Engine performance troubleshooting (Page 1/2)
altownsend AUG 29, 05:01 PM
1986 Fiero Base, 4-speed manual, V6 engine

I purchased someone else's Lambo project with the 1986 Fiero base. The engine will run, but seems to be back firing/mis-firing, and it has erratic idle, and it will stall after about 5 minutes of idle. While idling, it will spit and sputter if I throttle. Or, the idle will fluctuate up and down in RPM. I have not found any write-up that addresses my problem and have the following request:

Is an engine specialist/person for the Fiero V6 in or near Houston? I want to use this engine until I get ready to upgrade, and I can make a good engine swap decision at that time. I am located in Missouri City, Texas. I need help with assessing this engine to determine if it can be fixed.

It is not leaking oil, or smoking. It is just not running smoothly, spits and sputters when I accelerate, will not hold idle, idle fluctuates. The car's original interior is gone, so I am not able to pull codes. I really need someone whom is familiar with the engine and can diagnose it manually. Please reach out to me to give me some of your time - thanks
lou_dias AUG 31, 10:09 AM
If the interior is gone, finding the ALDL port should be even easier for you to pull codes...but you would only have to do that if your SES light is coming on.

If you bought someone else's project....chances are it was sitting for a while. You probably have a bad sensor...perhaps after 5 minutes the engine has reached operating temperature and is now reading the O2 sensor and making fuel adjustments. I would replace that sensor if it idles good when the engine is cold.

But would perhaps put in some fresh fuel.

Another note is if the battery was dead at some point, you'll need to drive the car over 35 mph to re calibrate the IAC (idle air controller). See how it idles after that before you go changing sensors.
fierofool AUG 31, 12:03 PM
Two things need to be verified. That the plug wires are in the right order and that the timing is set correctly.

The cylinder numbers on the front side of the engine near the rear window are, left to right as viewed from the back of the car, 6, 4, 2.
The cylinder numbers on the back side of the engine near the trunk, left to right as viewed from the back of the car, 5, 3, 1.

The firing order is 1,2,3,4,5,6, so once you locate the #1 on the distributor cap, every other wire should go to the trunk side, in clockwise order.

To check for correct timing, you will need to locate the ALDL diagnostic port. On the stock Fiero, it's located underneath the center console armrest. Locate that, even if you must remove your center console.

Looking at the diagnostic port, you will find 2 terminals, side by side, at one corner. These are used to retrieve trouble codes through the SES light, and to set the timing.

With the ignition turned OFF, insert a paper clip into these 2 terminals. You can start the car and it will operate on default settings. Let the engine warm up a bit. Using the #1 cylinder the timing mark on the balancer should be set at 10-12* BTC as a starting point. If your spark plug wires are routed correctly, the engine should run smoothly.

Now, once you have adjusted the timing, turn the ignition OFF before removing the paper clip from the ALDL diagnostic port. This allows the ECM to operate on the information provided by the sensors on the engine. As Lou said, you will need to drive the car at operating temperatures at speeds over 35 mph for 5 to 10 minutes to allow the ECM to 'relearn' the engine. If you have spark knock at acceleration, you can adjust the timing up or down without jumping the ALDL and the ECM will adjust to the new setting.

ALWAYS have the ignition in the OFF position when inserting or removing the ALDL jumper to prevent possible damage to the ECM. If you have any trouble codes other than 12, once you've addressed them, the code can be cleared by disconnecting the round barrel connector located near the battery, for about 30 seconds. This is the power for the ECM. The car will again run erratically until it's run through the relearning cycle described above.
altownsend AUG 31, 02:08 PM
lou_dias, thanks for the valuable response.

I do have access to the ALDL and have been using it to diagnose other issues. I have a recent problem and used it to confirm that the fuel pump was/is working.

Now, the original instrument panel and dash has been replaced. So, the SES light is missing, and all of the instruments that came with the original car have been replaced by Stewart Warner gauges.

Note: I do have fresh gas in the tank. Interesting point: when I got the car home, I installed new plugs, wires, cap and rotor, and new IAC and a couple of other sensors, and the cart ran relatively well. I let the gas run out just to keep fresh gas in it. My issues sort of pop up. It has not been inspected or registered yet, so I have not had it on the road yet. I am getting it road worthy now, so that I can at least tow it to a place where I can drive it.

The battery has been replaced, and has never run down since I had it in the car and starting the engine and running it for a long time when it runs. Its performance has been inconsistent.

fierofool, thanks for your added valuable response.

I have access to the ALDL, but the SES light has long since been removed. Perhaps we can find another way to get some sort of reconciliation. Let me ask, please, what is the most efficient way of determining which cylinder is number on the distributor cap? How do I determine if the timing is correct; what method, tool can I use to confirm or adjust timing. Once I determine number cylinder, I will confirm firing order.

Secondary, newest development:

I recently cleaned the engine, and it looks real nice. Something happened and now, the fuel pump is not activating, even with the oil pressure switch back up and pressure built to activate the fuel pump relay. When I spray starting fluid in the intake, the engine fires but dies right away, as expected.

Let's back up to the current problem and get it resolved. We can revert back to the performance issue once we get the engine to fire/fuel pump relay issue resolved.

So, problem: I turn the engine over and release the key, no fuel pump relay activation, even when the engine oil pressure builds up. With 12VDC, I have tested the fuel pump at the ALDL, and the fuel pump activates. I tested the fuel pump at the oil pressure switch (tan and white wire), and fuel pump activates. I tested the fuel pump at the tan and white wire at the fuel pump relay plug with relay removed, and the fuel pump activates. I have fuel in the tank (fresh gas), and I have 45 PSI at the check valve (constant pressure).

I ordered a new fuel pump relay because I got lots of water in the plug when I cleaned the engine. I presumed that I got water in there and shorted the relay out.

Are there any other things to check that might resolve the fuel pump/relay issue? Thanks in advance
fierofool AUG 31, 10:04 PM
Timing:
I use the terminal directly in line with the distributor hold-down screw nearest the coil as my #1 plug terminal. Any one of them can be used, but that's just my habit. It also gives me a reference screw hole on the distributor base plate when the cap is removed.

If the car is a manual transmission, it's pretty easy to put the shifter in 3rd gear with the car on a level surface. You can bump the starter until you get the Big Timing Slot on the balancer to come into view. Then you can give the car little nudges to rotate the engine to the timing mark at TDC. If you pass TDC, back it way back so that when you go forward again you will take up any slack in the timing chain.

Check to see that the rotor button is pointing to where your number one terminal is on your distributor cap. The distributor reluctor wheel and the pickup should be perfectly aligned at the #1 position. It's also possible that it could be pointing at #4, as both 1 and 4 will fire on the TDC mark. If it's at #4, rotate the engine another 180* to bring it to #1.

If the distributor pickup points don't align exactly, loosen the distributor and align #1 position. You would want the ignition module terminals to be oriented so that the heat shield doesn't interfere with unplugging them to change modules when needed. Again, that's just my method.

If you need to disconnect the wires to relocate them on the distributor cap, trace the wires by hand from each plug and label them with a piece of masking tape, by cylinder number.

The relays can be killed by getting water into them. I once purchased a headlight isolation relay, paying $56 for one of the last ones I could find at any GM dealer. Instead of mounting it on its bracket, I just left it hanging loose underneath the left headlight. The first rain did it in. You always want the terminal side of the relays to point downward. New relays can be filled with clear dielectric grease instead of the black dielectric that GM used.

I don't know if you can power the fuel pump through the ALDL if the fuel pump fuse is blown but it's worth checking the fuse. You might even check all of them.
altownsend SEP 01, 12:04 AM
fierofool,

Thanks for the critical information. I have copied and filed for my next troubleshooting of the engine performance.

Thank you for the information about the relay getting wet. I am waiting for my reasonably priced relay to come in. Unfortunately, I had both the AC relay and the fuel pump relay together, and both of them were upside down, with the relay terminals pointing up, allowing water to get into the plug and the relay. I concluded that the problem is the relay. The engine ran before I washed the engine.

Question:

Do you have, or do you know someone who has an ECM for the 1986 4-Speed Manual?
fierofool SEP 01, 09:10 AM
Contact TopNotch. He's Georgia Fiero Club's Vice President. The club's Fiero Parts barn is at his house and there's a dozen or so ECM's stored there. Any Fiero V6 ECM with a manual broadcast code will work. It doesn't have to be for an 86 4-speed. Give him the numbers on your ECM and see if he can match it. He's a member on this forum. But I would speculate that you have nothing wrong with your ECM.
altownsend SEP 01, 06:24 PM
fierofool,

Thank you for the additional information. I will contact him to get an ECM just for the sake of having it. I really need a knowledgeable person standing there with me to assess my situation. I know nothing about the Fiero engine. I am a Chevy V-8 guy. However, I am hungry for knowledge about what I am working on now.

I plan to replace the fuel pump relay and see if that it the problem with the engine 'Not' starting now. that knowledgeable person might be able to go right to the problem. I just don't have the level of experience yet to manage or nurse my engine performance to an acceptable level of performance.

If any of you have ideas about what I can do to solve my issues, please chime in. I need the knowledge, need to apply it, and need to pass it on to the next person.
cmechmann SEP 01, 06:31 PM
The issues you are running into are not Fiero specific. Any mid 80s GM with a 2.8 MFI (batchfire not SFI and with distributor) will have almost the same parts on it. Off the top of my head.
Celebrity, Firebird and Camaro, 6000, Cavalier Z24. At one time, close to 15% of GM cars. So these parts should be readily available. Those relays should be gravy to source.
Being a manual, makes it easier to match from other body lines. Most of the Fiero specific parts are body, suspension, brake and interior. Other than specific accessory brackets, most of the drive train was cross platform. I know that ECM carries over to other models. However, you may need to swap the prom chip or burn one. Try to find someone who has a prom/memory chip reader/writer to try to read the prom. I have having a hard time finding "real" 64, 128 and 256 EEproms.
When it makes you scratch your head, go back to the 3 basic steps.
1.compression (example: Engine sat for a while and 2 to 4 of the valves and seats have rust on them.) Get this one early. check and get it out of they way of uncertainty.
2.fire ignition
3.fuel
altownsend SEP 01, 07:13 PM
Yes, cmechmann,

Thanks, and I do use that methodology when assessing my gremlins. I may be getting stuck with the V-6 vs V-8 ideology. Any way, I am learning as I go. I was not able to get the fuel pump prime system to work, so I wired in a momentary push button to prime with the key on. It worked. I need to fix that. I concluded that it was an ECM issue since the manual switch fixed the problem. I want to get the next two things resolved, so that I can continue with the project:

1) Get the engine running again
2) Get the engine performance consistent enough to have confidence that the engine will perform in a daily driver capacity.

Yes, I can get the fuel pump relay easily, but, in my market, they cost between $17 to $35.00. I am buying them as I did the initial two, via the internet.

Question: What product can I introduce to the fuel system to clean the engine (Intake, valves, ports)? And, where/how should it be introduced? I put inexpensive Walmart ($.94) gas/injector cleaner in the fuel tank of my Porsche 944 (base Model), and my tail pipe is clean like it is new. I would like to get the engine running 'normally' and introduce a product to the fuel system that cleans the intake, ports, and valves. Any ideas, please share.

I plan to drop the fuel tank because my fuel gauge is not working. I presume that the sender has an issue. Can it be tested prior to removing the tank?