Steph74

I have searched, read, scratched my head and in the end I am more confused.
Symptoms are :

-Low rpm at cold start for sometime, then increase rpm to 1500, then go back to low rpm when warm. This seems to be normal right ?

-rpm decrease when I turn on the A/C and that doesn;t sound normal

-very low rpm (<500 mark) when it is warm and the engine looks like it is going to stall and this is when I can hear a loud clanking coming from the back (I want to say knock but not sure). The noise disappear if I pull the cable a little to bring rpm to about 750. Could the low speed idling be responsible for the knock because it doesn;t bring enough oil or something ? Oil pressure usually comes down to less than 5psi too

So from what i read, the culprit could be the IAC and I should probably replace it, but at that price, I want to be sure any insight ?


-Looks like my alternator is dying too and the gauge is fluctuating big time.... i am going to get it tested soon but could this be part of the problem too ?


Thanks

CodeXJ

Sounds OK, idle speed should be around 750 RPM when warm.

This is normal. The RPMs should drop slightly at idle when the A/C kicks on, then come back up when the engine adjusts for the additional drag. Unless your IAC is gummed up and not working, in which case it'll stick at the lower RPM since the engine will be unable to compensate.

Yes. 5PSI is way too low for oil pressure. The clanking likely means that this isn't a new problem and the bearing journals have worn a bit, especially if it goes away when oil pressure comes back up. Your idle should not be below 500RPM, so you need to get that addressed. What is your oil pressure when the RPMs are around 750? Should be about 16-20PSI, if it's lower then you may need to run a thicker oil (10w40, maybe?) to compensate for engine wear.

Try cleaning it. Remove the IAC from the throttle body and spray it down liberally with carb cleaner/WD40. You can work the plunger by hand as well until it starts to move freely. Also clean out the throttle body where it goes. If the IAC is gummed up and sticking, this may fix it. Mine was occasionally sticking, same for my brother's ZJ (his would stall). Cleaned everything up and both are good to go.


Is it fluctuating at idle, or throughout the RPM range? If it's idling at 500RPM, the alternator is going to have a hard time making a steady 12v. However I don't see this effecting your 'running' problems, usually if the alternator goes bad you just end up with a dead battery. To be honest, most of your problems seem to be related to a low/unstable idle. This will likely either be caused by a vacuum leak, or a stuck/failed IAC. Other problems can contribute, though, such as worn plugs or a damaged/worn cap/rotor.

Steph74

thanks for all these advices..... plugs / wires/ rotor / cap are new 9less than 300miles).

Since I have no experience, could I have place the plugs wrong and created a timing issue or something like that ? I did check the gap on all of the plugs before putting them in and they were as good as i can tell

Alternator gauge is not fluctuating at idle, it is more like steadily going down while I am driving it.

Oil pressure goes up while driving too (above 10/15 psi which is still low from your comment)... just drops at stop


So you think I could be all right if I fix the low idle problem ? or this bearing journal thing (need to check what it is later) problem will likely increase ? Just wondering

CodeXJ

Nah, if you gapped the plugs correctly you should be fine there. The only way to screw up the timing is if you rotated the distributor, which I can't imagine why you would do that since it requires unbolting it from the block.

Alternator going down could be a bad ground or a faulty alternator. Get it tested, it's really the only way to be sure.

As for the oil pressure, you are maxing at just over 15psi? Wow, that's... that's horribly low. Since you are hearing clanking at idle, we can probably assume that to be fairly close to accurate. You are either running way too think of oil, the pump is worn out, or you have badly worn bearing journals. You may be getting close to rebuild time.

Steph74

arghhhh don;t say that
oil is 10W30 for high mileage vehicles
doesn;t max out at 15psi, it is going to 35/40 when on the highway for exemple...
Yes I am going to get the alternator tested

CodeXJ

Ah, OK, that sounds better. 15psi at highway speed is into the realm of "You're !"

35-40 at highway speed is fine. Try putting 10w40 high mileage in, bet that bumps the pressure up a bit at lower RPMs. Also, get your idle fixed, if your at 15psi at 750-1000RPMs that's OK. I wouldn't want to be lower than that, though. Then just keep an ear open for clanking, clanking is bad.

CAEMI

I'd recommend reading this:

http://ferrarichat.com/forum/faq.php?faq=haas_articles

Then decide if your oil pressure is a problem. You'll know in a page or two.


The low idle is a problem...the clanking is the sound of the motor "lugging" at that low rate. Not good for it.

Also, at low idle your ALT will not charge the battery...so the battery needs to be charged back up at speed. When it reaches full charge, the charge RATE shown on your guage will lessen. This is good. I think Codexj pegged this one. All your issues are related to low idle. Lubricate the mechanical parts and see if that helps.

Isn't there an adjustment for idle somewhere?

Steph74

thanks CAEMI, yes I had seen that page before.... I guess i just have to read it now, it looked way complicated at the time....
I have also read something about setting the idle rpm by playing with the pin in the IAC (??) is that correct ? Like I said I am a newbie and I am getting confused....

Anyway I'll give it a good cleaning as suggested and then will have the ALT tested. i have a free coupn for testing of ignition and charging system at a hyundai dealer.... might be more thourough than the system check at Autozone (maybe I don;t know)

I will report back when I get a chance

CodeXJ

Good luck!

CAEMI

Get the idle fixed...then if you still have a problem in the charging system use that Hyundai coupon.

I don't know what the IAC is...I probably ought to look it up.

CodeXJ

Idle Air Controller

It's a little electrically actuated motor that is able to adjust the amount of air going into the engine at idle, it's controlled by the ECM.

Steph74

Thanks...
haha I know what it stands for and that it is what is adjusting the amount of air through the TB.... that is about it.... Maybe there is no on the later models?

rich

OIL PRESSURE AT HOT IDLE 13-15 PSI. READ the book if you what to give the right answer.10 psi for every 1000 rpm up to a reasonable psi roughly 35 -50 psi, lower for an older motor. For the I6 as long as you have pressure your fine. You should try a mechanical gauge, for a spot on reading.

rich

Dont put much faith into autozoned out or advandceauto for reading your alternater.

Steph74

made some progress (I guess)...let me know what you guys think...
(please remember it is a Renix engine)

Cleaned IAC and throttle body....
check TPS with the voltmeter as shown on the Renix Manual
Checked all the grounds that I know of to make sure they are clean
This didn;t change much (I did unplug the battery to reset computer), meaning the jeep idle high (1500rpm for 2 seconds then down to less than 500 and looks like it wants to die)

Removed the rear CCV thingy (the one on the back of the valve cover) and cleaned it.... removed and broke the CCV front valve (getting replaced today)

Jeep starts idling better.... goes up to 1500rpm on cold start, then down to 750 rpm.... then increases progressively as the engine warms up to over 1000rpm with whistle.... maybe a manifold pb there too).... when temp is just under 200 it goes back to between 750 and 1000 rpm and is really steady....

Then ..... temp pass the 210 mark and it starts going south..... rpm goes down to less than 500, engine tick/knock, sputter in the exhaust

Checked all sensor as shown on the Lunghd page and the only one that doesn;t seem to fit in is the oxygen sensor.

Assuming that the O2 sensor is dead, would that be causing the problem as soon as the engine gets to 210 ?