Engine performance problem?

[ndsnewleg]

Thanks to all who offer their expertise and experience on this site. I've been reading it for awhile now trying to narrow down a problem I have been having for some time. I have a 90 EJ22 MT, 170K. I have improved engine performance but not to satisfaction. It seems to run pretty normally from start to near operating temp. Then starts to lose smooth power after about 15 min and at 30 min runs rough as if engine was out of balance w/loss of power. I can cruise on the flat at 80 mph all day long but exceleration is flat and hills are worse. On occasion I have a lifter stick on start up but can hear a slight lifter noise continuously when listening closely under hood. I've also had it sound like it had no muffler once on start up. That was weird.

 

My question is can this lifter noise be cause of problem.

 

Codes I have had. MAF (replaced w/rebuilt unit). IAC (cleaned but have no idle problem except when 10 degrees or colder). Vapor purge solenoid (tested and swapped).

 

Replaced new: O2 sensor, temp sensor, knock sensor, plugs, wires, air/fuel filters.

 

Swapped: sensors - crank, cam, ignitor, tps, purge solenoid, ecu, coil.

 

Cleaned and/or tested: tps, fuel pump, injector cleaners, Sea foam into combustion chamber and oil. Cat looked at 3 times, once examining back end, 2 said it was ok 3rd said I needed a new one but I clearly got the impression they needed the work.

 

Cleaning injectors and combustion chambers seems to have made most improvement.

 

Seems like I have left a number of things out but I think that covers most of it.

 

I've done a lot of work on this car and it still seems strong but for this vexing problem. Would like to keep it for another 50K. Appreciate any help.

 

Thanks, Ron

[Setright]

The engine runs a slightly rich mixture at start-up to get things warmed up faster.

Signals from the O2 sensor are ignored until the engine coolant reaches normal operating temperature. This is because the catalyst needs to be hot to work properly.

 

SO, I would suspect that something is up with your O2 sensor or circuit. If the new sensor can be trusted, then I think it is likely that you have a GROUND problem. The O2 sensor uses the exhaust piping as ground connection. If it's old and rusty....you need to fit a "three wire" O2 sensor or replace the exhaust. Probably cheapest to get a three wire sensor - the third is the ground.

 

Good luck!

[ndsnewleg]

Thanks for the reply. Do you think I would expect to see much of a rise in HC or CO if O2 sensor wasn't grounding. Last emissions test was march 04 and HC went down slightly and CO was up about 1.4 gpm from previous test to 7.7932 gpm which is well within Pass range. Cat and O2 sensor also read Pass. I've considered a failing injector but when I have done an Ohm test they are all slightly above normal parameters. Are the 3 wire O2 sensors from later models and if so do you know which ones. Thanks again.