Cold weather engine miss

edfiero1

Member
Joined
Apr 6, 2017
I've got an 84 hot air car, converted to 87 ECU.
For a few years now I have had an odd problem that shows itself in cold weather. When the outside temp gets below 55 degrees, I get an engine miss when the engine is under load.

The car will idle fine, but when you give it throttle before it is fully warmed up, the engine cuts out randomly for a second or two. This is not like a misfire on just one or two cylinders. Its more like a complete loss of power. After the car is fully warm, then the problem mostly goes away. There is no backfire. Just loss of power.

Since the problem began I've changed the fuel pump and ECU for other reasons, and the problem is still there. Fuel pressure is good.

Anyone got ideas on where the problem might be? What to troubleshooting I could try, or what to replace?
 
I , Myself , can't help... Brother. However, I know the others will be willing to advise going forward. I've been chasing a very similar thing on my '84 for 4 years.
Thanks for posting this , I'll be following.....
....Richie
 
Check the tps with an ANALOG VOM.
You are looking for a smooth needle swing as you run it thru the range. Any glitches or non smooth changes in the swing, replace it. Tps's generally develop a "flat spot" in the light cruise range around 1500 2000 rpm. That's where the throttle is most of the time when driving. Other possibility is the map sensor, the diaphragm gets harder and develops a glitch too. Whenever a turbo car comes in with a drivability issue, I check the O2, TPS, and MAP FIRST. A change in weather translates into a change in throttle opening and map readings due to denser air. Or I am full of it.....
TIMINATOR
 
Check the tps with an ANALOG VOM.
You are looking for a smooth needle swing as you run it thru the range. Any glitches or non smooth changes in the swing, replace it. Tps's generally develop a "flat spot" in the light cruise range around 1500 2000 rpm. That's where the throttle is most of the time when driving. Other possibility is the map sensor, the diaphragm gets harder and develops a glitch too. Whenever a turbo car comes in with a drivability issue, I check the O2, TPS, and MAP FIRST. A change in weather translates into a change in throttle opening and map readings due to denser air. Or I am full of it.....
TIMINATOR
Hmm had not thought about the TPS. Guess I can try to measure the voltage. But don't think it would be MAP. MAF maybe, but not MAP.
 
Methinks UR correct, as the MAP only runs the boost gauge on these.
Just tested the TPS with my multi-meter. It looks good. Voltage increases nice and smooth, with no hiccups as the throttle is pressed. All the way up to about 4v at WOT.
 
What is it at idle? 4 v seems low at wot. Somebody will chime in and tell you.
TIMINATOR
 
I Read somewhere that the wot Voltage does not matter that much .... as long as it's over 4 , we're good.
Could be wrong.....as I have been once or twice before.
 
I Read somewhere that the wot Voltage does not matter that much .... as long as it's over 4 , we're good.
Could be wrong.....as I have been once or twice before.
My understanding as well.
I think we can eliminate TPS as the problem.
Other things to check????
 
I , Myself am trying to get the IAC correct? Just wonder'n if you have ever read this :
 

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