Stock 5.0, misses at 1200rpm?

PureStreet · 10-10-2001, 12:03 PM

Stock 5.0 misses at 1200rpm?
Help, this might be a long post. I bought a 92 LX recently and I've been working out the kinks to getting it to run properly before throwing the money into it. This is my 3rd Mustang, so let's assume that I've tried the basic stuff.
I bought it with 130,000 miles, bone stock with flowmasters. It sat for 14 months in the same spot. I gave it the basic tune up with plugs, wires, cap and rotor, and fuel filter. Set the timing to 14, threw in a K&N, and changed the oil. Still misses a bit. Checked the TPS, read TOTALLY off the wall, so I replaced it and set it to .98V. Helped, and runs much much better than when I started, but at 1200-1500 rpm, the intake shakes a little bit as well as the steering wheel, you can feel that it's missing just a tad. I've recently tried some other things like swap out the mass air meter, with a good one.... No luck. Tried new O2 sensors (even though there is no check engine light), no luck.
I've been told by one shop that it could be the distributer pick up. I haven't tried this yet, as I know very little about where or what the distributer pick up is or does.
Any ideas guys?

Thanks for the help!

jimberg · 10-10-2001, 12:17 PM

You may want to move piston #1 to 30 degrees BTDC and verify that the distributor is in correctly. The #1 cyl cap contact should be in the middle 3rd of the contact on the end of the rotor. If it's not, your distributor may be off a tooth.

Did you reset your computer after making all of those changes? If not, you probably should.

------------------
351W 89 Mustang GT Convertible

PureStreet · 10-10-2001, 03:11 PM

If by resetting the computer, you mean disconnecting the battery for 20 minutes, yes I have. I also swapped in a different set of injectors thinking that one of them might have been clogged. No luck there either.

Thanks

90dpscoupe · 10-11-2001, 05:21 AM

i was about to post the same thing? mine (a 90 lx notch) misses, kinda shakes when i rev it up, then let off, and the rpms cross that area.

i know i was gonna chaqnge the pickup in the dist, but couldnt get the old one out, also my injectors sound like there in bad shape, im thinking i need to get rid of the ads chip, and back my timing off to stock.

stay posted. btw, my car doesnt bog, or stumble on acceleration, just a rough idle issue through that rpm, and iab and tb is clan.

------------------
90 lx coupe: 5spd, energy susp trans mounts, fms hd clutch, Mac coldair fenderwell, Mac h-pipe, supercoil, ADS chip, 160 stat, aluminum D/S, Black magic fan, 3.27grs.
Best time: 13.9116(on 225/60/15 firehawks)
Best mph: 98.17
Best 60': 1.9607

someday mods:4.10's, slicks.

jimberg · 10-11-2001, 01:08 PM

If you suspect a cylinder, one way to isolate it would be to do a cylinder balance test. You can do this by running the Key On Engine Running test and when it is complete you just tap the accelerator a little. The RPMs should rise for a while and then at the end it will start flashing the cylinders that were weak. If it flashes a 9 they are all okay. It will flash each code twice.

You can do these tests without a code reader. All you need is a jumper wire. Jumper it according to the photo below:

Make sure the engine is warm. Install the jumper. Hop in and turn the ignition key to the on position. It will run the Key On Engine Off test at this point. Each code will flash twice. The first set are the quick test codes which will be followed by a long pause and single flash, long pause and then the continuous codes will start flashing. I think your 92 will have 3-digit codes so keep that in mind.

After the KOEO test, start the car and it will run the KOER test. Write down the codes from that, too. When it's done, do the cyl balance test.

------------------
351W 89 Mustang GT Convertible

[This message has been edited by jimberg (edited 10-11-2001).]

onefastlx420 · 10-11-2001, 10:16 PM

hey 90 coupe i heard that u should not put anything below a 180 stat in, if this is wrong please let me know so i can switch to the 160

------------------
89lx cocaine white,cobra wing/emblems,chrome 18in cobra r's/nitto xtremes, gt40 longblock from ccm,forged pistons,f303,1.6 rockers,performer rpm intake,70mm tb,75mm bullet,bbk fenderwell induction,24#inj,190l pump,bbk fuel pressure regulator,140amp alt,msd ignition/disributor,aluminum 3 row radiator,bbk shorty's,off road h pipe,flowmasters,king cobra clutch,world class t-5,3.73's,strut tower brace,subframe connectors

jimberg · 10-12-2001, 12:36 AM

If the 160 degree thermostat opens at the correct temp and your radiator is efficient enough to maintain the temp at 160 degrees then it would force the computer to stay in warm-up (open loop) mode all the time. Running in open loop mode would cause your car to run rich all the time and lead to quickly fouled plugs and catalytic converters if you still have them.

------------------
351W 89 Mustang GT Convertible

90dpscoupe · 10-12-2001, 12:51 AM

Yea, i think im running a bit rich, but what i did was adjust my electric fan to make it run around 170-180, i think, but that means my fan is usually off, now ABOUT THIS TOPIC, I BELEIVE I FOUND MY PROBLEM< SEE MY POST ABOUT MY HARMONIC BALANCER.

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10-10-2001, 12:03 PM	#1
PureStreet Registered Member Join Date: Apr 1999 Location: Ashburn, VA US Posts: 294	Stock 5.0, misses at 1200rpm? Stock 5.0 misses at 1200rpm? Help, this might be a long post. I bought a 92 LX recently and I've been working out the kinks to getting it to run properly before throwing the money into it. This is my 3rd Mustang, so let's assume that I've tried the basic stuff. I bought it with 130,000 miles, bone stock with flowmasters. It sat for 14 months in the same spot. I gave it the basic tune up with plugs, wires, cap and rotor, and fuel filter. Set the timing to 14, threw in a K&N, and changed the oil. Still misses a bit. Checked the TPS, read TOTALLY off the wall, so I replaced it and set it to .98V. Helped, and runs much much better than when I started, but at 1200-1500 rpm, the intake shakes a little bit as well as the steering wheel, you can feel that it's missing just a tad. I've recently tried some other things like swap out the mass air meter, with a good one.... No luck. Tried new O2 sensors (even though there is no check engine light), no luck. I've been told by one shop that it could be the distributer pick up. I haven't tried this yet, as I know very little about where or what the distributer pick up is or does. Any ideas guys? Thanks for the help!

10-10-2001, 12:17 PM	#2
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	You may want to move piston #1 to 30 degrees BTDC and verify that the distributor is in correctly. The #1 cyl cap contact should be in the middle 3rd of the contact on the end of the rotor. If it's not, your distributor may be off a tooth. Did you reset your computer after making all of those changes? If not, you probably should. ------------------ 351W 89 Mustang GT Convertible

10-10-2001, 03:11 PM	#3
PureStreet Registered Member Join Date: Apr 1999 Location: Ashburn, VA US Posts: 294	If by resetting the computer, you mean disconnecting the battery for 20 minutes, yes I have. I also swapped in a different set of injectors thinking that one of them might have been clogged. No luck there either. Thanks

10-11-2001, 05:21 AM	#4
90dpscoupe Registered Member Join Date: Jun 2000 Location: sanantonio, Tx, usa Posts: 1,407	i was about to post the same thing? mine (a 90 lx notch) misses, kinda shakes when i rev it up, then let off, and the rpms cross that area. i know i was gonna chaqnge the pickup in the dist, but couldnt get the old one out, also my injectors sound like there in bad shape, im thinking i need to get rid of the ads chip, and back my timing off to stock. stay posted. btw, my car doesnt bog, or stumble on acceleration, just a rough idle issue through that rpm, and iab and tb is clan. ------------------ 90 lx coupe: 5spd, energy susp trans mounts, fms hd clutch, Mac coldair fenderwell, Mac h-pipe, supercoil, ADS chip, 160 stat, aluminum D/S, Black magic fan, 3.27grs. Best time: 13.9116(on 225/60/15 firehawks) Best mph: 98.17 Best 60': 1.9607 someday mods:4.10's, slicks.

10-11-2001, 01:08 PM	#5
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	If you suspect a cylinder, one way to isolate it would be to do a cylinder balance test. You can do this by running the Key On Engine Running test and when it is complete you just tap the accelerator a little. The RPMs should rise for a while and then at the end it will start flashing the cylinders that were weak. If it flashes a 9 they are all okay. It will flash each code twice. You can do these tests without a code reader. All you need is a jumper wire. Jumper it according to the photo below: Make sure the engine is warm. Install the jumper. Hop in and turn the ignition key to the on position. It will run the Key On Engine Off test at this point. Each code will flash twice. The first set are the quick test codes which will be followed by a long pause and single flash, long pause and then the continuous codes will start flashing. I think your 92 will have 3-digit codes so keep that in mind. After the KOEO test, start the car and it will run the KOER test. Write down the codes from that, too. When it's done, do the cyl balance test. ------------------ 351W 89 Mustang GT Convertible [This message has been edited by jimberg (edited 10-11-2001).]

10-11-2001, 10:16 PM	#6
onefastlx420 Registered Member Join Date: Jul 2001 Location: augusta ga usa Posts: 54	hey 90 coupe i heard that u should not put anything below a 180 stat in, if this is wrong please let me know so i can switch to the 160 ------------------ 89lx cocaine white,cobra wing/emblems,chrome 18in cobra r's/nitto xtremes, gt40 longblock from ccm,forged pistons,f303,1.6 rockers,performer rpm intake,70mm tb,75mm bullet,bbk fenderwell induction,24#inj,190l pump,bbk fuel pressure regulator,140amp alt,msd ignition/disributor,aluminum 3 row radiator,bbk shorty's,off road h pipe,flowmasters,king cobra clutch,world class t-5,3.73's,strut tower brace,subframe connectors

10-12-2001, 12:36 AM	#7
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	If the 160 degree thermostat opens at the correct temp and your radiator is efficient enough to maintain the temp at 160 degrees then it would force the computer to stay in warm-up (open loop) mode all the time. Running in open loop mode would cause your car to run rich all the time and lead to quickly fouled plugs and catalytic converters if you still have them. ------------------ 351W 89 Mustang GT Convertible

10-12-2001, 12:51 AM	#8
90dpscoupe Registered Member Join Date: Jun 2000 Location: sanantonio, Tx, usa Posts: 1,407	Yea, i think im running a bit rich, but what i did was adjust my electric fan to make it run around 170-180, i think, but that means my fan is usually off, now ABOUT THIS TOPIC, I BELEIVE I FOUND MY PROBLEM< SEE MY POST ABOUT MY HARMONIC BALANCER.