- This topic has 56 replies, 8 voices, and was last updated 12 years, 2 months ago by
.
-
Topic
-
1996 Doge Neon
287,??? miles
DOHC 4 cyl
5 spd manualLooking for SECOND opinions as to what should be the first step to take.
Wife has been complaining that when going at slow speeds only, and when putting the CLUTCH IN (not shifting to Neutral) to stop at a stop sign or traffic light, the idle goes low, almost to the point of the car stopping (engine not running stopping that is). This seems to have been happening for some time now and there has been no CEL. Yesterday on her way home the CEL came on and a P0172 code has been stored.
Trouble Code Conditions:
Engine running in closed loop, IAT (Intake Air Temperature) Sensor signal over 20ºF, altitude less than 8,000 feet, and the PCM (Power Control Module) detected too large an amount of Fuel Trim correction due to a rich A/F (Air/Fuel) condition.
Possible Causes:
Base engine fault (i.e., cam timing incorrect, oil level too high)
EVAP vapor recovery system failure (e.g., canister full of fuel)
Fuel control Sensor is out of calibration (e.g., ECT, IAT (Intake Air Temperature) or MAP (Manifold Absolute Pressure)
Fuel delivery component fault (injector leak, high fuel pressure)
O2 element is contaminated, deteriorated or it has failed
O2 heater is damaged or it has failedDidn’t get all the information last night from the scanner but will try to get it tonight when wife gets home (if the CEL is still on and the code is still stored) I did not reset the code. I believe it will extinguish the light if it does not detect the problem again within ? cycles.
Cam Timing ? If sensor says yes should it be OK
Oil level if anything was a little low was just changed 5 days ago.———————————————————————————-
With engine running at idle in neutral Parking Brake on.
Using Snap On MT2500 scanner.*EVAP – Don’t know, I think I can purge it with the scanner. Will update
IAC (Idle Air Control)- Could easily move the idle up to 2000 RPMS + and back down smoothly and without problems.
CAM Sensor – Yes Crank Sensor – Yes
*ETC – ? What is it?
*IAT/MAP (Intake Air Temperature / Manifold Absolute Pressure) – TBD (To Be Determined) I think I saw +5V there with the scanner last night will check and verify tonight).STFT (Short Term Fuel Trim)- varied from +2 to -2 (mostly between +1 and -1
*LTFT(Long Term Fuel Trim) – will update (but think it was around 12 don’t know whether + or –
———————————————————————————–
Fuel injectors did not seem to be leaking.
Fuel Pressure – will check tonight if possibleO2 element – has never been replaced since I’ve owned the vehicle (from 130,000 to 287,??? miles).
O2 heater – has never been replaced since I’ve owned the vehicle (from 130,000 to 287,???miles).Will update this thread as I find the missing info to post here.
-
Replies
-
Ya, low idle fix is the high priority. Can’t have it stalling on the expressway in rush hour traffic and keep on stalling when trying to start it. Hopefully no problems on return trip.
Consider where you’re going with this. Your problem isn’t during shut off it’s while the engine is running. What your testing with the engine off is the check valve in the fuel pump which IS important for when you first start it up but not when the engine is running. If the pump was a problem your fuel PSI readings would not be in spec which based on what you posted I would say that you are in spec.
Based on what I saw with those plugs you have a LOT of oil contamination which quite probably means compression loss. If you have significant compression loss no amount of fuel and spark is going to correct for that. You MUST address mechanical issues before anything else when it comes to performance problems.
Just checked compression. There was a little bit of oil in cylinder tubes 2 & 3 when I pulled those plugs out. Yes, I know I’ve already got the new valve cover gasket with all the tube seals and everything else that I need for that job. No oil on the spark plug threads though. The readings that I indicate for those cylinders I indicate as wet readings as I assume the oil in the tubes went into the cylinders when the plugs were removed thus a wet reading. The numbers seem consistent as there seemed to be a little more oil in cylinder tube 3 than was in 2 so it may explain why 2 was a little lower.
Cylinder 1 2 3 4
Dry 180 85
Wet 193 185 192 115
I am working on rigging up a hose connection to inject some air into cylinder 4 after I get it at TDC and see if it’s a top or bottom end leakage. It seems strange that there is such a drastic difference between #4 and #’s 1 2 3. With the mileage I have on the vehicle I would have expected #’s 1 2 3 to have much less compression than what I found. (288,??? miles mostly 85% highway driven). There has never been any major engine work on the vehicle since I have owned it.
Comments welcome. Will keep you updated as I continue with this endeavor.
Cylinder leakage test is the way to go next.
Eric has a video on this testing method.
Keep us posted.
I think we’re going to look for another 1st generation Neon for the wife this weekend. Another 5 speed DOHC 4 door with about 200,000 less miles on it. I’ll probably keep this one as a parts car if I can find a place to keep it maybe try and fix it, not really sure.
I’m thinking the fuel pressure regulator should be considered. They aren’t “forever” parts, after all. It’s a valve, and valves do get sticky, hang, etc..
Might be worth looking at, and would explain the erratic pressures, as well as the bleed down..
The fuel pressure is fine once I found the small leak in the nylon double quick connect hose that connected the steel fuel line at the firewall to the fuel rail and replaced it.
The low compression in cylinder #4 is what is now causing the consistent P0304 cylinder misfire. Have yet to acquire or fabricate the tool I need to do a leak down test on cyl #4 to determine whether it is a top or bottom end problem (rings or valves).
- You must be logged in to reply to this topic.