Weird intermittent power loss (1 Viewer)

Joined
Jun 22, 2011
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69
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Springfield, OR
Hola

Trying to sort out why my 91 is acting up.

What happens is i'll be cruising along suddenly lose all power. Still have electrics. It's doesn't "bog" like when you suddenly lose spark, it's like i've taken my foot off the gas. It doesn't die, just goes down to idle and there is no power available. So far on each occasion i've been able to put it in neutral, leave partial throttle and it will suddenly run right as rain.

The first time it happened i did the natural thing for an Alfa Romeo guy and gave her a good ole italian tune up. I ran it full throttle up to redline through 1st 2nd and 3rd a few times and the problem went away for a few weeks.

Then it started again last week. It's never been very bad, lasting only a few seconds.

Only last night it happened twice on the way home from work and i actually spent a minute on the shoulder of the highway before i got power back.

The truck is pretty new to me. It has a check engine light. paperclip trick reveals o2 sensor. The nut of course is rusted to the stud and i can't get it off without wrecking it. Someone with more savvy than me is skeptical that it's an o2 sensor and is suspecting part of the smog system. I'm in Oregon and i can de-smog it if i want.

So not sure what to think. MAF? TPS? o2? Cap & rotor? In what order to i do start replacing parts?
 
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Joined
Jan 12, 2014
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Big Rock IL
O2 sensor fix

Most O2 sensors are not bad, just clogged up. The job for you Is the STUDS, oh my what a PITA, A lot of heat and a grabits will often work but not always. Sometimes you just have to drill um out and retap.
 

CruiseOrlando

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Feb 19, 2011
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Does it change behavior if you floor it?

If so, it's the O2 sensor... might even just be the connector. Check for water in it, use WD40 to clean it out and dielectric grease to put it back together...
 
Joined
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Springfield, OR
Nope, no change. It's as though I've taken my foot off the gas. No rough running, back fire etc. Just smoothly idles down regardless off throttle position.
 
Joined
Dec 8, 2006
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Nope, no change. It's as though I've taken my foot off the gas. No rough running, back fire etc. Just smoothly idles down regardless off throttle position.
Please explain this to me in more detail.
Are you saying that when this occurs you can put the transmission in neutral or park, vary the throttle position from end stop to end stop and there is no response from the motor?
 
Joined
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Springfield, OR
My brother in law has owned a few 80s and he thinks its smog related. He wants me to go buy some 1/8" caps and hes going to walk me through some process over the phone.
 
Joined
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Correct jonheld. If I put it in neutral it just idles, absolutely no response from throttle input whatsoever.
Have you tried doing this manually under the hood?
The fact that it sometimes works and sometimes does not is bizarre.
Please pull the 15 amp EFI fuse from the underhood fuse box and wait 10 minutes. Reinstall the fuse and see what you have going on. This will reset the ECU and clear any existing codes.
If it still is happening, you need to check the TPS according to the FSM. At the very least make sure all sensor connections under the hood are clean and in good shape.
 
Joined
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Thanks jonheld, will do.
You need to be certain that the mechanicals on the throttle body are working correctly. Make sure all linkage is intact.
If there is a problem with the TPS, you may or may not get a error code. This is 1986 technology.
 
Joined
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My brother in law has owned a few 80s and he thinks its smog related. He wants me to go buy some 1/8" caps and hes going to walk me through some process over the phone.
Please explain how any part of the emissions system can have this effect. This is very unlikely an emissions issue IMO. Emissions can effect how efficiently the engine runs, but it would not cause a total disconnect like what you're seeing here. It also would not be intermittent.

There is complete disconnect from throttle input. That leaves mechanicals as a primary candidate.
 
Joined
Jun 22, 2011
Messages
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Springfield, OR
No idea, but it fixed it.

I removed the egr vm (i think, see pic). Capped some lines as described by my brother in law and it's running smooth with no issues. Could be my imagination but throttle response seems better.

KIMG0145.jpg
 
Joined
Jun 5, 2014
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Anchorage, AK
Please explain how any part of the emissions system can have this effect. This is very unlikely an emissions issue IMO. Emissions can effect how efficiently the engine runs, but it would not cause a total disconnect like what you're seeing here. It also would not be intermittent.

There is complete disconnect from throttle input. That leaves mechanicals as a primary candidate.

It's a 3fe and they don't like un metered air being entered in to the system. Smog will do this and open vacuum lines.
 
Joined
Jun 22, 2011
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Springfield, OR
Thanks Josh! That was a $2 fix.

Feel bad for people in smog states. Probably would have been considerably more.

Also thanks for the help Jonheld, i really apreciate your time.
 
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It's a 3fe and they don't like un metered air being entered in to the system. Smog will do this and open vacuum lines.
Sorry, but I call bulls***. Unmetered air will cause all sorts of running issues and possible stalling. The OP had no idle issues and no symptoms other than no throttle response. It was also intermittent. This has little to do with emissions. I would be willing to bet this issue has not been resolved.
 

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