1987 Iron Duke, DIS ignition, manual tranny.. So 6 months ago she started to rough start. For the first 5 minutes, it runs very rough, clearly with a strong miss. And VERY rich. After a little bit of warmup, it smooths (and idle rises) dramatically. For that matter, it goes from rough to smooth in only moments. After a little more warming, the idle drops to normal. At this point, I can drive it with fairly normal behavior. If I drive it before this, it will stall frequently. Once it is warm, and I drive it, it does have one odd behavior. At full accel, the exhaust has a Shashashashasha sound to it. It usually thows a 45 code, which is rich O2.. which one would expect. So the list; In the fall, new fuel pump. New ignition module, two coils, pickup, wires, plugs. Did not like the plugs, put the originals back. Found duff fuel regulator, slight improvement. When fixing fuel reg, damaged injector, replaced with a new one. Missing engine ground wire, installed two of them in two locations. Have swapped out the computer, I have two, both appear to be good units. Have swapped back in the original ignition components, but does not help. Borrowed a snap on system with the right ALDL adapter, which worked, allowing me to find.. A bad MAT sensor (no, it is not 145 deg C in the winter OR summer), no improvement. I did take a video of the snap on unit operating, but did not see any odd things in the video, but am not adept at understanding things like integration and advance. But knowing that I have a miss, I have this little pen shaped device with a neon bulb in it.. when you put it against the ignition wire, it blinks. On all 4 wires. I am a firm believer in test and troubleshoot.. but now that I have replaced all of the ignition parts, I am not sure what to try next.. Have not checked compression. New alternator is keeping the battery well charged. Old belt was shredding, new one, I am bypassing the compressor. I do not hear any odd valve noise. Although rough running on start, it always starts up quick and easy. The cat has cracks in it to the point that I may as well not have a muffler, which may explain the odd sounds on accel. At this point, I am open to any advice and ideas.
An '87 duke was my first Fiero. I never liked that DIS 4-banger. Would you believe that the factory ignition timing at an idle for that engine is 38°BTDC ... and it's nonadjustable. Makes for a rough idle and a filthy exhaust. For more details have a look at this ancient PFF thread Here.
What are these original plugs you put back in? Are you reusing the old delcos? I would pull them and see if they are fouled and check the overall condition of each. Accel makes acceptable replacements too.
So I have the duke running right now. The new plugs that I put in in the spring were left at a 45 gap. I bought new ones and put them in with a 60 gap, It is a marked difference. It still starts up a little rough when cold, going blup blup blup, but smooths out pretty quickly. It also can be driven sooner without stalling out. And is a bit smoother through the whole range. When I figured it out, I could picture Ogre next to the car saying "I told you that!"
Running rich and therefore missing can also be caused by a bad coolant temp sensor. But if you read the ALDL live data I guess you saw it was correct.
My '85 duke runs very rich when cold - to the point I have to start it always twice, because after the first start it just floods within a second. Also goes "blup blup blup" as you described it for a few seconds.
Did you read the TPS live data? What was it showing at idle?
TPS was showing 0.5V, and when pedal pressed, it would go up. Coolant temp was correct, and warmed as it warmed up. MAT sensor was pegged, and replaced that.
I love watching a professional. Because I am not.. and I would not figure that out. It is snowing now, and supposed to be ugly tomorrow, so in a few days I will run that test.. easy pleasy.
I think it may be a little beyond the point, now, but I wanted to correct my previous post in here where I had recommended accel plugs. I had intended to say "Autolite". Those two names always get mixed up in my mind! Autolite are the acdelco equivalents that I find give the same performance when delco is either not immediately available or if troubleshooting demands what's on hand at the shop. Forgive my mix-up!
My 2.5L has had running issues since I brought it home from storage last winter.
Since everything had a warranty and I'm friends with the local parts store folks; I brought every electronic component in because I didn't want to waste time trouble shooting. Didn't fix it. Tried all 4 of my spare computers and even check voltage at every wire.
Turned out to be the little plastic guide the goes in the harness port of the map sensor was missing. It had fallen out when I cleaned my K&N air filter.
I tend to throw parts at things too, pretending that I am troubleshooting. But I am trying to break that habit, slowly. And on Viperines plugs, I put the ACdelco R43TS6's in it. I find that Auto Zone has had an awfully high percentage of the stuff that I need for the car.. if I do not have time to Rockauto.
Fiero ignition systems do not like removing spark plug wires. You can loose an ICM doing that. The engine shown is from 2002, and the world had changed a lot by then.
Fiero ignition systems do not like removing spark plug wires. You can loose an ICM doing that. The engine shown is from 2002, and the world had changed a lot by then.
I agree here. At best, an in-line spark indicator fully connected with a test bulb would show the same results with less harm to the ignition system.
That's why I didn't say nothing about the first part of the video. I only meant to show how to check that intake manifold gasket for vacuum leaks in the later part of the video.
I agree 100% and should've mentionted that - don't remove the wires. You also might get shocked.
[This message has been edited by cebix (edited 02-09-2017).]
As this 87 is a DIS, each coil serves two plugs of course. I see what he was doing with completing the path on that plug to keep the other plug working. I agree, that is dicey. But what I want is a widget or test unit that can tell when the quality of the spark is poor. A magic indicator that the spark on that plug or wire is "15% under ideal" or something.
An intake vacuum leak or an exhaust manifold leak could make it run rough cold, then smooth out as it gets hot and expands to seal. One of my motorhomes has some broken exhaust manifold studs (50K) on the 454 engine. It runs a bit rough and noisy for the first few minutes, then quiets right up and smooths out soon as its got some heat. Im not going to even bother with it at this point since its fine 98% of the time.
... and it's nonadjustable. Makes for a rough idle and a filthy exhaust. For more details have a look at this ancient PFF thread 
