Chrysler Repair: No acceleration 97 2.5L V-6, mixture problem, coolant temp

Question
QUESTION: 97 Cirrus 2.5L. Started missing badly and running rough - P0305 then P0303 then P0300. Replaced ign. wires, dist cap and rotor - plugs new 25km ago and looked fine. Problem was poor connection (corroded) at #5 ign wire to cap. Started right up after reassembly and appeared to run OK. Took for test drive have no power on acceleration. Drove 30 - 40 KM no change. Idles fine most of time with occasional stumble but never stalled in 10 minutes of idling. Acceleration had not been a problem up to now. Had EGR (rough idling and stalling) a month ago and fixed that by cleaning EGR valve - has been good since. Appreciate your thoughts.

ANSWER: Hi Allen,
Have you disconnected the battery to clear the codes, then driven it, then checked for new fault codes? If so, let me know what they are. When you cleaned the egr did you lubricate the stem with some penetrating oil? Try that, if not, just spray some WD-40 on the stem where it enters the body of the valve and move it back and forth with the tip of a screwdriver inserted in the slot of the stem.
Roland
PS Use the 'thank/rate' tabe to get back to me without having to wait for me to be available to take a question. There is a space for comments, th which I will reply. Sorry for the delay...I just found your question in the 'pool' to which it had been referred.

Roland Codes cleared while I was installing ign wires, dist. cap and rotor. After Aprox 100km of driving get P0304, 302, 300. EGR valve is free and responds to vacuum pump. Fuel pressure while running is 51psi and no leak down. Runs fine cold. Miss and hesitates when at operating temp. Sorry delay responding - a foot snow slowed me down and I wanted to do more testing before I responded. Thanks. Allen


Hi Allen,
It does appear that you have a multiple cylinder misfire.
If you have good power when the engine is cold, then I would suspect a mixture problem when the engine is warm. This could be due to a coolant temp sensor that isn't changing its resistance (downward as the engine warms, so see if it drops from initial 10k or so ohms cold down to be in the range of 700-1000 ohms at operating temp). Same test for the intake air temp sensor. Check the PCV valve, replace if quite old. Look over evap emission control hoses/clamps. On the spark side: check the resistance of pin 1 (of the 2-pin socket of the distributor) so as to verify primary winding is 0.6-0.8 ohm to ground. Check resistance between same pin 1 to tower of distributor to measure secondary resistance to be be 12k-18k ohms.
Check wiring to injectors. Listen to sound of injectors.
All the other possibilities involve mechanical issues with the engine that don't seem to be evident?
Thanks for the nomination. Do let me know if you find the answer.
Roland

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QUESTION: Roland
I should have added in my last note - the hesitation and missing is at acceleration only. Runs fine if you baby it up to speed. As high as 100km with no apparent problem. We're wondering about coil/distributor issue. Was replace 2years 30000km ago with reman unit. Difficult to measure distributor resistance on a hot engine!

Allen

Answer
Hi Allen,
I wonder how things worked out with the headlamps? You can report back if you like by the 'thank/rate' tab below, without having to wait for me to be 'available' to take a question. While you are there, if my answer was helpful I would appreciate a vote of 'yes' for the 'nomination to be expert of the month'. I am in a close race for that honor so every vote is helful. Thanks in advance.
Roland







Hi Allen,
I understand that difficulty, but perhaps of-value readings would show up in measuring it cold, or at least cooled to the point where you can handle the 2-wire plug and tower/distributor cap removal task.
If indeed the issue is hesitation on acceleration, rather than missing when cruising at highway speed, you might want to test the smoothness of the resistance changing of the throttle position sensor wiper as you very the throttle opening. Slight mechanical/electrical glitches in that interface can cause stuttering at cruise when you move the throttle. Also consider cleaning the throttle body throat and both sides of the butterfly plate.
Roland