Renix. Is there a smell of gas at the vacuum line of the Fuel Pressure Regulator FPR nipple when you pull it? If yes, then FPR diaphragm is leaking fuel into the engine by passing the injectors and computer.

Bad Cat is a possible cause.

Bad TPS is very possible cause on Renix. It can be tested with an ohm meter, with power off. I published the normal and bad TPS specs that cause this years ago he in a thread named "The RenX Files" Google it, the data is about 1/2 way into the 300 some odd post thread. The rest is a great read for any one with an 87-90 Renix jeep.

CPS on a Renix, to my knowledge will not cause this, it might on HO, they use a different kind of TPS.

My money is on a bad TPS or cat, or both. I had both when I bought my first renix.

In fact my first renix had a plugged, major cold spots radiator, leaking coolant bottle at the cap, totally bad O2 sensor, bad TPS on the rear transmission side, but not on the engine ECU-TPS side that caused it take 3 minutes at WOT to go from 0-60 mphs, , a very clogged Cat, Transmission leak from hell at the dipstick o-ring seal, just for starters. My 87 Wagoneer

av8or2k said:

Does it get worse the hotter the engine gets? That's really the tell tale sign of the Cat. My 98 XJ would be okay(not right) when I first started it up, would buck if I tried to give it too much gas, and would get worse as I approached operating temperature. 1/2 the insides of the cat was missing and clogging the system. Once that was changed out, it ran great and not as hot.

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Every bad Cat I had but one was so bad it showed up revving the engine cold in park or in gear. Some times you can tap the casing and hear the guts move around loose, not need to run the engine. One recent one showed up as a cylinder 1 misfire on my 96 Ford Taurus, OBD-II. That was a fun one to figure out. But the Cats were plug pretty bad....it had no issues yet with a lack of power that I know of, but it had been run with coolant head gasket leaks that clogged up the Cats over time.

car good fuels system good. it is partially my rubber hose on the fuel pump was leaking. now i tihnk i have a TPS/IAC problem to work out.

thank you mike

Gunter said:

car good fuels system good. it is partially my rubber hose on the fuel pump was leaking. now i tihnk i have a TPS/IAC problem to work out.

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I have seen several of these with similar problems turn out to be that fuel pump hose. Hard to test with a scanner or meter LOL. But doesn't it show up with a fuel pressure leak down test?

How old are your spark plugs?