Misfire at Full Throttle

[villevol666]

Hello,

I am a first time poster but a longtime lurker! :P

I have been having issues with a strange misfire for the last 6 months or so.

The car:
11009 :)
Starts/Idles perfectly regardless of Cold/Hot Start
Drives perfectly around town without issue.
Use to have a turbo, removed by last owner

Relevant work done right before I purchased it:
Spark plugs replaced
Spark plug wires replaced
Fuel injectors flushed
Fuel injector seals replaced
Fuel distributor rebuilt

Description of the Problem:
I live at the bottom of a massive hill that I climb on the way to and from work everyday at freeway speeds. On the way to work, when the car has just been started, I fly up the hill with no problems. Now on my way home, after sitting in traffic for 15 mins, when I press the pedal to the floor during the hill climb, I can barely maintain the speed limit. The car feels as though it is running too lean and will stutter more as I apply more throttle. The curious thing is, the same behavior is displayed when the car is cold if there is an excess use of power, for example, manually starting the fans by turning on the AC.

What I have done so far:
Swapped out the alternator. (This lessened the number of misfires I was experiencing on the hill.)
Replaced the ground cable and added a second ground cable from the frame to the transmission. (This smoothed out the misfires, made them less pronounced.)
Replaced the fans with new lower amp fans. (This did nothing besides reducing the sound the old fans made. :P)
Tested full throttle micro-switch for functionality with ohm meter.

So while it felt like an electrical problem initially, i'm starting to think it could be a mixture of electrical and fuel.

My Theories:
Fuel pump might be going bad or may not be getting enough voltage? Maybe I could isolate the fuel pump circuit to test?
Maybe the fuel enrichment circuit is bad even though the switch is functional? Is there an easy way to test this?
Because the car use to be a turbo, maybe the fuel mixture is a bit off? But why would the problem have only started 6 months ago?
There is a demon in the engine compartment that wants me to suffer everyday on the way home. Does anyone know an exorcist?

Questions:
Is there a quick way for me to dump more fuel into the engine during the hill climb for testing purposes? Maybe by manually tripping the warm up regulator? It would be great to eliminate electrical as a problem without having to fuss with the fuel mixture screw.

Thanks,

Brandon

[Jonathan]

If it feels like you aren't getting enough fuel, then keep it simple and focus on that. Meaning the fuel pump.

If there is a true correlation between electrical load and lack of power and not just one with a hot engine, I would go through the electrical connections affecting the pump and ensure all are clean and in good condition.

This will include (at the very least) the connections on the top of the pump itself as well as any quick connector that might be in use. The RPM relay in the fuse and relay area behind the passenger seat. And the inertia switch underneath the driver's footwell area. Inspect the wires and metal connector surfaces to see they are all clean, tight and in good overall condition.

Had you not mentioned a correlation to electrical load specifically and thought it was just hot engine related, I'd suggest seeing how the pick-up hose attached to the bottom of the fuel pump looks. This might not be a bad idea anyway, that is to inspect the fuel pump as it sits in the fuel tank and see if anything looks amiss. Hot weather combined with hot engine coolant and then hot fuel means those rubber pick-up hoses can get a bit soft and can collapse enough to temporarily starve the engine of fuel.

[David T]

You say the car had a turbo that was removed. I would check that the vacuum and mechanical advance was returned back to stock specs. Also wouldn't hurt to dive into the gas tank and make sure it is clean and if you have the OE fuel pick-up it is clean and the pick-up hose is not kinking or collapsing. Among the things that would lean out the mixture is vacuum leaks. A hose could have slipped off or cracked.

[villevol666]

Thanks for the suggestions! I have additional data as of last night that could be beneficial.

On the way home last night, less than a mile from home, the car died while I was driving it. When I pressed on the gas pedal, it killed the engine. This happened on the freeway, at speeds. I popped the hood to see if there were any obvious problems, and to my dismay, the exhaust manifold was glowing red hot. I did some searching around on the forums, and it seems like this could be a symptom of the engine running to lean, which is what I already believed was true.

Looking for suggestions on what to try next.

Thanks,

Brandon

55134

[Bitsyncmaster]

That looks like the CAT is glowing. Have you checked that your lambda is working and set correctly?

[villevol666]

No, I can take a look at it tomorrow. Any tips?

[David T]

Running too rich if the cat is glowing red.

[villevol666]

I pulled the injectors to test the spray patterns. Only one of them was properly spaying, 2 not spaying at all, the other 3 were severely under performing.

Would the car running lean for an extended period of time cause the cat to overheat\fail?

[Elvis]

this is the cat - and the glows if mixture set too rich !!!

you say 2 injectors didn't spray at all ? how can the car run ?
must sound like crap

[villevol666]

Thank you all for your help.

I ended up cleaning the injectors and replacing the following items:
Frequency Valve
Fuel Lines
Fuel Filter
Distributor
Rotor
Coil
Plugs
Wires
Vacuum Lines

I also tuned the CO to be within the acceptable range.

The car runs great now, and i believe my problems were caused by a flurry of issues including:
Non-Functioning Frequency Valve
Bad coil wire
Clogged injectors