: 4.9 Horrible Idle



Enigmaticwraith
01-24-11, 04:54 PM
I've recently fixed the timing (it was at 6) and the ISC Motor on my car, and it now idles worse than it did before. It has idled badly every since the engine was replaced, but now it just keeps revving the engine up and down from about 600-1200 rpms. I am fairly sure it has a vacuum leak somewhere now, because it dies when attempting to set minimum air, but why would it get worse after making these adjustments? I've noticed the PCV valve is fairly loose, is this normal or could it be where my vacuum leak is? Also one of the fuel injectors can rotate back and forth, is this also a possible location for a vacuum leak? Also the driver's side of the defroster vent doesn't blow out hot air like the passenger's. I think the vents are controlled by vacuum, but I don't hear any hissing from anywhere in the dash though. The alternator's pulley is also wobbly and its fan is missing a fin and may be hitting the housing, but I wouldn't think that this would be enough to create this much of a problem. The alternator may also be bad, since I have a battery/charging problem, could this possibly create the problem? Sorry for such a long post.

the recluse
01-25-11, 12:02 AM
I've recently fixed the timing (it was at 6) and the ISC Motor on my car, and it now idles worse than it did before. It has idled badly every since the engine was replaced, but now it just keeps revving the engine up and down from about 600-1200 rpms.

The question is key: What was it before? The base timing is 10...

As far as the vacuum leak issues, did you test all possible areas with the carb cleaner to pinpoint? I wouldn't use it under the dash, of course, but if you're looking for a quick and easy way to pinpoint a vacuum leak, that's it...

The alternator may cause a surging in the fact that it may not be supplying a constant and consistent voltage for the electronics to read true. If you know your having an issue with it, change it out.

With the items you know are bad; replace them to rule them out. With the plethora of problems, start with the known's first.

Enigmaticwraith
01-25-11, 12:31 AM
The question is key: What was it before? The base timing is 10...

What was the idle, or what was the timing before? The idle used to be fairly stable around 650-700 rpm. The timing was at 6 deg, and I adjusted it to 12, which has made the engine run way better than previously... except at idle.

cadillac_al
01-25-11, 08:22 AM
Is the SES light on? Are there any codes? Have you checked out all the threads here about ISC adjustment and cleaning EGR tubes? Probably should clean the throttle body too. The owners manual has a idle relearn procedure you could try if everything else is in spec. When I'm stumped I always check the vacuum and look for leaks.

Enigmaticwraith
01-25-11, 10:41 AM
Is the SES light on? Are there any codes? Have you checked out all the threads here about ISC adjustment and cleaning EGR tubes? Probably should clean the throttle body too. The owners manual has a idle relearn procedure you could try if everything else is in spec. When I'm stumped I always check the vacuum and look for leaks.
The SES light isn't on, and there aren't any codes. I already cleaned the EGR tubes and throttle body, and I also already adjusted the ISC screw/plunger and performed the idle learn procedure.

cctgene
01-25-11, 12:53 PM
Just a thought, when you set the timing did you put a jumper on the A & B terminals of the ALDL connector?

Enigmaticwraith
01-25-11, 01:03 PM
Just a thought, when you set the timing did you put a jumper on the A & B terminals of the ALDL connector?
Yeah.

the recluse
01-25-11, 07:22 PM
If you've run a vacuum test and found none, then you'll probably have to move onto the MAP sensor, clogged CAT, fuel pressure sensor, and start testing the injectors; as these are notoriously nasty buggers for epic failing...

To test the injectors, remove the air cleaner assembly form the engine bay and disconnect the harnesses that connect the ECM to the injectors. From here you can ohm out all the injectors to see if any are failing.

the recluse
01-25-11, 07:23 PM
Double Post

Enigmaticwraith
01-25-11, 08:38 PM
I won't have time to test anything until Friday, however the car has 243000 some miles on it, and the fuel injectors have never been replaced to my knowledge, so I will defiantly check them.

the recluse
01-25-11, 11:06 PM
...the car has 243000 some miles on it...

:holycrap: WOW.

I wish I knew this awhile ago, the laundry list of possibilities can be lloooonnnngg.

Enigmaticwraith
01-25-11, 11:24 PM
:holycrap: WOW.

I wish I knew this awhile ago, the laundry list of possibilities can be lloooonnnngg.
The engine only has about 32000, and the transmission about 140000.

cadillac_al
01-26-11, 09:29 AM
I'm stumped. Tell us more about the battery/charging problem. Low voltage can cause lots of problems in any vehicle. Is the alternator putting out 13.5 volts?

Enigmaticwraith
01-26-11, 05:40 PM
The alternator puts out 13 volts. It keeps the battery charged, but if I let the car sit for more than two or three days it won't start. So, I'm thinking it might have a shorted diode. Also it seems that the pulley and fan are warped. I already tried pulling all the fuses one by one to look for a source of the drain, but it wasn't any of them. I haven't went through the other fuse bank under the hood yet, though.

the recluse
01-26-11, 11:20 PM
you could just have a dead battery...

Enigmaticwraith
01-26-11, 11:31 PM
The battery's been replaced twice in the last year...

daniel58
01-27-11, 04:23 AM
Having problems with the ISC on my 90/4.5 myself. I removed the ISC completely and jacked the min idle screw up to get 700rpm and the car runs fine with no codes. Worth a try to narrow down the causes.

the recluse
01-27-11, 07:09 PM
The battery's been replaced twice in the last year...

You've got a direct short to ground.

Enigmaticwraith
01-30-11, 08:29 PM
I finally had some time to test some stuff. I couldn't find a vacuum leak anywhere, and I checked the resistance of the injectors. 5 of them read 16.4 ohms, one reads 16.7 and the other two 16.9.

the recluse
01-30-11, 10:39 PM
I finally had some time to test some stuff. I couldn't find a vacuum leak anywhere, and I checked the resistance of the injectors. 5 of them read 16.4 ohms, one reads 16.7 and the other two 16.9.

Well that's good, they're within spec.

Another possible issue here is a faulty FPS or fuel pressure sensor. Can be had for about $15 and changed out in about an hour. This little number can cause idle issues, hard starts, and stalls. Most of all, it doesn't trip codes. You can test if you have a fuel pressure gauge, but for the cost of one of those you can just replace it....

Enigmaticwraith
01-30-11, 10:56 PM
Well that's good, they're within spec.

Another possible issue here is a faulty FPS or fuel pressure sensor. Can be had for about $15 and changed out in about an hour. This little number can cause idle issues, hard starts, and stalls. Most of all, it doesn't trip codes. You can test if you have a fuel pressure gauge, but for the cost of one of those you can just replace it....
Thanks, I'll replace it as soon as I have time to work on it again. Another thing I noticed today: when I opened the throttle blades to double check the EGR tubes, I noticed that I could smell gas coming up out of the open throttle blades. Also, when I tested to check if the PCV valve was working, I noticed that the engine ran much more smoothly for the short time that the valve wasn't in place.

Enigmaticwraith
02-01-11, 01:03 PM
On the way to class today some new problems came up. The SES light came on and I have codes E98 (High RPM P/N to D/R in ISC Range) and E27 (Open Throttle Switch Signal). Also, when the car gets past around 15 mph, it now starts accelerating by itself until it hits about 30-35 mph.

the recluse
02-01-11, 07:32 PM
Run/re-run ISC procedure now that the TPS is back in place.

Enigmaticwraith
02-01-11, 07:35 PM
Run/re-run ISC procedure now that the TPS is back in place.
I already have. It's been adjusted to the correct gap, and it's had the idle learn performed.

drewsdeville
02-01-11, 09:18 PM
You are making progress. The new codes tell you that either the TPS is either grossly misadjusted or it's faulty (probably the reason it was disconnected). If correctly adjusting the TPS fails, replace it.

Enigmaticwraith
02-01-11, 09:31 PM
Well, the codes can be crossed off the list of symptoms, along with the other stuff in that post. It seems the ISC connector came loose.

the recluse
02-01-11, 11:11 PM
Well, the codes can be crossed off the list of symptoms, along with the other stuff in that post. It seems the ISC connector came loose.

:histeric::histeric::histeric::histeric::histeric: :histeric: Fire your mechanic, he forgets to plug s**t back in...

Enigmaticwraith
02-02-11, 08:01 PM
:histeric::histeric::histeric::histeric::histeric: :histeric: Fire your mechanic, he forgets to plug s**t back in...
If only firing myself would actually accomplish anything...
Anyway, I think it's definitely the alternator. I trickle charged the battery overnight and the idle was almost completely smooth this morning when I started it up. However, on the way to class my throttle got stuck open, which was a little scary. I pulled over to look, and the throttle cables were slack and the arm wasn't resting on the minimum air screw or the ISC plunger; it just seemed to have frozen. I fixed it by manually moving back up against the ISC plunger and it didn't do it again for the rest of the drive.

Enigmaticwraith
02-07-11, 04:38 AM
So, I replaced the alternator and it seems that all previous idle problems have been eliminated. Thanks for the help!
One thing that was never answered and I'm still wondering about though is whether it's normal for some of the fuel injectors to be able to spin back and forth?

the recluse
02-07-11, 09:01 PM
The injector is only pushed in and held with a rubber ring on the bottom and top. The the top has a snap ring as a back up and the bottom is bolted down. Beyond that, the injector can rotate back and forth....