Finally ROUGH IDLE may be cured!!

Topic: Finally ROUGH IDLE may be cured!! (Read 4466 times) previous topic - next topic

Finally ROUGH IDLE may be cured!!

October 19, 2010, 08:19:30 PM

Guys I am still fighting a rough idle. In the last few days I've been driving the car as much as possible and things have gotten worse.

'88 T-bird 5.0 converted to HO. Car has 188,000 miles and was converted to HO about 2000 miles ago. I'm still running Speed Density (car has a Lincoln HO SD computer). Only real mods are bbk headers, off-road h pipe, & smog pump delete.

The car will run super-duper rich at idle and sounds like its cammed out. The idle fluctuates and is very rough. When you drive the car cold it seems to miss on acceleration (makes a popping noise) or under load. Shove it into neutral and rev it and it runs fine. WOT it runs great after warmed up. Once the car is warmed up it seems to idle decent at around 700 rpms and accelerates normally with no miss.

The car also has a peculiar habit of running down the highway at highway speeds and suddenly surging (almost as if I had a foot on the brake the whole time and let it off). Rarely under WOT it will surge like it had a hit of NOS (lol, sounds silly but that's my best description). The surging was present before the swap, just not as noticable. I dont know if the two (idle and this surge) are interrelated or not.

Following was done at time of HO swap and since then:
1.) valve job
2.) new cap/rotor/plugs/plug wires
3.) New IAC, did base idle reset procedure
4.) checked the timing
5.) checked for vacuum leaks
6.) had complete new gasket set at time of head/intake/cam swap
7.) new timing chain
8.) has one new o2 sensor and one original one
9.) new fuel pump (its higher volume than stock but I can't remember how many lph it is)
10.) changed the fuel filter

I tried to pull codes tonight with a code reader but it does nothing.

Tonight I tried a base idle reset again. TPS output is .85v or so. I tried to get it close to .99 but it won't go that far. If I set it to .99, the screw holes on the TPS don't line up with the holes on the intake. I also double checked the timing and I currently have it bumped a few degrees over the base 10 degrees. I have noticed that since I messed with the timing the miss on acceleration has gotten much worse.

I also went over all my vacuum lines and thought I found the cure. The PCV valve was totally pulled out of the intake. I shoved it back in but if anything the problem got worse.

So I am at a loss. Could it be a bad EGR? The one on the car is the original one. Fuel Pressure Regulator? Again it is the original stock T-bird FPR. HELP!

I try to do most of the work on my car but this is about enough to make me take it somewhere before all my hair is pulled out. (or set it on fire)

Finally ROUGH IDLE may be cured!!

Reply #1 – November 02, 2010, 12:38:27 AM

Did you check the screen under the PCV valve to see if it's plugged up?
Are the oxygen sensor wires on the correct side?

That computer ran fine in my car so you can rule that out;)

Finally ROUGH IDLE may be cured!!

Reply #2 – November 02, 2010, 05:43:34 AM

Quote from: thunderjet302;340093

Did you check the screen under the PCV valve to see if it's plugged up?

+1

did you have the spout out when you reset your timing?

Finally ROUGH IDLE may be cured!!

Reply #3 – November 02, 2010, 07:46:05 AM

new cap/rotor/plugs/plug wires

Is the firing order correct? Firing order is different between SO and HO setups.

Finally ROUGH IDLE may be cured!!

Reply #4 – November 02, 2010, 10:11:49 AM

hmm... A lot of us are having idle problems lately....

Finally ROUGH IDLE may be cured!!

Reply #5 – November 02, 2010, 01:33:37 PM

Quote

Are the oxygen sensor wires on the correct side?

I would check this first, followed by a check of the PIP and the injectors.....

Finally ROUGH IDLE may be cured!!

Reply #6 – November 02, 2010, 04:10:44 PM

Thanks for the response guys. While the forum was down, I deleted the EGR so we can rule that out (there was no change afterwards).

Quote from: thunderjet302;340093

Did you check the screen under the PCV valve to see if it's plugged up?
Are the oxygen sensor wires on the correct side?

That computer ran fine in my car so you can rule that out;)

I will pull it back out and look at the screen...man the pcv valve is a PITA to get to! I assume the o2 sensor wires are on the correct side...never thought of that though. I will have to check into it.

Quote

+1

did you have the spout out when you reset your timing?

Yep! Spout was out! (hey that rhymes)

Quote

new cap/rotor/plugs/plug wires

Is the firing order correct? Firing order is different between SO and HO setups.

Yes we definatley changed the firing order from SO to HO...it runs fine most of the time. Just when it is 1st started up and tries to idle and when it is cold and under load. After you drive it awhile it may act totally fine.I did the HO swap several months ago, so this miss under load is a recent problem. It never has idled right since the HO swap, however.

Quote

I would check this first, followed by a check of the PIP and the injectors.....

I never even thought of the oxygen wire thing. What is a PIP? I'm familiar with 'PIMP' (I used to fancy myself as one), lol.

I will check everything out tonight and let you all know what I find out. I am also going to check the spark plug gap...who knows they may have been gapped wrong.

Finally ROUGH IDLE may be cured!!

Reply #7 – November 02, 2010, 09:43:38 PM

OK guys the saga continues. Tonight I did the following:

1.) pulled the PCV valve and the screen was completely clean
2.) pulled the plugs and a couple of them looked wet (due to running rich). I checked the gap and they were all gapped wrong at around .039-.043. I re-gapped them all to .054.
3.) Tried to run codes again to no avail. I can hear one sensor click at the beginning of the test and then it just stops. Not sure what the devil that means.
4.) pulled the vacuum line off the FPR and there was no fuel squirting out
5.) checked the 02 sensor wires and they look to be routed correctly. I really don't think these could have gotten swapped around on us, but I could be wrong. I would not have thought we would have gapped the plugs wrong either, so what do I know lol. My buddy that helped me do the swap builds class-winning pulling trucks with wicked BBF motors, so he knows his stuff.
6.) Double checked that the firing order is correct (I was 99.999% sure on this one but just wanted to rule it out)

After all of this, I took the car for a test run. Fired her up and it idled great. Pulled out into the road and let it shift through the 1st three gears and there was no miss under a load! I started to get a little optimistic at this point. So I took the car to the gas station and filled 'er up with 89 octane.

Leaving the gas station the darn thing missed really badly when I was pulling a hill. It pissed me off so at the next stoplight I layed into the throttle pretty hard and it popped and missed big time. I threw it into neutral and revved it and it sounded awesome (no miss).

After returning to the garage I parked it and it idled well with a very slight surge. It did not smell rich.

I turned the car off and thought "hmmm wonder what it will do if I start it again". Started it again pretty much immediately after shutting it off and took a video clip I will load later. As you will see it idles like a$$. My eyes were almost watering the darn thing was running so rich.

So how can you check the injectors? They were honestly a little crusty looking when I pulled them from the donor motor but I figured they would be fine. I wonder if a can of that parts store "fuel injector cleaner" would make a difference? My wife thinks I am obsessed with fixing this problem and she's right! This sort of stuff drives me CRAZY.

Any suggestions?

Finally ROUGH IDLE may be cured!!

Reply #8 – November 02, 2010, 10:06:25 PM

my car had the EXACT same issue and i found my o2 sensor wires were rubbed through and grounding out...

Finally ROUGH IDLE may be cured!!

Reply #9 – November 02, 2010, 10:11:25 PM

Here is the video: http://www.youtube.com/watch?v=Kv-GzlySvUE

Quote

my car had the EXACT same issue and i found my o2 sensor wires were rubbed through and grounding out...

Hmmm...wonder if the wires are rubbing anywhere or have gotten burnt on the headers or h-pipe. I will definately check into that!

Finally ROUGH IDLE may be cured!!

Reply #10 – November 02, 2010, 11:38:34 PM

That sounds like it's got a cam. Hell mine doesn't even sound like that with a very mild cam:hick:

I'd look at the o2 wires and see how they look.

It's not good that you can't run codes. I know you can with that computer as I was able to do it. What ever the problem is you should be able rule out the computer as it worked fine in my car when I had it.

Finally ROUGH IDLE may be cured!!

Reply #11 – November 03, 2010, 10:29:09 AM

Quote from: thunderjet302;340326

That sounds like it's got a cam. Hell mine doesn't even sound like that with a very mild cam:hick:

I'd look at the o2 wires and see how they look.

It's not good that you can't run codes. I know you can with that computer as I was able to do it. What ever the problem is you should be able rule out the computer as it worked fine in my car when I had it.

Yeah it sounds like a pro stock drag car when it throws a fit.

I'm not worried about the computer since you used it on your car. I am going to check the wires going to the o2's tonight and see what I can find out.

Finally ROUGH IDLE may be cured!!

Reply #12 – November 03, 2010, 10:17:36 PM

Try pulling spark plug wires one at a time.

If you have a problem with a plug, wire, valve or injector this is the best way to tell.

Just pull one off for about 10 seconds, and listen to see if it sounds any different. It should make it run a little worse since you will be misfiring that cylinder. Just keep going around the dizzy one by one until you find the one that either makes no difference, or might even make it run better. Then you can narrow it down to that cylinder and go from there.

If this doesnt work then you know it is a problem with something that affects your whole engine, like sensors or whatever.

Finally ROUGH IDLE may be cured!!

Reply #13 – November 04, 2010, 12:36:03 AM

If you can get the thing to put out codes you can run a cylinder balance test which may help you pin point the problem.

Finally ROUGH IDLE may be cured!!

Reply #14 – November 04, 2010, 12:37:24 AM

Another thought but what did you do with the wiring when the swap was done? Did you change anything in the EEC harness? The SD HO swap does not require any harness repining. Also when you deleted the smog pump what did you do with the Thermactor TAB and TAD sensors?