I have been through the same...in my case it was failing ignition coil...which was causing misfiring...I tried all solution which has been discussed on this thready but none helped, finally after a month I got CEL for cylinder 5 misfiring, I replaced it and problem solved...in fact their is a dedicated thread on this issue where their are tons of solution...each one getting issue resolve differently...so hope you find yours

 

now what would i have to do with mine? i got a 4th gen at 240k, it blows smoke everynow and then. more often lately. i think its the lifters valves because when i start it, it blows a lot of smoke, and when i drive, you hear chattering by the valves and it blows more. but other then that, it runs smooth

 

OK, so here's what I did tonight:

1. I checked the TPS, it is fine...at idle it was a little low on resistance at 400, but I adjusted the screws and moved it until it read 520. Full throttle was 4100.

2. I check the plugs and coils. All the coils are fine. The plugs look ok too but they are Bosch Platinum +4's. I'm going to swap them out with the full Laer Platinums above (PFR5G-11) which are the FSM recommended plugs.

We'll see what the plug change does...I'll update tomorrow.


Below are the coil testing results:

 

check all your vacume lines and make sure there on tight and theres no cracks or holes. it doesnt take much of a crack or hole to make the idle go funny. also check the pcv valve make sure it it isn't stuck. take it out and gently shake it it should make a easy rattling. if it is a slow sloshy rattle it should be replaced

 

95maxse3000,

I'd already replaced the PCV valve at one point simply because it was cheap maintenance.

However, good news...maybe. I replaced the Bosch plugs with NGK OEM Laser Platinums @ $10/each and then adjusted the idle per the Chilton manual. This appears to have fixed the issue. Idle in drive at a stop light is now at 700rpm.

Even though my TPS appears good, I still think either it is bad or something isn't quite right still.

I say this because my idle in Park after a drive is at 1000rpm.

When I adjusted the idle with the TPS unplugged and set it at 700, when I reattached the TPS the idle died to around 450. I opened the idle screw until it was back up to 700.

Can I adjust the TPS screws that make minor changes to the TPS while the car is on? I'm wondering if I shouldn't adjust the idle again with it unplugged and then plug it back in and then adjust the screws on it that hold it on and see if the idle goes up without changing the IACV screw?

 

I think the proper way to adjust the idle is to disconnect the TPS and then adjust the green screw atop the IACV. Of course, ensure you've got the TPS calibrated properly first, but it sounds as if you do.

 

Yeah, that's what I did.

I had calibrated my TPS based on the resistance levels needed (500 at idle and 4000 at WOT). Then I adjusted idle with it disconnected. But when I reconnected it the idle shot back up to around 1000 rpms. I was wondering if I shouldn't see if the TPS at idle is now registering more than it should as far as resistance goes now?

Regardless, this is day 2 of no more rough idle so far...but the real test will be tomorrow when I return to work and have the morning commute.

 

check the vacuum lines make sure theres no cracks or holes in any of them. if there is it can cause a funky idle. For a 95 auto the idle in park should be 600 to 700 rpm in drive it should be 550 to 650 rpm.

 

So final post in this thread (hopefully).

All is well now, it appears that the Bosch spark plugs were to blame. They ran fine for about a year and I guess one of them must have been going bad.

$60 later after getting the PFR5G-11 NGK plugs (OEM replacement recommended by FSM) and then setting the idle again, everything is great. In fact, it now idles right around 700 in both drive and park.

I'm going to edit Post #1 so that people don't have to go through this whole thread if they see no need.