'96 XLT rough warm idle

[CrownRoyalRacing]

Hey Guys,
I've read a lot about the EGR system on here. I've tried most if it and still have my rough idle issue. It does kick out a CEL light intermittently. Sometimes the light clears itself and sometimes I clear it manually. The code refers to the EGR system. First off, I've electrically tested the IAC and MAF sensor per Autozone website procedures and they work correctly. So I decided to change the EGR valve. In the process of that, I broke the EGR inlet tube, and EGR valve pressure sensor. All parts have been replaced with new parts. The inlet tube was loose and seemed to be cracked so I assumed this was my problem. Now that it's all changed, I stall have the rough idle when the car warms up, but the CEL hasn't come back on yet. I checked all hoses for blockage and they were all fine. The only thing left is the EGR Vacuum Solenoid. (EVR?) Would this cause the rough idle?? Any help would be greatly appreciated!!

Thanks in advance!!

 

[Shen2187]

Try this.

1. Vacuum leaks. Make sure that all vacuum lines are and in good condition. (free of cracks, tears or punctures) Use a stethoscope or length of fuel line held against your ear to listen for a hissing sound while the engine is running. A soapy water solution can also be used (It'll bubble where leaks may be. I use a spray bottle.) Check for leaks around the intake manifold gasket.

2. Since you replaced the EGR, Check the PCV valve to make sure it isn't plugged.

3. Check your air filter. Make sure it's not too dirty.

4. Fuel pump could be plugged up or worn out. (Check your fuel filter as well)

5. Could be a leaking head gasket but I doubt that. (You would know if this were happening)

6. Run a bottle of injector cleaner through it.

 

[CrownRoyalRacing]

OK.....Where exactly is the PVC valve located? I have a replacement but have never been able to locate it. A little more background......the head gasket is leaking.....but it's a small leak that leaks externally. The only reason i haven't changed it is because I bought this X in Chicago and it lived it's whole life there. (the amount of rust under the hood is amazing) The head bolts look like they'd be extremely difficult to remove and this is the only vehicle I have right now. I've had the leak for a while and the rough idle has only recently started. I figure if it was a vacuum leak, that it would idle rough all the time? It runs great for about 20 minutes of driving!! After that, it pretty much idles rough at every stop. There is no hesitation while driving. The air filter was just changed about 500 miles ago. Fuel filter and dirty injectors maybe.....I will check the filter and run a bottle of injector cleaner thru it. But again, I would think it would idle rough all the time if they were the issue.

Thanks for taking the time to respond!!

 

[Shen2187]

Weird PCV valve isn't shown in my manual for the 4.0L It only shows it for the 5.0L I don't think that's causing your problem though. I don't really know what else it could be.

 

[CrownRoyalRacing]

I found the PCV valve......see link below. I pulled it out and it looked very clean considering I have no idea when it was last changed. It rattled as it should. I replaced it anyway ($2.97 at the local Autozone) Hose was cleaned up and reinstalled. No cracks visible. Still idles rough once it gets warm.

http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c1528018e9bb

 

[Shen2187]

It's got to be a fuel delivery issue then. Have you ran the injector cleaner through yet or had the pump looked at?

 

[CrownRoyalRacing]

Not yet but I'm heading to the Autozone now to pick up a EVR sensor. It's the last sensor in the EGR system that I haven't replaced and the code I was getting before was for the EGR system. I will pick up some injector cleaner too while I'm there. I'll let you know later how it goes. Thanks again for the help!!

 

[CrownRoyalRacing]

OK, so I installed the EVR sensor this afternoon and on the drive home the rough idle came back. The CEL light is still yet to come on. So now I'm wondering if I had 2 different problems to begin with. I fixed the EGR fault with one of the EGR parts that I installed, but my current rough idling had nothing to do with the fault in the first place? That's the only thing I can figure at this point. Has anyone ever electrically check the IAC but still had it turn out bad? And does the IAC determine the idle only after the engine warms up? I'm gonna install spark plugs and wires this weekend cause it's over due anyway, but I can't imagine that this would be the problem. Maybe I'll pull the intake completely apart and inspect all of the hoses while I'm at it. Let me know if you guys have any other ideas. Thanks for the help so far!!

 

[Tbars4]

...Very well could be the IAC and it does regulate both cold, and warm idle...

...Your vehicle being in tune is also part of the equation...Your electronic sensors change to acomodate other changes...Once you get out of range, your CEL will show there is a fault it can't compensate for...

...My first question would be what codes are you getting???...This can save you a bunch of time and money..

 

[CrownRoyalRacing]

Before I changed every part in the EGR system, I was getting a 401 code if I remember right. Since I've changed the parts, I haven't gotten the CEL light again. That's what makes me think I had 2 problems to begin with.

 

[Tbars4]

...The IAC will cause problems and not give a CEL or if it does, it will be intermittent..

...Do a search on IAC for cleaning it...

 

[CrownRoyalRacing]

I did have the IAC off and it was a little dirty........I sprayed some brake cleaner thru it and it cleaned up a bit......I performed the Electrical check that I found on AZ's website and the resistance was within the tolerance stated. But that was when the car was cold......I also gained access to the MAF and it looked brand new......I didn't mess with it but did do the electrical check on it and the output voltage was within the tolerance per the AZ website too.

 

[CrownRoyalRacing]

Before the CEL light came on that last time it used to be intermittent. It would come on one day......go out the next. It did this for about 3 months and that was when I checked it and got the EGR fault. I just wonder if the IAC resistance stays the same even after the engine warms up and that's confusing the ECM and causing he EGR issue. Or maybe i should just forget about the EGR system and look elsewhere!!

 

[CrownRoyalRacing]

I took the weekend off cause I was a bit frustrated but I pulled the IAC off this morning and cleaned it really well with a brush and some electronics cleaner. It didn't make a difference. Still no CEL. I would say at this point that the EGR code issue was completely separate from the rough idle issue. Somewhere along the line I got some advice to spray some brake cleaner around all of the intake hoses. I tried this and the engine didn't run any worse or better. No sure if I achieved anything by that!! If it's any help, the exhaust smells a bit lean to me. I'm out of ideas.......

 

[CrownRoyalRacing]

I removed the MAF again and hosed it down with some electrical cleaner. I put everything back together and it didn't seem to make a difference. I did notice after doing this and cleaning the IAC, I can remove the IAC connector with the engine running and it won't kill the engine. Before it would die as soon as I pulled it. It runs BAD when removed, but it stays lit when it didn't before. I think I'm grasping at straps........

 

[CrownRoyalRacing]

So I'm changing my plugs and wires tonight. No sure that it'll make a difference but it's due for the change anyway so it can't hurt. I bought an Actron CP9175 code reader today from AA so I could see live sensor data. If you are familar with this unit, it's not capable. It reads the code, tells you what the code is, and erases it if necessary. Check out the specs online. If anyone is interested in it, let me know. It won't do what I bought it for and I'm too honest to take it back to the parts story after I opened it and it was MY mistake. I paid $135 and have the receipt for warranty. It's less than 6 hours old!! lol......let me know if looking for something like this. Free shipping!!

 

[Tbars4]

...You need to be an "Elite " member to sell anything on this Forum, Forum Rules...

...Changing your plugs and wires will be a plus as you may find the problem right there...Btw, did you find anything with the code reader at all?

 

[CrownRoyalRacing]

Sorry about that.............Changing the plugs and wires did nothing. The computer is not throwing a code. Supposedly, it's peachy keen!! I know better.......it never had the rough idle before. I have no idea where to go from here..........

 

[Tbars4]

...Here's a couple things to check...

...Did you unplug your negative cable for about 15 minutes to reset your computer???

...Look very closely for vacuum leaks everywhere, even cracks on hoses and plastic fittings..

...At the same time, double check all electronic connections...

...EDIT: Did you ever post your CEL code in this thread???

 

[CrownRoyalRacing]

I have unplugged the battery for that long when I was originally cleaning the code. I was getting the P0401 code but that has since been fixed when I replaced every part of the EGR system. I thought then that the rough idle and the EGR code were linked. Now I don't think they were linked at all. I've checked every hose/fitting that I can find. I even started the engine and sprayed brake cleaner (extremely flammable) around every and all intake fittings/hoses I saw. The engine didn't react at all. There is a hose from the intake manifold that routes over to a drum on the driver side. (I think it has something do do with the brakes??) I let the car sit for about 1.5 hours and went out and wiggled that hose and it released pressure. So I think the whole vacuum system is tight or it wouldn't have kept that pressure?? I re-checked all electrical connections tonight that I've touched in the last 2 weeks while I changed the plug wires. Earlier today, i started the engine after it was already warm and then unplugged the MAF. At first, it seemed to idle a little better disconnected. If i hooked up the MAF while the engine was still running, it would almost stall. I thought i might have found something, but I turned the engine off......restarted it without the MAF hooked up......and then plugged it back in while it was still running and it seemed to run better hooked up that time. I did all of this a couple different times and couldn't consistenly put the blame on the MAF.