poor low rpm performance

jelly man · Post by **jelly man** » Wed Sep 17, 2008 4:59 am

I have a 92 EJ22 in my 85 wagon. It ran fine after the swap for about a year then it started running weak at low rpm. Under about 2500 rpm it barely accelerates, then when it passes a certain rpm (about 2500 my tach isn't hooked up) the engine kicks in and runs normal. This behavior is independent of throttle setting, engine temperature or vehicle speed. I've replaced the thermostat, maf sensor, O2 sensor and checked the tps(it's ok). It's runs rich at low rpm evidently. It started a couple months before my emissions test. It fouled out plugs and wiped out the O2 sensor (all were covered with black soot. It was running way rich at both low and high rpm. When I replaced the O2 sensor the high rpm passed but the low rpm was still rich-about 3 times the maximum allowable HC and CO limits. The new cat brought low speed emissions into compliance also but if I keep running it I'll wipe out the O2 sensor and the cat again. The computer isn't setting any codes. I'm stumped - any ideas?

93forestpearl · Post by **93forestpearl** » Wed Sep 17, 2008 5:04 am

My beater ran like until I changed the plugs. The set that was in there was at .075" gap - not good, considering the spec is .040-.042".

jelly man · Post by **jelly man** » Wed Sep 17, 2008 8:05 am

already checked that - plugs are fine - just starting to show a very little fouling again that was easily cleaned off.

BXSS · Post by **BXSS** » Wed Sep 17, 2008 2:11 pm

Sounds like its running like crap on closed loop & ok on open loop (? the exact rpm# for your particular motor - my OBDII PII 2.2 does open loop @ 3700RPMS).

Based on what you wrote you covered almost all the bases, but you did not change the coolant temp sensor & if it is bad it can cause crazy afr's...

jelly man · Post by **jelly man** » Thu Sep 18, 2008 12:01 am

My mistake -- I meant to say that I replaced the coolant temperature sensor -- not the thermostat. It's running bad on closed loop mode also. It's independent of engine temperature - It only depends on rpm.

ericem · Post by **ericem** » Thu Sep 18, 2008 12:09 am

I wonder if your knock sensor is cracked. I don't know if it would make that huge of a performance difference but it can help indeed.

BXSS · Post by **BXSS** » Thu Sep 18, 2008 2:19 pm

HMMMM, looks like you did cover just about every base.

?????

ciper · Post by **ciper** » Thu Sep 18, 2008 8:18 pm

I know you said it ran fine for a year but check this thread out -

http://bbs.legacycentral.org/viewtopic.php?t=35236

Essentially the intake cancels out some pulses that prevent the MAF from getting confused at low rpm.

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poor low rpm performance

poor low rpm performance