Loss of power when warm

Tiny
BRIAN DRYER
  • MEMBER
  • 2003 CHRYSLER SEBRING
  • 2.4L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 135,000 MILES
I originally thought this was a transmission problem but have since begun to believe it is an engine problem. 2.4L DOHC.

Car runs and shifts perfectly when started cold. Idles well and goes into gear smoothly to leave home. After ten to fifteen minutes it holds gears a very long time and I must feather off the accelerator to get it to up-shift. Then I have to feather back on the gas or it will downshift again. After a long enough time it works its way all the way to high gear and doing the speed limit. Any hard accelerator is an instant downshift. To gain speed I must just slowly increase accelerator and let the vehicle speed very slowly increase. No codes. All fluids clean and clear.

Done so far:
1. Replaced shift solenoid and input/output sensors. Had TCM quick learn completed at dealer. No indication of a TCM failure and no codes.
2. Replaced plugs and wires. Did make it idle smoother and at lower rpm's, but did not solve main issue.
3. Replace TPS. No change.
4. Replaced MAP sensor. No change
5. Cleaned MAF sensor with proper cleaner. It is intact and no change.
6. Pulled IAC and it moves in and out, cleaned with spray and reinstalled. No change.
7. Pulled fuel rail, removed all injectors and used nine volt battery to open and spray carburetor cleaner through them to clean jets. New o-rings and reinstalled. No change.
8. Bought IR thermometer and measured temperature at catalytic converter (part of exhaust manifold on the four cylinder) and it was 338 at inlet and 438 at rear. Measured at what I believe is a resonator (is this correct?) And it was the same in and out and noticeably cooler than at the catalytic converter.
9. Disconnected front o2 sensor wire to default to normal rich/lean without o2 adjustment. No change. Also wanted to see if ECM was capable of throwing a code and it did instantly. Reconnected.
10. Used IR Thermometer to measure engine coolant temp at thermostat housing (didn't trust gauge which was perfectly center on temp) and it read 194 degrees after a long stumbling drive home from buying the IR.
11. Cleaned throttle body and replaced air filter. No obstructions. No change.
12. Removed PCV valve. Rattled nicely. Sprayed with cleaner and reinstalled.
13. Checked for vacuum leaks at all hoses with carburetor cleaner and no engine reaction.
Not burning oil visibly. Minor blow back at oil cap when running but not major. No coolant loss.

Could it be coil getting hot? Exhaust obstruction even though cat seems okay? Temperature sensor? Fuel pump? Running out of options here. I have no means to check fuel pressure but tank is full and dropping it would be tough. I have not explored that much because acceleration and fuel seems fine until engine is warmed up. Any advice is greatly appreciated.
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Tuesday, July 11th, 2017 AT 8:08 AM

4 Replies

Tiny
HMAC300
  • EXPERT
First thing you should do is to scan for codes and check fuel pressure with a gauge as it could be either. Auto parts rent gauge start there then check all fuses as well under hood with a test light/voltmeter. See link.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Tuesday, July 11th, 2017 AT 9:42 AM
Tiny
BRIAN DRYER
  • MEMBER
I'll try to be more specific instead of short winded. 2003 2.4L dohc sebring. Has new map sensor, new tps, new coolant sensor, new plugs and wires, cleaned ambient air sensor - no maf sensor, verified IAC is functioning and cleaned, new shift solenoid, new in/out sensors, new air cleaner, new o2 sensors (2 on 4 cyl), new engine oil, new tranny oil. TCM checked and quick learned after fluid change. No codes, no dash lights. $10K scanner shows only batt disconnect when working on it. No pending or current codes. Vacuum is 25+ pounds and holds at 2500 rpm. Drops and returns quickly to 25+ pound when snap throttle. Temp at cat increased with new o2 sensors. Reading on OBD2 at shop yesterday showed cat at 1000 degrees. Assuming it wouldn't get that hot if not working? Also assuming no drop in vacuum indicates no obstruction? Haven't tried loosening the manifold connection to allow leak, but thinking it's a waste of time with vacuum test. With the new o2 sensors it is worse that previously. Will max out at 10mph with throaty sounding intake pretty quickly.
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Friday, July 14th, 2017 AT 9:59 AM
Tiny
BRIAN DRYER
  • MEMBER
Oh. And fuel rail pressure at 60 pounds even when acting up (guage taped to windshield)
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Friday, July 14th, 2017 AT 10:00 AM
Tiny
HMAC300
  • EXPERT
1000 @ converter no blog deal disconnect exhaust at converter are if improves repost question as I am unable to get to manual until next week
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Friday, July 14th, 2017 AT 10:18 AM

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