Sequential VS regular multiport fuel injection -
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Unread 10-28-2011, 08:35 PM   #1
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1995 YJ Wrangler 
Join Date: Mar 2011
Location: Grande Prairie, Alberta
Posts: 9
Sequential VS regular multiport fuel injection

So I just managed to figure out my Jeep originally came with a 95 I6 and was swapped to a 91 I4 and wow is it confusing when you get parts for a 95 based on your VIN (which says 95 I4) which inst your VIN cause somebody swapped your windshield frame so your VINs don't match and you think somebody swapped your vehicle with somebody else's and didn't realize it (my registration is the chassis VIN).

Anyway, confusion aside, from what I can tell the only real difference (correct me if I'm wrong) between the 95 and 91 engines is the distributor and that the 95 has sequential multi port injection instead of simultaneous multi port inject like the 91 has. Is it a worthwhile endeavour to convert the 91 to sequential or is it a time waster? What would have to be swapped out? Is there any performance or fuel consumption differences?

Thanks for any help guys.

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Unread 10-28-2011, 10:40 PM   #2
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2000 XJ Cherokee 
Join Date: Mar 2010
Location: Scottsdale, AZ
Posts: 664
It doesn't make that much difference. Engine management controls improved over the years, but HP and efficiency didn't change that much. Not sure of the Wrangler numbers, but for an XJ, between '87 and 2001, the HP jumped from 177 up to a whopping 196(the biggest improvement involved the TB, intake and head, not the electronics).
Kind of confused about your post, but if you Jeep is a '95, and has a '91 motor in it, odds are it still has the '95 FI setup. If the chassis is a '91, and has a '95 block, it's probably using the '91 electronics.(Usually, when we swap the 4.0s between chassis, the simple method is to strip the accessories from the block and use the controls and sensors from the vehicle)

The injector sequence is set by the computer. The injectors themselves are identical. To swap from the early to the late system involves swapping the computer, harness and sensors.
"Never attribute to malice that which can be adequately explained by stupidity, but don't rule out malice."
My other car is also a Jeep,.. and so is the other one,.. and that one too. How many do you own before it's "a herd" ?
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Unread 10-28-2011, 11:26 PM   #3
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1995 YJ Wrangler 
Join Date: Mar 2011
Location: Grande Prairie, Alberta
Posts: 9
The chassis and tub are '95 and originally had a 4.0L I6 in it, one of the PO's put a 91 2.5L I4 in it along with a new windshield frame, hood and fenders, the computer must have been swapped because it went from a 6 cylinder to a 4. What year computer is in it I do not know for sure, but I would assume it came with the engine, so that means 91 unless its REALLY been frankensteined.

On the note of computers, How would one find out if the sensors between 91 and 95 are different? I have changed the O2 and noticed that afterwards it has run rather rich and I'm just now considering that that may have caused it
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Unread 10-29-2011, 10:48 AM   #4
Cobra Jeep
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1993 YJ Wrangler 
Join Date: Aug 2005
Location: , Alabama
Posts: 1,365
All 91 and newer 4 and 6 cyl engine are sequencial injection. A few parts changed here and there over the years, but they are all basicly the same engine management system. The only big change was in 96-97 when they changed to OBD-2.
So your 91 4 cyl is already sequencial injection.
The 90 and older were carb on the 6 cyl, and tbi injection on the 4 cyl.
'93 YJ 4.0L, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, WJ knuckle/brake conversion, hydroboost. Warn M10000 winch. Hope to some day build a stroker for it.

'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
Future mods: NV4500, NP205, high pinion D60 front and smooth bottom D60 rear, e-lockers front & rear. SOA with 35X12.50's
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