Occasional low idle almost stalling , now a P0304

[John B Kobberstad]

1996 Doge Neon
287,??? miles
DOHC 4 cyl
5 spd manual

Looking 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 failed

Didn’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 possible

O2 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.

Topic

[EricTheCarGuy]

That plug is oil fouled big time. I would say your miss is the result of a mechanical issue in that cylinder.

[hbvx]

Is that cylinder with the fouled plug nearest the PCV? Stuck rings in that cylinder?

You may could try piston soakings before each oil change. There are some products you can ‘safely’ run with a shorter oil change interval, and I can give some reliable advice in that area as I’ve read/researched it for 3 years now if you want some product/procedure recommendations if it’s an oil control ring issue.

[John B Kobberstad]

Last night I removed R&R’d all the stark plugs. I found that the gap on all plugs was about 0.045 Spec is between 0.033 and 0.038 set all to the correct gap. When I drive it the vehicle runs fine. If I’m going 50 and let off the gas and put the clutch in the idle falls to 500 RPM sometimes it will go back up to about 900 and other times it will go down to 0 and die. Since my wife drives to the city and traffic is stop and go a lot of the time I can’t have her driving a car that is stalling all the time. Since it hasn’t started raining yet next thing is to check the fuel pressure and spark. After that check the MAP / IAT sensor in the intake manifold. Last night at idle (if I could get it to idle) MAP was reading 2.8V to 3.0V which I’m not sure but I think is too high. For some reason I think it should be down to about 1.8V max at idle. Off to do some checking!

[John B Kobberstad]

Just checked fuel pressure. Spec is 49 Psi, it was 0 Psi when I initially connected to the rail. Key on (not on start) 45 Psi. Start and running (cold start) needle vibrating between 46 and 49 PSI at idle. At the time when the idle got lower, and really bad, the Psi had a wider variation between 45 Psi and 49 Psi, then would go back to a smoother idle and 47 to 49 Psi. I just put a new pump motor in back in May I think it was. Power washed the inside of the plastic gas tank got it nice and clean and dried it and filled with fresh gas. Looks like I may need to replace it again.

[John B Kobberstad]

25 minutes after engine was shut off and I’ve lost pressure from 45 down to 39.

[John B Kobberstad]

40 minutes after shut off it’s down to 25 Psi Pressure is not holding do not see any leaks or smell any gas fumes.

[college man]

If a new fuel pump is needed.Try a different brand from
what was used last time. (Delphi)

[John B Kobberstad]

Got a Carter to put in. Tested it and it HOLDS the pressure at spec (49 Psi) which is above the 45 Psi that the one that’s in there now has and then looses.

Attachments:

• NeonCarterP74732MFPM.JPG

[John B Kobberstad]

Old pump has now lost pressure down to 10 Psi after less than 2 hours.

[mckrishes]

Inconsistent fuel pressure readings. Sounds like the fuel pump unless there is a leak somewere, but you’ve checked that already.

[Charles]

I read through all your posts and think you found the problem but kinda dismissed it. You stated you tested the injectors and the #4 did not affect the engine when disabled? What if the injector is leaking (sticking open)? Fuel pressure would bleed off. Mixture would be too rich. Engine would idle bad. Etc. Remove the injector and test it off the car or replace it. Personally, I’m so cheap I would go to U-pull-it or Pull-a-part and pick up the whole fuel rail with injectors and regulator for about 30 bucks. Pick up a connector for the injector as well and use 12 volts to open and carburetor cleaner to spray through.

You might also want to check for an intake leak. Just get the garden hose out and run a medium stream of water over the intake to see if you cause a difference in idle. If the idle changes you can investigate that area further but it will probably be a bad gasket. Shop guys don’t do this because they have to go outside.

[John B Kobberstad]

I’ve got a set of 4 used injectors for the 1st gen Neon DOHC that I bought last week. I’m hoping they will arrive here tomorrow. Don’t have U-pull-it or Pull-a-part near me wish I did.

[dreamer2355]

I would definitely do a injector leak down test as stated above, you may have a leaking injector.

Also, for the fuel pressure, did you try to crimp off the return line (if its not a return-less system) to see if the pressure holds?

I would yield Eric’s advice too and do a quick compression test and cylinder leak down test.

Keep us posted.

[John B Kobberstad]

This past weekend was on and off rain so I didn’t get everything I wanted to get done done. Removed the quick connect fuel line from the rail to the line at the fire wall after I noticed what I thought was oil on the quick connect fitting and up about 1 1/2 inches from the fuel rail. Moved it, and found a small gas leak which turned into a small pinhole leak and started spraying out when I moved it again. Checked fuel pressure at the line at the firewall and it was 48 Psi. Went to the basement and got a length of gas line hose and a couple clamps and repaired it. Cleaned and saved the quick connect fittings as they should still be good and a new nylon hose of proper length should be able to repair it later. This did not fix the problems, but I decided not to replace the fuel pump as the pressure was now acceptable (and I really did not want to get under the vehicle, drain the tank, remove the tank and go through the rest of what is required to replace the pump module). Next I used the Snap On MT2500 and checked the MAP / IAT sensor (single sensor located in the intake manifold) readings seemed high 2.8 to 3.0 at idle. Scanner said it should be 1.3 to 1.8 at idle and it said that the IAT temperature should be lower than coolant temperature which it was not . It was 19 degrees higher than the coolant temp 227 / 208. Next setp was th remove and clean MAP / IAT sensor. Took the 2 mounting screws out of the sensor and removed it from the intake manifold (nasty black soot tar). Removed the 4 pin plug from the sensor and found corrosion in the plug and on the pins. Just remembered I forgot to put some dielectric grease on that before I put it back together. Cleaned the sensor with some soap and water and a small cleaning brush like you would use to clean the a paint sprayer, rinsed and blew it out with air compressor. Re installed the sensor and reset codes. Took it for a couple rides locally and the idle seems to be much better. Had my wife take it for a ride and had no issue with the vehicle stalling. The P0304 code came back on this morning so I reset it and she drove it 75 miles to work. She sent me a text, when she got to work, that she had no stalling issues. She didn’t say whether the CEL /MIL came on but I would imagine it will on the trip home.

Got my OTC 7448 fuel injector cleaner out yesterday and have it set up to do a fuel injector cleaning. Have 4 used injectors being delivered today and will probably try putting one in cyl 4 and see if that helps. Will also check the spark plugs after the injector cleaning and re clean if necessary.

I am in the process of purchasing a used fuel rail and will modify it so that I can clean injectors off the vehicle and filter (recycle) the cleaner for reuse if possible.

[mckrishes]

So far so good. So it seems like a combination of things that is leading to your low idle/stalling problem and your getting it done one by one.

[Author]

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