rough idle, popping, hesitating at speed

[Johnathn]

(Hope this is in the right forum)
We have a 95 Talon ESI (160k) that we are going to race in the Chumpcar league. Our first race is in a week at the Newton Speedway in Iowa and we have a rough idling/running car. We’ve tried to the keep the engine stock for reliability purposes except for a 3” exhaust that came on the car. I’ve been through a few dozen of these posts, trying different “solutions”, spending money with no results so I was hoping somebody could give some suggestions to our specific issues? (I have a Chiltons that seems to have ½ the needed info in it)

symptoms: Car will immediately die after first starting then fire up and idle on the 2nd try. Smooth at first then gets rough. Shakes the car pretty bad when idling. RPM is consistent around 900-1000 but “pops” or misses in a random pattern. Slow to return to idle. Acceleration is smoother but dips especially at higher speeds. Engine seems to have decent power when not hesitating. Haven’t noticed any smoke.

The key on-off-on-off-on test indicated the following codes:
12 (Airflow sensor) and
55 (Idle air control valve)

LIttle more history: Right after getting the car we took out the transmission to replace the main rear seal (I think) and did the timing belt, tensioner, all the hoses, belts, removed the thermostat... basically anything we could get to. Here’s what I’ve tried recently to get this issue figured out:

- checked the timing marks: lined up with each other and the mark on the case
- smoke test for vacuum leaks: none found
- replaced the crankshaft position sensor: no difference
- just replaced the idle air controller valve: no difference (unplugged it with the car running and it makes no difference???)
- took off the throttle body and cleaned it, new gasket: disgusting, but no difference
- replaced the ECT sensor: fixed the temp light on the dash
- took off the MAP sensor and cleaned off the gunk: no difference
- checked the TP sensor with an meter and it appeared fine.
- replaced O2 sensor by the cat: no difference (had bad wires so needed to replace it)
- replaced the plugs with iridium plugs. Haven’t touched the wires or coil pack.
- new fuel filter: no difference
- compression test: 170-175 across all cylinders

- car came with a rebuilt ECU
- car came with a replaced camshaft sensor

I’m sure there’s other stuff we’ve tried but I can’t think of it right off hand. As for the codes I don’t even see an Airflow sensor on this engine? Is there one? The car came with an aftermarket intake that we replaced with a stock one from a junkyard, (racing rules) could there of been some sensor that the previous owner removed that would effect this? The car has acted this way since we got it. I’m thinking of running back out and grabbing some new plug wires for it. Any suggestions would be appreciated. We need to get this smoothed out before the race. Thanks!!!

 

[BoostedPhoenix]

Not sure where you found your error code descriptions, but 12 is power disconnected in the last 50 starts, and 55 is end of codes...nothing abnormal there...Does this car still have all the emissions ? EVAP and EGR ?

 

[zcox122]

im guessing you did plugs and wires? Make sure that the wires are in the correct order and the coil pack is working ok.

 

[Johnathn]

thanks for the reply(s).

I got the codes from a link in a post on this forum:

http://www.troublecodes.net/Eagle/

I'm still learning the abbreviations. EGR is the thing under the intake tube. Yes, that's still hooked up. I was looking at closing it off but I wanted to get this figured out first. What's an EVAP?

Just did new wires this afternoon. No change. Is there a way to test the coil pack?

One thing I noticed tonight was an unhooked vacuum line coming out of the vapor canister??? (outside and below the overflow tank) I looked through the vacuum diagrams in the Chiltons but couldn't figure out what that did. There's a vacuum line coming out of the intake plenum, can I remove that line and cap that off? It looked like it had something to do with the fuel tank?

thanks

 

[zcox122]

Im not positive because i have a 1g but that could be the pcv line and it needs to be hooked up. (Could also be causing some of this problem)

 

[Johnathn]

thanks for the reply: the PVC is a separate line coming out of the front of the intake plenum and it's still hooked up. this is coming out of the top throttle body, not the intake plenum like I previously posted. (oops)

The canister has 2 metal lines coming out of it and a rubber tube. One of the metal lines is coming from the throttle body and the other goes back to... I have no idea. Maybe the cruise control? The rubber tube is unhooked. We removed the A/C compressor way back and I wonder if the rubber tube was part of that?

I should clarify the vacuum diagram in the Chiltons mentioned something about a line running from this canister back to the fuel tank. So maybe I shouldn't remove this?

 

[BoostedPhoenix]

EVAP would be your charcoal canister and the related hoses and valves. I have never removed EVAP from a 420a so I do not know the symptoms it might cause, but I have removed EGR and found it to cause idle quality problems (though not severe enough to cause vibrations). The EGR tube will clog up with carbon and have the same effect as blocking it off. I have heard of '95 ECUs to be problematic so I would not rule that out. But keep a spare coil pack around, they are not immune to failure, especially in a racing environment. Where is your "custom" exhaust started at, is it still a stock manifold and downpipe ? Just wondering what effect it could be having on the O2 sensor.

Also I would be curious to know your fuel pressure due to it not starting on the first try.

 

[zcox122]

http://www.dsmtuners.com/forums/articles-engine-fuel/100294-2gnt-engine-bay-tutorial.html

This help?

 

[Johnathn]

I'm not going to remove the evap then. I don't want to complicate it any more than it already is.

I'll pull that tube off the EGR (I'm assuming it's the one that goes up and into the intake?) and clean it out.

The exhaust is the mystery to me. It's headers (wrapped in fiberglass tape I think) then something there that's allot smaller than a catalytic converter then back to one of those big, tube mufflers. I don't think it has a cat on it. The whole exhaust is stainless, it's like a 3" pipe. Like I said it came with the car so we don't know much about it.

The car has ran like this since we got it. Could the exhaust be causing it to run rough and this is just the way it's going to be? Seems to random for that.

(it's staying running on the first try now)

 

[Johnathn]

OK, so a quick update on what's going on:

I drove the car about 20miles to a mechanic to have it aligned for the race. It starts fine, idle's smoothly for about 15 seconds then gets rough. Not a back fire, more like a miss. It's also slow to return to idle. Accelerating to interstate speeds it almost hesitates, randomly. Cruising at a constant speed it seems OK. The problem is mostly just at acceleration and idle.

So after the car was aligned we had the mechanic check the head gasket. Some sort of test of the antifreeze. It came back with no exhaust gasses so the head gasket is supposedly OK? The 3 mechanics on duty at the shop all looked the car over and came to the consensus that it was carbon buildup on the valves. Does that make sense to anyone? The last compression check I did was actually a little low and I thought it had to be higher if it had substantial carbon buildup? They sold us a can of BG44R to put in the gas and clean out the carbon deposits. This making sense to anyone in the know?

thanks

 

[LIL RED GS-TT]

Dose it idle like it has a big cam my brothers rs dose the same thing after we changed the timing belt. I couldn't pull up any codes so i did a vacuum test and as far as the instructions on the vacuum gauge say it's bad timing hope this helps?

 

[Johnathn]

Thanks for the reply. As I understand it the only way to screw up the timing is put the belt on wrong but if you do it will give you a CEL?

One thing occurred to me last night. A while back I stuck some Bosch iridium plugs in it. I'm going to go grab some normal copper plugs and see if that makes a difference.

We did the Seafoam in the vacuum line thing and then filled up the gas tank and added a can of BG44K into it. Hopefully that helps clean things out.

thanks

 

[Johnathn]

I think that helped. Still popping but didn't notice the hesitation. Have to go put it through it's paces this afternoon. Thanks for all the help.

 

[BoostedPhoenix]

For one thing get that bosch garbage out of there, use NGK exclusively, despite manufacturers best efforts to make products universal, some just work better than others. It could be excessive carbon buildup, if there is a bunch of carbon on the intake valves then you will get inconsistant air/fuel charge entering the combustion chamber. The seafoam and just driving the car might be the best thing for it. Also did you figure out how the O2 sensor is installed ? No exhaust leaks before the O2 sensor right ?

 

[Johnathn]

It was definitely a carbon build up issue. Thanks for all the help. During the race we got black flagged twice for these large puffs of blue smoke that happened while we were burning through the tank of gas with the fuel treatment in it. 2nd fuel up it was fine, and ran better.

I'm going to write up a post on our race and stick it on this site explaining how our little Eagle talon was wrecked TWICE and kept going to complete a 24hr endurance race. It's pretty good with pics and video.