Tough one for you guys

[DBguy]

Hey guys,
I've got an 89 4af engine swapped into a dune buggy and I'm trying to work out all the bugs.

I swapped it in and followed the factory wiring schematic, ran power to the emission control computer, cold mixture heater and engine main relay. The engine is still lacking power, running a little lean+hot and will occasionally backfire on hard decel under load (letting my foot off the gas at 5000rpm still in gear) so something's off. I've double checked all my wiring and connections and made sure I'm getting resistance at the oxygen sensor.Also when I start it up on colder days as the choke opens up when the engine gets up to about 2500rpm sometimes it starts to pulse up and down 500rpm, I have already replaced the throttle position switch, I noticed once that by restricting the air coming through the carb smoothed it out at 3000rpm hence why it's running lean...and I've also checked for vacuum leaks using a piece of hose and some propane...

What am I missing? looking for any insight and thoughts a little stumped at the moment...

[eberbs1]

I have a 88 corolla with the 4af and had some of the issues you are discribing.
backfiring on trailing throttle, lack of power and rpm's jumping when the choke is closed.
I changed my thermostat after i noticed my car was having a hard time warming up.
After replacing the thermostat all the issuse where sloved!
I think it had somthing to do with the thermo vac switches not opening\closing due to lack of heat.

I would change your thermostat.

[DBguy]

hmm...that sounds exactly like it...My setup is a little different with a rear mounted rad and dual fans and the fans come on with the ignition (they run full time) I guess it's possible the thermostat isn't opening all the way...I'll try shutting off the fans first otherwise I'll take your advice and grab a thermostat would be an $8 fix . I'll come back with an update

Any other thoughts/insight/questions while I'm at it?

[dylangumby]

PICS of this dunebuggy!

I just saw a really nice looking buggy here in Calgary for sale $1500 I think he said with a honda motor in it if I'm not mistaken!

[DBguy]

I bought a new thermostat and the idiot at the counter gave me the wrong one even though I argued and told him it looked different from the last time I pulled it...
Anyways I pulled the stat altogether and it's running much better and cooler (it was running way hot before). I'm not sure if that completely solved the problem I'll have to wait t'ill I get insurance on it and drive it...I'll be back with an update




@dylangumby
Sorry missed your reply,

1500 is actually a really good deal especially if it's running. There's a few buggies there in Calgary. Not sure about it having a honda engine, unless it's the K series they spin the wrong way...

Here's a pic, still gotta get the matching front wheels mounted and a few other bits and pieces

[ayang951]

oh wow nice buggy... it looks like itll even help you solve mysteries... 5stars for you!!!

[DBguy]

Thanks guys, nothing like a classic buggy with reliable Toyota power . Although the 4af only make about 100hp it still rips in a 1500lb car!

Right now I'm thinking about scrapping the whole emissions stuff and doing a weber conversion. It's definitely running lean (white plugs) and I've checked over all the vacuum lines a hundred times over. The emissions computer must be picking something up causing it to lean out the mixture and I'm tired of dealing with it. I'll post up another thread about it