Was out driving today, got stuck in traffic. Temp was around 220, a few times, when I went to accelerate, the car felt “bogged down”. Then something suddenly changed and it was fine again. Smooth acceleration. What would suggest I check out? 1986 V6 Auto.

If its all good now, I wouldn't buy yourself any trouble.

Its hard to diagnose a car that's running right.

There is a good chance that your fuel started boiling in the fuel lines and fuel rail. Hazards of a hot day and hot engine compartment. I presume everything returned to normal once you got moving and things cooled down. sleek

quote Originally posted by sleek fiero: There is a good chance that your fuel started boiling in the fuel lines and fuel rail. Hazards of a hot day and hot engine compartment. I presume everything returned to normal once you got moving and things cooled down. sleek

Interesting... I knew this was an issue with a lot of carbureted motors back in the day... I wonder if there's something we can do to our fuel lines to help solve this problem?

I ended up changing from a 195 degree thermostat to a 180 which helped. then i got a new 3 core aluminum radiator - problem solved. My original 37 year old rad was cruded up with white calcium build up in the tubes. good investment well overdue. I might have done a chemical flush but I think the new rad was a better answer because of the age. Anyway no more problems with vapor locking the fuel system. sleek

Coolant seeing 220°F isn't a problem here. nor is 235° when stuck in traffic.

But other things got hotter then normal often because little to no air flow to cool the alt, distributor, etc.
Worse if missing heat shields etc blocking IR from the exhaust or have exhaust leaks.

Once air moves, cools whatever that hate you then drive normal again.
Somethings take longer to get hot and cool down then others. So if problem stops fast then look a small/thin things.

Also see cave ECM Heat as this or sensor(s) can heat up too and to odd crap that can take days to months to find what is pissed off.

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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

Start with battery and alternator.

quote Originally posted by RWDPLZ: Start with battery and alternator.

Hot engine, stuck in traffic, rad fan and trunk blower kick on, (possibly A/C on as well)... yeah, I can imagine the engine might possibly feel sluggish with the added electrical draw, especially if one or both items in the quote above are questionable.

Yes Mr. Ogre, even fuel injection systems can vapor lock under the right heat conditions. Just check online and I'll bet you can find psb's for this especially on older systems. With hot fuel returning constantly to the tank you can loose efficiency of the fuel pump and even fuel pump failure. Older cars like ours had lots of fuel pump failures in the heat of summer and I know you are old enough to remember that. Haha sleek

Thanks very much for the replies - Haven't had much time to go over the car much, but I think it might have been the fan causing the drain as mentioned above.

Hmmm, it happened this morning about a block from my house. weather is in the 50's, the engine was on for about a minute. Was going about 15mph, stepped on the gas, and nothing...it felt kinda like someone was tryin' to pull the car back with a rope, I thought "ooooh crap." let off the gas, and then it felt normal when I pressed the gas again.


Not sure that it's the cause of what I felt this morning, but I think the Cat might be 'unhappy' (loose pieces bonking around) - I don't hear the "bonkity-bonk" at idle, but when I accelerate, I will hear it. Hafta replace that.

[This message has been edited by TheDigitalAlchemist (edited 05-03-2023).]

quote Originally posted by TheDigitalAlchemist: Not sure that it's the cause of what I felt this morning, but I think the Cat might be 'unhappy'...

My experience with an internally disintegrating and plugged cat was that the engine ran fine at low RPMs, but couldn't breathe enough to allow for higher RPMs. Would basically choke at anything above 2500 RPM.

I suspect you have a fuel issue, due to either lack of fuel pressure and/or a faulty sensor (ie TPS, MAP etc). A scan tool or WinALDL would really come in handy.

quote Originally posted by Patrick: My experience with an internally disintegrating and plugged cat was that the engine ran fine at low RPMs, but couldn't breathe enough to allow for higher RPMs. Would basically choke at anything above 2500 RPM. I suspect you have a fuel issue, due to either lack of fuel pressure and/or a faulty sensor (ie TPS, MAP etc). A scan tool or WinALDL would really come in handy.

Thanks for your reply, is there a particular scan tool you would recommend?

quote Originally posted by TheDigitalAlchemist: ... is there a particular scan tool you would recommend?

I'm not very familiar with standalone Scan tools. WinALDL is what I use. A cable is required to connect to a laptop. It's possible there's also an android version that would connect via bluetooth. Check with PFF member phonedawgz's site to see what he has.

quote Originally posted by sleek fiero: Yes Mr. Ogre, even fuel injection systems can vapor lock under the right heat conditions. Just check online and I'll bet you can find psb's for this especially on older systems. With hot fuel returning constantly to the tank you can loose efficiency of the fuel pump and even fuel pump failure. Older cars like ours had lots of fuel pump failures in the heat of summer and I know you are old enough to remember that. Haha sleek

Sorry, I'm with Theorge on this one. There is no way that circulating hot fuel (and I think it is warm at best) back to the tank in going to effect fuel pump efficiency or reliability. I live in Texas where it is 90+ 'F six months of the year and Fiero owners do not see increased fuel pump failures in the summer.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged