engine runs out of breath in hot weather

[Ivy Mike]

got an 89 Bronco 2 with the 2.9 and noticed something when the summer started heating up here. Now Las Vegas summers, for the uninitiated, are blazing stinking hot. We're talking 105+ everyday. Today it was 112.

Anyway, the B2 is fine in the morning and in cooler weather but this summer got hot and the engine feels like it runs out of steam at about 3k RPM. I don't know if it is the engine computer pulling timing (can the old beast even do that?) or maybe some odd vacuum problem.
Has anyone had a similar experience? I am a little perplexed.

 

[Ivy Mike]

nobody?

 

[holyford86]

I have had the same problem, mine hates the heat... Dunno why, I've tested every sensor on it and it all checks out great, must just be a 2.9 thing...

 

[Vince Waldon]

Actually I'm subscribed to this thread 'cause I know of a 4.0 that's doing the same thing... on hot summer days... and so far no one's been able to figure it out either. Engine has been given a completely clean bill of health by a very competent mechanic, but it definitely starts to fall on its face towing a small trailer as the ambient summer temperatures climb.

 

[holyford86]

Actually I'm subscribed to this thread 'cause I know of a 4.0 that's doing the same thing... on hot summer days... and so far no one's been able to figure it out either. Engine has been given a completely clean bill of health by a very competent mechanic, but it definitely starts to fall on its face towing a small trailer as the ambient summer temperatures climb.

Mine dosen't fall on it's face, it seems to lack power is all.

 

[Vince Waldon]

Hmmm... well... we might be talking about the same thing... or not. If not I'll not hijack the thread further. ;-)

Mine seems to have good power unless its a hot day... then it has a noticeable lack of power. The change is noticeable when the morning has been cool and then it starts to bake in the afternoon.

 

[holyford86]

Hmmm... well... we might be talking about the same thing... or not. If not I'll not hijack the thread further. ;-)

Mine seems to have good power unless its a hot day... then it has a noticeable lack of power. The change is noticeable when the morning has been cool and then it starts to bake in the afternoon.

yep, that's my issue. No thread jack

 

[cammeddrz]

ok so 105 degrees huh? is it possible that it is a simple reason? the much hotter, therefore much thinner/ less dense air is not delivering enough oxygen to the engine?

or maybe the fuel is boiling in the fuel rails making it full of bubbles and therefore delivering less fuel to the engine?

just spitballing here

 

[Ivy Mike]

if that were the case cammeddrz, then I would expect power loss through the whole RPM range. The motor is fine until it approaches 3k RPM at which point it is almost like the truck suddenly gained a load of bricks in the back. I can keep my foot in it and eventually it gets it's power back but this is still a problem. Merging onto a freeway is interesting to put it mildly.

 

[Ranger Kip]

could be that the heat is not helping the intake, it needs air to start, hot air wont help it start.

even in my trucks current state with starting issues, once it hits dead winter, at about 45 degrees, it will start up like it was new.

Maybe it needs some water!

 

[cammeddrz]

catalytic converters function entirely on heat. that being said i once had the exact same problem you're describing on a 1984 v6 camaro. it turned out to be a clogged cat.

 

[holyford86]

catalytic converters function entirely on heat. that being said i once had the exact same problem you're describing on a 1984 v6 camaro. it turned out to be a clogged cat.

I have no cats, I still have the issue.

 

[Ivy Mike]

I'm going to have to tear into it this weekend. I wish I could find a copy of a real service manual instead of the Haynes one I've got. Anyone know where one might be available in PDF form?

 

[b2rich]

I have the same issue with my 87 with a the a4ld. up a 6% grade it dogs like crazy. I didnt really notice how bad it was till i moved to this are. up in portland i never had this issue.

i am thinking of putting a 2 row radiator and an electric fan in to see if that would help give it a little more umph by cooling the motor a little more.

 

[Ivy Mike]

a slight modification to the original symptoms. If I rev at partial throttle it doesn't always (but sometimes does) have the same hole in the rev range. Once it gets past 3300rpm or so it seems to pick back up.
Does the 2.9 use vacuum advance? Maybe that is screwing up in the heat.