Hello again! I am back with my next dilemma.

After getting my fuse links replaced, I found my egr valve was bad on my '84 2.5L so I replaced that. Right now, I'm taking it to the muffle shop so they can find an exhaust leak.

An issue I was hoping the egr would fix has occurred again... My fiero will randomly stop accelerating when I'm trying to maintain speed on the freeway. Feels as if the engine isn't even trying to accelerate. Sometimes, it will kick back with a huge kick but usually, the engine will just die once it slows to about 40mph.

I've already spotted a fluid leak underneath my intake on the block and I read somewhere that the pick up coil may cause these issues. Are there any other parts I should look at first?

Have you replaced your fuel filter and checked the fuel pump output for proper pressure?

Nelson

Idle Air Control. I struggled with coils, clean out EGR, etc. My problems turned out to be the IAC. Around $50 at NAPA and a 51mm socket to remove the old and replace with the new. Several short drives and restarts needed for the ECM to get to know the IAC.

Sounds like you’re losing fuel pressure. I’d check for leaks, including the one you have found. It may not be a fuel leak but if it is, it would explain the loss of power. Does it happen at lower RPM as well?

I have not checked fuel pressure yet. Tried to have my mechanic do it but they said they had no way of hooking up to the fuel line without modifications being made to it first. More on that in a minute...

The IAC in the car right now is brand new. I had purchased it off the Fiero store and seems like it is working properly if the diag tool (Also from the fiero store) is to be believed.

So, muffler shop sealed the leak. From muffler shop to mechanic, which is about a 22 mile drive, the car died again while traveling at highway speeds (~70mph) after about 15 miles. AAA to the rescue, drop the car off at the mechanic and let them take a look.

...They can't get it to happen again...

Pick the car up, drive it home but stay off the freeway. About 19 mile drive. No problems. Car drives smooth, no idle issues, perfectly fine.

I've taken it for a few quick trips and haven't had any further issues. Decide to take it onto the freeway and drive about 25 miles back and forth, taking it even up past 80. No problems UNTIL I finally get off the freeway. 2 miles on the road back home going about 40 mph and the issue starts up again. It feels like only one cylinder is firing, car is jerking forward with a single quick burst, and nothing else happening, no matter how much throttle I give it. I am able to put the car in neutral, cut the engine (as it won't shut off while I'm rolling) and cut it back on. Able to drive for a minute before it starts up again. I managed to pull into a gas station and I keep off the gas and it sounds like metal clunking as the car finally just dies when I come to a near stop.

I took the time to go ahead and put some gas in the car since I'm right above a quarter tank, car sits for a moment and when I turn the car on, I noticed the temp gauge jumped up about 30 degrees from when the car died. Started up great, drove home which was about a mile away and I made it home safely.

I'm pretty lost at this point. Haynes manual doesn't give me any advice. Haven't been able to find anything from the factory manual either. This issue just seems so unpredictable but always hits me when I don't want it to.

I will take a stab...kinda sounds like maybe ignition control module?? Ignition cutting out? Maybe ignition coil, but that is more rare to go out. Sounds like engine warms up and bam, problem. Maybe...

quote Originally posted by Crasian: I will take a stab...kinda sounds like maybe ignition control module?? Ignition cutting out? Maybe ignition coil, but that is more rare to go out. Sounds like engine warms up and bam, problem. Maybe...

Possibly. Seems it only happens when I really push the engine hard. Stay off the highway, and all is well. Punch it on the highway and eventually it will cut. It's started stumbling when running at 70 and even when cruising at 40. Is there a way to test these modules? Haynes says to take it to a dealer... Don't think that's happening... Car is more or less factory with 129k miles so it is definitely possible that it is failing.

Get another "mechanic."
GM TBI Fluid pressure testing just needs an adapter. See my Cave, TBI Test Adaptor search here for current PN for small adapter.
Then add this 4 cyl engine needs 9-13 psi and too low to be accurate on many test sets that reads 75-100 psi. Nearly all gauges are not very accurate at bottom or top of scale. Long story short on time to post why. Test Gauge for them should 0-20 psi (0-30 max) w/ 1 psi marks. Example: (This is liquid filled but the feature isn't needed.)


Ignore all above for a bit.

Warning: Leaking coolant is bad for engine and not the obvious problem to most people. Coolant getting to ignition and other wiring won't help because coolant very conducive. You need to fix this first and maybe clean/fix/replace coolant drench electrical things.

Then pull C500 (1 bolt in the middle hold it together) on firewall and look for damage/burning. 84 has high current output for the alt that can fry large pins and melt/burn the connector.
Then check/fix wires to the starter solenoid. Have 2-3 fusible links to there that get problems.
Then check/fix all grounds listed in See my Cave, Wire Service At very minimum all engine grounds and G202.

ECM and HEI parts gets hot and can go "bad" while seems to work.
Unplug tach filter and leave it unplug until you find others. See my Cave, HE Ignition
Reduce ECM heat, See my Cave, ECM Heat and leave rear console off. If the Engine "dies" pull off the road then tap the ECM case. Sounds dumb but Weak solder joints etc in it may work for a while. You must pull over before trying because just 1iffy joint can completely fail too. If helps ECM is still "dead" and need a new ECM. Save PROM inside to put it in the new ECM.

alldata.com ( alldatadiy.com to you) has correct data for 84. If the "mechanic" does not have alldata then another reason to go elsewhere.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Got the fuel pressure readings and everything was looking good.

It was maintaining right around 10 PSI after priming the fuel pump a couple of times. Started it up and fuel pressure stayed consistent. However, once I turn the car off, the pressure started to bleed down. Now it's bleeding down consistently. Followed the diagnostic procedures in the Haynes manual and checking the flows in the factory manual. Even when I try to pinch the return line, fuel pressure still drops. I am not seeing any leaks at the couplings. Does this mean I need to go ahead and change the fuel pump?

EDIT: I decided to rewire the wires to the Temp sending unit in the thermostat housing right under the fuel filter. Saw they were exposed. Tucked them back and decided to do another test and the fuel pressure maintains 10 PSI even after running. Also watched the injector and its spraying a perfect cone. Not seeing anything bad around the engine compartment or at C500. Havent, check ECM yet, hopefully the problem lies there.

[This message has been edited by D43DLU5 (edited 05-28-2018).]