MayDay!! - Hard Accel Killed Idle

[87MJTIM]

Glad to see it worked for you.

[AnotherOldJeepGuy]

Well about 2 hours later and I am no where near to getting the old donut off .  I did manage to get the bolts loose, that was fairly easy.  And that allowed me to move the pipe enough to get some access to the donut.  I thought I was on a roll and could knock the old gasket off, put a new one on and just maybe fix something.  But I had no idea the old donut gasket would be made of of granite, or something about that hard!  It had no interest at all in coming off.  Decided the only chance I had was to remove the pipe to get it out of the way and give me as much room as possible to work, but I could not get the nuts loose just before the cat.  So I guess I'll take it to the muffler shop this week and get them to do it.  Probably have them straight pipe it to the muffler while they have it torn down that way if the cat is damaged and contributing to my issue, that will be gone also.  The project continues...

[Gojira94]

Good on ya for pressing onward. A lot of folks don't have the patience to go through it all, ask for help/ advice when needed and would have given up.

[AnotherOldJeepGuy]

I hear ya and thanks!  I've had this thing for too many years to give up!

 

Got my new test case spark plug wires in the mail ($6 ebay) and put them on.  I wanted to test the theory that different wires would not arc and it was worth $6 for that experiment.  These plug are all the correct length (11" x4 and 13.5" x2) according to figure 8-5300 in the parts cat.  All wires in place, no arcs I can see in the daylight and none heard.  So my $6 set of wires may be all I need.  They are all I need for now anyway.  I'm taking it down to the muffler shop at close of business today so they can put it on the lift and let if cool off overnight and install the donut in the morning, and probably eliminate the cat but not 100% convinced of that yet.

[89 MJ]

2 hours ago, AnotherOldJeepGuy said:

probably eliminate the cat but not 100% convinced of that yet

Do it. You might even come out ahead on it. Some cats are expensive. 

[AnotherOldJeepGuy]

14 minutes ago, 89 MJ said:

Do it. You might even come out ahead on it. Some cats are expensive. 

Wellll, I talked to him about that and the answer was he can't do it, it's against federal law:(.  So for the moment at least the cat stays.  He did say he would do some kind of check by poking a hole in the pipe before and after the cat but I didn't really catch what that was going to do.  The ride down to the shop was very noisy since I didn't bother to reattach the pipe at the donut since they were going to take it right apart anyway, the shop is only a couple miles away.  Sounded like I was ready for the drag strip!

[AnotherOldJeepGuy]

Got back from the shop with the new donut.  First stall was before I left the shop .  That seems to be the most noticeable issue with the engine right now.  If I can keep it from stalling right at initial throttle, it runs.

 

The tech used a tube in the ear to check for leaks at the new gasket and he was satisfied it was not leaking.  It does sound better, a sign that perhaps the leak seen before at the donut is gone.  I will repeat the air-vac bubble test later when it cools down.

 

I did tell the mechanic about the other small bashful bubble leak I had seen off and on, his opinion was that if it was that small it should not cause any problem.  However if I can find it my plan is to try to plug it with JB Weld.  If it is really a pin hole and I can scrape it down to clean metal, JB weld should at least provide a temporary fix long enough to tell if it makes any difference.

 

He put a small hole in the pipe near the cat and fished a stiff wire through to check for possible flow blockage.  He said it seemed to him it was already vacant at this point and is essentially a straight pipe.  The guy's a 30 year mechanic at a muffler shop, seems like he would know.

 

I currently have the battery disconnected to do another ECU reset just in case it's off at the moment because it has not learned yet that the donut leak has been repaired.  A Hail Mary I know, but easy to do.

[watchamakalit]

I'm beginning to wonder if there isn't a mechanical problem. Like maybe the hard acceleration broke a rocker arm, stuck a lifter, popped a head gasket.   These are all just possibilities that haven't seemed to have been discussed.  At this point I think your on a goose chase with any kind of air leaks. Seems as though between you and the shops the air flow situation seems normal enough to run well. That's why I'm leaning towards something mechanical that may have been weak already and that accel was enough stress. 

 

Might be a good idea to pull the plugs and see what they look like. Maybe check compression while you there. 

[AnotherOldJeepGuy]

See pics on 5/26 and 5/27 (page 5 of this discussion) for what the plugs looked like back then.  The consensus was running rich.  I cleaned them all and put them back in.  Checked again on June 15 (page 9) after a lot of the work has been done and the couple I pulled that day (to allow me to do the index check) looked clean as far as I can tell, but you can tell me if you think differently?  I don't know that I have the tool for checking compression but I can probably find one somewhere.

 

It is idling pretty smooth now and other than the tendency to stall at maybe a 3%-5% throttle, the rest of the time engine seems to be running pretty well, would these other things you mentioned be an issue at minimal throttle but not be noticeable at idle and throttle above maybe 5%?  

[ratrapp]

without reading over the last 10 pages have you cleaned the throttle body out?does it run and start fine, just stalls out at low speed?

[AnotherOldJeepGuy]

1 hour ago, ratrapp said:

without reading over the last 10 pages have you cleaned the throttle body out?does it run and start fine, just stalls out at low speed?

 

It does start fine and idles fine when I start it.  It might cycle up/down at idle a tiny bit but it is not much.  It's just when I advance the throttle just a smidge, it wants to stall, that's my guess at maybe a 3%-5% throttle.  Once past that spot it seems to be running pretty well again, until I approach that same spot on decel, and when it gets down there it again wants to stall in that same small window, but if it get past that to 0 throttle without stalling, it goes back to idle without stalling.  It's really that 3-5% spot right now that is problematic.  I'll hook up the REM and see if I can identify an RPM range that is a problem and report back.

 

I cleaned the TB and the IAC thoroughly maybe around 18 months ago, it was stalling when I came to idle at a stop sign or light.  With this new issue I have inspected both to see if they were dirty again, but both are clean.  In fact cleaning these is what fixed it at that time.

 

Back 18 months ago when I was battling a stall, and before I cleaned the TB and IAC, I installed a new TPS because I had one.  Nothing changed but I left the new one in.  I kept the old one, I might put it back in just to see what happens.  (I have adjusted TPS to 17% at idle based on REM reading).

 

I did get 1 single small backfire earlier today as I took the throttle up and dropped it maybe a dozen times listening to hear anything useful.

[AnotherOldJeepGuy]

I went with video instead.

This 43s video demonstrates the "want to stall" state a few times, the most noticeable instance near the end.

https://drive.google.com/file/d/1FJgFQBm6sbe5DL0OHUJR9BRpVZYLkjcQ/view?usp=drive_link

 

As a reminder, this video is the original before any of the work has been done, or at least before most of it had been done,

https://drive.google.com/file/d/1y7lS4y-ZxsylCh9y-odN4-UIrnIeS3lh/view?usp=sharing

 

[ratrapp]

i would reinstall my old tps and try that.you could possibly have a sticking or failing iac.when i worked for jeep back in the 90s/earlys 2000s we had an iac exerciser that you hooked to the iac and you could manually increase or decrease the iac to make sure it worked.

[AnotherOldJeepGuy]

Yeah might as well try the old TPS.  I see that a new IAC is not very expensive so might try that also unless the TPS turns out to be a fix.