Idle and issue at low revs

I like the way you think. The AJ16 engines in these vehicles seem to have a life of their own. Mine likes to idle in gear at 650 without so much as a blip.
As for the ATF, I’d be willing to bet you are correct.

Yesterday I started it in my driveway, warmed it up and then put it through every gear with foot on brake. Returned it to idle. The fluid is midway in the hash mark area. Exactly where it was when I replaced the fluid a good while ago.

Today I planned to drive it and look at the fluid again. Its not idling smoothly but it does not sound like misfiring. I got halfway down my long driveway and stopped to reverse having forgotten something. It hesitated several times - very much like a fuel feed problem. I don’t believe its transmission fluid.

I got no codes.

I’m going to check out the fuel relay first. And its fine. I exchanged it for a known good new one and behavior was identical. Barely got back up drive in reverse. Feels like fuel starvation.

Clogged fuel filter?

AJ16 you say?

When was the last time you cleaned your throttle body?

How are the coils and plugs?

Where are you idling at? Is it a nice consistent idle. Does the needle move at all when engine is hot, at a stop light? You’d have to watch for about 60 seconds.

Could be the crank position sensor as well. Also the EGR. Lastly a vacuum leak. I had one at the intake manifold, and it seemed very difficult for mechanics to find.

This engine is so stingy with codes…

Its not that old but I’m going to change it anyway as a precaution.

While I’m doing these things I need to test fuel pressure. I opened up a separate thread on building a tester. I’d like to get the parts for that so I do not lose too much time.

Add a little transmission fluid…
Then you know its off the table.
Then if no codes, change your gas filter, run high octane .
Yes when HOT if the throttle body butterfly is built up with CARBON on the back off it along with the shaft…VERY common, you will get a stumble as the butterfly does not close all the way leaving a vacuum leak as its not sealed and draws too much air.
Do the above you should be fine…
Lastly , if there is CRAP in the tank and the level in the tank is low, your restricting the flow…
Fill tank,high octane then a bottle of chevron/techron black bottle only.
It will clean out the screen and the injectors…
AGAIN all this if there are NO CODES…
Good luck
gtjoey1314

20,000 miles would not be enough for you to go back in there, but take the hose off and take a look. If it’s gunky on from the outside, the gunk will be much worse inside the butterfly.

I had a slight drop in RPMs every 32 seconds with a hot engine at a stop light. With the AC, headlights, and other accessories on, that slight dip was amplified to something enough to stall the engine out. That came from a failing intake manifold gasket.

There’s a difference between the CPS and the CKPS. I’m sure you got the right one, the hidden one, but if you’re talking about the one looking at you when the hood is up from the passengers side, you don’t.

Clean the EGR again to see if it helps. I replace the darn thing. Was it giving you a problem, or were you just being proactive?

If the coils are originals, then that could easily be the culprit. Although it’s not all inclusive, check for cracks, or any damage to the rubber boot. While there, check for oil in the plug wells. If there’s oil there, your seals have perished. Lastly, replace the plugs while you’re looking around. If you can’t remember, then it’s time. At $3/ea and ten minutes of your time, it’ll be time well spent.

Add a little transmission fluid…
I am going to do that
Then you know its off the table.
Then if no codes, change your gas filter, run high octane .
Yes when HOT if the throttle body butterfly is built up with CARBON on the back off it along with the shaft…VERY common, you will get a stumble as the butterfly does not close all the way leaving a vacuum leak as its not sealed and draws too much air.
I plan on re-checking the air filter - MAF throttle body/butterfly
Do the above you should be fine…
Lastly , if there is CRAP in the tank and the level in the tank is low, your restricting the flow…
Fill tank,high octane then a bottle of chevron/techron black bottle only.
It will clean out the screen and the injectors…
The car is always filled with a 1/4 - 1/2 tank of gas left. Last week I put a bottle of Chevron/Techron in it and filled with high octane. It was driving ok then
AGAIN all this if there are NO CODES…

Veekay

Geekay

27m

There’s a difference between the CPS and the CKPS. I’m sure you got the right one, the hidden one, but if you’re talking about the one looking at you when the hood is up from the passengers side, you don’t.
I was referring to the Crankshaft Position Sensor. I did remove the connector and hard wire the new one as I saw cracks in the wiring near the connector. I plan on re-installing a 2 wire connector. Wires secured with Posi-locks and taped.

Clean the EGR again to see if it helps. I replace the darn thing. Was it giving you a problem, or were you just being proactive?
I was working on 2 codes. Secondary air and EGR. I replaced the connector on the air pump and cleaned the EGR valve and codes disappeared. That was 2-3 months ago.

If the coils are originals, then that could easily be the culprit. Although it’s not all inclusive, check for cracks, or any damage to the rubber boot. While there, check for oil in the plug wells. If there’s oil there, your seals have perished. Lastly, replace the plugs while you’re looking around. If you can’t remember, then it’s time. At $3/ea and ten minutes of your time, it’ll be time well spent.
Over the last 2 years or so I’ve replaced all the coils. Plugs too. I did extensive work on the camshaft cover because of the coil arcing problem. But…I am going to inspect everything again. I don’t believe the plugs are due. They are not that old. The way the car behaved felt like crankshaft sensor or fuel to me
Anytime I have had plugs or coil issues I have gotten codes.

My camshaft cover work:
Part 1
Part 2

Okay your on the right track
DONT ADD MORE CHEVRON , one is enought.
Get to the throttle body again.
Look the fuel pump can be the issue if its old…
If it gets better after the chevron, the pump could be collapsing inside as well.
ALSO USE FACTORY PLUGS.
GOOD LUCK.
GTJOEY1314

Oh I know you then! I’ve seen this work before!!! Impressive and educational. Would mind having access to a machine like that. I had my cover redone by some magnesium powdercoating expert in the UK…spoiler alert, don’t bother to powdercoat the inside of the camcover. Mine has started to crack up, so I’ll have to remove that powdercoat soon. Summertime job.

Replacing cracked wires is always a good thing, and could very well be the cause of this.

I’ve never had any luck with simply cleaning EGRs. The problem returned, and it takes some luck for the car to throw an EGR code in the first place! It stalled out my engine when passing through a toll booth. Luckily I had ample room to pull over. After replacing it, I never had a problem again…with the EGR.

Its raining here so I cannot work on the car until tomorrow afternoon. Garage is full. I am off in the morning to get parts for a fuel pressure test kit. I kept that thread separate as its likely going to be searched for as a topic of its own. Regarding the fuel pump I’d like to get opinions on this video in case it turns out to be the culprit. Video Link To Changing X300 Fuel Pump “The Easy Way”

I’ve used NGK since I’ve owned it at 80k. 276k now.

I’ve been through the EGR thing a few times. I really don’t think that is the issue.

One thing I need to re-visit. It seems to me that some years ago (7 or 8 perhaps) I had an issue with fuel that turned out to be a connector in the trunk/boot that ran across the fuel tank. As I recall the connector had burned (not good ) connections. I’m wondering if that was the line from the relay to the fuel pump. Hmm…just thought about that. I need to re-check that line. At least I think it was the X300 and not my XJ40. Dang!

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IMHO Techron doesn’t work very well. If you really want to dissolve the coating that comes from gasoline/petrol and carbon, buy Berryman’s Chemtool B-12. You can clean out deposits that Techron can’t. If you have 50,000 miles on your engine between fuel-system treatments, buy some Berryman’s B-60 “High Mileage” fuel system treatment. You can clean out every bit of carbon and sludge from both the fuel system and combustion chambers. Trust me on this one, you can’t beat the B-60 for cleaning every bit of carbon and varnish with which it comes in contact.
You can believe every word I say.

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I’ll make a note of Berryman’s.

Yesterday I changed the plugs -27k or so on Iridiums I have been using consecutively for 10 years or so. I went with the std. Champion hotter plug. I noticed that 5 of the 6 coils (QYL installed in May 2019 after misfire codes) have small cracks . I’ve ordered new ones.

After the above and cleaning out the throttle body (small oil traces) I started the car and it idles very well at about 750 rpm and the engine runs fine in neutral at 5,500 rpms. No sign of hesitation. When I tried to run the car up my driveway slope it tried to stall out under load. I’ve pulled it back into the parking spot. I’m going to change the relay to a brand new one and do a fuel pressure check. What will the fuel pressure check yield if everything is running normally at idle and with high revs applied? Can someone give me the correct fuel pressure reading for the X300 - idle with and without vacuum and with Mityvac applied?

I am going to add a small amount of ATF, change the fuel filter, check for vacuum leak and possibly re-clean the EGR.

I also saw this comment on another forum. Interested to hear more about this.
"The transmission connector on the transmission body left side , this is a " Deutsch " connector and has a unconventional way to remove it.This gives trouble around the 1st gear range from park as the transmission and engine ECU must coordinate with each other.

Interesting. Where did you find QYL coils for purchase?

I bought the QYL off Amazon. Disappointed that 5 are showing cracks after so few miles. Also of interest is that the Glyptal coating is flaking in the coil area of the cover in the same 5 cylinders.

UPDATE:
Yesterday I added some transmission fluid and also installed a new Flosser relay. I don’t normally change more than one thing at a time but I have to reduce the risk of my car stalling on my long one lane driveway - blocking all in and out access and requiring a tow truck.

I took the car for 2 test drives. 1st - a 15 mile each way trip with 90 percent hwy but about 6 stops on each leg. No issues. 2nd - a 20 mile round trip on country roads with 5-6 stops. No issues.

I can’t be certain which of the 4 changes I made in the last few days may have affected the issue:

  1. Changed plugs which looked fine.
  2. Cleaned throttle body which was not very dirty.
  3. Added some (1/2 -3/4 quart) transmission fluid.
  4. New fuel relay (the one I replaced was the original and tested fine).

I can say that the transmission fluid now reads high. After the 1st test drive I left the car idling and immediately tested the level. It is at the top of the bend in the dipstick. Previously it was in the center of the hatch marks when warm. That is quite a bit higher than the hatch marks.

More test driving today.

Btw - the fluid I am using is Castrol Transmax.

Not done:

  1. Fuel Pressure / Fuel Regulator tests
  2. Fuel filter (Current one is less than 20k miles old)
  3. Cleaning of transmission connector
  4. Vacuum test for leaks
  5. EGR clean ( was done not too long ago < 10k )

The car idles right at 700 rpm in gear at a standstill.

DONT OVER THINK OR KILL YOURSELF, Just add the fluid and enjoy the ride :slight_smile: With love, GTJOEY1314