Hey Guys,
I have a 95 XLT SWB 5sp (145,000) that doesnt seem to have the same power as my fathers 94 XL SWB 5sp(95,000). The truck starts and runs fine. It just doesnt have the pull through the gears like the 94 does.
From a dead stop,it pulls ok until about 1400-1700 rpm then lays down and doesnt make any more power. The 94 makes good power all around and is much snappier. The truck isnt throwing any codes and seems to idle nice and smooth.
I changed the plugs,cap,rotor,wires,fuel filter and air filter. The brakes arent dragging and the front end tracks nice and straight.
The only thing I can think of is comparing the timing settings, fuel pressure settings and compression readings. Visually, both engines look identical with the exception of the 95 having additional air injected into the exhaust ports at the head along with the converter air like on the 94. I dont think that would cause my problem.
Is there any way to check the converters to see if they are restricting the exhaust? Was there a compression ratio change from 94 to 95? My manual says a 95 combustion chamber volume is 65 to 68 cc. What is the spec on a 94? Could it be excessive EGR flow to meet emissions standards?(restrictor plate) Will an ignition module cause this? I still get about 17-18 mpg. The 94 feels almost like a v8 compared to the 95.
Any help would be greatly appreciated. Thanks Guys

 

Before getting too involved, what's the gearing in the rear end in comparison to each other?

Yours may have lousy 3.08s and he might have 3.55s or something of that sort.

 

They both have 2.73 rears and the same stock tire size.

 

A quick test for the converters is to install a vacuum gauge to manifold vacuum and note the idle vacuum reading. Then increase the rpm to 2000-2500 rpm. The vacuum should increase with rpm, or at least stay the same. If it drops significantly there is an exhaust restriction. You can also install a pressure tap in place of the O2 sensor and measure exhaust system back pressure with the vacuum gauge. The back pressure should be nearly non existant. Anything over 2 or 3 psi is questionable.

 

Just cut the damn converters off

 

cant remove the converters. **** emission state(NJ)

 

Just pull the pipe off behind the last converter, use a mallet and a steel punch or pipe of some sort and beat all the guts out of the last converter, trying to pull as much of it out as possible, idealy, getting it all out. I ended up doing that because mine had no power, the thing was plugged solid, but we have emissions here too, it still passes, even with only the one cat and still looks like it has two.

 

Shinoda, you a matallica fan eh??, thats a good song, especially on the S&M CD

 

Yes, it sure is, I like their Bob Seger cover as well.

 

I will give the vacuum test a try and then possibly the gutted converter route if vacuum looks funky. I will let you know.

 

The vacuum test showed 22 inches of vacuum with no drop at ~2000 rpm. The back pressure test is next. Timing was 6 degrees with the spout disconnected. I readjusted it to 10. Seemed a little better, but not my problem. I think I need to check for proper advance with the spout hooked up. It almost seems like the cam is too far retarded.( I know it sounds crazy, but I have seen in some of these posts the timing gears are ground with a 4 degree retard in them. Not all but some. Is this correct?) This engine has never been apart, so I figure it has the original timing setup. Could they have changed timing gears for 95 models? It pulls good to about 2250 rpm and then lays down almost like valve float. I am really leaning towards more ignition tests and a backpressure test. Thanks Guys...

 

I had the advance go out in my 85... caused some serious top end power loss, may be worth checking. Just hook everything back up... and watch for your timing advance when you rev the engine, if no advance have the dizzy checked out. I had problems in the module and pick-up coil and for what they wanted for that stuff I ended up just buying an aftermarket set-up that was a lot hotter. Also check your EGR valve, I have a 95 F250 with the 4.9Liter and I had some milliage probs. for a while, turns out the EGR was plugged up and not working, clogged up my cat and caused all kinds of carbon build up in the engine, especially around my injectors. Once I got everything changed out and cleaned up I got my milliage back and a noticable performance improvement too.

 

The back pressure test showed a fluctuating needle off 0 and didnt really make it to 1 psi. Didnt really indicate any kind of restriction. I decided to check ignition timing again to see what my advance was. Total advance came in at 25 degrees no more. Is that normal? I would have thougt it should have been more but I dont have the spec on it. What is the total timing supposed to be?

 

Yesterday I was able to compare compression and vacuum readings.The comp reading on the 95 was 105 psi and the 94 was 120 psi. Neither one of these engines burn a drop of oil. The vacuum readings showed the 95 with 22+ at idle and the 94 with 21. The Hollander Exchange shows the heads to be the same. Could there possibly have been a piston change resulting in lower compression for 95 vs 94?

 

Well, now I am really in it. The engine is pulled and an isky 256 supercam is going in. New timing gears, oil pump, oil pan, water pump, tstat, injectors, mild porting of the head, port matcthing of the intake/exhaust, two to one cat replacement and a gibson system. I think that ought to do something. I will keep all interested parties posted.