$40 to whoever figures out this problem! (93 explorer)

[rhauf]

I spent Saturday replacing the a4ld automatic transmission in my '93 explorer (second gear was gone). After it was installed i did a test drive, and found that it had horrible power, and could hardly rev past 3800rpm while in gear (would stumble and drop power, almost like a very crude rev limiter).

I thought it might have been because i had the exhaust cut off (i cut it a little after the o2 sensors, so i could get the trans out) so i put the exhaust back in but there was no change whatsoever.

i've gone around and around looking for vac lines or other things that got unplugged or came loose during the swap but can't find anything. i pulled codes and got code 33 (TPS noisey or something) so i swapped the TPS with one out of another explorer (which was running fine) and there was no change.

so, $40 (via paypal) to the first person who correctly diagnoses this issue. I've spent all day troubleshooting and gotten no where.

oh... and here's a video of said problem.
http://www.youtube.com/watch?v=4R2nBwfks-8

 

[hunterdan]

Plugged fuel filter, low fuel pressure?

 

[Heavymentill]

O2 sensor(s) or vacuum leak.

 

[BobWiersema]

If it wont rev past 3500 rpm while in gear, it probably thinks its in reverse.
The rpm's are limited while in reverse. I would check the trans range switch.


Bob


p.s. If Im right, spend the 40 bucks to buy an Elite membership.

 

[Anime]

Based on the vid, I'd say that transmission isn't much of an issue.

Revving past redline, nailing it and hitting 4000-5000 RPM?

The 4.0L OHV linked to the automatic makes max torque around 2200 RPM without serious internal mods. Going much past that is pointless since torque only decreases and you're just dumping fuel to make the engine wear faster.

Driving it like it's a rev-happy 4 cylinder and having unreasonable expectations of the stock motor/tranny combo might be the problem.

That said, the 4.0L is sensitive to exhaust flow, and something like cutting the Y-pipe and having basically open manifolds will do what open exhausts usually do, make torque drop like a rock. It should actually be more rev-happy wide open, but there will be nearly nothing behind it since the motor isn't tuned for mid/high RPM torque/power.

Aside from any disconnected vaccum lines/caps and electrical connectors, having a leak-free exhaust contributes greatly to having driveable torque, and having one with the correct velocity range of exhaust flow gets you the most torque without the decrease in power and RPMs caused by restrictions.

I'd say start from square one and disconnect the battery overnight, then reconnect and let the engine idle for 5 mins to re-learn it's parameters, then go take a drive. If you don't get any more codes but the engine still doesn't drive how you want, and there are no other vaccum/electrical possibilities, then it's a machanical issue with the transmission, or whatever else you did for the swap, either the exhaust system or anything else.

 

[Foxracin]

The way it acts to me in the video I would say its the torque converter doing some weird stuff. Did you change it also?

 

[rhauf]

If it wont rev past 3500 rpm while in gear, it probably thinks its in reverse.
The rpm's are limited while in reverse. I would check the trans range switch.


Bob


p.s. If Im right, spend the 40 bucks to buy an Elite membership.

You were right. I am now an Elite member

i would have never suspected a stupid neutral safety switch would impact the way the engine runs like that.. that's freakin' stupid.

Based on the vid, I'd say that transmission isn't much of an issue.

Revving past redline, nailing it and hitting 4000-5000 RPM?

The 4.0L OHV linked to the automatic makes max torque around 2200 RPM without serious internal mods. Going much past that is pointless since torque only decreases and you're just dumping fuel to make the engine wear faster.

Driving it like it's a rev-happy 4 cylinder and having unreasonable expectations of the stock motor/tranny combo might be the problem.
(snip)

Yes i know it makes max torque in the 2,000 - 2500 range.. which is why i wasn't thrilled to see it stalling at over 3,000 RPM.

When i spoke with the transmission builder, i told him i wanted it beefed up a bit, with a shift kit, and upgraded cluthes/bands (whatever will make it last longer) and that i would be using it for towing... after discovering the high stall point, i called him on the phone today and he said he included a higher stall torque converter since i'd be using it for towing, to "help it get moving, and take torque off the trans itself" or something like that.... (although he says he didn't realize it would stall at 3,000)

i always thought for towing applications it was more common to run a lower stall. and yes i realize that ideally, it should stall just at the beginning of the torque band, which would be around 2200rpm. the stock torque converter stalled at about 2500. my other explorer also stalls around 2300ish.

he did offer to send me another torque converter (with a lower stall) if i wanted.. but i don't think it's worth taking the whole trans out again to do so.

and yes, i realize the OHV 4.0 is not a top end screamer. i don't expect it to be, i just want things working as they should. i'll get the exhaust patched up next chance i get (with new muffler and cats since the old ones are thrashed) and see how it feels.

The way it acts to me in the video I would say its the torque converter doing some weird stuff. Did you change it also?

(yes new converter)

 

[section525]

Cool!

 

[BobWiersema]

You were right. I am now an Elite member

i would have never suspected a stupid neutral safety switch would impact the way the engine runs like that.. that's freakin' stupid.

Good to here you found the problem. Money was well spent on becoming an Elite member, I would have just spent it on beer.

Bob

 

[Maniak]

The 3000 stall converter is going to generate lots of heat..

Check with Turdle on what happened with his 3000 stall converter (on his 347 of course)... I don't think he could ever keep that thing cool (transmission)

Our X is running the 700r4 conversion and it stalls about 2800 or so. Its not easy keeping the tranmission cool.

We are using 2 transmission coolers and a 10" pusher fan in front and when towing 3000 lbs across town (100F or so weather) it will get the pan temp up to 195F.

Step 1 would be get a trans temp gauge on there. Step 2, is probably going to be swap out that converter...

The higher stall will help get you moving but it will also generate lots of heat when you < 3000 rpms.

Normally, towing converters are lower stall to generate less heat But if you don't have the torque you put in a converter that will stall at the bottom of your torque curve (or you change gearing to get more torque to the ground)

Performance converters are normally a higher stall since you don't care if you generate heat since your just try to get more acceleration..


~Mark